- Reaction of Singlet Oxygen with trans-4-Propenylanisole. Formation of [2 + 2] Products with Added Acid
-
We report the effects of added acid in the reaction of singlet oxygen with trans-4-propenylanisole (1). We provide evidence that solvent acidity modifies the behavior of the transient intermediates. Relative to reactions in aprotic solvent, enhanced dioxetane concentrations are observed in MeOH and in nonprotic solvents with acid. We suggest a new mechanism that invokes a proton transfer from MeOH and benzoic acid to perepoxide (2) and zwitterion (3) intermediates.
- Greer, Alexander,Vassilikogiannakis, Georgios,Lee, Kun-Chun,Koffas, Telly S.,Nahm, Keepyung,Foote, Christopher S.
-
-
Read Online
- Ruthenium(iv) catalysts for the selective estragole to trans-anethole isomerization in environmentally friendly media
-
Several ruthenium(iv) complexes have been tested as potential catalysts for the isomerization of estragole into anethole using water and glycerol as alternative green reaction media. Best results in terms of activity and E-selectivity were obtained with the dimeric species [{RuCl(μ-Cl) (η3:η3-C10H16)} 2] (C10H16 = 2,7-dimethylocta-2,6-diene-1,8- diyl) and the mononuclear derivative [RuCl2(η3: η3-C10H16){P(OMe)3}]. In particular, using a ruthenium loading of 1 mol%, almost quantitative and stereoselective formation of trans-anethole (trans/cis ratios = 99:1) could be reached at 80°C in short times (5-30 min) employing water-MeOH (EtOH) or glycerol-MeOH (EtOH) mixtures (1:1 v/v) as solvent. Recyclability issues have also been addressed.
- Lastra-Barreira, Beatriz,Francos, Javier,Crochet, Pascale,Cadierno, Victorio
-
-
Read Online
- Arylsulfonylacetamides as bifunctional reagents for alkene aminoarylation
-
Alkene aminoarylation with a single, bifunctional reagent is a concise synthetic strategy.We report a catalytic protocol for the addition of arylsulfonylacetamides across electron-rich alkenes with complete anti-Markovnikov regioselectivity and excellent diastereoselectivity to provide 2,2-diarylethylamines. In this process, single-electron alkene oxidation enables carbon-nitrogen bond formation to provide a key benzylic radical poised for a Smiles-Truce 1,5-aryl shift. This reaction is redox-neutral, exhibits broad functional group compatibility, and occurs at room temperature with loss of sulfur dioxide. As this process is driven by visible light, uses readily available starting materials, and demonstrates convergent synthesis, it is well suited for use in a variety of synthetic endeavors.
- Monos, Timothy M.,McAtee, Rory C.,Stephenson, Corey R.J.
-
-
Read Online
- Ruthenium-catalyzed estragole isomerization: High trans-selective formation of anethole
-
Complexes [RuCl2(η6-C6H 5OCH2CH2OH)(L)] (L = P(OMe)3 (1a), P(OEt)3 (1b), P(OiPr)3 (1c), P(OPh)3 (1d), PPh3 (1e)) have shown to be efficient catalysts for the isomerization of estragole into anethole, the best activities being obtained in polar solvents (water, methanol, ethanol). Interestingly, a complete selectivity toward trans-anethole could be reached under smooth conditions (80 °C) and in very short times (5-15 min). The catalytic experiments have been performed both under conventional and microwave heating, reaction rates being significantly enhanced under the latter conditions. The Royal Society of Chemistry 2010.
- Lastra-Barreira, Beatriz,Crochet, Pascale
-
-
Read Online
- Micellar promoted alkenes isomerization in water mediated by a cationic half-sandwich Ru(II) complex
-
Micellar media in water provide a simple and efficient environment to favor the double bond isomerization of terminal alkenes catalyzed by the cationic half-sandwich complex 1 at 95 °C. The micellar medium favors both catalyst dissolution in water by means of ion-pairing with the preferred anionic surfactants as well as substrate dissolution thus favoring its conversion into products.
- Sperni, Laura,Scarso, Alessandro,Strukul, Giorgio
-
-
Read Online
- Singlet state Cis,Trans photoisomerization and intersystem crossing of 1-arylpropenes
-
The temperature dependence of the singlet state lifetime and photoisomerization and fluorescence quantum yields for trans- and cis-1-phenylpropene have been determined in hexane solution. Calculated barriers for twisting about the double bond on the singlet potential energy surface are 8.8 and 4.6 kcal/mol for the trans and cis isomer, respectively. The barrier for the trans isomer is sufficiently high to prevent isomerization on the singlet state surface at or below room temperature. However, isomerization occurs at low temperatures as a consequence of intersystem crossing to the triplet state, which undergoes barrierless isomerization. The quantum yield for intersystem crossing, as determined by time-resolved photoacoustic calorimetry, is 0.60 ± 0.03 and the rate constant for intersystem crossing is 4.7 × 107 s-1. While internal conversion is not significant at or below room temperature, thermally activated internal conversion competes with singlet isomerization at high temperatures. The cis isomer undergoes isomerization predominantly via the singlet state at room temperature. Both electron-donating (p-methoxy) and electron-withdrawing (m- and p-cyano, p-carbomethoxy, and p-trifluormethyl) aromatic substituents are found to lower the barrier for singlet state isomerization. Increased solvent polarity (acetonitrile vs hexane) results in variable decreases in the barrier for singlet state isomerization. Photoisomerization of the p-cyano derivative at room temperature occurs predominantly via the triplet state in hexane solution and via the singlet state in acetonitrile solution. The effects of substituents and solvent are better correlated with the magnitude of the S2-S1 energy gap than the stability of either zwitterionic or biradical intermediates. Rate constants for intersystem crossing are, in most cases, not highly dependent upon aromatic substitution or solvent polarity.
- Lewis, Frederick D.,Bassani, Dario M.,Caldwell, Richard A.,Unett, David J.
-
-
Read Online
- A Facile, Convenient, and Green Route to (E)-Propenylbenzene Flavors and Fragrances by Alkene Isomerization
-
(E)-Propenylbenzene flavors and fragrances can be made and isolated in high yield and selectivity by using bifunctional catalyst 1, and the heterogenized analogues. Multigram-scale reactions can be performed neat and the products isolated either by distillation, using homogeneous catalyst 1 (0.1-0.5 mol%, r.t., 10-45 min), or by decantation from heterogeneous catalysts PS-1 or PSL-1 (0.5 mol%, 70 °C, 24 h; catalyst separation and re-use shown for 3-4 cycles; 10 cycles using distilled eugenol feedstock). Both purified starting materials and essential oil feedstocks could be used. Z Isomers were present at very low levels (from 0.4% to less than 0.1%) in the products.
