Domino Heck-Diels-Alder reactions of differently substituted cyclopropylallenes

Several substituted cyclopropylallenes were coupled under Heck conditions with aryl iodides and aryl bromides, respectively, and the 1,3,5-hexatrienes resulting with ring-opening of the cyclopropyl group, were captured in situ by a number of reactive dienophiles to yield oligosubstitated cyclohexene derivatives (8-86 %, 33 examples) with diastereomeric ratios ranging from 1.4:1 to 4.9:1. The influences of the number, the nature and the pattern of substituents have been elaborated. The [4+2] cycloaddition most probably proceeds in two steps through a mesomerically well stabilized 1,6-zwitterionic intermediate. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).