Synthesis of Cyclohexanes via [3+3] Hexannulation of Cyclopropanes and 2-Chloromethyl Allylsilanes

Lewis acid-assisted ring-opening/allylation of 1,1-cyclopropane diesters, followed by base-mediated ring closure, generates functionalized exo-methylenecyclohexanes in good yield. This two-step procedure is highlighted by expedient preparation of a pyrido[1,2-a]indole skeleton common to the chippiine class of Iboga indole alkaloids.