Substituted Isoquinolines by Noyori Transfer Hydrogenation: Enantioselective Synthesis of Chiral Diamines Containing an Aniline Subunit
摘要:
Transfer hydrogenation using the Noyori catalyst 5-Ts is effective for the enantioselective hydrogenation of imines containing fully substituted nitrogen groups (12 or 13). Analogues such as Ile could not be reduced in practical yield, apparently due to product inhibition of the catalyst. Asymmetric transfer hydrogenation of the aniline imine 8a was possible, but required. impractical purity levels for the substrate, and the nitro analogue 7 could not be reduced efficiently. The best results were Obtained with the bromophenyl imine 20, In the case of 20b, the product 21b was formed with 98.7% ee, and the material could be upgraded to >99% ee by crystallization of the hydrochloride salt. Reaction of 21b with NH3 or MeNH2 in the presence of Cu/CuCl gave the chiral anilines 10b or 23b. The latter substance is comparable to the commercially available 1 as a chiral proton donor fog amide enolates and provides access to the hitherto unavailable enantiomeric series.
Substituted Isoquinolines by Noyori Transfer Hydrogenation: Enantioselective Synthesis of Chiral Diamines Containing an Aniline Subunit
作者:E. Vedejs、P. Trapencieris、E. Suna
DOI:10.1021/jo990594s
日期:1999.9.1
Transfer hydrogenation using the Noyori catalyst 5-Ts is effective for the enantioselective hydrogenation of imines containing fully substituted nitrogen groups (12 or 13). Analogues such as Ile could not be reduced in practical yield, apparently due to product inhibition of the catalyst. Asymmetric transfer hydrogenation of the aniline imine 8a was possible, but required. impractical purity levels for the substrate, and the nitro analogue 7 could not be reduced efficiently. The best results were Obtained with the bromophenyl imine 20, In the case of 20b, the product 21b was formed with 98.7% ee, and the material could be upgraded to >99% ee by crystallization of the hydrochloride salt. Reaction of 21b with NH3 or MeNH2 in the presence of Cu/CuCl gave the chiral anilines 10b or 23b. The latter substance is comparable to the commercially available 1 as a chiral proton donor fog amide enolates and provides access to the hitherto unavailable enantiomeric series.
Enantioselective Enolate Protonation with Chiral Anilines: Scope, Structural Requirements, and Mechanistic Implications
作者:E. Vedejs、A. W. Kruger、N. Lee、S. T. Sakata、M. Stec、E. Suna
DOI:10.1021/ja994437m
日期:2000.5.1
substitution at the γ-carbon, γ-protonation can be a competing reaction in the case of the aliphatic substrates 12, 14b, 14d, and 18. The evidence is most consistent with a mechanism that involves proton transfer from 1a to a mixed aggregate consisting of enolate 4a and the lithiated amide 5, but direct proton transfer from 1a to the enolate is not ruled out.