Regioselective intramolecular carbon-hydrogen insertion in copper-catalyzed carbenoid decompositions of cis-1-methyl-3-arylcyclohexane-1-diazomethyl ketones : some synthetic applications

Abstract

Recently, we have developed a new route for the stereo-specific introduction of an angular carboxyl or functionalized methyl groups in a rigid hydrophenanthrene moiety. The key step in this approach is a regioselective intramolecular α-keto carbenoid insertion across the benzylic C-H bond (at C-4a) in CuSO₄-catalyzed thermal decomposition of the diazoketones and to the corresponding tetracyclic ketones and in moderate to good yields. A modified procedure of carbenoid decomposition of these diazoketones, in the presence of Cu₂O under irradiation with tungsten filament lamp, improves the yields of the desired C-H insertion products. Thus, the ketones and have been prepared now in consistently higher yields (53-55%) from the pure diazoketones , m.p. 125-127, and , m.p.