Synthesis of 5,6-Dihydro-α-Pyrone via Ring-Closing Metathesis and Intramolecular Horner–Wadsworth–Emmons Reactions

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.