Molecular cascades. 1. Tandem cyclopropyl iminium ion rearrangement- [4+2] cycloaddition reactions

Article abstract of DOI:10.1016/S0040-4020(97)90402-6

A tandem cyclopropyliminium ion rearrangement-Hofmann elimination affords rapid access to 3-vinyl Δ²-pyrrolines in some cases bearing an unsaturated tether in good yield. The resulting dienamines subsequently undergo both inter-and intramolecular [4+2] cycloaddition reactions. Good yields were obtained for a number of cases of intramolecular intermolecular cycloaddition reactions affording cycloadducts in good yields with sufficiently reactive dienophiles such as fumarate, acrylate and methacrolein. Evidence suggests a non-concerted pathway for these cycloaddition reactions.