- Microwave-assisted generation of lanthanide(II) halides in THF and simple quantitative determination
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Lanthanide(II) reagents (SmI2, SmBr2, YbI 2, EuI2) have been prepared rapidly in high yields using microwave-assisted heating. Samarium diiodide is obtained as a saturated solution in THF (0.13 M) within 5 min and ytterbium diiodide (0.065 M) after 45 min. A simple method for quantitative determination of LnX2 in THF is also described by utilizing the instantaneous reaction with ketones in the presence of an amine and water. This method establishes the concentration of the active single-electron-donor species, i.e. Ln2+. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Dahlen, Anders,Hilmersson, Goeran
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- Total synthesis of (+)-crotogoudin
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Fellowship of the ring: The first total synthesis of (+)-crotogoudin, a 3,4-seco-atisane diterpenoid natural product, is reported. Asymmetric access to the bicyclo[2.2.2]octane core is achieved through a desymmetrization of a meso-diketone with baker's yeast (LG=leaving group, PG=protecting group). A SmI2-induced radical cyclopropane-opening/annulation/elimination cascade affords the suitably decorated tetracyclic structure of (+)-crotogoudin. The synthesis led to revision of the reported optical rotation of the natural product and to assignment of its absolute configuration as an ent-atisane (5R,10R). Copyright
- Breitler, Simon,Carreira, Erick M.
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- Total Synthesis of Ritterazine B
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The first total synthesis of the cytotoxic alkaloid ritterazine B is reported. The synthesis features a unified approach to both steroid subunits, employing a titanium-mediated propargylation reaction to achieve divergence from a common precursor. Other key steps include gold-catalyzed cycloisomerizations that install both spiroketals and late stage C-H oxidation to incorporate the C7′ alcohol.
- Nakayama, Yasuaki,Maser, Michael R.,Okita, Tatsuya,Dubrovskiy, Anton V.,Campbell, Taryn L.,Reisman, Sarah E.
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- Selective Electron Transfer Reduction of Urea-Type Carbonyls
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Urea-type carbonyls in barbiturates undergo a highly chemoselective electron transfer reduction upon treatment with SmI2/H2O/LiBr. The process involves the formation, and further reduction, of unusual ketyl-type radical anions under mild conditions. Cyclic aminal products are obtained in good to excellent yield without recourse to preactivation of the substrate or the use of metal hydride reagents. Furthermore, varying the protic additive used in conjunction with SmI2 allows intermediate hemiaminals to be obtained.
- Huang, Huan-Ming,Procter, David J.
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- High-Affinity Proton Donors Promote Proton-Coupled Electron Transfer by Samarium Diiodide
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The relationship between proton-donor affinity for SmII ions and the reduction of two substrates (anthracene and benzyl chloride) was examined. A combination of spectroscopic, thermochemical, and kinetic studies show that only those proton donors that coordinate or chelate strongly to SmII promote anthracene reduction through a PCET process. These studies demonstrate that the combination of SmII ions and water does not provide a unique reagent system for formal hydrogen atom transfer to substrates.
- Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
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- Radical-Radical Cyclization Cascades of Barbiturates Triggered by Electron-Transfer Reduction of Amide-Type Carbonyls
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Radical-radical cyclization cascades, triggered by single-electron transfer to amide-type carbonyls by SmI2-H2O, convert simple achiral barbiturates in one step to hemiaminal- or enamine-containing tricyclic scaffolds containing up to five contiguous stereocenters (including quaternary stereocenters). Furthermore, we describe the surprising beneficial effect of LiBr on the most challenging of the radical-radical cyclization cascades. An alternative fragmentation-radical cyclization sequence of related substrates allows access to bicyclic uracil derivatives. The radical-radical cyclization process constitutes the first example of a radical cascade involving ET reduction of the amide carbonyl. Products of the cascade can be readily manipulated to give highly unusual and medicinally relevant bi- and tricyclic barbiturates.
- Huang, Huan-Ming,Procter, David J.
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- Cyclization of Imides to 2-Azabicycles via Aminoketyl Radicals by Using Samarium(II) Iodide-Water: Reaction Development, Synthetic Scope, and Mechanistic Studies
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The first highly selective method for direct addition of aminoketyl radicals [R-C?(O-)NR1R2], generated from five- or six-membered cyclic imides, to nonactivated π-systems by using the SmI2-H2/s
- Shi, Shicheng,Lalancette, Roger,Szostak, Michal
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- The Reaction of Samarium(III) Iodide with Samarium Metal in Tetrahydrofuran. A New Method for the Preparation of Samarium(II) Iodide
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Samarium(III) iodide reacts with samarium metal in tetrahydrofuran under mild conditions to afford samarium(II) iodide in almost quantitative yields.A solution of samarium(II) iodide in tetrahydrofuran is prepared from samarium metal and iodine.
- Imamoto, Tsuneo,Ono, Mitsumasa
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- Rare-earth iodides in ionic liquids: The crystal structure of [SEt 3]3[LnI6] (Ln = Nd, Sm)
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Crystals of [SEt3]3[LnI6] (Ln = Nd, Sm) were obtained by the reaction of LnI2 with the ionic liquid [SEt 3][Tf2N] [Tf2N = bis-(trifluoromethanesulfonyl) imide]. The compounds are characterized by octahedral [LnI6] 3- units that are surrounded by a distorted cube of triethylsulfonium cations.
- Babai, Arash,Mudring, Anja-Verena
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- Generation of SmII reductants using high intensity ultrasound
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Ultrasound (20 kHz) was used to prepare samarium(II) diiodide (SmI 2), samarium(II) dibromide (SmBr2), and samarium(II) triflate (SmOTf)2. The method described herein provides a straightforward and rapid approach to the synthesis of SmII compounds not accessible by other means. Of particular importance is the fact that this approach can be used to produce SmII-based reductants in a wide range of solvents including alcohols. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Teprovich Jr., Joseph A.,Antharjanam, P. K. Sudhadevi,Prasad, Edamana,Pesciotta, Esther N.,Flowers II, Robert A.
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- Catalytic Ni(II) in reactions of SmI2: Sm(II)-or Ni(0)-based chemistry?
