An asymmetric route to novel chiral cyclohexenones with spiro-connected cyclopentenes. Further utility of chiral bicyclic thiolactams and the [3,3] thio-Claisen products

Sequential allylation of chiral, nonracemic thiolactam 8 affords clean thio -Claisen [3,3] products ii. The stereoselectivity of the rearrangement was found to be on the order of 10-11:1, with the exo-endo products responsible for the mixture. Addition of hydride or methyllithium-cerium chloride gave clean addition to the thiolactam in the form of its iminium salts 12. Hydr olysis gave 4,4-dialkylcyclohexenones 16, which were cyclized to the cyclop entene derivatives 16 using Grubbs' catalyst.