- Larsen, Casey R.,Paulson, Erik R.,Erdogan, Gulin,Grotjahn, Douglas B.
-
-
Read Online
- Synthesis, Reactivity, and Coordination of Semihomologous dppf Congeners Bearing Primary Phosphine and Primary Phosphine Oxide Groups
-
This contribution reports the synthesis of two phosphinoferrocene ligands desymmetrized by an inserted methylene spacer, viz., a bis-phosphine combining primary and tertiary phosphine moieties in its structure, Ph2PfcCH2PH2 (2), and a structurally unique, stable phosphine-primary phosphine oxide Ph2PfcCH2P(O)H2 (7; fc = ferrocene-1,1′-diyl). Compounds 2 and 7, together with 1,1′-bis(diphenylphosphino)ferrocene (dppf), the bis-tertiary phosphine Ph2PfcCH2PPh2, and the adduct Ph2P(BH3)fcCH2PH2 (6), were studied as ligands in Ru(II) complexes bearing auxiliary ν6-arene ligands and both free ligands and the isolated complexes were structurally authenticated, using spectroscopic methods and X-ray crystallography, and further investigated by cyclic voltammetry. The results suggest that distinct donor moieties in the unsymmetric ligands differentiate the otherwise identical coordinated metal centers and that the phosphine moiety in phosphine-phosphine oxide ligand 7 is preferably coordinated to Ru(II), before the phosphine oxide group, which must tautomerize into the hydroxyphosphine form prior to coordination.
- Horky, Filip,Císa?ová, Ivana,?těpni?ka, Petr
-
p. 427 - 441
(2021/02/06)
-
- Highly Z-Selective Double Bond Transposition in Simple Alkenes and Allylarenes through a Spin-Accelerated Allyl Mechanism
-
Double-bond transposition in alkenes (isomerization) offers opportunities for the synthesis of bioactive molecules, but requires high selectivity to avoid mixtures of products. Generation of Z-alkenes, which are present in many natural products and pharmaceuticals, is particularly challenging because it is usually less thermodynamically favorable than generation of the E isomers. We report a β-dialdiminate-supported, high-spin cobalt(I) complex that can convert terminal alkenes, including previously recalcitrant allylbenzenes, to Z-2-alkenes with unprecedentedly high regioselectivity and stereoselectivity. Deuterium labeling studies indicate that the catalyst operates through a π-allyl mechanism, which is different from the alkyl mechanism that is followed by other Z-selective catalysts. Computations indicate that the triplet cobalt(I) alkene complex undergoes a spin state change from the resting-state triplet to a singlet in the lowest-energy C-H activation transition state, which leads to the Z product. This suggests that this change in spin state enables the catalyst to differentiate the stereodefining barriers in this system, and more generally that spin-state changes may offer a route toward novel stereocontrol methods for first-row transition metals.
- Kim, Daniel,Pillon, Guy,Diprimio, Daniel J.,Holland, Patrick L.
-
supporting information
p. 3070 - 3074
(2021/03/08)
-
- Facile Synthesis of Chiral Arylamines, Alkylamines and Amides by Enantioselective NiH-Catalyzed Hydroamination
-
Regio- and enantioselective hydroarylamination, hydroalkylamination and hydroamidation of styrenes have been developed by NiH catalysis with a simple bioxazoline ligand under mild conditions. A wide range of enantioenriched benzylic arylamines, alkylamines and amides can be easily accessed by nitroarenes, hydroxylamines and dioxazolones, respectively as amination reagents. The chiral induction in these reactions is proposed to proceed through an enantiodifferentiating syn-hydronickellation step.
- Meng, Lingpu,Yang, Jingjie,Duan, Mei,Wang, You,Zhu, Shaolin
-
supporting information
p. 23584 - 23589
(2021/09/28)
-
- An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
-
The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.
- Huang, Zhidao,Wang, Yulei,Leng, Xuebing,Huang, Zheng
-
supporting information
p. 4824 - 4836
(2021/04/07)
-
- Electro-mediated PhotoRedox Catalysis for Selective C(sp3)–O Cleavages of Phosphinated Alcohols to Carbanions
-
We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage of C(sp3)?O bonds of phosphinated alcohols to alkyl carbanions. As well as deoxygenations, olefinations are reported which are E-selective and can be made Z-selective in a tandem reduction/photosensitization process where both steps are photoelectrochemically promoted. Spectroscopy, computation, and catalyst structural variations reveal that our new naphthalene monoimide-type catalyst allows for an intimate dispersive precomplexation of its radical anion form with the phosphinate substrate, facilitating a reactivity-determining C(sp3)?O cleavage. Surprisingly and in contrast to previously reported photoexcited radical anion chemistries, our conditions tolerate aryl chlorides/bromides and do not give rise to Birch-type reductions.
- Barham, Joshua P.,K?nig, Burkhard,Karl, Tobias A.,Reiter, Sebastian,Tian, Xianhai,Yakubov, Shahboz,de Vivie-Riedle, Regina
-
supporting information
p. 20817 - 20825
(2021/08/18)
-
- A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
-
Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
- Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
-
p. 6684 - 6690
(2021/05/31)
-
- Rapid synthesis method of biomass-based olefin
-
The invention discloses a rapid synthesis method of biomass-based olefin, which comprises the following steps: by taking a biomass ketone compound as a substrate and 2-pentanol as a hydrogen source and a solvent at the same time, under the action of hafnium/zirconium-based catalysts such as hafnium phenylphosphonate and Zirconium phenylphosphonate, hafnium phytate andzirconium phytate and hafnium polydivinylphenylphosphonate and zirconium polydivinylphenylphosphonate, selectively converting a biomass-based ketone compound into a corresponding alcohol compound, and continuously dehydrating to prepare olefin. According to the present invention, the time required by the system reaction is substantially shortened and is at least 2 h, the target product selectivity is significantly improved, the conversion rate of the representative reaction 4 '-methoxypropiophenone can at least achieve 99.8%, and the anethole yield can achieve 98.1%.
