Unusual Oxaphosphoranes by Acyl Transfer from o-Acetoxy-o'-diphenylphosphanyltolane.

A striking red color appears upon heating the colorless title compound 1 due to rearrangement to the oxaphosphorane 3. The initiating event in this transformation may involve intramolecular O-to-P acyl transfer to give 2, followed by P-to-C acyl transfer, or an unprecedented concerted addition of acetyl and phosphanyl groups to the triple bond.