Application of an Intramolecular Stetter Reaction to Access trans,syn,trans-Fused Pyrans

The use of a commercially available thiazolium salt facilitated an intramolecular Stetter reaction between an aliphatic aldehyde and an acrylate unit, which delivered a trans,syn-fused bicyclic pyranone in high yield as a single diastereomer. The pyranone was used to synthesize a trans,syn,trans-fused polycyclic ether array and was ring expanded to give the corresponding oxepanone.