Synthesis 2008(15): 2467-2475  
DOI: 10.1055/s-2008-1078596
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Rhodium-Catalyzed Ring-Opening Reactions of N-Boc-azabenzonor­bornadiene with Chiral Amine Nucleophiles Derived from Amino Acids

Yong-Hwan Cho, Nai-Wen Tseng, Hisanori Senboku, Mark Lautens*
Davenport Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
Fax: +1(416)9468185; e-Mail: mlautens@chem.utoronto.ca;
Further Information

Publication History

Received 17 December 2007
Publication Date:
17 July 2008 (online)

Abstract

The rhodium-catalyzed ring-opening of azabenzonorbornadienes with chiral amino nucleophiles derived from amino ­acids such as (S)-proline and (R)-phenylglycine is reported. The desired products were obtained as a mixture of diastereomers, which could be easily separated in high yield. Enantiomerically pure ring-fused nitrogen heterocycles and 1,2-diamines were also obtained by further transformation of the ring-opened products.

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For the preparation of 15.0 g of the ring-opened product 3 from 8.0 g of the starting material 1, 2.7 g of (S,S′)-(R,R′)-C2-Ferriphos would be required to ensure high enantio-selectivity in the catalytic ring-opening reaction.

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To a solution of (S)-proline methyl ester hydrochloride in MeOH (0.5-1.0 M) was added 1.0 equiv of NaI solution in MeOH dropwise at r.t. The mixture was stirred at r.t. for an additional 1 h. After filtration to remove the NaCl, the solution was concentrated and the residue was dissolved in CH2Cl2 and the insoluble precipitate was filtered off again. After removal of all volatile substrates, the corresponding iodide (quantitative yield) was obtained.

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Crystal data for 4: C15H16N2O, M = 240.30, orthorhombic, space group P212121, a = 7.3032 (2) Å, b = 12.2966 (6) Å, c = 13.5897 (6) Å, α = 90˚, β = 90˚, γ = 90˚, V = 1220.42 (9) ų, Z = 4, Dc = 1.308 Mg/m³, m(Cu-Ka) = 0.083 mm, F(000) = 512 reflections were collected, of which 9593 were considered to be observed with I > (I). The structure was determined by direct methods using the SHELXTLTM suite of programs. Hydrogen atoms were placed in calculated positions. Full-matrix least squares refinement based on F ² with anisotropic thermal parameters for the non-hydrogen atoms led to agreement factors R1 = 0.0360 and wR2 = 0.0887. Crystallographic data for the structure 4 reported in this paper have been deposited at the Cambridge Crystallographic Data Centre as supplementary material No. CCDC-639749. Copies of the data may be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44 1223 33603 or e-mail: deposit@ccdc.cam.ac.uk).

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Chiral stationary phase columns (Chiralcel AS for 3b and AD for 3b′).

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Crystal data for 3b: C21H30N2O3, M = 358.47, monoclinic, space group P21, a = 9.4130 (4) Å, b = 19.6173 (12) Å, c = 11.8127 (7) Å, α = 90˚, β = 110.225 (3)˚, γ = 90˚, V = 2046.81 (19) ų, Z = 4, Dc = 1.163 Mg/m³, m(Cu-Ka) = 0.078 mm, F(000) = 776 reflections were collected, of which 111510 were considered to be observed with I > (I). Full-matrix least squares refinement based on F ² with anisotropic thermal parameters for the nonhydrogen atoms led to agreement factors R1 = 0.0491 and wR2 = 0.1115. Crystallographic data for the structure 3b reported in this paper have been deposited at the Cambridge Crystallographic Data Centre as supplementary material No. CCDC-639748. Copies of the data may be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44 1223 33603 or e-mail: deposit@ccdc.cam.ac.uk).

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Chiral stationary phase columns (Chiralcel AD for 9).