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The addition of catalytic amounts of Ni(II) salts provide enhanced reactivity and selectivity in numerous reactions of SmI2, but the mechanistic basis for their effect is unknown. We report spectroscopic and kinetic studies on the mechanistic role of catalytic Ni(II) in the samarium Barbier reaction. The mechanistic studies presented herein show that the samarium Barbier reaction containing catalytic amounts of Ni(II) salts is driven solely by the reduction of Ni(II) to Ni(0) in a rate-limiting step. Once formed, Ni(0) inserts into the alkyl halide bond through oxidative addition to produce an organonickel species. During the reaction, the formation of colloidal Ni(0) occurs concomitantly with Ni(0) oxidative addition as an unproductive process. Overall, this study shows that a reaction thought to be driven by the unique features of SmI2 is in fact a result of known Ni(0) chemistry.
- Choquette, Kimberly A.,Sadasivam, Dhandapani V.,Flowers, Robert A.
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- Enantioselective Intermolecular Aminoalkynylation of Styrenes via Copper-Catalyzed Radical Relay
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A novel copper-catalyzed intermolecular aminoalkynylation of alkenes through a radical relay process has been developed in this work, in which N-fluoro-N-alkylsulfonamides (NFASs) are used as nitrogen-centered radical precursors and alkynyltrimethoxysilanes as alkynylating reagents. This method presents an efficient and straightforward approach to various enantioenriched 2-alkynyl-2-arylethylamines in good yields with excellent enantioselectivity, and these products can be readily converted into a series of synthetically useful chiral terminal alkynes, allenes, alkenes, amines, amino acids, and N-heterocycles.
- Hu, Zhoumi,Fu, Liang,Chen, Pinhong,Cao, Weiguo,Liu, Guosheng
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- Total Syntheses of Scaparvins B, C, and D Enabled by a Key C-H Functionalization
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The clerodane diterpene family possesses an impressive range of bioactivities and high synthetic challenge due to their unique amalgamation of rings, stereocenters, and oxygenation. Herein, we disclose the first total syntheses of three members, scaparvin
- Ye, Qinda,Qu, Pei,Snyder, Scott A.
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- Radical Anions from Urea-type Carbonyls: Radical Cyclizations and Cyclization Cascades
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Radical anions generated from urea carbonyls by reductive electron transfer are exploited in carbon–carbon bond formation. New radical cyclizations of urea radical anions deliver complex nitrogen heterocycles and, depending upon the proton source used in the reactions, a chemoselective switch between reaction pathways can deliver two heterobicyclic scaffolds. A computational study has been used to investigate the selectivity of the urea radical processes. Furthermore, radical cyclization cascades involving urea radical anions deliver unusual spirocyclic aminal architectures.
- Huang, Huan-Ming,McDouall, Joseph J. W.,Procter, David J.
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- Synthesis of Rings DEF of Solanoeclepin A
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An improved synthesis of rings DEF of solanoeclepin A has been achieved from ent-Hajos Parrish ketone. A key tricyclo[5.3.2.01,6]decene intermediate having an additional vinyl group as a precursor of a hydroxyl functionality was synthesized, in which the key steps included (i) a [2,3]-Wittig rearrangement to provide trans-hydroindene with C11(R)-configuration, (ii) the introduction of a vinyl group as a masked OH at C6, (iii) an oxymercurative aldol to synthesize the tricyclo[5.3.2.01,6]decene moiety, (iv) an oxidative C-C bond cleavage to yield an aldehyde and an unsaturated methyl ketone, and (v) a radical cyclization for the cyclobutane ring formation to provide the tricyclo[5.2.1.01,6]decene compound.
- Chuang, Hsiang-Yu,Isobe, Minoru
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- Cyclooctatetraenide derivatives of divalent samarium
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Owing to the lack of suitable precursor complexes and applicable synthetic methodology, few soluble divalent organosamarium compounds are known.Recently, a facile route to SmI2(THF)2 proceeding from the bulk metal powder and several organic halides has been described by Kagan and co-workers.We demonstrate herein that this material or the desolvated salt can be used directly in metathetical syntheses (as illustrated by the synthesis of insoluble Sm(C8H8) and the THF-soluble K2Sm(C8H8)2).
- Wayda, Andrea L.,Cheng, Suzanne,Mukerji, Ishita
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- Mechanistic studies of proton-donor coordination to samarium diiodide
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Three's a crowd: Initial coordination of diethylene glycol to SmI 2 liberates THF or iodide, thus providing open coordination sites for substrates and enhancing reactivity. Concentrations of diethylene glycol that lead to coordinative saturation of SmI2 (see structure) reduce its reactivity. Replacement of a hydroxy proton with a methyl group decreases the affinity of the chelate for SmI2, resulting in a decrease in the reactivity of the complex. (Figure Presented).
- Teprovich Jr., Joseph A.,Balili, Marielle N.,Pintauer, Tomislav,Flowers II, Robert A.
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- Indole synthesis from N-allenyl-2-iodoanilines under mild conditions mediated by samarium(ii) diiodide
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A novel method for indole skeleton synthesis under mild conditions mediated by samarium(ii) diiodide has been developed. The reaction of N-allenyl-2-iodoaniline derivatives with SmI2 in the presence of HMPA and i-PrOH at 0 °C afforded indole derivatives in high yields. This journal is the Partner Organisations 2014.
- Iwasaki, Hiroki,Suzuki, Kenji,Yamane, Mitsunari,Yoshida, Shohei,Kojima, Naoto,Ozeki, Minoru,Yamashita, Masayuki
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- Reductive cyclisations of amidines involving aminal radicals
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Amidines bearing simple alkenes undergo aminal radical cyclisation upon treatment with SmI2. The mild, reductive electron transfer process delivers medicinally-relevant, polycyclic quinazolinone derivatives in good to excellent yield and typically with complete diastereocontrol.
- Huang, Huan-Ming,Adams, Ralph W.,Procter, David J.
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- Electrochemical reduction of samarium triiodide into samarium diiodide
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Electrochemical reduction of samarium triiodide (SmI3) into samarium diiodide (SmI2) is investigated as a model reaction to reuse samarium compounds in catalytic ammonia production under ambient reaction conditions. Potentiostatic electrolysis of SmI3 with carbon electrode as a cathode in the presence of bis(trifluoromethylsulfonyl)imide anion based ionic liquids as electrolytes in tetrahydrofuran gives SmI2 in high yields with a high Faradaic efficiency.
