Sustainable Pd(OAc)₂/Hydroquinone Cocatalyst System for Cis‐Selective Dibenzoyloxylation of 1,3‐Cyclohexadiene

Abstract

The 1,4‐diacyloxylation of 1,3‐cyclohexadiene (CHD) affords valuable stereochemically defined scaffolds for natural product and pharmaceutical synthesis. Existing cis‐selective diacyloxylation protocols require superstoichiometric quantities of benzoquinone (BQ) or MnO2, which limit process sustainability and large‐scale application. In this report, reaction development and mechanistic studies are described that overcome these limitations by pairing catalytic BQ with tert‐butyl hydroperoxide as the stoichiometric oxidant. Catalytic quantities of bromide enable a switch from trans to cis diastereoselectivity. A catalyst with a 1:2 Pd:Br ratio supports high cis selectivity while retaining good rate and product yield. Further studies enable replacement of BQ with hydroquinone (HQ) as a source of cocatalyst, avoiding the handling of volatile and toxic BQ in large‐scale applications.