Regioselective transannular cyclization of Deslongchamps's diketone. New entries to polycyclic cage structures: reductive opening of a cyclobutyl ketone with lithium in liquid ammonia and its photochemical rearrangement to a bridged cyclopentyl ether

Abstract

Regioselective bromination of Deslongchamps's diketone (6), followed by base-induced transannular cyclization, leads to tetracyclo[5.3.0.^2,6.0^3,9]decane-5,8-dione (8), together with minor amounts of the isomeric tetracyclo[5.2.1.0^2,6.0^3,8]decane-4,9-dione (9). The chemistry and photochemistry of the monoacetals of (8) have been studied, and structural assignments confirmed either by X-ray diffraction analysis or 2D n.m.r. spectroscopy.