A Recyclable Organocascade Reaction System: Stereoselective Precipitation of Optically Active cis- Delta d-Lactols with Quaternary Stereocenters during the Michael-Hemiacetalization Reaction

A cascade Michael-hemiacetalization reaction between Delta *b-substituted Delta *b-nitroethanols and , Delta *b-unsaturated aldehydes is described, which provides a convenient and efficient synthesis for cis- Delta *d-lactols with quaternary stereocenters in moderate yields with excellent enantioselectivity. Based on the selective precipitation of cis- Delta *d-lactols, which were isolated by filtration, the catalytic system in the filtrate can be reused directly and recycled for eight times without any obvious deterioration in enantioselectivity.