The asymmetric hydrogenation of 2-phenethylacrylic acid as the key step for the enantioselective synthesis of Citralis Nitrile^®

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• 作者：Alberto Scrivanti ; Sara Bovo ; Aless ; ra Ciappa ; Ugo Matteoli
• 关键词：Acrylic acids ; Enantioselective hydrogenation ; Atropisomeric diphosphine ; Ruthenium ; Iridium ; Fragrance chemistry ; Citralis Nitrile^® ;
• 刊名：Tetrahedron Letters
• 出版年：2006
• 出版时间：25 December 2006
• 年：2006
• 卷：47
• 期：52
• 页码：9261-9265
• 全文大小：145 K

文摘

A catalytic approach to the enantioselective synthesis of Citralis Nitrile^® (3-methyl-5-phenyl-pentanenitrile, a citrus-type odorant) is described. The key step is the transition-metal catalyzed asymmetric hydrogenation of 2-phenethylacrylic acid. Among the different catalysts tested, the most efficient appears to be the one formed by combining in situ [Ru(benzene)Cl₂]₂ with the atropisomeric diphosphine MeOBIPHEP and triethylamine, which allows us to obtain enantiomeric excesses up to 98 % under mild conditions. Very good results (ees >80 % ) have also been obtained using iridium cationic complexes in combination with a phosphinooxazoline ligand.