A Simple Synthesis of Stable Phosphorus Ylides Derived from 2-Benzoxazolinone and 2-Mercaptobenzoxazole

Abstract

The reaction of triphenylphosphine with dialkyl acetylenedicarboxylates in the presence of a strong SH-acid or NH-acid, such as 2-mercaptobenzoxazole and 2-benzoxazolinone, has been studied. In some cases, stable phosphorus ylides are obtained in excellent yields. The ylide moiety of these compounds is strongly conjugated with the adjacent carbonyl group, and the rotation about the partial double bond in (E) and (Z) geometrical isomers is slow on the NMR time scale at an ambient temperature. Thus, these exist as a mixture of geometrical isomers.

Keywords:

• Acetylenic ester
• dialkyl acetylenedicarboxylates
• NH-acid
• SH-acid
• stable phosphorus ylides
• triphenylphosphine

Acknowledgments

Note from the editor: This article was originally submitted to the publisher on December 9, 2004. For an unknown reason, it was not published at that time. Therefore, this article was resubmitted for publication on June 6, 2006.