The regioselectivity of the oxidative coupling of the enolate anion of (lR)-(+)-verbenone (97% ee) has been examined with CuC12 and FeC13 as catalysts. With Cu(II), selective formation of the y,y-product is observed. An increase in temperature above -40 “C results in further oxidation of the intra-ring ethano bridge to a trans double bond, provided that excess LDA has been added. In the presence of Fe(III), the coupling is partially diverted to the a,y-product, which has proven amenable to direct conversion to that Cz-symmetric “dimer” having the carbonyl groups in a para relationship. The second CZ “dimer” featuring meta orientation of the ketone functionalities has been conveniently prepared from the trienedione or its derived diol by thermal or photochemical trans - cis equilibration, thermal 6n electrocyclization with concurrent aromatization, and PCC oxidation. Some potential applications of this conformationally rigid benzenoid system to enantioselective synthesis are outlined.
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