- -
-
Paragraph 0020; 0032-0035; 0041-0046
(2021/07/31)
-
- Synthesis, antiepileptic effects, and structure-activity relationships of α-asarone derivatives: In vitro and in vivo neuroprotective effect of selected derivatives
-
In the present study, we compared the antiepileptic effects of α-asarone derivatives to explore their structure-activity relationships using the PTZ-induced seizure model. Our research revealed that electron-donating methoxy groups in the 3,4,5-position on phenyl ring increased antiepileptic potency but the placement of other groups at different positions decreased activity. Besides, in allyl moiety, the optimal activity was reached with either an allyl or a 1-butenyl group in conjugation with the benzene ring. The compounds 5 and 19 exerted better neuroprotective effects against epilepsy in vitro (cell) and in vivo (mouse) models. This study provides valuable data for further exploration and application of these compounds as potential anti-seizure medicines.
- Zhang, Jian,Mu, Keman,Yang, Peng,Feng, Xinqian,Zhang, Di,Fan, Xiangyu,Wang, Qiantao,Mao, Shengjun
-
-
- Method for synthesizing 1, 2-disubstituted olefin through reaction of terminal group olefin and sulfoxide
-
The invention discloses a method for synthesizing 1, 2-disubstituted olefin by reaction of terminal olefin and sulfoxide. According to the method, terminal olefin with sulfoxide make reaction in one pot in the presence of ferric salt and hydrogen peroxide to generate the 1, 2-disubstituted olefin. sulfoxide is simultaneously used as a hydrocarbylation reagent and a solvent of olefin, and a reaction product is 1, 2-disubstituted olefin of which a terminal carbon atom in terminal olefin is coupled with a sulfoxide alkyl group, so that an olefin carbon chain is increased; the reaction conditionsare mild, the selectivity is high, the yield is high, and industrial production is facilitated.
- -
-
Paragraph 0053-0054; 0057-0062; 0074
(2021/02/10)
-
- METHODS OF BORYLATION AND USES THEREOF
-
The present invention relates, in general terms, to methods of borylation and uses thereof. In particular, the present invention provides a method of borylating an alkene compound by contacting the compound with a boron compound, a Fe pre-catalyst and a protic additive. The borylation occurs at a vicinal (β) position to an electron donating or electron withdrawing moiety of the compound.
- -
-
Page/Page column 61-62
(2021/04/30)
-
- PET-RAFT single unit monomer insertion of β-methylstyrene derivatives: RAFT degradation and reaction selectivity
-
Reversible addition-fragmentation chain transfer (RAFT) single unit monomer insertion (SUMI) of β-methylstyrene derivatives into diverse RAFT agents presented fast reaction kinetics, but significant degradation of the SUMI products occurred due to a hydrogen abstraction reaction. Fortunately, such degradation can be suppressed through appropriate design of initial RAFT agents attributed to effective chain transfer and selective photoactivation.
- Lin, Shiyang,Liu, Ruizhe,Xu, Jiangtao,Zhang, Lei
-
supporting information
p. 10759 - 10762
(2021/10/20)
-
- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
-
We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
-
p. 13337 - 13347
(2021/11/20)
-
- Spicing up olefin cross metathesis with the renewables estragole and methyl sorbate
-
Diene moieties conjugated to a carbonyl group are ubiquitous in nature and are present in compounds with relevant biological properties. Herein we investigate the cross metathesis (CM) of the renewable cross partners estragole and methyl sorbate (MeSo) to produce methyl 6-(4-methoxyphenyl)hexa-2,4-dienoate. By the judicious choice of the ruthenium-based metathesis catalysts, as well as the reaction conditions, it was possible to obtain good conversion and selectivity for the desired product in catalyst loadings as low as 50 ppm (0.005 mol%), with a minimal amount of solvent.
- Ferreira, Leonildo A.,Silva, Josiane T.,Alves, Raissa G.,Oliveira, Kelley C.B.,dos Santos, Eduardo N.
-
-
- Iron Catalyzed Double Bond Isomerization: Evidence for an FeI/FeIII Catalytic Cycle
-
Iron-catalyzed isomerization of alkenes is reported using an iron(II) β-diketiminate pre-catalyst. The reaction proceeds with a catalytic amount of a hydride source, such as pinacol borane (HBpin) or ammonia borane (H3N?BH3). Reactivity with both allyl arenes and aliphatic alkenes has been studied. The catalytic mechanism was investigated by a variety of means, including deuteration studies, Density Functional Theory (DFT) and Electron Paramagnetic Resonance (EPR) spectroscopy. The data obtained support a pre-catalyst activation step that gives access to an η2-coordinated alkene FeI complex, followed by oxidative addition of the alkene to give an FeIII intermediate, which then undergoes reductive elimination to allow release of the isomerization product.
- Woof, Callum R.,Durand, Derek J.,Fey, Natalie,Richards, Emma,Webster, Ruth L.
-
supporting information
p. 5972 - 5977
(2021/03/17)
-
- Cycloaddition Reactions of Alkene Radical Cations using Iron(III)-Phenanthroline Complex
-
Single electron oxidation of electron-rich alkenes using the iron(III)-phenanthroline complex produced electrophilic alkene radical cations, which promoted efficient radical cation [2+1] cycloaddition reactions with diazo compounds. Subsequent chain propagation afforded tri- and tetra-substituted cyclopropanes. This methodology was also expanded to [3+2] cycloaddition reactions with vinyl diazoesters, validating this sustainable, first-row transition metal iron system for the single electron redox reactions. (Figure presented.).
- Cho, Yong Hyun,Kim, Jae Hyung,An, Hyeju,Ahn, Kwang-Hyun,Kang, Eun Joo
-
supporting information
p. 2183 - 2188
(2020/04/29)
-
- Electronic properties of a cationic triphenylphosphine ligand decorated with a (η5-C5H5)Fe group in late-transition-metal complexes
-
The synthesis and characterization of a series of novel cationic multimetallic transition-metal complexes based on the cationic phosphine ligand (η6-diphenylphosphinobenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate (1) are reported. Complexes of ligand 1 with the late transition metals ruthenium, osmium, rhodium, and iridium as well as palladium and platinum were isolated in generally good yields, and the solid-state structures of most of them were determined. On the basis of the 195Pt?31P NMR coupling constant measured for trans-(1)2PtCl2 and the carbonyl absorption band in the IR spectrum of trans-(1)2Rh(CO)Cl, the electronic influence of the ligand on the metal center was evaluated. These measurements are supported by density functional theory (DFT) calculations, performed on the corresponding tricarbonylnickel(0) complex in order to determine the Tolman electronic parameter (TEP) of ligand 1.