- Arashiba, Kazuya,Himeda, Yuichiro,Kanega, Ryoichi,Nishibayashi, Yoshiaki
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- Synthesis of Cycloprodigiosin Identifies the Natural Isolate as a Scalemic Mixture
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The enantiomers of the natural product cycloprodigiosin were prepared using an expedient five-step synthetic sequence that takes advantage of a Sch?llkopf-Barton-Zard (SBZ) pyrrole annulation with a chiral isocyanoacetate and a nitrocyclohexene derivative
- Johnson, Rebecca E.,De Rond, Tristan,Lindsay, Vincent N. G.,Keasling, Jay D.,Sarpong, Richmond
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- Synthesis and characterization of isopropylamine complexes of lanthanide(II) diiodides: Molecular structure of TmI2(PriNH2)4 and EuI2(PriNH2)4
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It was found that the lanthanide diiodides LnI2 (1) (Ln = Nd, Sm, Eu, Dy, Tm, Yb) are dissolved in isopropylamine (IPA) without redox transformations. Stability of the formed solutions decreases in a row Eu ≈ Yb > Sm > Tm > Dy > Nd. Removing of a solvent in vacuum leaves complexes LnI2(IPA)x (2) (Nd, x = 5; Sm, Eu, Dy, Tm, Yb, x = 4) as crystalline colored solids. Stability of 2-Nd,Dy,Tm is higher than that of known THF or DME coordinated salts. Divalent state of metal in the products is confirmed by data of UV-Vis spectroscopy, magnetic measurements and their chemical behavior. Structure of 2-Eu and 2-Tm was established by X-ray diffraction analysis. Oxidation of 2-Nd,Dy in IPA affords amine-amides (PriNH)Ln(IPA)y (3) (Nd, y = 4; Dy, x = 3). n-Propylamine also dissolves the iodides 1-Sm,Eu,Dy,Tm,Yb but stability of the solutions is significantly lower. 1-Nd vigorously reacts with PrnNH2 even at -30 °C which hampers the formation of the solution.
- Bochkarev, Mikhail N.,Khoroshenkov, Georgy V.,Kuzyaev, Dmitry M.,Fagin, Anatoly A.,Burin, Mikhail E.,Fukin, Georgy K.,Baranov, Eugeny V.,Maleev, Alexander A.
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- Development of an additive-controlled, SmI2-mediated stereoselective sequence: Telescoped spirocyclisation, lactone reduction and Peterson elimination
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Studies on SmI2-mediated spirocyclisation and lactone reduction culminate in a telescoped sequence in which additives are used to "switch on" individual steps mediated by the electron transfer reagent. The sequence involves the use of two activ
- Sautier, Brice,Collins, Karl D.,Procter, David J.
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- Construction of the [6-7-5-5] tetracyclic core of all the carbocyclic frameworks of yuzurimine-type alkaloids
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Yuzurimine-type alkaloids make up a sub-family of Daphniphyllum alkaloids structurally featuring a [6-7-5-5] tetracarbocyclic core framework. In this manuscript, we describe our construction of the [6-7-5-5] tetracarbocyclic core of yuzurimine-type alkalo
- Hayakawa, Ichiro,Niida, Keisuke,Kigoshi, Hideo
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- Development of a unified enantioselective, convergent synthetic approach toward the furanobutenolide-derived polycyclic norcembranoid diterpenes: Asymmetric formation of the polycyclic norditerpenoid carbocyclic core by tandem annulation cascade
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An enantioselective and diastereoselective approach toward the synthesis of the tetracyclic scaffold of the furanobutenolide-derived polycyclic norditerpenoids is described. Focusing on synthetic efforts toward ineleganolide, the synthetic approach utilizes a palladium-catalyzed enantioselective allylic alkylation for the construction of the requisite chiral tertiary ether. A diastereoselective cyclopropanation-Cope rearrangement cascade enabled the convergent assembly of the ineleganolide [6,7,5,5]-tetracyclic scaffold. Investigation of substrates for this critical tandem annulation process is discussed along with synthetic manipulations of the [6,7,5,5]-tetracyclic scaffold and the attempted interconversion of the [6,7,5,5]-tetracyclic scaffold of ineleganolide to the isomeric [7,6,5,5]-core of scabrolide A and its naturally occurring isomers. Computational evaluation of ground-state energies of late-stage synthetic intermediates was used to guide synthetic development and aid in the investigation of the conformational rigidity of these highly constrained and compact polycyclic structures.
- Craig, Robert A.,Smith, Russell C.,Roizen, Jennifer L.,Jones, Amanda C.,Virgil, Scott C.,Stoltz, Brian M.
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- Unified Enantioselective, Convergent Synthetic Approach toward the Furanobutenolide-Derived Polycyclic Norcembranoid Diterpenes: Synthesis of a Series of Ineleganoloids by Oxidation-State Manipulation of the Carbocyclic Core
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Late-stage synthetic efforts to advance the enatio- and diastereoselectively constructed [6,7,5,5]-fused tetracyclic scaffold toward the polycyclic norditerpenoid ineleganolide are disclosed. The described investigations focus on oxidation-state manipulation around the central cycloheptane ring. Computational evaluation of ground-state energies of dihydroineleganolide is used to rationalize empirical observations and provide insight for further synthetic development, enhancing the understanding of the conformational constraints of these compact polycyclic structures. Advanced synthetic manipulations generated a series of natural product-like compounds termed the ineleganoloids.
- Craig, Robert A.,Smith, Russell C.,Roizen, Jennifer L.,Jones, Amanda C.,Virgil, Scott C.,Stoltz, Brian M.
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- Experimental and Theoretical Studies on the Implications of Halide-Dependent Aqueous Solvation of Sm(II)
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The addition of water to samarium(II) has been demonstrated to have a significant impact on the reduction of organic substrates, with the majority of research dedicated to the most widely used reagent, samarium diiodide (SmI2). The work presented herein focuses on the reducing capabilities of samarium dibromide (SmBr2) and demonstrates how the modest change in halide ligand results in observable mechanistic differences between the SmBr2-water and the SmI2-water systems that have considerable implications in terms of reactivity between the two reagents. Quantum chemical results from Born-Oppenheimer molecular dynamics simulations show significant differences between SmI2-water and SmBr2-water, with the latter displaying less dissociation of the halide, which results in a lower coordination number for water. Experimental results are consistent with computational results and demonstrate that the coordination sphere of SmBr2 is saturated at lower concentrations of water. In addition, coordination-induced bond-weakening of the O-H bond is demonstrably different for water bound to SmBr2, leading to an estimated O-H bond-weakening of at least 83 kcal/mol, nearly 10 kcal/mol larger than the bond-weakening observed in SmI2-H2O. Experimental results also demonstrate that the use of alcohols in place of water with SmBr2 leads to substrate reduction, albeit several orders of magnitude slower than for SmBr2-water. The difference in rates resulting from the change in proton donor is attributed to a rate-limiting proton-coupled electron transfer in SmBr2-water and a sequential electron transfer then proton transfer in SmBr2-alcohol systems, where electron transfer is rate-limiting.
