Lewis Acid Catalyzed Cyclopropane Ring-Opening-Cyclization Cascade Using Thioureas as a N,N-bisnucleophile: Synthesis
Andreas Ratzenböck1, Manuel Kobras1, Anna Rustler1
1University of Regensburg, Institute of Organic Chemistry, Universitätsstr. 31, 93053, Regensburg, Germany.
Abstract:
Fused bicyclic cyclopropanes were converted by Lewis acid-catalysis with thioureas to furo-, pyrano, and pyrrololactams with yields of up to 99 % and high diastereoselectivity. The formation of the title compounds, representing 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 N-substituted γ-lactam moiety.
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