Substrate-controlled switchable asymmetric annulations to access polyheterocyclic skeletons

Abstract

An unexpected domino process from Morita–Baylis–Hillman carbonates of isatins and acrylate and α-cyano-α,β-unsaturated ketones to deliver highly enantioenriched tetrahydrofuro[2′,3′:4,5]pyrano[2,3-b]indoles catalysed by cinchona-derived tertiary amines, involving α-regioselective cyclopropanation, ring-opening, and ring-closure cascade reactions, was disclosed. In contrast, spirooxindoles incorporating a cyclopentene motif were produced through [3+2] annulations by employing Morita–Baylis–Hillman carbonates from isatins and acrylonitrile under similar catalytic conditions. Density functional theory calculations were conducted to elucidate the novel domino process and the switchable annulation reactions.