Housane radical cation chemistry and its application to natural product synthesis using indirect electrolysis

Oxidation of housanes leads to cleavage of a strained sigma bond and is followed by a Wagner-Meerwein rearrangement to transform the framework to a cyclopentene, once a back electron transfer occurs. The rearrangement of housane cation radicals is initiated by both a chemical electron transfer pathway and an electrochemically mediated pathway. Indirect electrolysis using tris(4-bromophenyl)amine as an electrocatalyst is preferred as the oxidation method. Application of this transformation en route to the synthesis of the (n.3.0) framework of natural products requires the assembly of functionalized housanes that will lead to regioselective rearrangement. The mechanistic investigation of electrochemically mediated rearrangement reactions of housane cation radicals, the characterization of the intermediates by quantum calculations, and electron transfer dynamics are described. Using the electrocatalytic transformation as a key step, daucene, a well-known member of the carotane class of sesquiterpenes, was synthesized in a concise manner from a functionalized spiro(4.5)decane system.