Lewis Acid Catalyzed Cyclopropane Ring-Opening-Cyclization Cascade Using Thioureas as a N,N-bisnucleophile: Synthesis of Bicyclic Furo-, Pyrano-, and Pyrrololactams via a Formal [4+1]-Addition.

ABSTRACT

Fused bicyclic cyclopropanes were converted by Lewis acid-catalysis with thioureas to furo-, pyrano, and pyrrolo-lactams with yields of up to 99% and high diastere-oselectivity. The formation of the title compounds, repre-senting a formal [4+1]-cycloaddition to a donor-acceptor substituted cyclopropane, follows a cascade reaction involving SN1-type ring-opening addition and cyclization. Thiourea, being a cost-effective and odorless reagent, acts as an N,N-bis-nucleophile to generate bicyclic compounds containing an N­substituted γ-lactam moiety.