Catalytic Asymmetric Hydrogenation of 2,3,5-Trisubstituted Pyrroles
2007; American Chemical Society; Volume: 130; Issue: 3 Linguagem: Inglês
10.1021/ja7102422
ISSN1943-2984
AutoresRyoichi Kuwano, Manabu Kashiwabara, Masato Ohsumi, Hiroki Kusano,
Tópico(s)Catalysis for Biomass Conversion
ResumoCatalytic asymmetric hydrogenation of N-Boc-protected pyrroles proceeded with high enantioselectivity by using a ruthenium catalyst modified with a trans-chelating chiral bisphosphine PhTRAP. The ruthenium catalyst prepared from Ru(η3-methallyl)2(cod) and (S,S)-(R,R)-PhTRAP in the presence of triethylamine was the most enantioselective for the asymmetric hydrogenation of methyl pyrrole-2-carboxylate, giving the desired (S)-proline derivative with 79% ee in 92% yield. Moreover, 2,3,5-trisubstituted pyrroles bearing a large substituent at the 5-position were hydrogenated with 93−99.7% ee. The asymmetric reduction of 4,5-dimethylpyrrole-2-carboxylate gave only all-cis isomer and created three chiral centers with high degree of stereocontrol in a single process. This is the first highly enantioselective reduction of pyrroles.
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