32248-43-4Relevant articles and documents
Microwave-assisted generation of lanthanide(II) halides in THF and simple quantitative determination
Dahlen, Anders,Hilmersson, Goeran
, p. 3020 - 3024 (2004)
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.
Total Synthesis of Ritterazine B
Nakayama, Yasuaki,Maser, Michael R.,Okita, Tatsuya,Dubrovskiy, Anton V.,Campbell, Taryn L.,Reisman, Sarah E.
, p. 4187 - 4192 (2021)
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.
High-Affinity Proton Donors Promote Proton-Coupled Electron Transfer by Samarium Diiodide
Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
, p. 6033 - 6036 (2016)
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.
Cyclization of Imides to 2-Azabicycles via Aminoketyl Radicals by Using Samarium(II) Iodide-Water: Reaction Development, Synthetic Scope, and Mechanistic Studies
Shi, Shicheng,Lalancette, Roger,Szostak, Michal
, p. 1825 - 1854 (2016)
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
Rare-earth iodides in ionic liquids: The crystal structure of [SEt 3]3[LnI6] (Ln = Nd, Sm)
Babai, Arash,Mudring, Anja-Verena
, p. 8168 - 8169 (2005)
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.
Catalytic Ni(II) in reactions of SmI2: Sm(II)-or Ni(0)-based chemistry?
Choquette, Kimberly A.,Sadasivam, Dhandapani V.,Flowers, Robert A.
, p. 10655 - 10661 (2011)
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.
Total Syntheses of Scaparvins B, C, and D Enabled by a Key C-H Functionalization
Ye, Qinda,Qu, Pei,Snyder, Scott A.
, p. 18428 - 18431 (2017)
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
Synthesis of Rings DEF of Solanoeclepin A
Chuang, Hsiang-Yu,Isobe, Minoru
, p. 2045 - 2058 (2017)
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.
Mechanistic studies of proton-donor coordination to samarium diiodide
Teprovich Jr., Joseph A.,Balili, Marielle N.,Pintauer, Tomislav,Flowers II, Robert A.
, p. 8160 - 8163 (2007)
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).
Reductive cyclisations of amidines involving aminal radicals
Huang, Huan-Ming,Adams, Ralph W.,Procter, David J.
, p. 10160 - 10163 (2018)
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.
Synthesis of Cycloprodigiosin Identifies the Natural Isolate as a Scalemic Mixture
Johnson, Rebecca E.,De Rond, Tristan,Lindsay, Vincent N. G.,Keasling, Jay D.,Sarpong, Richmond
, p. 3474 - 3477 (2015)
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
Development of an additive-controlled, SmI2-mediated stereoselective sequence: Telescoped spirocyclisation, lactone reduction and Peterson elimination
Sautier, Brice,Collins, Karl D.,Procter, David J.
, p. 1443 - 1447 (2013)
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
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
Craig, Robert A.,Smith, Russell C.,Roizen, Jennifer L.,Jones, Amanda C.,Virgil, Scott C.,Stoltz, Brian M.
, p. 3467 - 3485 (2018)
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.
Experimental and Theoretical Studies on the Implications of Halide-Dependent Aqueous Solvation of Sm(II)
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.
, p. 16731 - 16739 (2018)
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.
Pinacol Coupling Strategy for the Construction of the Bicyclo[6.4.1]tridecane Framework of Schiglautone A
Werner, Bettina,Kalesse, Markus
, p. 1524 - 1526 (2017)
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
Synthetic study of solanoeclepin A: Cyclobutane cyclization via SmI2-additive-mediated reaction and D ring functionalization
Chuang, Hsiang-Yu,Isobe, Minoru
, p. 2705 - 2714 (2017)
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.
Kinetic solvent effects in the reduction of alkyl halides by {Sm[N(SiMe3)2]2(THF)2}
Chciuk, Tesia V.,Maity, Sandeepan,Flowers, Robert A.
, p. 52 - 57 (2018)
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.
Formal Total Synthesis of (-)-Jiadifenolide and Synthetic Studies toward seco-Prezizaane-Type Sesquiterpenes
Gomes, José,Daeppen, Christophe,Liffert, Raphael,Roesslein, Joel,Kaufmann, Elias,Heikinheimo, Annakaisa,Neuburger, Markus,Gademann, Karl
, p. 11017 - 11034 (2016)
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.
Synthesis of Enantiopure 6,11-Methylene Lipoxin B4 Methyl Ester
Trippe, Lukas,Nava, Analuisa,Frank, Andrea,Nubbemeyer, Udo
supporting information, p. 1156 - 1167 (2021/02/03)
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.