- Ramírez-Solís, Alejandro,Bartulovich, Caroline O.,Chciuk, Tesia V.,Hernández-Cobos, Jorge,Saint-Martin, Humberto,Maron, Laurent,Anderson, William R.,Li, Anna M.,Flowers, Robert A.
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- Proton donor effects on the reactivity of SmI2. Experimental and theoretical studies on methanol solvationvs. Aqueous solvation
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Proton donors are important components of many reactions mediated by samarium diiodide (SmI2). The addition of water to SmI2creates a reagent system that enables the reduction of challenging substrates through proton-coupled electron-transfer (PCET). Simple alcohols such as methanol are often used successfully in reductions with SmI2but often have reduced reactivity. The basis for the change in reactivity of SmI2-H2O and SmI2-MeOH is not apparent given the modest differences between water and methanol. A combination of Born-Oppenheimer molecular dynamics simulations and mechanistic experiments were performed to examine the differences between the reductants formedin situfor the SmI2-H2O and SmI2-MeOH systems. This work demonstrates that reduced coordination of MeOH to Sm(ii) results in a complex that reduces arenes through a sequential electron proton transfer at low concentrations and that this process is significantly slower than reduction by SmI2-H2O.
- Bartulovich, Caroline O.,Boekell, Nicholas G.,Flowers, Robert A.,León-Pimentel, César Iván,Ramírez-Solís, Alejandro,Saint-Martin, Humberto
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- Pinacol Coupling Strategy for the Construction of the Bicyclo[6.4.1]tridecane Framework of Schiglautone A
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The synthesis of the tricyclic carbon framework of schiglautone A (1) is reported herein. The generation of the bicyclo[6.4.1]tridecane 19 was accomplished via a SmI2-mediated pinacol coupling of dialdehyde 18. The side chain in 18 was introduc
- Werner, Bettina,Kalesse, Markus
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- Quantitation of the Interactions of Alcohols and Amines with SmI2: Pros and Cons of VIS and NMR Spectroscopies
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While additives play an important role in the reactions of samarium iodide, ligand-SmI2 complexation constants are scarce. Here, VIS spectroscopy was harnessed along with NMR to determine the first complexation constant for most of the alcohols and amines used in SmI2 reactions. The second equilibrium constant was determined for selected ligands. In cases where both methods could be applied, in general, a good correlation between the equilibrium constants was obtained.
- De, Suranjan,Hoz, Shmaryahu
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- Synthetic study of solanoeclepin A: Cyclobutane cyclization via SmI2-additive-mediated reaction and D ring functionalization
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The construction of tricyclo[5.2.1.01,6]decene skeleton was achieved by cyclobutane ring formation via improved radical reaction using SmI2-H2O-HFIP and SmI2-LiCl conditions in good yields. Those additives were studied to increase the reactivity of SmI2. Two interesting reactions via neighboring group participations are described for introducing the C4 oxygen functionality by the assistance of C6 substituent in a regioselective manner.
- Chuang, Hsiang-Yu,Isobe, Minoru
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- Syntheses of a Pair of Simplified Model Compounds of the Dihydroxycyclopentenone Core of the Kodaistatins A–D
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The kodaistatins A–D (1–4) are natural products from Aspergillus terreus with the potential of representing leads for a novel cure of type-2 diabetes. They possess an unusually and highly substituted dihydroxycyclopentenone core. Whether its OH groups are cis- or trans-configured remained unknown by spectroscopy. Previous syntheses of kodaistatin model compounds (cis-5, cis- and trans-6) allowed to make NMR comparisons with kodaistatin A (1). They led to the insight that the natural product 1 must be a trans-diol. These findings are corroborated by the synthesis and ensuing NMR study of another pair of cis/trans-isomeric kodaistatin models (cis- and trans-7) described here. Its first key-step was a syn-selective aldol addition. An oxidation/reduction sequence allowed reaching to the corresponding anti-aldol. Each aldol furnished a kodaistatin model in eight additional steps. The most noteworthy transformation was an SmII-induced intramolecular aldolization of a bromodiketone.
- Peter, David,Brückner, Reinhard
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- Kinetic solvent effects in the reduction of alkyl halides by {Sm[N(SiMe3)2]2(THF)2}
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The rate of reduction of two representative alkyl halides, 1-bromododecane and 1-chlorododecane by {Sm[N(SiMe3)2]2(THF)2} was examined in five different solvents. Reductions were several orders of magnitude faster in nonpolar, non-coordinating solvents than in polar coordinating solvents. Good correlations between the rate of reduction and coordination index of each solvent was obtained whereas excellent correlations were obtained between rates and dielectric (as a measure of solvent polarity). The basis of this effect is proposed to be a consequence of solvent coordination to the inner sphere of Sm(II) leading to a deceleration of ET in coordinating solvents and possible transition state stabilization by nonpolar solvents.
- Chciuk, Tesia V.,Maity, Sandeepan,Flowers, Robert A.
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- Formal Total Synthesis of (-)-Jiadifenolide and Synthetic Studies toward seco-Prezizaane-Type Sesquiterpenes
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Synthetic studies toward highly oxygenated seco-prezizaane sesquiterpenes are reported, which culminated in a formal total synthesis of the neurotrophic agent (-)-jiadifenolide. For the construction of the tricyclic core structure, an unusual intramolecular and diastereoselective Nozaki-Hiyama-Kishi reaction involving a ketone as electrophilic coupling partner was developed. In addition, synthetic approaches toward the related natural product (2R)-hydroxy-norneomajucin, featuring a Mn-mediated radical cyclization for the tricycle assembly and a regioselective OH-directed C-H activation are presented.
