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241.
Dr. Kumar Bhaskar Pal Dr. Ester Maria Di Tommaso Dr. A. Ken Inge Prof. Berit Olofsson 《Angewandte Chemie (International ed. in English)》2023,62(20):e202301368
We report an efficient radical-mediated C−C coupling through photoredox-catalyzed reactions of 4-alkyl-dihydropyridines (DHPs) and vinylbenziodoxol(on)es (VBX, VBO). This transition-metal-free and mild photocatalytic method has excellent functional group tolerance and affords vinylated products in good yields, with complete retention of the alkene configuration. The utility of the methodology is demonstrated by the diastereoselective synthesis of C-vinyl glycosides. Preliminary mechanistic studies suggest that the C−C bond formation is stereospecific and proceeds through a concerted radical coupling transition state. 相似文献
242.
Jingjie Yang Zhuofan Gui Yuli He Prof. Shaolin Zhu 《Angewandte Chemie (International ed. in English)》2023,62(28):e202304713
An attractive approach to selective functionalization of remote C−H bonds is a metal/hydride shift/cross-coupling reaction sequence. Complimentary to the heavily exploited 1,2-nickel/hydride shift along an sp3 chain, a chain-walking process, the 1,4-nickel/hydride shift along an sp2 chain is more complex. Here we report an unprecedented aryl-to-vinyl 1,4-nickel/hydride shift reaction, in which the migratory alkenylnickel species generated in situ is selectively trapped by one of various coupling partners, such as isocyanates, alkyl bromides, aryl chlorides or alkynyl bromides, allowing regio- and stereoselective access to trisubstituted alkenes. In contrast to the well-reported ipso-aryl coupling reactions, this strategy provides remote alkenyl C−H functionalized products with good yield and with excellent chemo-, regio- and E/Z-selectivity. 相似文献
243.
NiH-catalyzed multicomponent reductive hydrofunctionalization of alkenes is an attractive but poorly explored approach to rapidly increasing molecular complexity. In this process, the selective generation of the desired product can be challenging. Herein, we report that a highly chemo-, regio- and enantioselective reductive hydrocarbonylation of alkenes has been achieved using a chloroformate ester as a source of CO. A wide range of structurally diverse α-hydroxy ketones, privileged structural elements in bioactive molecules and useful building blocks, were obtained from such reactions with high enantiomeric purity. 相似文献
244.
Jef R. Vanhoof Pieter J. De Smedt Jan Derhaeg Rob Ameloot Dirk E. De Vos 《Angewandte Chemie (International ed. in English)》2023,62(49):e202311539
1,2-Dioxygenation of alkenes leads to a structural motif ubiquitous in organic synthons, natural products and active pharmaceutical ingredients. Straightforward and green synthesis protocols starting from abundant raw materials are required for facile and sustainable access to these crucial moieties. Especially industrially abundant aliphatic alkenes have proven to be arduous substrates in sustainable 1,2-dioxygenation methods. Here, we report a highly efficient electrocatalytic diacetoxylation of alkenes under ambient conditions using a simple iodobenzene mediator and acetic acid as both the solvent and an atom-efficient reactant. This transition metal-free method is applicable to a wide range of alkenes, even challenging feedstock alkenes such as ethylene and propylene, with a broad functional group tolerance and excellent faradaic efficiencies up to 87 %. In addition, this protocol can be extrapolated to alkenoic acids, resulting in cyclization of the starting materials to valuable lactone derivatives. With aromatic alkenes, a competing mechanism of direct anodic oxidation exists which enables reaction under catalyst-free conditions. The synthetic method is extensively investigated with cyclic voltammetry. 相似文献
245.
Benedikt Wolff Dr. Zheng-Wang Qu Prof. Dr. Stefan Grimme Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2023,62(29):e202305295
An enantioselective reduction of simple carbenium ions with cyclohexadienes containing a hydridic C−H bond at an asymmetrically substituted carbon atom is disclosed. The net reaction is a transfer hydrogenation of alkenes (styrenes) only employing chiral cyclohexadienes as dihydrogen surrogates. The trityl cation is used to initiate a Brønsted acid-promoted process, in which a delicate intermolecular capture of a carbenium-ion intermediate by the aforementioned chiral hydride source is enantioselectivity determining. Exclusively non-covalent interactions are rendering one of the transition states energetically more favored, giving the reduction products in good enantiomeric ratios. The computed reaction mechanism supports the present findings as well as previous results obtained from studies on other transfer-hydrogenation methods involving the cyclohexadiene platform. 相似文献
246.
Péter Angyal András M. Kotschy Ádám Dudás Dr. Szilárd Varga Dr. Tibor Soós 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202214096
A widely applicable, practical, and scalable synthetic method for efficient ene-type double oxidation of alkenes is reported via a two-step alkenyl thianthrenium umpolung/Kornblum-Ganem oxidation strategy. This chemo- and stereoselective procedure allows easy access to various α,β-unsaturated carbonyls that may be otherwise difficult or cumbersome to synthesize by conventional methods. For α-olefins, this metal-free transformation can be tuned according to synthetic needs to produce either the elusive (Z)-unsaturated aldehydes or their (E) counterparts. Moreover, this strategy has enabled streamlined synthesis of distinct butadienyl pheromones and kairomones. 相似文献