Enantioselective hydrogenation of functionalized olefins catalyzed by Rh-chiral bidentatephosphite complexes
作者:Qing-Lu Zhao、Xiao Miao、Lai-Lai Wang
DOI:10.1016/j.tetasy.2012.12.001
日期:2013.2
A novel catalytic system for the hydrogenation of dimethyl itaconate has been developed by using rhodium-diphosphite complexes. These chiral diphosphite ligands were derived from glucopyranoside, D-mannitol derivatives, and binaphthyl or H-8-binaphthyl phosphochloridites. The ligands based on the methyl 3,6-anhydro-alpha-D-glucopyranoside backbone and (R)- and (S)-binaphthol and/or (R)- and (S)-2,2'-dihydroxy-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthol gave almost complete conversion of the dimethyl itaconate and both enantiomers of dimethyl 2-methylsuccinate with excellent enantioselectivities. The stereochemically matched combination of methyl 3,6-anhydro-alpha-D-glucopyranoside and H-8-(S)-binaphthyl in ligand 2,4-bis[(S)-1,1'-H-8-binaphthyl-2,2'-diyl]-phosphite} methyl 3,6-anhydro-alpha-D-glucopyranoside was essential to afford dimethyl 2-methylsuccinate with up to 98% ee. The sense of the enantioselectivity of products was predominantly determined by the configuration of the biaryl moieties of the ligands. An initial screening of [Rh(cod)(2)]BF4 with these ligands in the hydrogenation of (E)-2-(3-butoxy-4-methoxybenzylidene)-3-methylbutanoic acid was carried out. Good enantioselectivity (75% ee) and low yield for (R)-2-(3-butoxy-4-methoxybenzyl)-3-methylbutanoic acid were obtained. (C) 2012 Elsevier Ltd. All rights reserved.