ASYMMETRIC-SYNTHESIS OF SPIRO 2-PYRROLIDIN-5-ONES AND 2-PIPERIDIN-6-ONES

Bicyclic lactams 14-17 are isomerised on treatment with alu minium tri chloride in 1,2-dichloroethane to give spiro lactams in high yield and >3:1 diastereoselectivity; from the structures of 19a and 22b determi ned by X-ray crystallography, it follows that the indenes 19 and 21 ar e formed preferentially with retention of configuration at the spiro c arbon atom and the naphthalenes 20 and 22 with inversion.