ChemInform Abstract: Synthesis and Evaluation in Asymmetric Hydrogenation of Carbohydrate- Derived 1,3-Bisphosphines.

Abstract

Abstract 1,3-Bisphosphines and 1,3-phosphine sulfides have been prepared from 1,6-anhydro-β- d -glucopyranose in view of their application as bidentate ligands in transition-metal-catalyzed asymmetric hydrogenation. Reaction of 1,6:3,4-dianhydro-2- O -( p -toluenesulfonyl)-β- d -galactopyranose ( 1 ) with Ph 2 PH in the presence of AlMe 3 gave 1,6:2,3-dianhydro-4-deoxy-4-(diphenylphosphino)-β- d -mannopyranose ( 6 ) which, upon treatment with LiPPh 2 , led to 1,6-anhydro-2,4-dideoxy-2,4-bis(diphenylphosphino)-β- d -glucopyranose ( 9 ). Esterification of 9 with 1-naphthoyl chloride yielded the naphthoate 11 . Upon exposure to air, 9 and 11 were oxidized to the corresponding bisphosphine dioxides 10 and 12 . Treatment of 6 with PhSH and DBU led to 1,6-anhydro-2,4-dideoxy-4-(diphenylphosphino)-2-phenylthio-β- d -glucopyranose ( 13 ) and, after oxidation with air, to the corresponding phosphine oxide 14 . Similarly, 1 was transformed into 1,6-anhydro-2,4-dideoxy-2-(diphenylphosphino)-4-phenylthio-β- d -glucopyranose ( 16 ) and its oxide 17 . Attempted ring opening of 1 by Ph 2 PH/KOH or by Ph 2 PH/AlMe 3 and oxidative work-up gave 1,6-anhydro-3,4-dideoxy-4-(diphenylphosphoryl)-β- d - threo -hex-3-enopyranose ( 3 ). In the presence of HCl, both 3 and 7 (obtained by air oxidation of 6 ) were transformed into 1,6-anhydro-2-chloro-2,4-dideoxy-4-(diphenylphosphoryl)-β- d -glucopyranose ( 8 ). The structure of 8 was established by an X-ray analysis. 1 H-, 13 C-, and 31 P-n.m.r. spectroscopy showed that the phosphines ( 9, 11, 13 , and 16 ) prefer a 1 C 4 and the phosphine oxides ( 8, 10, 12, 14 and 17 ) a B 3,O conformation. The results of the rhodium- or ruthenium-catalyzed asymmetric hydrogenation with the phosphines 9, 11, 13, and 16 ligands are presented. In the hydrogenation of olefins (geraniol or the α-acetamidoacrylic acid 19 ), low enantioselectively is observed. Better enantiomeric excesses were obtained in the hydrogenation of α- and β-ketoesters (ketopantolactone, e.e.