Scope of the intramolecular titanocene-catalyzed Pauson-Khand type reaction

A Pauson-Khand type conversion of enynes to bicyclic cyclopentenones employ ing the commercially available precatalyst titanocene dicarbonyl is describ ed. This methodology shows excellent functional group tolerance for a group 4 metallocene-catalyzed process. The scope and limitations of this cycliza tion with respect to 1,6-, 1,7- and 1,8-enynes with a variety of terminal a lkyne substituents, chiral enynes, and enynes containing substituted olefin s are described in detail. A mechanism involving carbonylation of an interm ediate titanacyclopentene has been proposed.