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

A cascade Michael–hemiacetalization reaction between β‐substituted β‐nitroethanols and α,β‐unsaturated aldehydes is described, which provides a convenient and efficient synthesis for cis‐δ‐lactols with quaternary stereocenters in moderate yields with excellent enantioselectivity. Based on the selective precipitation of cis‐δ‐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.