Article
Chemistry, Organic
Yusuke Tomita, Naoto Haraguchi, Sayori Kiyota, Nobuyuki Komine, Masafumi Hirano
Summary: A traditional cobalt catalyst system has been found to exhibit previously undiscovered reactivity. Depending on the choice of tertiary phosphines and substrates, this catalytic system can catalyze diverse cycloadditions, yielding various cyclic compounds. The bite angles of the ligands used significantly contribute to the catalytic diversity.
Article
Chemistry, Organic
Kento Nagai, Suguru Morishitabara, Yuji Nishi, Chihiro Kajimoto, Motohiro Yasui, Takashi Yumura, Shigeyuki Yamada, Tsutomu Konno
Summary: In this study, highly regioselective hydrosilylation of cyclohexa-1,3-dienes bearing a tetrafluoroethylene group was achieved under mild conditions using 1-10 mol % Co-2(CO)(8) as the catalyst. Mechanistic studies and DFT calculations demonstrated that the reaction proceeds via the modified Chalk-Harrod mechanism, leading to the exclusive formation of homoallylsilanes. The successful synthesis of a tetrafluorinated negative-type liquid crystal showcased the synthetic utility of this hydrosilylation reaction.
Article
Chemistry, Organic
Gautam Kumar, Debkanta Bhattacharya, Parag Mistry, Indranil Chatterjee
Summary: A unique and valuable method has been developed for the hydrogenation of aromatic and aliphatic alkenes. The catalytic InBr3, 1,3-benzodioxole, and residual H2O in the reaction mixture are utilized as a practical source of deuterium incorporation. Experimental studies demonstrate that the transfer of hydride from 1,3-benzodioxole to carbocationic intermediate remains the critical step.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Feng Zhong, Zhi-Zhou Pan, Si-Wei Zhou, Hai-Jun Zhang, Liang Yin
Summary: The study demonstrates a regioselective asymmetric allylation of ketones using commercially available 1,4-pentadiene as a pronucleophile. Chiral tertiary alcohols with a terminal (Z)-1,3-diene unit are produced with high (Z)/(E) ratio and enantioselectivity. The partial isomerization of (E)-allylcopper(I) species to (Z)-allylcopper(I) species is observed during the reaction.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Organic
Xue-Hua Deng, Jia-Xi Jiang, Qin Jiang, Ting Yang, Bo Chen, Long He, Wen-Dao Chu, Cheng-Yu He, Quan-Zhong Liu
Summary: In this study, the asymmetric cross reductive coupling reaction of conjugated dienes and ketoimines using copper hydride as a catalyst was achieved for the first time. The reaction, catalyzed by chiral Ph-BPE ligand, provides a rapid and efficient access to homoallylic amines with two vicinal stereogenic centers.
Article
Chemistry, Organic
Zeyu Zhang, Danyun Li, Chanjuan Xi
Summary: CO2-promoted and Ni-catalyzed direct hydroallylation of terminal alkynes with allylic alcohols has been achieved. Various 1,4-dienes could be synthesized in good yield with excellent Markovnikov selectivity for alkyl- and aryl-substituted terminal alkynes under mild reaction conditions. A gram-scale reaction gives considerable yield. Preliminary mechanistic studies support the reaction pathway through sequential carboxylation/allylnickelation/lithium bicarbonate nickelation/transmetalation in the hydroallylation of alkynes with allylic alcohols in the presence of CO2.
Article
Chemistry, Organic
Jiajin Zhao, Guoxiong Xu, Xue Wang, Jiren Liu, Xiang Ren, Xin Hong, Zhan Lu
Summary: A cobalt-catalyzed multipositional isomerization of conjugated dienes using an 8-oxazoline iminoquinoline ligand has been reported. This reaction is simple and efficient, yielding disubstituted 1,3-dienes with good yields and stereoselectivity.
Article
Chemistry, Organic
Hai-Jiao Long, Yin-Long Li, Bing-Qian Zhang, Wen-Ying Xiao, Xiao-Ying Zhang, Ling He, Jun Deng
Summary: Catalytic enantioselective desymmetrizing bromoaminocyclization of prochiral cyclohexa-1,4-dienes was achieved using chiral anion phase-transfer catalysis, providing a range of enantioenriched cis-3a-arylhydroindoles. The methodology demonstrated potential application in natural product total synthesis through the asymmetric synthesis of (+)-Mesembrane.
