DOI: 10.1002/adsc.200600654 New C 2 -Symmetric Diphosphite Ligands Derived from Carbo- hydrates: Effect of the Remote Stereocenters on Asymmetric Catalysis M. Rosa Axet, a Jordi Benet-Buchholz, b Carmen Claver, a, * and Sergio Castillón c, * a DepartamentdeQuímicaFísicaiInorgànica,UniversitatRoviraiVirgili,MarcelliDomingos/n,43007Tarragona,Spain Fax:(+ 34)-97-755-9563;e-mail:carmen.claver@urv.cat b InstituteofChemicalResearchofCatalonia(ICIQ),Av.PaïsosCatalans16,43007Tarragona,Spain c DepartamentdeQuímicaAnalíticaiQuímicaOrgànica,FacultatdeQuímica,UniversitatRoviraiVirgili,Marcelli Domingos/n,43007Tarragona,Spain;e-mail:sergio.castillon@urv.cat Received:December31,2006 SupportinginformationforthisarticleisavailableontheWWWunderhttp://asc.wiley-vch.de/home/. Abstract: The synthesis of new modular chiral di- phosphite ligands with C 2 -symmetry and carbohy- drate backbone is reported. We also report here the synthesis of the corresponding rhodium complexes [RhACHTUNGTRENNUNG(COD)(L)]BF 4 (L = diphosphite). All these spe- cies have been characterised in solution by NMR spectroscopy and in some cases in the solid state by X-ray diffraction. The solution structures of the hy- dridorhodiumcarbonyl species [RhH(CO) 2 (L)], where L = diphosphites 12a–14a, 12b, have been studied using high-pressure NMR spectroscopy. The configuration and substitution of the remote stereo- centres in positions 2 and 5 of the tetrahydrofuran ring of the diphosphite ligands were observed to haveaconsiderableinfluenceontheresultsobtained in the rhodium-catalysed hydroformylation and hy- drogenation reactions. Thus, the configuration of the major isomer obtained in the hydroformylation reac- tionmaybecontrolledbychangingtheconfiguration ofthesestereocentres. Keywords: asymmetric catalysis; carbohydrates; di- phosphites;hydroformylation;hydrogenation Introduction Inhomogeneousasymmetriccatalysisbasedontransi- tion metals, the design of new ligands is, perhaps, the mostcrucialsteptoachievethehighestlevelsofreac- tivity and selectivity. One of the simplest ways of ob- taining chiral ligands is to transform natural chiral compounds, thus making optical resolution proce- dures unnecessary. This fact, that can be considered an advantage from a synthetic point of view, is also one limitation for catalytic purposes, since only one enantiomer is accessible. However, this limitation may be partially overcome by using the so-called pseudoenantiomer ligands as will be shown in this contribution. Carbohydrate derivative ligands have many advantages: they are readily available, highly functionalised, and they may be systematically modi- fied. [1] Some carbohydrate derivative ligands are showed in Figure1. The pyranoside diphosphinite li- gands 1 were successfully used in rhodium-catalysed asymmetric hydrogenation of enamido acids, [2] and nickel-catalysed hydrocyanation of alkenes. [3] Ligand 2 proved to function as a pseudoenantiomer of 1 pro- viding the opposite enantiomer in the asymmetric hy- drogenationofprochiralolefins. [4] During the last years we have focused in the use of furanose derivatives of C 1 -symmetry as ligands in asymmetriccatalysis.Someoftheseligandshavebeen Figure 1. Representative carbohydrate derivative ligands (1– 5)withpyranoidandfuranoidskeleton. Adv. Synth. Catal. 2007, 349,1983–1998 #2007Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim 1983 FULL PAPERS