Protected syn -Aldol Compounds from Direct, Catalytic, and Enantioselective Reactions of N -Acyl-1,3-oxazinane-2-thiones with Aromatic Acetals.

A direct and asymmetric syn -aldol reaction of N -acyl-1,3-oxazinane-2-thiones with dialkyl acetals from aromatic acetals in the presence of 2-5 mol % [DTBM-SEGPHOS]NiCl 2 , TMSOTf, and lutidine has been developed. It has been established that the oxazinanethione heterocycle, used for the first time as a scaffold in asymmetric carbon-carbon bond-forming reactions, can be smoothly removed to give access to a variety of enantiomerically pure compounds with high synthetic value.