Article
Chemistry, Multidisciplinary
Greg J. Baker, Andrew J. P. White, Ian J. Casely, Damian Grainger, Mark R. Crimmin
Summary: The reversible activation of dihydrogen with a molecular zinc anilide complex has been investigated. The mechanism involves the addition of H-2 across the Zn-N bond through a four-membered transition state. The resulting zinc hydride complex is highly effective for the hydrozincation of C=C bonds, particularly alkynes, and this discovery has led to the development of a catalytic system for the semi-hydrogenation of alkynes.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Wei Sun, Meng-Yang Hu, Zhan-Sheng Lu, Ming-Yao Huang, Xin-Yu Zhang, Shou-Fei Zhu
Summary: This article reports a method for stereoselective transformation using an iron catalyst to synthesize Z-allylsilanes with high regioselectivity and exclusive stereoselectivity from E/Z mixtures. The mechanism of this reaction differs from previously reported mechanisms.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Xiang Ren, Zhan Lu
Summary: A series of new 8-OIQ cobalt complexes were synthesized and used for cobalt-catalyzed 1,4-hydroboration of enones with HBpin to access chiral beta,beta-disubstituted ketones with good to excellent selectivities. The protocol is operationally simple and has a broad substrate scope.
Article
Chemistry, Multidisciplinary
Peng Lu, Hongliang Wang, Yihui Mao, Xin Hong, Zhan Lu
Summary: Investigation on asymmetric hydrogenation of olefins is vital for the synthesis of pharmaceutical molecules and chemical industry. A cobalt-catalyzed enantioconvergent hydrogenation method has been developed for common minimally functionalized E/Z-olefin mixtures.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Organic
Gautam Kumar, Zheng-Wang Qu, Stefan Grimme, Indranil Chatterjee
Summary: Catalytic hydroarylation reactions of conjugated dienes using tris(pentafluorophenyl)borane as a Lewis acid catalyst show a broad substrate scope for highly regioselective functionalization of sterically hindered aniline derivatives. Experimental and theoretical studies reveal the crucial role of residual water and B(C6F5)(3) complex in the reaction mechanism.
Article
Chemistry, Organic
Zefeng Song, Weijia Wang, Zhixin Liu, Yue Lu, De Wang
Summary: An interesting remote delta-C 1,6-addition and an isomerization cascade reaction for phosphine-catalyzed activated alkynes have been disclosed, yielding products featuring a functional diene and a 1,1-diaryl methyl motif in moderate to good yields (30-86%) with high regioselectivity and stereoselectivity. The methodology shows a wide scope of compatible substrates (35 examples) such as indolyl, oxindolyl, ester, and cinnamyl, expanding its utility. Plausible mechanism and potential applications have also been presented.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Organic
Ke Li, Zhenjie Gan, Er-Qing Li, Zheng Duan
Summary: A novel phosphine-catalyzed (4 + 2) cyclization reaction has been reported for the generation of functionalized dihydropyran skeletons from electron-deficient conjugated dienes and enones. Mechanistic investigation reveals the formation of a new phosphonium zwitterion, which undergoes consecutive reactions. An asymmetric variant has also been developed through efficient and economical chiral phosphine catalysis.
