Asymmetric synthesis of spiro 2-pyrrolidin-5-ones, 2-piperidin-6-ones and 1-isoindolin-3-ones. Part 2: N-Acyliminium ion cyclisations with an internal alkene nucleophile

Chiral non-racemic bicyclic and tricyclic oxylactams obtained in two steps from N-(2-hydroxy-1(R)-phenylethyl)-succinimide and phthalimide are cyclised diastereoselectively in formic acid to give spiro[cyclohexane-1,2′-pyrrolidin]-5-ones and spiro[cyclohexane-1,1′-isoindolin]-3-ones, respectively.