Alkynyl Moiety for Triggering 1,2‐Metallate Shifts: Enantiospecific sp²–sp³ Coupling of Boronic Esters with p‐Arylacetylenes

Abstract

The enantiospecific coupling of secondary and tertiary boronic esters to aromatics has been investigated. Using p-lithiated phenylacetylenes and ar ange of boronic esters coupling has been achieved by the addition of Nbromosuccinimide (NBS). The alkyne functionality of the intermediate boronate complex reacts with NBS triggering the 1,2-migration of the group on boron to carbon giving ad earomatized bromoallene intermediate.A tt his point elimination and rearomatization occurs with neopentyl boronic esters,g iving the coupled products.H owever,u sing pinacol boronic esters,t he boron moiety migrates to the adjacent carbon resulting in formation of ortho boronincorporated coupled products.T he synthetic utility of the boron incorporated product has been demonstrated by orthogonal transformation of both the alkyne and boronic ester functionalities.