Chiral Lewis base promoted trichlorosilane reduction of ketimines. An enantioselective organocatalytic synthesis of chiral amines |
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Authors: | Stefania Guizzetti Franco Cozzi Rita Annunziata |
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Institution: | Dipartimento di Chimica Organica e Industriale, Universita' degli Studi di Milano, Via Golgi 19-20133 Milano, Italy |
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Abstract: | The reduction of the carbon-nitrogen double bond is an important transformation. Here we report our studies on a family of chiral organic catalysts able to promote the stereoselective reduction of ketimines with trichlorosilane. The very cheap, metal-free catalysts were easily prepared in one step from commercially available products, namely a chiral aminoalcohol and picolinic acid derivatives. The catalyst structure was extensively modified in a study that allowed to identify an extremely active species, able to promote the reduction on a large variety of substrates with high efficiency (up to 95% ee). A three component methodology has been also developed, where the enantiomerically enriched amine was isolated after performing the reaction by mixing a ketone and an amine in the presence of trichlorosilane and the catalyst. Its synthetic potentiality was demonstrated by employing the present metal-free catalytic procedure in the preparation of (S)-metolachlor, a potent and widely used herbicide. |
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Keywords: | Pyridine N-oxides Organocatalysis Monoterpenes Allyltrichlorosilane Epoxide opening |
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