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
摘要:
The regioselectivity of the oxidative coupling of the enolate anion of (1R)-(+)-verbenone (97% ee) has been examined with CuCl2 and FeCl3 as catalysts. With Cu(II), selective formation of the gamma,gamma-product is observed. An increase in temperature above -40 degrees 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 alpha,gamma-product, which has proven amenable to direct conversion to that C-2-symmetric ''dimer'' having the carbonyl groups in a para relationship. The second C-2 ''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 6 pi electrocyclization with concurrent aromatization, and PCC oxidation. Some potential applications of this conformationally rigid benzenoid system to enantioselective synthesis are outlined.
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
摘要:
The regioselectivity of the oxidative coupling of the enolate anion of (1R)-(+)-verbenone (97% ee) has been examined with CuCl2 and FeCl3 as catalysts. With Cu(II), selective formation of the gamma,gamma-product is observed. An increase in temperature above -40 degrees 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 alpha,gamma-product, which has proven amenable to direct conversion to that C-2-symmetric ''dimer'' having the carbonyl groups in a para relationship. The second C-2 ''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 6 pi electrocyclization with concurrent aromatization, and PCC oxidation. Some potential applications of this conformationally rigid benzenoid system to enantioselective synthesis are outlined.
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
作者:Leo A. Paquette、Eugene I. Bzowej、Bruce M. Branan、Kenetha J. Stanton
DOI:10.1021/jo00127a037
日期:1995.11
The regioselectivity of the oxidative coupling of the enolate anion of (1R)-(+)-verbenone (97% ee) has been examined with CuCl2 and FeCl3 as catalysts. With Cu(II), selective formation of the gamma,gamma-product is observed. An increase in temperature above -40 degrees 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 alpha,gamma-product, which has proven amenable to direct conversion to that C-2-symmetric ''dimer'' having the carbonyl groups in a para relationship. The second C-2 ''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 6 pi electrocyclization with concurrent aromatization, and PCC oxidation. Some potential applications of this conformationally rigid benzenoid system to enantioselective synthesis are outlined.