Vinylogous aldol reaction of heterocyclic silyloxy dienes. Application in synthesis

A versatile, readily accessible triad of 2-enoxy silane synthons derived from furan,
pyrrole, and thiophene is presented. These heterocycles, in reacting with carbonyl and carbonyl-
related acceptors, act as vinylogous nucleophile modules, giving rise to diverse, functionality-
rich, γ-substituted α,β-unsaturated carbonyl constructs. These, in turn, are invaluable
platforms onto which further functional elements and chirality may be introduced. A
couple of appealing applications—the variable construction of a repertoire of carbasugars
and a library of annonaceous acetogenin segments—have been chosen to illustrate the viability
of this vinylogous aldol approach.