Enantionterically pure 2-alkylidenetetrahydrofurans have been prepared by TiCl4 mediated enantiospecific reactions of 1,3-bis-silyl enol ethers with enantiomerically pure epichlorohydrin. In addition, the enzymatic kinetic resolution of 2-alkylidenetetrahydrofurans, using Candida antarctica lipase B (CAL-B), was studied. Enzymatic kinetic resolution of monocyclic 5-vinyl-2-alkylidenetetrahydrofuran with CAL-B afforded the enantiomerically pure ester with 97% ee. For a bicyclic 2-alkylidenetetrahydrofuran, this proceeded with excellent enantioselectivity (E > 100) affording the enantiomerically pure acid with 98% ee. 2-Alkylidenetetrahydrofurans were prepared by [3+2] cyclization reactions of 1,3-dicarbonyl dianions ('free dianions') or 1,3-bis-silyl enol ethers ('masked dianions'). (c) 2006 Published by Elsevier Ltd.
O-Heterocycle Synthesis via Intramolecular C–H Alkoxylation Catalyzed by Iron Acetylacetonate
作者:Yuyang Dong、Alexandra T. Wrobel、Gerard J. Porter、Jessica J. Kim、Jake Z. Essman、Shao-Liang Zheng、Theodore A. Betley
DOI:10.1021/jacs.1c02074
日期:2021.5.19
ethereal), while greater catalyst loadings or elevated reaction temperatures are required to fully convert substrates with benzylic, secondary, and primary C–H bonds. The transformation is highly functional group tolerant and operates under mild reaction conditions to provide rapid access to complex structures such as spiro and fused bi-/tricyclic O-heterocycles from readily available precursors.
New carbon carbon bond forming reactions of cyclic sulfate esters and cyclic sulfamidates
作者:Melanie K Pound、Darren L Davies、Melanie Pilkington、Maria M de Pina Vaz Sousa、John D Wallis
DOI:10.1016/s0040-4039(02)00138-7
日期:2002.3
Carbon–carbon bonding forming reactions of two cyclicsulfate esters and a cyclic sulfamidate are reported, the former with lithium dianions to give substituted tetrahydrofuran derivatives with displacement of sulfate, and the latter undergoes ring-opening monosubstitution reactions with stabilised organolithiums and an organocuprate species.