Pergamon Tetrahedron: Asymmetry 9 (1998) 329–340 New carbohydrate bisphosphites as chiral ligands Renat Kadyrov, Detlef Heller and Rüdiger Selke ∗ Institut für Organische Katalyseforschung an der Universität Rostock, e.V.Buchbinderstr. 5–6, 18055 Rostock, Germany Received 20 November 1997; accepted 4 December 1997 Abstract The synthesis of the 2,3-bisphosphite derivatives of phenyl 4,6-O-benzylidene-β-D-glucopyranoside leads to new chelating ligands. Their rhodium(I) and platinum(II) complexes have been tested as catalysts for the asymmetric hydroformylation of vinyl acetate, allyl acetate and p-methoxystyrene. Good regioselectivity (>90% branched product), but an enantioselectivity of only ≤36% ee were found under mild reaction conditions (25–40°C, 40–70 bar syngas). © 1998 Elsevier Science Ltd. All rights reserved. Investigations of carbohydrate vicinal bisphoshinites as chiral chelating ligands in asymmetric hydrogenations 1 and hydroformylation 2 of prochiral olefinic substrates with enantioselectivities reaching 99 or 72% ee, respectively, culminated in an industrial application for L-Dopa synthesis. 3 The fact that phosphites are suitable ligands for rhodium(I) catalyzed hydroformylation 4 tempted us to try the preparation of analogous hexopyranoside-2,3-O-bisphosphites. Previously high catalytic activities of diphosphite rhodium(I) chelates in hydroformylation reactions have been published 4 a–c but asymmetric induction was restricted to cases such as the hydroformylation of styrene with diphosphites based on chiral pentane-2,4-diol (90% ee). 4d The highest enantioselectivity in an asymmetric hydroformylation was obtained with the phosphine–phosphite ligands introduced by Takaya and co-workers. 5 Since aryl 4,6-O-benzylidene-β-D-glucopyranoside with only equatorial substituents led to the ligands with the highest enantioselectivity in asymmetric hydrogenation, 6 we started our synthetic work with that compound. We are aware that application of such phosphites, in particular in other reactions, might show distinct deviations to the case of the asymmetric hydrogenation with bisphosphinite chelates. However, we thought that the range of electronic properties and particularly steric requirements of the residue R in 2 may be large enough to generate interesting differences. ∗ Corresponding author. E-mail: rselke@chemie1.uni-rostock.de 0957-4166/98/$19.00 © 1998 Elsevier Science Ltd. All rights reserved. PII: S0957-4166(97)00622-8 tetasy 2129