Domino Ring-Closing Metathesis/Intramolecular Transfer of an Alkenyl Subunit: A Direct Formation of Functionalized Butenolides and Pyrones from α,β- and β,γ-Unsaturated Esters

Abstract

A direct synthesis of butenolides and β,γ-unsaturated 8-lactones has been devised by combining a ring-closing metathesis (RCM) with a cross-coupling metathesis (CM) process. The first step of the reaction generates a new carbene group, which is able to functionalize the lateral unsaturated chain during the second coupling reaction. In this way, the transfer of the alkyl group R, initially fixed on the acid chain, avoids the use of an alkene partner introduced in large excess.