Homogeneous asymmetric catalytic hydrogenation

Chiral Phosphine Ligands for Homogeneous Asymmetric Catalytic Hydrogenation... 

Homogeneous asymmetric catalytic hydrogenation of olefmic and carbonyl bonds mediated by enantiopure ruthenium(II) BINAP complexes. The substrates must have coordinating functionalities in neighboring positions which serve as directing groups during the transformation ... 

Homogeneous Asymmetric Catalytic Hydrogenation Examples Involving l-DOPA, (S)-Naproxen, and Aspartame... 

There are some reports on the asymmetric catalytic hydrogenation of C=N double bonds. Rhodium phosphine complexes do not have high activity, and the stereoselectivity is low. - Homogeneous hydrogenation of oximes, Schiff s bases and cyclic imines " have been reported. A cyano cobalt complex has been used for the homogeneous catalytic hydrogenation of oximes and Schiff s bases but the degree of asymmetric induction is unknown. 

H. Takaya, T. Ohta, and K. Mashima, New 2,2 -Bis(diphenylphosphino)-l,l -binaphthyl-Ru(II) Complexes for Asymmetric Catalytic Hydrogenation, in Homogeneous Transition Metal Catalyzed Reactions, W.R. Moser and D.W. Slocum, Eds., American Chemical Society Washington, DC, 1992, pp. 123-142. It should also be noted that one advantage of Ru-based catalysts over Rh-based is that the cost of Ru is about 10% that of Rh. 

Jessop and co-workers have pointed out that homogeneous catalysis in supercritical fluids can offer high rates, improved selectivity, and elimination of mass-transfer problems.169 They have used a ruthenium phosphine catalyst to reduce supercritical carbon dioxide to formic acid using hydrogen.170 The reaction might be used to recycle waste carbon dioxide from combustion. It also avoids the use of poisonous carbon monoxide to make formic acid and its derivatives. There is no need for the usual solvent for such a reaction, because the excess carbon dioxide is the solvent. If the reaction is run in the presence of dimethy-lamine, dimethylformamide is obtained with 100% selectivity at 92-94% conversion.171 In this example, the ruthenium phosphine catalyst was supported on silica. Asymmetric catalytic hydrogenation of dehydroaminoacid derivatives (8.16) can be performed in carbon dioxide using ruthenium chiral phosphine catalysts.172... 

Horner, L. Siegel, H. Biithe, H. Asymmetric catalytic hydrogenation with an optically active phosphinerhodium complex in homogeneous solution. Angew. Chem., bit. Ed. Engl. 1968, 7,942-943. 

Asymmetric reduction with very high ee values has also been achieved with achiral reducing agents and optically active catalysts. The two most important examples are (1) homogeneous catalytic hydrogenation with the catalyst 2,2 -bis(diphenylphosphino)-1,1 -... 

Asymmetric synthesis (i) has gained new momentum with the potential k use of homogeneous catalysts. The use of a transition metal complex with chiral ligands to catalyze a synthesis asymmetrically from a prochiral substrate is beneficial in that resolution of a normally obtained racemate product may be avoided. In certain catalytic hydrogenations of olefinic bonds, optical purities approaching 100% have been attained (2,3,4,5) hydrogenations of ketones (6,... 

M. Freifelder, Catalytic Hydrogenation in Organic Synthesis Procedures and Commentary, J. Wiley Sons, New York (1978), Chpt 4 Syn 85 (1981) (homogeneous asymmetric hydrogenation)... 

Wilkinson s (I) discovery that the soluble rhodium(I) phosphine complex, [Rh(PPh3)3Cl], was capable of homogeneous catalytic hydrogenation of olefins immediately set off efforts at modifying the system for asymmetric synthesis. This was made possible by the parallel development of synthetic methods for obtaining chiral tertiary phosphines by Horner (2) and Mislow (3,4, 5). Almost simultaneously, Knowles (6) and Horner (7) published their results on the reduction of atropic acid (6), itaconic acid (6), a-ethylstyrene (7) and a-methoxystyrene (7). Both used chiral methylphenyl-n-propyl-phosphine coordinated to rhodium(I) as the catalyst. The optical yields were modest, ranging from 3 to 15%. 

Review. Noyori has reviewed homogeneous asymmetric catalysis, particularly by complexes of (R)- and (S)-BINAP with ruthenium. He suggests possible reasons for the high efficiency of Ru-BINAP complexes in catalytic hydrogenation (40 references). 

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