3,3′-Br2-BINOL-Zn complex:: A highly efficient catalyst for the enantioselective hetero-Diels-Alder reaction

graphic A BINOLate-zinc complex prepared in situ from Et2Zn and 3,3'-dibromo-1,1'-bi-2-naphthol (3,3'-Br-2-BINOL) was found to be a highly efficient catalyst for the enantioselective hetero-Diels-Alder reaction of Danishefsky's diene and aldehydes to give 2-substituted 2,3-dihydro-4H-pyran4-one in up to quantitative yield and 98% ee.