A VERSATILE APPROACH TO CYCLIC ETHERS - SYNTHESIS OF DISUBSTITUTED OXEPANES AND OXOCANES

A synthetic sequence for the preparation of alpha,alpha'-disubstituted cyclic ethers of various ring sizes and either relative stereochemist ry (cis or trans) is presented. It is based on the hetero Diels Alder reaction of a monoactivated diene and an aldehyde, yielding a silyleno l pyrone which is transformed into a linear ether. This ether is cycli zed by an intramolecular nucleophilic substitution reaction to the des ired cyclic ethers. The viability of this route is demonstrated by the preparation of two examples, an oxocane and an oxolane.