Synthesis of 5,6-dihydro-α-pyrone via ring-closing metathesis and intramolecular Horner-Wadsworth-Emmons reactions

Abstract

Ring-closing metathesis (RCM) and intramolecular Horner-Wadsworth-Emmons (HWE) reactions were assessed for synthesis of cis-5-methyl-6-phenylethyl-5,6-dihydro-α-pyrone. The RCM reaction employing Grubbs' second generation catalyst afforded a 96% yield at 80 °C in toluene. The HWE reaction under modified Masamune-Roush conditions delivered only 23% yield due to a competitive elimination reaction.