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Oxidative coupling of the enolate anion of (1R)-(+)-verbenone with Fe(III) and Cu(II) salts: two modes of conjoining this bicyclic ketone across a benzene ring.
Oxidative coupling of the enolate anion of (1R)-(+)-verbenone with Fe(III) and Cu(II) salts: two modes of conjoining this bicyclic ketone across a benzene ring. (1995)
  • E. I. Bzowej
  • B M. Branan
  • L. A. Paquette
  • K. J. Stanton (Frisby), Butler University
Abstract

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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Publication Date
1995
Citation Information
Paquette, L. A., E. I. Bzowej, B. M. Branan, and K. J. Stanton (Frisby). 1995. Oxidative coupling of the enolate anion of (1R)-(+)-verbenone with Fe(III) and Cu(II) salts: two modes of conjoining this bicyclic ketone across a benzene ring. Journal of Organic Chemistry 60: 7277-7283.