- Malchau, Christian,Loose, Florian,Mees, Yannick,Duppe, Jens,Sun, Yu,Niedner-Schatteburg, Gereon,Thiel, Werner R.
-
p. 3335 - 3343
(2020/10/05)
-
- Cobalt-Catalyzed Z to e Isomerization of Alkenes: An Approach to (E)-β-Substituted Styrenes
-
An efficient cobalt-catalyzed Z to E isomerization of β-substituted styrenes using the amido-diphosphine ligand was developed, delivering the (E)-isomers with good functional tolerance and high stereoselectivity. The reaction could be scaled up to gram-scale with a catalyst loading of 0.1 mol %, using a mixture of (Z)- and (E)-alkene as the starting material. Preliminary mechanistic studies indicated that cobalt(I)-hydride and a benzylic-cobalt species were probably involved in the reaction, as supported by experiments and DFT calculations.
- Liu, Hongmei,Xu, Man,Cai, Cheng,Chen, Jianhui,Gu, Yugui,Xia, Yuanzhi
-
supporting information
p. 1193 - 1198
(2020/02/04)
-
- Radical-Mediated Strategies for the Functionalization of Alkenes with Diazo Compounds
-
One of the most common reactions of diazo compounds with alkenes is cyclopropanation, which occurs through metal carbene or free carbene intermediates. Alternative functionalization of alkenes with diazo compounds is limited, and a methodology for the addition of the elements of Z-CHR2 (with Z = H or heteroatom, and CHR2 originates from N2 CR2) across a carbon-carbon double bond has not been reported. Here we report a novel reaction of diazo compounds utilizing a radical-mediated addition strategy to achieve difunctionalization of diverse alkenes. Diazo compounds are transformed to carbon radicals with a photocatalyst or an iron catalyst through PCET processes. The carbon radical selectively adds to diverse alkenes, delivering new carbon radical species, and then forms products through hydroalkylation by thiol-assisted hydrogen atom transfer (HAT), or forms azidoalkylation products through an iron catalytic cycle. These two processes are highly complementary, proceed under mild reaction conditions, and show high functional group tolerance. Furthermore, both transformations are successfully performed on a gram-scale, and diverse γ-amino esters, γ-amino alcohols, and complex spirolactams are easily prepared with commercially available reagents. Mechanistic studies reveal the plausible pathways that link the two processes and explain the unique advantages of each.
- Su, Yong-Liang,Liu, Geng-Xin,Liu, Jun-Wen,Tram, Linh,Qiu, Huang,Doyle, Michael P.
-
supporting information
p. 13846 - 13855
(2020/09/21)
-
- Semihydrogenation of Alkynes Catalyzed by a Pyridone Borane Complex: Frustrated Lewis Pair Reactivity and Boron–Ligand Cooperation in Concert
-
The metal-free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5 bar H2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal-free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H2 is reminiscent of the reactivity of an intramolecular frustrated Lewis pair. However, it is the change in the coordination mode of the boroxypyridine upon H2 activation that allows the dissociation of the formed pyridone borane complex and subsequent hydroboration of an alkyne. This change in the coordination mode upon bond activation is described by the term boron-ligand cooperation.
- Wech, Felix,Hasenbeck, Max,Gellrich, Urs
-
supporting information
p. 13445 - 13450
(2020/09/23)
-
- Rhodium-Catalyzed Deoxygenation and Borylation of Ketones: A Combined Experimental and Theoretical Investigation
-
The rhodium-catalyzed deoxygenation and borylation of ketones with B2pin2 have been developed, leading to efficient formation of alkenes, vinylboronates, and vinyldiboronates. These reactions feature mild reaction conditions, a broad substrate scope, and excellent functional-group compatibility. Mechanistic studies support that the ketones initially undergo a Rh-catalyzed deoxygenation to give alkenes via boron enolate intermediates, and the subsequent Rh-catalyzed dehydrogenative borylation of alkenes leads to the formation of vinylboronates and diboration products, which is also supported by density functional theory calculations.
- Tao, Lei,Guo, Xueying,Li, Jie,Li, Ruoling,Lin, Zhenyang,Zhao, Wanxiang
-
supporting information
p. 18118 - 18127
(2020/11/26)
-
- Nickel-Catalyzed Alkylation or Reduction of Allylic Alcohols with Alkyl Grignard Reagents
-
By choosing different phosphine ligands, nickel-catalyzed selective alkylation and reduction of allylic alcohols with alkyl Grignard reagents were performed. The reaction using Ni(dppe)Cl2 as the catalyst resulted in the cross-coupling of allylic alcohols with primary alkyl Grignard reagents and cyclopropylmagnesium bromide. The reaction catalyzed by the combination of Ni(PCy3)2Cl2 and dcype led to the reduction of allylic alcohols. Secondary alkyl Grignard reagents except cyclopropylmagnesium bromide always led to reduction of allylic alcohols using either Ni(dppe)Cl2 or Ni(PCy3)2Cl2/dcype as the catalyst. In the reductive reaction β-H-containing alkyl Grignard reagents were required.
- Yang, Bo,Wang, Zhong-Xia
-
p. 4772 - 4784
(2020/05/01)
-
- ISOMERIZATION OF ALKENES
-
The present invention relates to an isomerization method for alkenes, comprising of reaction an alkene with a Ni(I)-compound. By this method, E-Alkenes are obtained in excellent yield.
- -
-
Page/Page column 20-21
(2020/04/25)
-
- Method for isomerizing cis-anethole by using catalyst
-
The invention discloses a method for isomerizing cis-anethole by using a catalyst in the technical field of anethole preparation. The method comprises the following steps: 1, heating cis-anethole to 95-110 DEG C; 2, adding sodium hydrogen sulfate into the heated cis-anethole to obtain a mixture, heating the mixture for 8-10 min until the temperature of the mixture is 155-200 DEG C, and keeping thetemperature of the mixture constant for 1-1.2 hours to obtain a reaction product, wherein the weight ratio of the sodium bisulfate to the cis-anethole before heating is (1-5): 100; 3, cooling the reaction product to room temperature, carrying out liquid separation treatment to obtain a mixed solution, adding a sodium carbonate solution into the mixed solution, carrying out an oscillation reactionfor 5-6 min to obtain a neutralization solution, and separating the neutralization solution to obtain an upper-layer trans-anethole mixed solution, wherein the weight ratio of the sodium carbonate solution to the cis-anethole is (1-1.2): 10. According to the scheme, sodium hydrogen sulfate is adopted as a catalyst, isomerization of cis-anethole can be achieved by heating and stirring for 1 h at the temperature of 150-200 DEG C in the presence of sodium hydrogen sulfate, use of rare metals such as rhodium chloride is avoided, and the cis-anethole isomerization cost is greatly reduced.
