Compound 5, a product whose formation must involve a rearrangement, is produced in the reaction of carboethoxycarbene with allylic alcohol 1. The most reasonable pathway for formation of 5 is reaction of the carbene with 1 to form an ylide which undergoes subsequent rearrangement. Our results thus confirm the formation of oxonium ylides in reactions of carboethoxycarbene with alcohols.

Acknowledgement We thank the donors of the Petroleum Research fund, administered by the American Chemical Society, and the Illinois State University Research Grant Program for support of this research.