Vinylogous aldol reaction of heterocyclic silyloxy dienes. Application in synthesis

A versatile, readily accessible triad of 2-enoxy silane synthons derived fr om furan, pyrrole, and thiophene is presented. These heterocycles, in react ing with carbonyl and carbonyl-related accepters, act as vinylogous nucleop hile modules, giving rise to diverse, functionality-rich, gamma -substitute d alpha,beta -unsaturated carbonyl constructs. These, in turn, are invaluab le platforms onto which further functional elements and chirality may be in troduced. 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 appr oach.