- -
-
Paragraph 0013; 0030-0080; 0085-0088
(2020/09/23)
-
- Method for synthesizing E-methyl styrene compound
-
The method for preparing E-pyridyl or alkyl-substituted,bipyridine, in a solvent, in the presence of nitrogen protection, in, reaction 0 °C -50 °C in the presence of a metal nickel salt 24 - 36h, ligand and an additive is E, and the preparation method disclosed by the invention has the advantages, cheap 2,2 ’ - raw materials, easiness in obtaining 2,2 ’ - and the like. The ligand is,bipyridine or an alkyl-substituted bipyridyl compound, in the. presence of a nitrogen, protection agent, in a solvent.
- -
-
Page/Page column 6
(2020/03/25)
-
- Tandem Olefin Isomerization/Cyclization Catalyzed by Complex Nickel Hydride and Br?nsted Acid
-
We disclose a nickel/Br?nsted acid-catalyzed tandem process consisting of double bond isomerization of allyl ethers and amines and subsequent intramolecular reaction with nucleophiles. The process is accomplished by [(Me3P)4NiH]N(SO2CF3)2 in the presence of triflic acid. The methodology provides rapid access to tetrahydropyran-fused indoles and other oxacyclic scaffolds under very low catalyst loadings.
- Kathe, Prasad M.,Caciuleanu, Alexandru,Berkefeld, Andreas,Fleischer, Ivana
-
p. 15183 - 15196
(2020/11/30)
-
- Iron-Catalyzed Tunable and Site-Selective Olefin Transposition
-
The catalytic isomerization of C-C double bonds is an indispensable chemical transformation used to deliver higher-value analogues and has important utility in the chemical industry. Notwithstanding the advances reported in this field, there is compelling demand for a general catalytic solution that enables precise control of the C═C bond migration position, in both cyclic and acyclic systems, to furnish disubstituted and trisubstituted alkenes. Here, we show that catalytic amounts of an appropriate earth-abundant iron-based complex, a base and a boryl compound, promote efficient and controllable alkene transposition. Mechanistic investigations reveal that these processes likely involve in situ formation of an iron-hydride species which promotes olefin isomerization through sequential olefin insertion/β-hydride elimination. Through this strategy, regiodivergent access to different products from one substrate can be facilitated, isomeric olefin mixtures commonly found in petroleum-derived feedstock can be transformed to a single alkene product, and unsaturated moieties embedded within linear and heterocyclic biologically active entities can be obtained.
- Yu, Xiaolong,Zhao, Haonan,Li, Ping,Koh, Ming Joo
-
supporting information
p. 18223 - 18230
(2020/12/04)
-
- Ni-Catalyzed hydrocyanation of alkenes with formamide as the cyano source
-
CN generation from formamide dehydration! A novel Ni-catalyzed hydrocyanation of various alkenes to provide aliphatic nitriles is developed by generating hydrocyanic acid in situ from safe and readily available formamide. Excellent linear or branched regio-selectivity, wide substrate scope, cheap and stable nickel salt as a pre-catalyst, a safe cyano source, slow generation of CN to obviate catalyst deactivation and convenient experimental operation would render this hydrocyanation attactive for laboratory synthesis of aliphatic nitriles.
- Shu, Xiao,Jiang, Yuan-Yuan,Kang, Lei,Yang, Luo
-
supporting information
p. 2734 - 2738
(2020/06/17)
-
- Iron-catalyzed regiodivergent alkyne hydrosilylation
-
Although tremendous effort has been devoted to the development of methods for iron catalysis, few of the catalysts reported to date exhibit clear superiority to other metal catalysts, and the mechanisms of most iron catalysis remain unclear. Herein, we report that iron complexes bearing 2,9-diaryl-1,10-phenanthroline ligands exhibit not only unprecedented catalytic activity but also unusual ligand-controlled divergent regioselectivity in hydrosilylation reactions of various alkynes. The hydrosilylation protocol described herein provides a highly efficient method for preparing useful di- and trisubstituted olefins on a relatively large scale under mild conditions, and its use markedly improved the synthetic efficiency of a number of bioactive compounds. Mechanistic studies based on control experiments and density functional theory calculations were performed to understand the catalytic pathway and the observed regioselectivity.
- Hu, Meng-Yang,He, Peng,Qiao, Tian-Zhang,Sun, Wei,Li, Wen-Tao,Lian, Jie,Li, Jin-Hong,Zhu, Shou-Fei
-
supporting information
p. 16894 - 16902
(2020/10/09)
-
- Superelectrophilic Fe(III)-Ion Pairs as Stronger Lewis Acid Catalysts for (E)-Selective Intermolecular Carbonyl-Olefin Metathesis
-
An intermolecular carbonyl-olefin metathesis reaction is described that relies on superelectrophilic Fe(III)-based ion pairs as stronger Lewis acid catalysts. This new catalytic system enables selective access to (E)-olefins as carbonyl-olefin metathesis products. Mechanistic investigations suggest the regioselective formation and stereospecific fragmentation of intermediate oxetanes to be the origin of this selectivity. The optimized conditions are general for a variety of aryl aldehydes and trisubstituted olefins and are demonstrated for 28 examples in up to 64% overall yield.
- Albright, Haley,Schindler, Corinna S.,Vonesh, Hannah L.
-
supporting information
p. 3155 - 3160
(2020/04/21)
-
- Radical Cation Diels-Alder Reactions by TiO2 Photocatalysis
-
Radical cation Diels-Alder reactions by titanium dioxide (TiO2) photocatalysis in lithium perchlorate/nitromethane solution are described. TiO2 photocatalysis promotes reactions between electron-rich dienes and dienophiles, which would otherwise be difficult to accomplish due to electronic mismatching. The reactions are triggered by hole oxidation of the dienophile and are completed by the excited electron reduction of the radical cation intermediate at the dispersed surface in the absence of any sacrificial substrate.
