Reductive α-borylation of α,β-unsaturated esters using NHC-BH₃ activated by I₂ as a metal-free route to α-boryl esters.

ABSTRACT: Useful α-boryl esters can be synthesized in one step from α,β-unsaturated esters using just a simple to access NHC-BH₃ (NHC = N-heterocyclic carbene) and catalytic I₂. The scope of this reductive α-borylation methodology is excellent and includes a range of alkyl, aryl substituted and cyclic and acyclic α,β-unsaturated esters. Mechanistic studies involving reductive borylation of a cyclic α,β-unsaturated ester with NHC-BD₃/I₂ indicated that concerted hydroboration of the alkene moiety in the α,β-unsaturated ester proceeds instead of a stepwise process involving initial 1,4-hydroboration; this is in contrast to the recently reported reductive α-silylation. The BH₂(NHC) unit can be transformed into electrophilic BX₂(NHC) moiet

SUBMITTER: Radcliffe JE 

PROVIDER: S-EPMC6354834 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature