The development of the first catalytic asymmetric Pauson-Khand type cyclization of enynes is described. The active catalyst, (S,S)-(EBTHI)Ti(CO)(2) (1), is generated in situ from (S,S)-(EBTHI)TiMe2 (2). A variety of 1,6-enynes can be converted to the corresponding cyclopentenones in high yield (70-94%) with excellent ee's (87-96%). Limitations of the catalyst with respect to substrate structure are discussed. The absolute configurations of several of the enone products have been ascertained, and these assignments represent a reversal with respect to an assignment in the initial report. A rationale for the sense and levels of enantioselectivity for this catalyst is proposed.
“An Intramolecular Titanium-Catalyzed Asymmetric Pauson−Khand Type Reaction”, J. Am. Chem. Soc., 1999, 121(30), 7026-7033.