Unprecedented formation of a 14-membered dihydropyran macrocycle via sequential olefin cross metathesis-intramolecular hetero Diels–Alder reaction

Formation of a 2,3-dihydro-4H-pyran containing 14-membered macrocycle by sequential olefin cross metathesis and a highly regiospecific hetero Diels–Alder reaction was observed in the reaction of a hydroxydienone derived from tartaric acid with Grubbsʹ second generation catalyst. It was found that the free alcohol in the hydroxyenone led to the macrocycle formation, while protection of the hydroxy group formed the ring closing metathesis product.