Article
Chemistry, Multidisciplinary
Zhi-Yuan Zhao, Ming Cui, Elisabeth Irran, Martin Oestreich
Summary: This study successfully achieved highly enantioselective silylation of 3-substituted 2H-azirines using a copper-catalyzed reaction with a silyl boronic ester as a latent silicon nucleophile. The resulting C-silylated, unprotected (N-H) aziridines were obtained in high yields and with excellent enantioselectivities, and they can be further converted into valuable compounds without significant loss of enantiomeric excess.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Yi Peng, Martin Oestreich
Summary: Opening the ring of cyclic amines by selectively breaking the carbon-nitrogen bond greatly expands the range of available nitrogen-containing structures. However, methods that can directly open secondary amines are limited. This study presents an efficient reductive ring opening of cyclic amines using PhSiH3 under B(C6F5)(3) catalysis, allowing for the transformation of unstrained cyclic amines into acyclic amines in a simple one-step process. Experimental evidence supports a stepwise mechanism involving silylammonium ions and reductive cleavage of carbon-nitrogen bonds.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Tao He, Hendrik F. T. Klare, Martin Oestreich
Summary: The method of methylation of various arenes with methanol is disclosed. The reaction is initiated by counteranion-stabilized silylium or arenium ions, which form Meerwein's salt-like oxonium ions with methanol as the active methylating agents. The silylated methyloxonium ions are stronger electrophiles than their protonated congeners, allowing the Friedel-Crafts alkylation to proceed more efficiently and at a lower reaction temperature. The regeneration of these superelectrophiles within the catalytic cycle is accomplished by the addition of a tetraorganosilane additive, that releases a silylium ion through protodesilylation by the Bri nsted acidic Wheland intermediate, thereby acting as a productive proton-into-silylium ion generator. By this method, even the C-H methylation of electronically deactivated aryl halides with methanol is achieved. The protocol is also applicable to nonactivated primary as well as pi-activated benzylic alcohols. Dialkyl ethers are also competent alkylating agents in the presence of the quaternary phenylsilane additive.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Organic
Supriya Rej, Hendrik F. T. Klare, Martin Oestreich
Summary: Geminal alkenes with an aryl and an allenyl group exhibit the structure of [3]dendralenes. The central alkene double bond in these polyenes can react with a silylium ion, initiating a Nazarov cyclization. The resulting ionic intermediate is captured by hydride in the presence of excess hydrosilane. The benzannulated methylenecyclopentene derivatives with a silylalkyl group then undergo silylium-ion regeneration and an unusual endo-selective intramolecular hydrosilylation. This cascade reaction eventually leads to the formation of a silicon-containing bicyclo[3.2.1]octane skeleton.
Review
Chemistry, Organic
Nektarios Kranidiotis-Hisatomi, Martin Oestreich
Summary: Enantioconvergent transition-metal-catalyzed cross-coupling reactions of racemic a-silyl and a-boryl reagents are important for the synthesis of highly enantioenriched a-chiral silanes and boranes. Palladium, nickel, and copper catalysis are used with a-silyl and a-boryl electrophiles. Numerous chiral ligands have extended the scope of this field. This review summarizes the progress made in this rapidly evolving area.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Organic
Avijit Roy, Haopeng Gao, Hendrik F. T. Klare, Martin Oestreich
Summary: The electrophilic silylium ions were used to investigate the intramolecular Friedel-Crafts-type cyclization of aryl tethered 1,1-difluoroalkenes. The preference for electrophilic silylation of the carbon-carbon double bond over vinylic C(sp(2))-F bonds activation initiates the reaction. Subsequent cyclization and hydrodefluorination of the resulting C(sp(3))-F bonds produce the final product in moderate to good yields. Unlike previous reports, the reaction proceeds with perfluorinated tetraphenylborate counteranion under ambient conditions without the need for a carborate counteranion associated with the silylium ion intermediates.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Organic
Lucie Finck, Sarah Dabrowski, Martin Oestreich
Summary: A denitrogenative palladium-catalyzed C(sp(2))-C(sp(2)) cross coupling reaction of aryl-substituted diazenes capped with a trimethylsilyl group and functionalized aryl bromides is described. The use of a PEPPSITM catalyst in the presence of NaOt-Bu enables the activation of the N-aryl-N'-silyldiazene pronucleophile, leading to the loss of dinitrogen and subsequent coupling with the in-situ-formed aryl nucleophile. This methodology provides access to biaryl compounds with various substituents.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Multidisciplinary
Benedikt Wolff, Zheng-Wang Qu, Stefan Grimme, Martin Oestreich
Summary: This study presents a method for the enantioselective reduction of simple carbenium ions using cyclohexadienes with a hydridic C-H bond at an asymmetrically substituted carbon atom. Chiral cyclohexadienes are used as dihydrogen surrogates for the transfer hydrogenation of alkenes (styrenes). The reaction mechanism involves the initiation by trityl cation and a delicate intermolecular capture of a carbenium-ion intermediate by the chiral hydride source, resulting in good enantiomeric ratios of the reduction products.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Honghua Zuo, Hendrik F. T. Klare, Martin Oestreich
Summary: A catalytic silylium-ion-promoted intramolecular alkyne carbosilylation reaction is reported, involving electrophilic activation of the C-C triple bond by a silylium ion and maintenance of the catalytic cycle through protodesilylation of an allylsilane reagent. The reaction exhibits exclusive 7-endo-dig selectivity and results in fully substituted vinylsilane derivatives of silylated benzocycloheptenes. Control experiments demonstrate that the catalytically active silylium ion can be regenerated by protodesilylation of the vinylsilane product.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Daniel Broesamlen, Martin Oestreich
Summary: A newly developed hept-4-yl-substituted Pybox ligand enables a nickel-catalyzed enantio- and regioconvergent alkylation of regioisomeric mixtures of racemic germylated allylic electrophiles with alkyl nucleophiles, yielding various chiral gamma-germyl alpha-alkyl allylic building blocks with excellent yields and enantioselectivities. The regioconvergence is attributed to the steering effect of the bulky germyl group. The resulting vinyl germanes can be easily halodegermylated without racemization of the allylic stereocenter, providing synthetically valuable gamma-stereogenic vinyl halides.
