摘要:
Diels-Alder reactions of 2-methoxy-6-methyl- and 2-methoxy-5-methyl-1,4-benzoquinones with various substituted dienes are promoted by a chiral complex prepared from TiCl4, Ti((OPr)-Pr-i)(4), and (2R,3R)-2,3-O-(1- phenylethylidene)-1,1,4,4-tetraphenyl-1,2,3,4-butanetetrol. The products from several dienes are formed in moderate to good ee and are obtained enantiomerically pure after simple recrystallization steps.