- Gomes, José,Daeppen, Christophe,Liffert, Raphael,Roesslein, Joel,Kaufmann, Elias,Heikinheimo, Annakaisa,Neuburger, Markus,Gademann, Karl
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- Deoxygenative Cross-Coupling of Aromatic Amides with Polyfluoroarenes
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Considering the ubiquitous nature and ready synthesis of amides, and the great significance of organofluorine-containing species, the cross-coupling of amides and polyfluoroarenes, leading to new carbon–carbon bond-forming methodologies, would find useful applications in synthesis, late-stage functionalization, and rapid generation of molecular diversity. Herein, we present a novel synthesis of α-polyfluoroaryl amines via Sm/SmI2-mediated deoxygenative cross-coupling of aromatic amides with polyfluoroarenes through direct C?H functionalization. The structural and functional diversity of these readily available precursors provides a versatile and flexible strategy for the streamlined synthesis of α-polyfluoroaryl amines. Combining experimental and theoretical studies, a novel plausible mechanism of the α-aminocarbene-mediated C?H insertion has been revealed, which may stimulate future work for the development of novel methods in amine synthesis.
- He, Youliang,Wang, Yuxiao,Li, Shi-Jun,Lan, Yu,Wang, Xiaoming
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supporting information
(2022/02/01)
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- Synthesis of Enantiopure 6,11-Methylene Lipoxin B4 Methyl Ester
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The synthesis of Lipoxin B4 analogs (LXB4) to gain access to stabilized inflammation resolving compounds is an actual field of research. Focusing on variation and stabilization of the conjugated E,Z,E,E C6–C13 tetraene moiety of natural LXB4, a methylene bridge introduced between C6 and C11 suppresses any Z/E isomerization of the C8–C9 olefin. Intending to enable prospective structure variations in connection with the C1–C5 and C14–C20 fragments, a convergent total synthesis has been developed. Optically active C1–C12 building blocks were build-up from cycloheptatriene 1-carbonester (C6–C11, C21) and glutaryl chloride (C1–C5) using Friedel-Crafts-type acylation and chiral HPLC. The C13–C20 segment had been generated via a five-step sequence starting from heptanoyl chloride. Horner key olefination enabled the assembly of the carbon backbone. A final five-step sequence including a chelate Cram reduction of the unsaturated ketone moiety afforded the target 6,11-methylene LXB4 methyl ester.
- Trippe, Lukas,Nava, Analuisa,Frank, Andrea,Nubbemeyer, Udo
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supporting information
p. 1156 - 1167
(2021/02/03)
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- Asymmetric Total Synthesis of Taxol
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Taxol is one of the most famous natural diterpenoids and an important anticancer medicine. Taxol represents a formidable synthetic challenge and has prompted significant interest from the synthetic community. However, in all the previous syntheses of Taxol, there have been no reports of closing the desired eight-membered ring through C1-C2 bond formation. Furthermore, the existence of Taxol-resistant tumors and side effects of Taxol make the development of new approaches to synthesize Taxol and its derivatives highly desirable. Here, we report the asymmetric total synthesis of Taxol using a concise approach through 19 isolated intermediates. The synthetically challenging eight-membered ring was constructed efficiently by a diastereoselective intramolecular SmI2-mediated pinacol coupling reaction to form the C1-C2 bond. The unique biomimetic oxygen ene reaction and the newly developed facile tandem C2-benzoate formation and C13 side chain installation improved the efficiency of the synthesis. The mild oxygen ene reaction under light conditions would be an alternative reaction involved in Taxol biosynthesis. This new convergent approach will allow the diverse creation of Taxol derivatives to enable further biological research.
- Hu, Ya-Jian,Gu, Chen-Chen,Wang, Xin-Feng,Min, Long,Li, Chuang-Chuang
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supporting information
p. 17862 - 17870
(2021/11/04)
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- P-Anisaldehyde-Photosensitized Sulfonylcyanation of Chiral Cyclobutenes: Enantioselective Access to Cyclic and Acyclic Systems Bearing All-Carbon Quaternary Stereocenters
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The photosensitized p-Anisaldehyde-mediated addition of sulfonylcyanides onto the I -system of cyclobutenes is shown to afford highly functionalized cyclobutanes in high yields and diastereocontrol. The homochiral cyclobutene precursors are accessible on multigram scale in two steps through an asymmetric [2 + 2] cycloaddition/vinyl thioether reduction sequence. The enantiopure cyclobutylnitriles can be elaborated further through SmI2-mediated ring opening or converted into new enantiopure cyclobutenes through base-mediated sulfone elimination.
- Pirenne, Vincent,Traboulsi, Iman,Rouvière, Lisa,Lusseau, Jonathan,Massip, Stéphane,Bassani, Dario M.,Robert, Frédéric,Landais, Yannick
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supporting information
p. 575 - 579
(2020/01/09)
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- 7-Siloxy-Substituted Hexahydronaphthalene Derivatives: Samarium Diiodide Promoted Synthesis and Typical Reactions
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The samarium diiodide promoted reductive cyclization of a series of γ-aryl ketones with acetoxy, alkoxy, and siloxy groups in ortho -, meta -, and para -positions was investigated. Only precursors with p -acetoxy, p - tert -butoxy, or p -siloxy substituen
- Niermann, André,Reissig, Hans-Ulrich
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p. 2721 - 2730
(2020/09/15)
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- Enantioselective Total Synthesis of Cotylenin A
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A convergent enantioselective total synthesis of cotylenin A is described. The A-ring fragment, prepared via the catalytic asymmetric intramolecular cyclopropanation developed in our laboratory, and the C-ring fragment, prepared from a known chiral compound via a modified acyl radical cyclization, were successfully assembled by the Utimoto coupling reaction. The formidable carbocyclic eight-membered ring of cotylenin A was efficiently constructed by a palladium-mediated cyclization. All the hydroxy groups in the scaffold were stereoselectively introduced, and a modified reducing reagent, Me4NBH(O2CiPr)3, has been developed. The sugar moiety fragment was prepared via three consecutive carbon-oxygen bond-forming reactions, and the glycosylation was accomplished using Wan's protocol.
- Nagatani, Kotaro,Nakada, Masahisa,Osada, Ryunosuke,Sugiyama, Ryoji,Uwamori, Masahiro
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supporting information
p. 5556 - 5561
(2020/04/10)
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- Samarium Diiodide Catalyzed Radical Cascade Cyclizations that Construct Quaternary Stereocenters
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SmI 2 -catalyzed radical cascade cyclizations were used to generate complex carbocyclic products bearing quaternary stereocenters with high selectivity. Bicyclic scaffolds containing four contiguous stereocenters and one quaternary stereocenter
- He, Qiong,Huang, Huan-Ming,Procter, David J.
