Nitrous Oxide-Promoted Pauson-Khand Cycloadditions.

A Pauson-Khand cycladdition of alkynes, alkenes, and carbon monoxide, promoted by cobalt carbonyl and nitrous oxide to furnish cyclopentenones is described. Preliminary mechanistic experiments suggest that nitrous oxide functions in a similar manner to the -oxide promoters typically employed in Pauson-Khand reactions. Only dinitrogen and carbon dioxide are produced as a consequence of the activation mechanism, thus avoiding high molecular weight reagents and the build up of basic byproducts.