Article
Chemistry, Organic
Daniel Bro''samlen, Martin Oestreich
Summary: A Ni-H-catalyzed hydroalkylation of vinylsilanes and -germanes as well as allylsilanes with unactivated alkyl iodides is described. In contrast to reactions with styrene or vinyl boronate esters, the addition across the C-C double bond exhibits anti-Markovnikov selectivity, yielding the linear regioisomer. Mechanistic control experiments confirm a radical mechanism, and a competition experiment demonstrates the chemoselectivity favoring the vinyl group over the allyl group.
Article
Chemistry, Organic
Peng-Wei Long, Tao He, Hendrik F. T. Klare, Martin Oestreich
Summary: This Account summarizes the fascinating chemistry of cyclopropyl-stabilized silylium ions, which can be readily obtained from vinyl-cyclopropanes (VCPs). Depending on the nucleophilic partner, these reactive intermediates undergo direct ring opening or ring expansion, leading to the formation of nonclassical alkene-stabilized silylium ions. The latter can also be obtained by gold and proton electrophiles from silicon compounds containing unsaturated C-C bonds. These reaction cascades can be terminated by the formation of C-H or C-C as well as Si-O bonds, revealing the versatility of these complex reactions.
Article
Chemistry, Physical
Min Zhu, Martin Oestreich
Summary: A group-selective monosilylation of silanediols using List's counteranion-directed silylation methodology is described. The enantioselectivity is achieved by generating a silylium-ion-like silicon electrophile from an allylic silane paired with an imidodiphosphorimidate (IDPi), enabling discrimination of the two hydroxy groups attached to the prochiral silicon atom. Furthermore, the enantioselectivity is improved by a subsequent kinetic resolution, resulting in silicon-stereogenic disiloxanes with high enantiocontrol.
Article
Chemistry, Multidisciplinary
Yuanjiu Xiao, Lei Tang, Tong-Tong Xu, Jiang-Yi-Hui Sheng, Zhongyan Zhou, Lei Yue, Guoqiang Wang, Martin Oestreich, Jian-Jun Feng
Summary: A boron Lewis acid-catalyzed intermolecular carboacyloxylation of ynamides with esters is reported, which provides a direct and efficient way to access fully substituted acyclic enol esters. The reaction shows high regio- and Z/E selectivity and is compatible with readily available allylic carbonates. This strategy allows the construction of acyclic beta,beta-disubstituted enol carbonates of amides and can be applied to the synthesis of enantioenriched alpha-quaternary amides.
Review
Chemistry, Organic
Lucie Finck, Martin Oestreich
Summary: This perspective provides an overview of the underexplored chemistry of diazenes and highlights their potential in synthetic transformations. The stability and reactivity of diazenes have been enhanced by using silicon protection. The generation of aryl, diazenyl, and alkyl anionic intermediates under catalytic conditions opens up new synthetic approaches as alternatives to existing methodologies.
JOURNAL OF ORGANIC CHEMISTRY
(2023)