-
supporting information
p. 45 - 50
(2019/12/30)
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- Stereoselective Cascade Cyclizations with Samarium Diiodide to Tetracyclic Indolines: Precursors of Fluorostrychnines and Brucine
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A series of γ-indolylketones with fluorine, cyano or alkoxy substituents at the benzene moiety was prepared and subjected to samarium diiodide-promoted cyclization reactions. The desired dearomatizing ketyl cascade reaction forming two new rings proceeded
- Beemelmanns, Christine,Nitsch, Dominik,Bentz, Christoph,Reissig, Hans-Ulrich
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supporting information
p. 8780 - 8789
(2019/06/17)
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- Contrasting Effect of Additives on Photoinduced Reactions of SmI2
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The work described herein compares the effect of additives (HMPA, methanol, ethylene glycol, pinacol, N-methylethanolamine) on thermal and photochemical reactions of samarium diiodide (SmI2). In thermal reactions, additives that coordinate to SmI2 induce a significant increase in reaction rate. In photochemical reactions, the presence of an electronegative atom with a highly localized negative charge on the substrate leads to a rate deceleration. In order to benefit from the columbic interaction with the positively charged samarium cation, these substrates react preferentially by an inner sphere reduction mechanism. The addition of ligands prevents this close interaction causing rate retardation. Furthermore, studies demonstrate that excited state quenching of SmII by ethylene glycol and other additives indicate that it is unlikely to be the major cause for the observed rate retardation. This effect provides a simple diagnostic tool to distinguish between an inner and an outer sphere reduction mechanism.
- Nimkar, Amey,Maity, Sandeepan,Flowers, Robert A,Hoz, Shmaryahu
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p. 10499 - 10504
(2019/07/15)
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- Stereocontrolled Construction of ABCD Tetracyclic Ring System with Vicinal All-Carbon Quaternary Stereogenic Centers of Calyciphylline A Type Alkaloids
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A unique approach to the synthesis of an ABCD tetracyclic core bearing the vicinal all-carbon quaternary stereogenic centers of the calyciphylline A type alkaloids is reported. The synthesis features two C-C bond formations at a sterically congested position: one is an intramolecular pinacol coupling to construct the central A ring; the other is a semipinacol rearrangement to construct a quaternary stereogenic center adjacent to another quaternary center.
- Sasano, Yusuke,Koyama, Junpei,Yoshikawa, Kaori,Kanoh, Naoki,Kwon, Eunsang,Iwabuchi, Yoshiharu
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supporting information
p. 3053 - 3056
(2018/05/28)
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- Synthesis and complete structure determination of a sperm-activating and -attracting factor isolated from the ascidian ascidia sydneiensis
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For the complete structure elucidation of an endogenous sperm-activating and -attracting factor isolated from eggs of the ascidian Ascidia sydneiensis (Assydn-SAAF), its two possible diastereomers with respect to C-25 were synthesized. Starting from ergosterol, the characteristic steroid backbone was constructed by using an intramolecular pinacol coupling reaction and stereoselective reduction of a hydroxy ketone as key steps, and the side chain was introduced by Julia-Kocienski olefination. Comparison of the NMR data of the two diastereomers with those of the natural product led to the elucidation of the absolute configuration as 25S; thus the complete structure was determined and the first synthesis of Assydn-SAAF was achieved.
- Watanabe, Tomohiro,Shibata, Hajime,Ebine, Makoto,Tsuchikawa, Hiroshi,Matsumori, Nobuaki,Murata, Michio,Yoshida, Manabu,Morisawa, Masaaki,Lin, Shu,Yamauchi, Kosei,Sakai, Ken,Oishi, Tohru
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p. 985 - 997
(2018/05/04)
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- Total Synthesis of Ripostatin B and Structure-Activity Relationship Studies on Ripostatin Analogs
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Described is the total synthesis of the myxobacterial natural product ripostatin B and of a small number of analogs. Ripostatin B is a polyketide-derived 14-membered macrolide that acts as an inhibitor of bacterial RNA-polymerase, but is mechanistically distinct from rifamycin-derived RNA-polymerase inhibitors that are in use for tuberculosis treatment. The macrolactone ring of ripostatin B features two stereocenters and a synthetically challenging doubly skipped triene motif, with one of the double bonds being in conjugation with the ester carbonyl. Appended to the macrolactone core are an extended hydroxy-bearing phenylalkyl side chain at C13 and a carboxymethyl group at C3. The triene motif was established with high efficiency by ring-closing olefin metathesis, which proceeded in almost 80% yield. The side chain-bearing stereocenter α to the ester oxygen was formed in a Paterson aldol reaction between a methyl ketone and a β-chiral β-hydroxy aldehyde with excellent syn selectivity (dr >10:1). The total synthesis provided a blueprint for the synthesis of analogs with modifications in the C3 and C13 side chains. The C3-modified analogs showed good antibacterial activity against efflux-deficient Escherichia coli but, as ripostatin B, were inactive against Mycobacterium tuberculosis, in spite of significant in vitro inhibition of M. tuberculosis RNA-polymerase.
- Glaus, Florian,Dedi?, Darija,Tare, Priyanka,Nagaraja, Valakunja,Rodrigues, Liliana,Aínsa, José Antonio,Kunze, Jens,Schneider, Gisbert,Hartkoorn, Ruben C.,Cole, Stewart T.,Altmann, Karl-Heinz
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p. 7150 - 7172
(2018/07/15)
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- Total Synthesis of (±)-Phomoidride D
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Described herein is a synthetic strategy for the total synthesis of (±)-phomoidride D. This highly efficient and stereoselective approach provides rapid assembly of the carbocyclic core by way of a tandem phenolic oxidation/intramolecular Diels–Alder cycloaddition. A subsequent SmI2-mediated cyclization cascade delivers an isotwistane intermediate poised for a Wharton fragmentation that unveils the requisite bicyclo[4.3.1]decene skeleton and sets the stage for synthesis completion.
- Leung, Joyce C.,Bedermann, Aaron A.,Njardarson, Jón T.,Spiegel, David A.,Murphy, Graham K.,Hama, Naoto,Twenter, Barry M.,Dong, Ping,Shirahata, Tatsuya,McDonald, Ivar M.,Inoue, Munenori,Taniguchi, Nobuaki,McMahon, Travis C.,Schneider, Christopher M.,Tao, Nancy,Stoltz, Brian M.,Wood, John L.