- Nakayama, Kaii,Maeta, Naoya,Horiguchi, Genki,Kamiya, Hidehiro,Okada, Yohei
-
supporting information
p. 2246 - 2250
(2019/04/10)
-
- Hydrophilic (ν6-Arene)-Ruthenium(II) Complexes with P-OH ligands as catalysts for the isomerization of allylbenzenes and C-H bond arylation reactions in water
-
Half-sandwich ruthenium(II) complexes containing ν6-coordinated 3-phenylpropanol and phosphinous-acid-type ligands, namely, [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)R2}] (R = Me (2a), Ph (2b), 4-C6H4CF3 (2c), 4-C6H4OMe (2d), OMe (2e), OEt (2f), and OPh (2g), have been synthesized in 44-88% yield by reacting [RuCl2{ν6:κ1(O)-C6H5CH2CH2CH2OH}] (1) with the appropriate pentavalent phosphorus oxide R2P(═O)H. The structure of [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)Me2}] (2a) was unequivocally confirmed by X-ray diffraction methods. Compounds 2a-g proved to be catalytically active in the isomerization of allylbenzenes into the corresponding (1-propenyl)benzene derivatives employing water as the sole reaction solvent, with [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)(OPh)2}] (2g) showing the best performance and a broad substrate scope (73-93% isolated yields with E/Z ratios around 90:10 employing 1 mol % of 2g and 3 mol % of K2CO3, and performing the catalytic reactions at 80 °C for 4-24 h). The results herein presented show for the first time the utility of phosphinous acids as auxiliary ligands for metal-catalyzed olefin isomerization processes, reactions in which a cooperative role for the P - OH unit is proposed. On the other hand, the utility of complexes 2a-g as catalysts for ortho-arylation reactions of 2-phenylpyridine in water is also briefly discussed.
- González-Fernández, Rebeca,Crochet, Pascale,Cadierno, Victorio
-
supporting information
p. 3696 - 3706
(2019/10/11)
-
- Oxidative [4+2] Cycloaddition of α-(N-Arylamino) Carbonyls with Aryl Alkenes by Multiple C-H Functionalizations and [1,2]-Aryl Shifts
-
A new, general copper-catalyzed oxidative tandem [4+2] cycloaddition of α-(N-arylamino) carbonyl compounds with aryl alkenes to produce highly substituted quinolines has been developed, which allows the formation of three new C-C bonds through a sequence of multiple C-H functionalizations, annulation, and [1,2]-aryl shifts.
- Wei, Wen-Ting,Teng, Fan,Li, Yang,Song, Ren-Jie,Li, Jin-Heng
-
supporting information
p. 6285 - 6288
(2019/09/06)
-
- Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
-
A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
- Matt, Christof,K?lblin, Frederic,Streuff, Jan
-
supporting information
p. 6983 - 6988
(2019/09/09)
-
- Introduction of Cyclopropyl and Cyclobutyl Ring on Alkyl Iodides through Cobalt-Catalyzed Cross-Coupling
-
A cobalt-catalyzed cross-coupling between alkyl iodides and cyclopropyl, cyclobutyl, and alkenyl Grignard reagents is disclosed. The reaction allows the introduction of strained rings on a large panel of primary and secondary alkyl iodides. The catalytic system is simple and nonexpensive, and the reaction is general, chemoselective, and diastereoconvergent. The alkene resulting from the cross-coupling can be transformed to substituted cyclopropanes using a Simmons-Smith reaction. The formation of radical intermediates during the coupling is hypothesized.
- Andersen, Claire,Ferey, Vincent,Daumas, Marc,Bernardelli, Patrick,Guérinot, Amandine,Cossy, Janine
-
p. 2285 - 2289
(2019/03/29)
-
- Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
-
We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
- Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
-
supporting information
p. 5723 - 5728
(2019/04/03)
-
- E-Olefins through intramolecular radical relocation
-
Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach.We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.
- Kapat, Ajoy,Sperger, Theresa,Guven, Sinem,Schoenebeck, Franziska
-
p. 391 - 396
(2019/02/03)
-
- Stereoselective Synthesis of 1-Arylpropan-2-amines from Allylbenzenes through a Wacker-Tsuji Oxidation-Biotransamination Sequential Process
-
Herein, a sequential and selective chemoenzymatic approach is described involving the metal-catalysed Wacker-Tsuji oxidation of allylbenzenes followed by the amine transaminase-catalysed biotransamination of the resulting 1-arylpropan-2-ones. Thus, a series of nine optically active 1-arylpropan-2-amines were obtained with good to very high conversions (74–92%) and excellent selectivities (>99% enantiomeric excess) in aqueous medium. The Wacker-Tsuji reaction has been exhaustively optimised searching for compatible conditions with the biotransamination experiments, using palladium(II) complexes as catalysts and iron(III) salts as terminal oxidants in aqueous media. The compatibility of palladium/iron systems for the chemical oxidation with commercially available and made in house amine transaminases was analysed, finding ideal conditions for the development of a general and stereoselective cascade sequence. Depending on the selectivity displayed by selected amine transaminase, it was possible to produce both 1-arylpropan-2-amines enantiomers under mild reaction conditions, compounds that present therapeutic properties or can be employed as synthetic intermediates of chiral drugs from the amphetamine family. (Figure presented.).
- González-Martínez, Daniel,Gotor, Vicente,Gotor-Fernández, Vicente
-
p. 2582 - 2593
(2019/05/15)
-
- Production technique to prepare anethole by catalyzing dewatering of 3-(4-methoxyphenyl)-1-propanol
-
The invention discloses a production technique to prepare anethole by catalyzing dewatering of 3-(4-methoxyphenyl)-1-propanol. The production technique comprises: using acid alumina and/or aluminum hydroxide weak-acidity solid material to catalyze dewatering of 3-(4-methoxyphenyl)-1-propanol at 100-150 DEG C to generate anethole. The production technique has the advantages that the reaction process is free of waste gas, the reaction rate is high, the yield is high, few polymer impurities occur to anethole, the economic value is high, the reaction requires no post-treatment or solvent, the requirement on equipment is low, and the production technique is easy to industrially popularize.
