A stereocontrolled approach to the cis-decalin framework of clerodane diterpenes and biologically active quinone sesquiterpenes is reported. Starting from an inexpensive optically pure tetrahydroindanone, Birch reductive alkylation builds two new contiguous chiral centers-one of which is quaternary and all-carbon-substituted. Also featured is a highly regioselective diazoalkane-carbonyl homologation reaction to prepare the 6,6-bicyclic skeleton. Therein, the utility of Sc(OTf)₃ as a mild catalyst for formal 1C insertion in complex settings is demonstrated.
Keywords: (trimethylsilyl)diazomethane; 5-epi-ilimaquinone; 5-epi-isospongiaquinone; catalytic ring expansion; cis-decalin; hexahydroindanones; homologation; quaternary carbon synthesis; quinone natural products; scandium triflate.