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B( C 6 F 5 ) 3 ‐Catalyzed Hydroboration of Alkenes with N ‐Heterocyclic Carbene Boranes via B—H Bond Activation
Author(s) -
Wang Qiaotian,
Meng Wei,
Feng Xiangqing,
Du Haifeng
Publication year - 2021
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.202000489
Subject(s) - hydroboration , chemistry , boranes , carbene , borane , electrophile , alkene , hydride , carbocation , medicinal chemistry , stereochemistry , adduct , catalysis , organic chemistry , boron , hydrogen
Main observation and conclusion In this work, a novel mode for the activation of N ‐heterocyclic carbene boranes (NHC‐boranes) was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C 6 F 5 ) 3 in an frustrated Lewis pairs manner. A broad range of alkenes including stilbenes, β‐methylstyrenes, styrenes, and alkyl‐alkenes were suitable substrates for the B(C 6 F 5 ) 3 ‐catalyzed hydroboration to furnish the desired products in good to high yields. Significantly, excellent regioselectivities were obtained in some cases. Mechanistic studies indicate that the B—H bond cleavage is likely involved in the rate‐determining step. In addition, an electrophilic addition of NHC‐borenium cation to alkenes and the subsequent formation of carbocation are also postulated. The current work provides a promising method for the activation of stable borane adducts, which might lead to some interesting transformations in the future.