Synthesis of γ-, δ-, and ε-Lactams by Asymmetric Transfer Hydrogenation of N-(tert-Butylsulfinyl)iminoesters

Highly enantiomerically enriched. gamma- and delta-lactams have been prepared by a simple and very efficient procedure that involves the asymmetric transfer hydrogenation. of N-(tert-butylsulfinyl)iminoesters followed by desulfinylation of the nitrogen atom and spontaneous cyclization to the, desired lactams during the basic workup procedure: Five- and six-membered ring lactams bearing aromatic; heteroaromatic, and aliphatic substituents have been obtained in very high yields and ee's up to >99%. A slight modification of the procedure also allowed the preparation of epsilon-lactams in good yields and very high enantioselectivities. Both enantiomers of the final lactams could be prepared with equal efficiency by changing the absolute configuration of the sulfinyl chiral auxiliary.