Selective multifunctionalization ofN-heterocyclic carbene boranesviathe intermediacy of boron-centered radicals

Abstract

Selective difunctionalization of N-heterocyclic carbene (NHC) boranes with alkenes has been achieved via the decatungstate and thiol synergistic catalysis. The catalytic system also allows the stepwise trifunctionalization, leading to complex...

Switchable Access to Mono‐ and Di‐Alkylated Boranes via Visible‐Light‐Induced Hydroboration of Alkenes with NHC‐Borane

“…Very recently, Quan's group achieved the mono‐ and di‐functionalization of NHC boranes with alkenes via decatungstate and thiol synergistic catalysis (Scheme 1b). Although this method exhibited advance in its selectivity, the yields for the mono‐substituted boranes were not ideal and the use of a metal photocatalyst as the hydrogen‐abstracting reagent would lead to metal residuals in the reaction system [13] . Therefore, developing a greener method for the synthesis multi‐functionalized boranes is desirable.…”

“…Although this method exhibited advance in its selectivity, the yields for the mono-substituted boranes were not ideal and the use of a metal photocatalyst as the hydrogen-abstracting reagent would lead to metal residuals in the reaction system. [13] Therefore, developing a greener method for the synthesis multi-functionalized boranes is desirable. Herein, we reported a visible-light-induced1,2-diphenyldisulfane-catalyzed hydroboration of alkenes with NHC-boranes.…”

Recent advances of decatungstate photocatalyst in HAT process

“…Quan et al 66 have achieved the selective difunctionalization of N-heterocyclic carbene (NHC) boranes with alkenes via the use of decatungstate and thiol synergistic catalysis. Stepwise trifunctionalization is another attribute of the catalytic system which makes it possible to synthesize complex NHC boranes with three distinct functional groups which are difficult to synthesize by other methods.…”

Radical hydroboration for the synthesis of organoboron compounds

“…The Quan group recently reported the mono-, di-and trihydroboration reactions of NHC-borane 2 on one, two or three molecules of aryl-substituted alkenes 37 for the synthesis of multifunctionalised organoboranes 38 (Scheme 11). 42 Selective synthesis of mono-, di-and trisubstituted alkylboranes was achieved by modulating the ratios of alkene and NHC-borane. Utilising the dual catalysis of tetrabutylammonium decatungstate (TBADT) and thiol under light irradiation (390 nm), the excited TBADT abstracted a hydrogen atom from NHC-borane to deliver [W 10 O 32 ] 5À H + and NHC-boryl radicals.…”