Enantioselective Mukaiyama-Michael with 2-enoyl pyridine N-oxides catalyzed by PYBOX-DIPH-Zn(II)-complexes at ambient temperature

A chiral PYBOX-DIPH-Zn(II) catalyzed enantioselective Mukaiyama-Michael reaction of acyclic Ad enol ethers with 2-enoylpyridine N-oxides has been studied in external additive free conditions at ambient temperature. The methodology offers straightforward access to a variety of functionalized chiral 1,5-dicarbonyl compounds, which could easily be elaborated into synthetically viable pyrones via hydrolysis followed by cyclization. A transition state model has been proposed to explain the stereochemical outcome.