- -
-
Paragraph 0084-0099; 0169
(2018/09/13)
-
- Preferential Photoreaction in a Porous Crystal, Metal-Macrocycle Framework: PdII-Mediated Olefin Migration over [2+2] Cycloaddition
-
A nanosized confined space with well-defined functional surfaces has great potential to control the efficiency and selectivity of catalytic reactions. Herein we report that a 1,6-diene, which normally forms an intramolecular [2+2] cycloadduct under photoirradiation, preferentially undergoes a photoinduced olefin migration in a porous crystal, metal-macrocycle framework (MMF), and alternatively [2+2] cycloaddition is completely inhibited in the confined space. A plausible reaction mechanism for olefin migration triggered by the photoinduced dissociation of the Pd-Cl bond is suggested based on UV-vis diffuse reflectance spectroscopy, single-crystal XRD, and MS-CASPT2 calculation. The substrate scope of the photoinduced olefin migration in MMF was also examined using substituted allylbenzene derivatives.
- Yonezawa, Hirotaka,Tashiro, Shohei,Shiraogawa, Takafumi,Ehara, Masahiro,Shimada, Rintaro,Ozawa, Takeaki,Shionoya, Mitsuhiko
-
supporting information
p. 16610 - 16614
(2018/12/11)
-
- Enantioselective Oxy-Heck–Matsuda Arylations: Expeditious Synthesis of Dihydrobenzofuran Systems and Total Synthesis of the Neolignan (?)-Conocarpan
-
This work discloses the first examples of an effective enantioselective oxy-Heck–Matsuda reaction using a variety of styrenic olefins to generate chiral dihydrobenzofurans. The reaction proceeds in moderate to good yields, with high trans diastereoselectivity (up to 20:1) in enantioselectivities up to 90:10 using the N,N-ligand pyrimidine-bisoxazoline (PyriBox). The oxy-Heck–Matsuda reactions were carried out under mild conditions and rather low catalyst loadings. The feasibility and practicality of the process is demonstrated by a concise total synthesis of the neolignan (?)-conocarpan. X-ray diffraction of an advanced brominated intermediate in the route to (?)-conocarpan has allowed the unequivocal assignment of the absolute stereochemistry of the oxy-Heck–Matsuda aryldihydrobenzofuran products. A rationale for the mechanism operating in these enantioselective oxy-Heck–Matsuda reactions is also presented. (Figure presented.).
- Silva, Allan R.,Polo, Ellen C.,Martins, Nelson C.,Correia, Carlos Roque D.
-
p. 346 - 365
(2018/01/26)
-
- A Dual-Functional Catalyst for Cascade Meerwein–Pondorf–Verley Reduction and Dehydration of 4″-Methoxypropiophenone to Anethole
-
Anethole is an ingredient in many flavours, fragrances and pharmaceutical formulations. To reduce the dependence of its supply on natural oils, a green route for anethole synthesis was designed on the basis of Meerwein–Pondorf–Verley (MPV) reduction and dehydration of 4′-methoxypropiophenone. The one-pot cascade reactions were heterogeneously catalysed by dual-functional Zr-MSU-3, a predominantly Lewis-acidic catalyst with a Si/Zr ratio of 10 and pores with sizes in the range of 3.2–4.2 nm. The use of 2-pentanol as solvent and hydrogen donor for the MPV reduction was advantageous, as its high boiling point enhances the rate of the reactions, especially the dehydration of the MPV product, 1-(4-methoxyphenyl)-propan-1-ol. This dispenses with the need for a strong acid catalyst that could result in by-products of acid-catalysed reactions. Anethole yields of 91 % with a trans/cis isomer ratio of about 92:8, similar to that of natural anethole, were obtained. In comparison, microporous Zr-beta (Si/Zr 12.5) gave lower activity owing to pore-size constraints. Hence, through design of the reactions and catalyst, 4′-methoxypropiophenone can be efficiently converted to anethole in a sustainable and green manner.
- Zhang, Hongwei,Lim, Candy Li-Fen,Zaki, Muhammad,Jaenicke, Stephan,Chuah, Gaik Khuan
-
p. 3007 - 3017
(2018/08/03)
-
- Redox-Neutral Photocatalytic Cyclopropanation via Radical/Polar Crossover
-
A benchtop stable, bifunctional reagent for the redox-neutral cyclopropanation of olefins has been developed. Triethylammonium bis(catecholato)iodomethylsilicate can be readily prepared on multigram scale. Using this reagent in combination with an organic photocatalyst and visible light, cyclopropanation of an array of olefins, including trifluoromethyl- and pinacolatoboryl-substituted alkenes, can be accomplished in a matter of hours. The reaction is highly tolerant of traditionally reactive functional groups (carboxylic acids, basic heterocycles, alkyl halides, etc.) and permits the chemoselective cyclopropanation of polyolefinated compounds. Mechanistic interrogation revealed that the reaction proceeds via a rapid anionic 3-exo-tet ring closure, a pathway consistent with experimental and computational data.
- Phelan, James P.,Lang, Simon B.,Compton, Jordan S.,Kelly, Christopher B.,Dykstra, Ryan,Gutierrez, Osvaldo,Molander, Gary A.
-
supporting information
p. 8037 - 8047
(2018/07/03)
-
- Copper- and Nickel-Catalyzed Cross-Coupling Reaction of Monofluoroalkenes with Tertiary, Secondary, and Primary Alkyl and Aryl Grignard Reagents
-
A highly efficient cross-coupling reaction of monofluoroalkenes with tertiary, secondary, and primary alkyl and aryl Grignard reagents in the presence of a catalytic amount of copper or nickel catalyst, respectively, has been developed. The reactions proceeded smoothly at room temperature, providing (E)-alkene isomers in moderate to high yields. Plausible mechanisms of the Ni-catalyzed coupling reaction of monofluoroalkene with Grignard reagents are suggested.
- Shi, Hongyan,Dai, Wenpeng,Wang, Biyun,Cao, Song
-
supporting information
p. 459 - 463
(2018/02/17)
-
- Cobalt-Catalyzed Regioselective Olefin Isomerization under Kinetic Control
-
Olefin isomerization is a significant transformation in organic synthesis, which provides a convenient synthetic route for internal olefins and remote functionalization processes. The selectivity of an olefin isomerization process is often thermodynamically controlled. Thus, to achieve selectivity under kinetic control is very challenging. Herein, we report a novel cobalt-catalyzed regioselective olefin isomerization reaction. By taking the advantage of fine-tunable NNP-pincer ligand structures, this catalytic system features high kinetic control of regioselectivity. This mild catalytic system enables the isomerization of 1,1-disubstituted olefins bearing a wide range of functional groups in excellent yields and regioselectivity. The synthetic utility of this transformation was highlighted by the highly selective preparation of a key intermediate for the total synthesis of minfiensine. Moreover, a new strategy was developed to realize the selective monoisomerization of 1-alkenes to 2-alkenes dictated by installing substituents on the γ-position of the double bonds. Mechanistic studies supported that the in situ generated Co-H species underwent migratory insertion of double bond/β-H elimination sequence to afford the isomerization product. The less hindered olefin products were always preferred in this cobalt-catalyzed olefin isomerization due to an effective ligand control of the regioselectivity for the β-H elimination step.
