Attempts to develop new synthetic entries into the tricyclo[3.3.0.03,7]octane skeleton

Abstract

The attempts to synthesize dimethyl tricyclo[3.3.0.03,7]octane-1,5-dicarboxylate, 1, and some related compounds by formation of a C3—C7 bond from appropriate bicyclo[3.3.0]octane derivatives, either through intramolecular C—H carbene insertion or by ketone-to-cyclopentanol photocyclization, are described. Two alternative syntheses for the key precursor, dimethyl cis-3-oxobicyclo[3.3.0]octane-1,5-dicarboxylate, 2, are included. Also, the formation of dimethyl 3-hydroxytricyclo[3.3.0.03,7]octane-1,5-dicarboxylate, 24, by reduction of dimethyl cis-3,7,dioxobicyclo[3.3.0]octane-1,5-dicarboxylate, 9, under Clemensen-like reaction conditions is reported.