Vinylogous Mukaiyama–Michael Reactions between 2‐Silyloxyfurans and Cyclic Enones or Unsaturated Oxo Esters

Abstract

AbstractLewis acid catalyzed vinylogous Mukaiyama–Michael (VMM) reactions between 2‐(trialkylsilyloxy)furans 1 and α,β‐unsaturated cyclic enones 2 or oxo esters 4 have been investigated. Both substrates proved to be useful Michael acceptors in the title reaction, giving the butenolides 3 and 5 in good yields. A comparative study between the α,β‐unsaturated cyclic enones 2 and the oxo esters 4 as Michael acceptors showed better diasterecontrol with the latter class of compounds. In both series, crystal structures of the major isomers revealed anti relationships of newly formed stereogenic centers. From these data, two types of transition states could be proposed: an open TS with antiperiplanar orientation or a Diels–Alder‐like TS with exo approach.