Asymmetric Synthesis of Tropanes by Rhodium-Catalyzed [4 + 3] Cycloaddition

Abstract

Rhodium-catalyzed [4 + 3] cycloaddition between methyl 2-(siloxy)vinyldiazoacetate and pyrroles results in the enantioselective synthesis of highly functionalized 8-azabicyclo[3.2.1]octa-2,6-dienes (tropanes). The reaction proceeds via a rhodium−carbenoid intermediate and involves a tandem cyclopropanation/Cope rearrangement mechanism. The optimum chiral dirhodium catalyst for this transformation is the adamantyl glycine-derived complex, Rh 2 ( S -PTAD) 4 .