Highly Stereoselective 6π Electrocyclization of Bridged Bicyclic 1,3,5-Trienes
摘要:
Conjugated 1,3,5-hexatrienes encased in bridged bicyclic skeletons are prepared by cross-coupling followed by half-reduction of the resulting dienynes. The trienes undergo 6 pi electrocyclization at an ambient or elevated temperature to furnish complex, polycyclic cyclohexadienes. In all cases, complete selectivity in favor of cyclization from the exo face of the bridged bicyclic system was seen, in contrast to the corresponding 4 pi Nazarov cyclizations.