Metal-free tandem rearrangement/lactonization: Access to 3,3-disubstituted benzofuran-2-(3H)-ones

Abstract

A novel metal‐free synthesis of 3,3‐disubstituted benzofuran‐2(3H)‐ones from the reaction between α‐aryl‐α‐diazoacetates and triarylboranes is presented. Initially, triarylboranes were successfully investigated in α‐arylations of α‐diazoacetates, however in the presence of an ortho‐heteroatom substituent the boron enolate intermediate undergoes an intramolecular rearrangement to form a quaternary center. The intermediate cyclizes affording valuable 3,3‐disubstituted benzofuranones in good yield