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supporting information
p. 1991 - 1994
(2018/02/10)
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- Cyclopentane Formation from Flexible Precursors Using Samarium(II) Reagents
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Three efficient methods for five-membered ring carbocycle synthesis have been developed from simple starting materials using samarium(II) reagents. A Reformatsky aldol reaction proceeded efficiently with samarium(II) iodide using lithium bromide as an additive. A new intramolecular alkylation of a samarium enolate was realized with a pendant sulfonate ester leaving group. Pinacol cyclization of a simple diketone was also demonstrated giving a diol product in high stereoselectivity. A promising lead result has been established demonstrating enantioselectivity in a chiral ligand controlled Reformatsky aldol reaction.
- Aretz, Christopher D.,Escobedo, Humberto,Cowen, Bryan J.
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supporting information
p. 1880 - 1884
(2018/05/09)
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- Samarium(II) dibromide-promoted selective deprotection of a benzoyl protective group
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The selective deprotection of a benzoyl group was very important methodology in the field of organic synthesis. Various methods for debenzoylation were investigated and developed in the past six decades, but more useful and selective strategies are now being strongly desired. In response to this strong demand, we developed the novel and selective deprotection of a benzoyl group by use of samarium(II) dibromide and a proton source. This deprotective reaction proceeded smoothly and the desired compound was obtained in good to excellent yields. In this paper, we will report the details of this deprotective reaction.
- Yokoyama, Yasuo,Oyamada, Shun,Suzuki, Junya,Maruyama, Shou,Sakusabe, Takahiro,Suzuki, Shoko
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supporting information
p. 1025 - 1032
(2018/03/23)
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- A formal synthesis of (–)-kainic acid by means of SMI2-mediated radical cyclization
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A formal synthesis of (–)-kainic acid (1) starting from the known D-serine derivative 9 has been established in 14 steps. Construction of all the stereogenic centers on the pyrrolidine core of 1 was successfully achieved by application of SmI2-mediated radical cyclization to the α,β-unsaturated ester having an alkyne moiety, followed by hydroxy group directed diastereoselective hydrogenation over Wilkinson’s catalyst.
- Takahashi, Kazunori,Ito, Takumi,Yamada, Wataru,Tsubuki, Masayoshi,Honda, Toshio
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p. 882 - 894
(2018/06/04)
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- Mechanism of SmI2 Reduction of 5-Bromo-6-oxo-6-phenylhexyl Methanesulfonate Studied by Spin Trapping with 2-Methyl-2-nitrosopropane
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The radical formed by reduction of 5-bromo-6-oxo-6-phenylhexyl methanesulfonate, an α-bromoketone, with SmI2 was spin trapped with 2-methyl-2-nitrosopropane. Electron paramagnetic resonance spectra of the spin adduct and the adduct formed in the analogous reaction with selectively deuterated substrate identify the radical intermediate in this SmI2 reduction as a carbon-centered radical. This result supports the proposal that the formation of reactive Sm-enolates arises from reduction of the carbon-bromine bond rather than a ketyl radical anion.
- Aretz, Christopher D.,McPeak, Joseph E.,Eaton, Gareth R.,Eaton, Sandra S.,Cowen, Bryan J.
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p. 10688 - 10692
(2018/09/06)
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- Radical Heterocyclization and Heterocyclization Cascades Triggered by Electron Transfer to Amide-Type Carbonyl Compounds
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Radical heterocyclizations triggered by electron transfer to amide-type carbonyls, using SmI2-H2O, provide straightforward access to bicyclic heterocyclic scaffolds containing bridgehead nitrogen centers. Furthermore, the first radical heterocyclization cascade triggered by reduction of amide-type carbonyls delivers novel, complex tetracyclic architectures containing five contiguous stereocenters with excellent diastereocontrol.
- Huang, Huan-Ming,Procter, David J.
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supporting information
p. 14262 - 14266
(2017/10/20)
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- Total Syntheses of Lepadiformine Marine Alkaloids with Enantiodivergency, Utilizing Hg(OTf)2-Catalyzed Cycloisomerization Reaction and their Cytotoxic Activities
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The enantioselective total syntheses of lepadiformine marine alkaloids, azatricyclic natural products isolated from marine tunicates, were completed. These alkaloids have a unique chemical structure characterized by the trans-1-azadecalin (AB ring system) fused with the spirocyclic ring (AC ring system). Here we found that a cycloisomerization reaction from functionalized linear substrates to a 1-azaspiro[4.5]decane framework corresponding to the AC ring in lepadiformines is promoted by a catalytic amount of mercury(II) triflate (Hg(OTf)2). The total syntheses of (?)-lepadiformines A and B were achieved in 28 % and 21 % overall yields, respectively, through the novel cycloisomerization reaction. The syntheses of (+)- and (?)-lepadiformine C hydrochloride salts also enabled us to determine the absolute configuration of natural lepadiformine C. It has been found that a phenomenon of enantiodivergence occurs in lepadiformine alkaloids from a single species of marine tunicate, Clavelina moluccensis. The cytotoxic activities of synthesized lepadiformine hydrochloride salts and their synthetic intermediates were evaluated.
- Nishikawa, Keisuke,Yamauchi, Kengo,Kikuchi, Seiho,Ezaki, Shinnosuke,Koyama, Tomoyuki,Nokubo, Haruka,Matsumura, Kunihiro,Kodama, Takeshi,Kumagai, Momochika,Morimoto, Yoshiki
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supporting information
p. 9535 - 9545
(2017/07/22)
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- SmI2(H2O)n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer
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Samarium diiodide in the presence of water and THF (SmI2(H2O)n) has in recent years become a versatile and useful reagent, mainly for reducing carbonyl-type substrates. This work reports the reduction of several enamines by SmI2(H2O)n. Mechanistic experiments implicate a concerted proton-coupled electron transfer (PCET) pathway, based on various pieces of evidence against initial outer-sphere electron transfer, proton transfer, or substrate coordination. A thermochemical analysis indicates that the C-H bond formed in the rate-determining step has a bond dissociation free energy (BDFE) of ～32 kcal mol-1. The O-H BDFE of the samarium aquo ion is estimated to be 26 kcal mol-1, which is among the weakest known X-H bonds of stable reagents. Thus, SmI2(H2O)n should be able to form very weak C-H bonds. The reduction of these highly electron rich substrates by SmI2(H2O)n shows that this reagent is a very strong hydrogen atom donor as well as an outer-sphere reductant.
- Kolmar, Scott S.,Mayer, James M.
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supporting information
p. 10687 - 10692
(2017/08/15)
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- Secondary amides as hydrogen atom transfer promoters for reactions of samarium diiodide
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Two secondary amides (N-methylacetamide and 2-pyrrolidinone) were used as additives with SmI2 in THF to estimate the extent of N-H bond weakening upon coordination. Mechanistic and synthetic studies demonstrate significant bond-weakening, providing a reagent system capable of reducing a range of substrates through formal hydrogen atom transfer.
