Organocatalytic asymmetric synthesis of functionalized 3,4-dihydropyran derivatives

A study was conducted to demonstrate the organocatalytic enantioselective addition of 1,3-cycloalkanediones with α,β-unsaturated aldehydes to produce 3,4-dihydropyrans with enantioselectivies and diastereoselectivities for aromatic and aliphatic aldehydes. The study used a vial with magnetic stirring bar charged with catalyst, PhCO2H, and CH2Cl2. The study found that α,β-unsaturated aldehydes is transformed by catalyst and nucleophile into the Michael adduct. The study also observed that the stereo-center formed in the catalytic cycle is controlled by a reface attack of the nucleophile on the planar iminium ion. The study also performed a single-crystal X-ray analysis of unprotected compound to determine the absolute configuration of the stereoisomer.