SYNTHESIS OF SEVERAL CHIRAL PHOSPHINAMIDES AND THEIR APPLICATION IN THE ASYMMETRIC BORANE REDUCTION OF PROCHIRAL KETONES

INTRODUCTION The enantioselective reduction of prochiral ketones is an important route for the synthesis of optically active secondary alcohols ' ' ' which were widely used in the preparation of bioact ive substances ' ' .The enantioselevtive borane reduction catalyzed by oxazaborolidine prepared from chiral amino alcohols is one of the most efficient method"' which give excellent ee values and often have wide substrate scope. Other catalysts such as chiral sulfur reagents' ' 5,1 and chiral phosphorous reagents' were also used in this reaction. In recent years, great progress was achieved using chiral phosphorous reagents as catalysts for the reduction of prochiral ketones. In this paper, we reported several chiral phosphinamides compounds I, II and III prepared f rom (S) (+) -Be t t i Base , (D)-lR,2R-(-)threo-l-(p-Nitrophenyl)-2-amino-3-tr iphenylmethoxypropanol-1 and L-Serine respectively. Their application as ligand catalysts in the asymmetr ic borane reduction of prochiral ketones were investigated. M A T E R I A L S AND M E T H O D S 'H N M R and 3 I P N M R were recorded in CDCI3 as solvent on an AC-P200 instrument using T M S as internal standard and 85% H3PO4 as external standard, respectively. Elemental analyses were done on an MF-3 automatic analyzer. Melting points were determined on an MP-500 melting point apparatus. Optical rotations were measured on a Perkin-Elmer241MC Polarimeter. All temperatures were uncorrected. Preparation of l -(a-N-diphenylphosphinylaminobenzyl)-2-naphthol I (Scheme 1) Scheme I ph,,..C-NH2 ph|11.C_NHPPh2 OH Ph2P(0)CI ̂ S^J^o* j l| J Et3N/CH2Cl2 (S)-(+)Betti Base I

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