- Chciuk, Tesia V.,Li, Anna M.,Vazquez-Lopez, Andres,Anderson, William R.,Flowers, Robert A.
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supporting information
p. 290 - 293
(2017/11/27)
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- Reversibility of Ketone Reduction by SmI2-Water and Formation of Organosamarium Intermediates
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The reduction of ketones by SmI2-water has long been thought to proceed through a reversible initial electron transfer with the formation of organosamarium intermediates in a follow-up step. Kinetic experiments on the reduction of two model ketones and structurally similar ketones with a pendant alkene are shown to be consistent with a rate-limiting reduction by SmI2-water through a proton-coupled electron-transfer (PCET). Literature values for the rates of radical cyclizations and reduction of radicals by SmI2 and thermochemical data for radical reduction by SmI2-water further support a rate-limiting initial step for ketone reductions. These data suggest that discrete organosamarium species may not be intermediates in ketone reductions by SmI2-water.
- Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
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p. 4579 - 4583
(2017/12/18)
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- Selective construction of quaternary stereocentres in radical cyclisation cascades triggered by electron-transfer reduction of amide-type carbonyls
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Radical-radical cyclisation cascades, triggered by single-electron-transfer to amide-type carbonyls using SmI2-H2O-LiBr, result in the selective construction of quaternary carbon stereocentres. The cascades deliver tricyclic barbiturates with four stereocentres in good yield and with excellent diastereocontrol.
- Huang, Huan-Ming,Bonilla, Pablo,Procter, David J.
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supporting information
p. 4159 - 4164
(2017/07/10)
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- Aza versus Oxophilicity of SmI2: A Break of a Paradigm
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Ligands that coordinate to SmI2 through oxygen are prevalent in the literature and make up a significant portion of additives employed with the reagent to perform reactions of great synthetic importance. In the present work a series of spectroscopic, calorimetric and kinetic studies demonstrate that nitrogen-based analogues of many common additives have a significantly higher affinity for Sm than the oxygen-based counterparts. In addition, electrochemical experiments show that nitrogen-based ligands significantly enhance the reducing power of SmI2. Overall, this work demonstrates that the use of nitrogen-based ligands provides a useful alternative approach to enhance the reactivity of reductants based on SmII.
- Maity, Sandeepan,Flowers, Robert A.,Hoz, Shmaryahu
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p. 17070 - 17077
(2017/11/13)
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- Copper-Catalyzed Double Additions and Radical Cyclization Cascades in the Re-Engineering of the Antibacterial Pleuromutilin
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A general synthetic sequence involving simply prepared starting materials provides rapid access to diverse, novel tricyclic architectures inspired by pleuromutilin. SmII-mediated radical cyclization cascades of dialdehydes, prepared using a new
- Ruscoe, Rebecca E.,Fazakerley, Neal J.,Huang, Huanming,Flitsch, Sabine,Procter, David J.
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supporting information
p. 116 - 119
(2016/01/26)
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- Samarium-mediated intramolecular cross-couplings of an α,β-unsaturated N-acylpyrrole
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The first example of an α,β-unsaturated N-acylpyrrole undergoing a SmI2-mediated cyclization is reported. In contrast to other unsaturated units, the intermediate samarium enolate readily engages in aldol-type reactions, necessitating careful control of the reaction conditions.
- Law, Katherine R.,McErlean, Christopher S.P.
-
supporting information
p. 3113 - 3116
(2016/07/06)
-
- Total Synthesis of (-)-C/D-cis-Dehydro-3-O-methyl-estradiols
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A convergent synthesis of (-)-dehydro-3-O-methyl-C/D-cis-estradiol started from stereochemically defined substituted optically active 3-(2-arylethyl)-γ-butyrolactones. Regioselective bromination of the anisyl moiety, reductive ring opening of the iodolactone, and protecting-group changes led to a Weinreb amide. This then underwent an intramolecular Grignard reaction closing the B-ring to give a tetralone with defined configuration. Introduction of C-11 through an allyl Grignard addition and subsequent ring-closing metathesis gave a tetrahydro phenanthrene derivative. Oxidation of the side-chain alcohol resulted in the key aldehyde group, and a final samarium-diiodide-mediated reductive D-ring annulation resulted in the generation of the target dehydro-C/D-cis-estradiol derivatives with high stereoselectivity. Structure elucidation was carried out using NOEDS (nuclear Overhauser enhanced differential spectroscopy) analysis on the one hand, and conversion into known 3-O-methyl-13β-estradiols by double-bond hydrogenation on the other. Further efforts to use this estradiol synthetic strategy to generate more complex steroidal natural products and pharmaceutically interesting compounds are in progress.
- Kaluza, Nora M.,Schollmeyer, Dieter,Nubbemeyer, Udo
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supporting information
p. 357 - 366
(2016/02/12)
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- Synthesis and Biological Evaluation of Bromo- and Fluorodanicalipin A
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We disclose the syntheses of (+)-bromodanicalipin A as well as (±)-fluorodanicalipin A. The relative configuration and ground-state conformation in solution of both molecules was secured by J-based configuration analysis which revealed that these are identical to natural danicalipin A. Furthermore, preliminary toxicological investigations suggest that the adverse effect of danicalipin A may be due to the lipophilicity of the halogens. Halologs: The syntheses of bromo- and fluorodanicalipin A are reported and the ground-state conformation was determined by J-based configuration analysis (see scheme, R=H). A preliminary comparative study of their toxicology suggests that the adverse effect arises from the lipophilicity of the halogens which counterbalance the polar C14 sulfate.
- Fischer, Stefan,Huwyler, Nikolas,Wolfrum, Susanne,Carreira, Erick M.
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supporting information
p. 2555 - 2558
(2016/02/18)
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- Metal-Mediated Debromination of gem-Dibromoalkenes under Mild Conditions
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We describe the facile and efficient metal-promoted reduction of C-Br bonds of gem-dibromides. When the reaction is mediated by indium, the corresponding vinyl bromides are obtained in good yields and high E-stereoselectivities. Alternatively, when the reduction is mediated by samarium diiodide, vinyl bromides are obtained in moderate yields and good Z-selectivities.
- Soengas, Raquel G.,Rodríguez-Solla, Humberto,Silva, Artur M.S.
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p. 1096 - 1099
(2016/05/19)
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