Asymmetric Pauson-Khand cyclizations of 1-sulfinylenynes

The use of sulfoxides as chiral auxiliaries in intramolecular Pauson-Khand (PK) reactions is described. In particular, the tert-butylsulfinyl group ac ts as a very efficient chiral auxiliary in intramolecular PK reactions of 1 -sulfinyl-1,6-enynes. As the starting enynes are readily available in optic ally pure form and the final desulfinylation step is high yielding, this pr ocedure constitutes an efficient alternative to the synthesis of enantiomer ically pure bicyclo [3.3.0] oct-1-en-3-ones.