- Liu, Xufang,Zhang, Wei,Wang, Yujie,Zhang, Ze-Xin,Jiao, Lei,Liu, Qiang
-
supporting information
p. 6873 - 6882
(2018/05/30)
-
- Synthesis method of aryl olefin
-
The invention discloses a synthesis method of aryl-containing substituted olefin. The method is characterized in that aliphatic acetal is used as an alkylating agent to react with an aromatic compound; under the catalysis effect of a solid acid catalyst; at ordinary pressure or low pressure being 0.1 to 1.0MPa and at reaction temperature in the range being 90 to 160 DEG C, one-pot reaction is performed to directly obtain aryl substituted olefin such as anise camphor. The synthesis method has the following characteristics that (1) the synthesis method belongs to a novel synthesis route; the reaction is completed through one pot; (2) the aromatic compound is used as a reactant and is also used as a solvent; other organic solvents are not used; (3) the catalyst is solid acid such as a H-Betamolecular sieve and a metal ion modified molecular sieve; the catalytic amount of catalyst is used; (4) after produced alcohol is recovered, the alcohol can be cyclically used during the acetal synthesis; (5) the reaction can be intermittently performed, and can also be performed in a tubular reactor and a fixed bed reactor; (6) the aftertreatment is simple; no waste is generated in the reaction process; the synthesis method is a green and environment-friendly synthesis route.
- -
-
Paragraph 0031; 0032
(2018/05/16)
-
- A Stereoconvergent Cyclopropanation Reaction of Styrenes
-
The first stereoconvergent cyclopropanation reaction by means of photoredox catalysis using diiodomethane as the methylene source is described. This transformation exhibits broad functional group tolerance and it is characterized by an excellent stereocontrol en route to trans-cyclopropanes regardless of whether E- or Z-styrene substrates were utilized.
- del Hoyo, Ana M.,Herraiz, Ana G.,Suero, Marcos G.
-
supporting information
p. 1610 - 1613
(2017/02/05)
-
- A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts
-
A homogenous metal hydride (M?H) catalyst for isomerization normally requires rigorous air-free techniques. Here, we demonstrate a highly efficient protocol in which simple non-redox metal ions as Lewis acids can promote olefin isomerization dramatically with a commercially available RuH2(CO)(PPh3)3 complex in an open-flask system. Isomerization can be accomplished within a short time, and a satisfactory selectivity for different types of unsaturated compounds can be obtained. Meanwhile, an excellent turnover number up to 17208 was achieved under air, and open-flask gram-scale experiments further demonstrated the efficiency of the RuH2(CO)(PPh3)3/non-redox-metals system. We used FTIR spectroscopy, GC–MS, NMR spectroscopy and kinetics studies to evidence that in the sluggish RuH2(CO)(PPh3)3 catalyst, bloated PPh3 ligands cause steric hindrance for the coordination of the free alkene. Alternatively, the addition of non-redox metal ions could induce the dissociation of the PPh3 ligand to offer unoccupied coordination sites for the alkene and to form the Mg-bridged adduct OC?Ru?H2?Mg2+ as the highly active species, which benefited the isomerization significantly through the metal hydride addition–elimination pathway. Finally, this strategy was demonstrated as an impactful approach for hydride catalysts of other transition metals such as Os.
- Lv, Zhanao,Chen, Zhuqi,Hu, Yue,Zheng, Wenrui,Wang, Haibin,Mo, Wanling,Yin, Guochuan
-
p. 3849 - 3859
(2017/09/18)
-
- Nitrogen-Doped Carbon-Encapsulated Nickel/Cobalt Nanoparticle Catalysts for Olefin Migration in Allylarenes
-
Olefin migration in allylarenes is typically performed with precious-metal-based homogeneous catalysts. In contrast, very limited progress has been made with the use of cheap, Earth-abundant base metals as heterogeneous catalysts for these transformations—in spite of the obvious economic and environmental advantages. Herein, we report on the use of an easily prepared heterogeneous catalyst material for the migration of olefins, in particular, for allylarenes. The catalyst material consists of nickel/cobalt alloy nanoparticles encapsulated in nitrogen-doped carbon shells. The encapsulated nanoparticles are stable in air and are easily collected by centrifugation, filtration, or magnetic separation. Furthermore, we demonstrate that the catalysts can be reused several times and provide continuously high yields of the olefin-migration product.
- Kramer, S?ren,Mielby, Jerrik,Buss, Kasper,Kasama, Takeshi,Kegn?s, S?ren
-
p. 2930 - 2934
(2017/08/14)
-
- Mononuclear Ruthenium and Osmium Complexes with a Bicyclic Guanidinate Ligand: Synthesis and Catalytic Behavior in Olefin Isomerization Processes
-
The preparation of the first mononuclear RuII, RuIV, and OsII complexes containing the anion of the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (Hhpp) as a chelating ligand, namely [RuX{κ2-(N,N′)-hpp}(η6-arene)] [arene = p-cymene, X = Cl (2a), Br (2b), I (2c); arene = C6Me6, X = Cl (7)], [RuCl{κ2-(N,N′)-hpp}(η3:η3-C10H16)] (9; C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl), and [OsCl{κ2-(N,N′)-hpp}(η6-p-cymene)] (11), is described. Compounds 2a–c, 7, 9, and 11 have been fully characterized by elemental analysis, HRMS, IR and NMR spectroscopy. In addition, the structure of 2a has been unequivocally confirmed by single-crystal X-ray diffraction methods. The catalytic behavior of these metal guanidinate complexes in the base-free redox isomerization of allylic alcohols is explored, with the ruthenium(IV) derivative 9 showing the best performance (TOF up to 5940 h–1). All of the synthesized complexes have also proven to be active in the isomerization of the allylbenzene estragole into the industrially relevant 1-propenylbenzene anethole, with a trans selectivity of up to 95 %.
- Gámez-Rivera, Sebastián A.,Francos, Javier,Borge, Javier,Cadierno, Victorio
-
p. 4138 - 4146
(2017/09/28)
-