Catalytic, Asymmetric Dearomative Synthesis of Complex Cyclohexanes via a Highly Regio- and Stereoselective Arene Cyclopropanation Using α-Cyanodiazoacetates.

Arene cyclopropanation offers a direct route to higher-order, non-aromatic carbocycles; however, the inherent issue of dictating site selectivity has cumbered the development of novel intermolecular reactions that directly engage the arene pool. This paper describes a highly regio- and stereoselective, Rh2[(S)-PTTL]4-catalyzed arene cyclopropanation using α-cyanodiazoacetates to afford stable norcaradienes bearing three stereogenic centers, one of which is an all-carbon quaternary center. The enantioenriched norcaradienes served as tunable templates for further transformation into stereochemically dense, fused and bicyclic carbocycles containing transmutable functionality.

Kinetic Separation and Asymmetric Reactions of Norcaradiene Cycloadducts: Facilitated Access via H2O-Accelerated Cycloaddition.

We exploit the Buchner reaction to access 1,2-disubstituted cyclohexadiene synthons (norcaradienes), which participate in H2O-accelerated cycloaddition with dieneophiles to provide cyclopropyl-fused [2.2.2]-bicyclooctene derivatives in good yields. Regioisomeric mixtures can be kinetically separated by exploiting different reaction rates in Diels-Alder reactions. Meso-Diels-Alder products may be enantioselectively desymmetrized, providing highly substituted cyclohexanes with up to seven contiguous stereocenters.

Lewis acid catalyzed (3 + 2)-annulations of donor-acceptor cyclopropanes and ynamides.

The Sc(OTf)3-catalyzed (3 + 2)-annulation of donor-acceptor cyclopropanes and ynamides is described, providing the corresponding cyclopentene sulfonamides in good to excellent yield. Deprotection and hydrolysis of the resulting ensulfonamides delivers 2,3-substituted cyclopentanones with high diastereoselectivity.