38, A-1090 Vienna, Austria Institute of Applied Synthetic Chemistry, Vienna University of Technologies, Getreidemarkt 9/163, A-1060 Vienna, Austria ?Division of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge, U.K. College of Pharmaceutical Sciences, Capital Medical University, Beijing, No.10 Xitoutiao, You An Men Beijing 100069, People’s Republic of China Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164SC, A-1060 Vienna, AustriaS * Supporting InformationABSTRACT: Two representative Walphos analogues with an achiral 2,2-biferrocenediyl backbone had been synthesized. These diphosphine ligands were tested inside the rhodium-catalyzed asymmetric hydrogenation of many alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The outcomes have been compared with those previously obtained on using biferrocene ligands having a C2-symmetric 2,2-biferrocenediyl backbone also as with those obtained with Walphos ligands. The application of 1 newly synthesized ligand within the hydrogenation of 2-methylcinnamic acid gave (R)-2-methyl-3-phenylpropanoic acid with full conversion and with 92 ee. Exactly the same ligand was utilised to transform 2,4-pentanedione quantitatively and diastereoselectively into (S,S)-2,4-pentanediol with 98 ee.INTRODUCTION About 10 years ago we reported on the synthesis of a group of diphosphine ligands, the so-called Walphos ligand household, and their application within the asymmetric hydrogenation of alkenes, ketones, and imines.1 All of these ligands are based on a phenylferrocenylethyl backbone, and they differ only inside the substituents on their phosphino units (R1 and R2; Chart 1).ChartOriginally, these derivatives were created and made use of as ligands for hydrogenation catalysts, but several different added applications have subsequently been reported.2 Around the basis from the results of these ligands, we quite lately investigated Walphos analogues having a biferrocene as an alternative to a ferrocenylaryl backbone (Chart 1).3 In these ligands the aryl ring of the Walphos backbone is replaced by a ferrocenyl unit. In asymmetric hydrogenations the Walphos ligands and their analogous biferrocene compounds showed substantially different performances with respect to both solution ee values and absolute configuration.1,3-Diiodo-5,5-dimethylhydantoin Formula ?2014 American Chemical SocietyThe backbone of Walphos analogues for instance 1 and two with an R,Sp,Rp absolute configuration were constructed by a Negishi coupling in between (R)-1-(N,N-dimethylamino)ethylferrocene ((R)-3) and (S)-2-bromoiodoferrocene ((S)-4) (analogous for the reaction of (R)-3 and rac-4 shown in Scheme 1).Price of 4-(Aminomethyl)pyrimidine This reaction resulted within the intermediate (R,Sp,Rp)-5, which was converted in to the final ligands having a C 2-symmetric biferrocene-2,2-diyl backbone.PMID:23907051 It’s clear, on the other hand, that a coupling reaction in between (R)-3 and (R)-4 would lead to the diastereomeric intermediate (R,Sp,Sp)-5 with an achiral biferrocene-2,2-diyl backbone. Substitution of such an achiral biferrocene backbone with two nonidentical substituents would also result in chiral derivatives, and we were consequently curious as to how Walphos analogues with an R,S p ,S p absolute configuration would execute in asymmetric catalysis. We report here the synthesis of two biferrocene-based Walphos analogues (1 and 2) with an R,Sp,Sp configuration and their application in the rhodium-catalyzed hydrogenation of alkenes and the ruthenium-catalyzed hydrogenations of two ketones. The outcomes obtained with these bif.