2 ’- -1,1 ’-binaphthyl asymmetric hydrogenation

Catalytic asymmetric hydrogenation was one of the first enantioselective synthetic methods used industrially (82). 2,2 -Bis(diarylphosphino)-l,l -binaphthyl (BINAP) is a chiral ligand which possesses a Cg plane of symmetry (Fig. 9). Steric interactions prevent interconversion of the (R)- and (3)-BINAP. Coordination of BINAP with a transition metal such as mthenium or rhodium produces a chiral hydrogenation catalyst capable of inducing a high degree of enantiofacial selectivity (83). Naproxen (41) is produced in 97% ee by... 

I -BINAPHTHYL AS A LIGAND FOR RHODIUM-CATALYZED ASYMMETRIC HYDROGENATION. 36... 

Two interesting reports by Chan and co-workers of dendritic core-functionalized Ru-BINAP (BINAP = 2,2/-bis(diphenylphosphino)-l,l/-binaphthyl) catalysts, which were employed in asymmetric hydrogenations and which were fully recoverable, have appeared recently [40,41]. In particular, such dendrimers containing long alkyl chains in the periphery were synthesized and... 

Mainly the hydrogenations are mediated through a platinum-group-metal-catalysed reaction with chiral ligands bound to the metal. Koten and coworkers210 proposed the use of Ru- and Rh-containing catalysts immobilised on silica in asymmetric hydrogenation. As a chiral compound, they used BINAP (2,2 -bis(diphenylphosphino)-1,1 -binaphthyl) (Scheme 4). 

BINAP/DPEN/Ru(II)-catalyzed Asymmetric Hydrogenation of Simple Ketones. Ru(II) complexes having a formula of fra/w-RuCl2(diphosphine)(dpen) are most conveniently obtained by treatment of oligomeric RuCl2(diphosphine)(dmf) with 1.1 equiv of DPEN in DMF at room temperature [diphosphine = 2,2 -bis(diphenylphosphino)-1,1 -binaphthyl (BINAP), 2,2 -bis(di-4-tolylphosphino)-l,l -binaphthyl (TolBINAP), 2,2 -bis(di-3,5-... 

Introduction. DIOP was the first example of a C2 chelating diphosphine for transition metal complexes to be used in asymmetric catalysis. It was also one of the first examples of a useful C2 chiral auxiliary. DIOP can be considered as an example of the first generation of chelating diphosphine ligands with a chiral carbon skeleton, which were followed over the next 20 years by many examples of chelating diphosphines, one of the most efficient of which is BINAP [2,2 -Bis(diphenylphosphino)-l,l -binaphthyl] The ready availability of DIOP has stimulated research in asymmetric catalysis beyond the area of asymmetric hydrogenation. 

Kawano, H., Ikariya, T., Ishii, Y., Saburi, M., Yoshikawa, S., Uchida, Y., Kumobayashi, H. Asymmetric hydrogenation of prochiral alkenes catalyzed by ruthenium complexes of (R)-(+)-2,2 -bis(diphenylphosphino)-1,1 -binaphthyl. J. Chem. Soc., Perkin Trans. 11989, 1571-1575. 

Ashby, M. T., Halpern, J. Kinetics and mechanism of catalysis of the asymmetric hydrogenation of a,P-unsaturated carboxylic acids by bis(carboxylato) 2,2 -bis(diphenylphosphino)-1,1 -binaphthyl ruthenium(ll), [Rull(BINAP) (02CR)2]. J. Am. Chem. Soc. 1991,113, 589-594. 

Compared with the simple monophosphites, the monodentate phosphites derived from the easily available carbohydrates afforded considerably higher enantioselec tivities in the asymmetric hydrogenation of enamides. Zheng and coworkers developed a series of binaphthyl carbohydrate monodentate phosphites from D fructose and d glucose. The phosphite 29 (Scheme 8.11) exhibited a better enantioselectivity in the rhodium catalyzed asymmetric hydrogenation of arylena mides [37]. Fructose and glucose derived phosphites have several chiral centers and... 

A variety of octahydrobinaphthyl based carbohydrate monodentate phosphites have been synthesized [40]. Among them, the monophosphite 31 (Scheme 8.11) derived from d fructose showed the highest level of asymmetric induction in rhodium catalyzed hydrogenation of a arylenamides 1 (97.3 99.6% ee). In the asymmetric hydrogenation of p substituted Z/ mixtures of arylenamides 15a and 15b, the ligand 31 gave the N acetyl arylamines 16a and 16b with 97.3 and 99.0% ee, respectively (Scheme 8.11). The ee values obtained by octahydrobi naphthyl based monophosphite 31 are little lower than those obtained with the binaphthyl based ManniPhos (monophosphites 30, Table 8.2). 

Homogeneous catalytic asymmetric hydrogenation has become one of the most efficient methods for the synthesis of chiral alcohols, amines, a and (3-amino acids, and many other important chiral intermediates. Specifically, catalytic asymmetric hydrogenation methods developed by Professor Ryoji Noyori are highly selective and efficient processes for the preparation of a wide variety of chiral alcohols and chiral a-amino acids.3 The transformation utilizes molecular hydrogen, BINAP (2,2 -bis(diphenylphosphino)-l,l -binaphthyl) ligand and ruthenium(II) or rhodium(I) transition metal to reduce prochiral ketones 1 or olefins 2 to their corresponding alcohols 3 or alkanes 4, respectively.4... 

In 1980, Professor Noyori and the late H. Takaya consequently designed and synthesized a bidentate phosphine ligand BINAP (2,2 -bis(diphenylphosphino)-l,T-binaphthyl) 5, that contained an atropisomeric l,l -binaphthyl structure as a chiral element for use in transition metal catalyzed asymmetric hydrogenation reactions (Figure 1). 

Asymmetric hydrogenation was catalyzed by ruthenium clusters containing atropoisomeric diphosphines. Catalyst precursors were Ru4(/t-H)4(CO)]o (S)-(-)-BINAP (BINAP = 2,2 -bis(diphenylphosphino)-l,l -binaphthyl) and Ru4(/t-H)4(CO)io (S)-(-)-MOBIPH (MOBIPH = 2,2 -bis(diphenylphosphino)-6,6 -dimethoxy-l,l -diphenyl). Substrates included prochiral alkenes such as tiglic acid, (Z)- and ( )-2-methylbutendioic acids, ( )-2-methylbute-noic acid, and acetophenone. Optical purities up to 38% were obtained, but most results were low ee s. 

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