Synthesis Of 5,6-Dihydro-Alpha-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-alpha-pyrone. The RCM reaction employing Grubbs' second generation catalyst afforded a 96% yield at 80 degrees C in toluene. The HWE reaction under modified Masamune-Roush conditions delivered only 23% yield due to a competitive elimination reaction.