Ru/diphosphine/diamine

Ru-diphosphine-diamine complexes developed originally by Noyori for the hydrogenation of aryl ketones are also suitable for the hydrogenation of imines. The best results are obtained for N-aryl imines where a Ru-duphos-diamine complex achieved up to 94% ee, albeit with relatively low activity and productivity (entry 3.7) (for data relating to cyclic imines, see Table 34.5). 

Cyclic imines 8 and 9 are intermediates or models of biologically active compounds and can be reduced with ee-values of 88 to 96% using Ti-ebthi, Ir-bcpm or Ir-binap in the presence of additives (entries 5.7, 5.9), as well as with the transfer hydrogenation catalyst Ru-dpenTs (entries 5.8, 5.10-5.12). As pointed out earlier, Ru-diphosphine-diamine complexes are also effective for imines, and the best results for 7 and 8a were 88% and 79% ee, respectively [36]. Azirines 10 are unusual substrates which could be transfer-hydrogenated with a catalyst prepared in situ from [RuCl2(p-cymene)]2 and amino alcohol L12, with ee-values of 44 to 78% and respectable TOFs of up to 3000 (entry 5.13). 

The hydrogenation of a number of aromatic ketones is shown in Figure 37.30. Noyori s very effective Ru-diphosphine-diamine technology was developed by several companies. It is not clear on which scale the processes developed by Takasago (dm-binap = 3,5-xylyl-binap) [16] and Dow/Chirotech [109-111] for the reduction of substituted acetophenones are actually applied commercially. Using the Xyl-PhanePhos-dpen catalyst, a highly efficient bench-scale process was developed for the hydrogenation of p-fluoroacetophenone (ee 98%, TON 100000, TOF 50000 IT1 at r.t., 8 bar) [109]. Ru-P-Phos (licensed to Johnson Matthey [112]) achieved ee-values >99.9% and TON up to 100000 for sev-... 

Ru/diphosphine/diamine were shown by Noyori (For a recent account see [87]) to be effective hydrogenation catalysts of ketones without a- or (3-functionality. The absolute configurations of the P P and N N ligands have to be matched. The technology has been licensed by several companies using various biaryl diphosphines but it is not clear whether it is already used for concrete manufacturing purposes. 

Crabtree and co-workers discovered the dehydrogenative Paal-Knorr synthesis the reaction of 1,4-diols with primary amines in the presence of a Ru diphosphine diamine complex at 125 °C to afford 2,5-disubstituted pyrroles (Scheme 12.37)." Kempe and Milstein developed dehydrogenative conditions for the synthesis of pyrroles via C-N and C-C coupling of alcohols with vicinal amino alcohols (Scheme 12.37). These reactions require the use of KOfBu, which may facilitate a-deprotonation of the intermediate imine. 

The complex TolBINAP-Ru dichloride existing in aggregate form is incapable of catalyzing the hydrogenation reaction. In the presence of (S,S)-DPEN, however, a monomeric diphosphine/diamine complex is readily formed to facilitate catalytic hydrogenation. In other words, under the hydrogenation conditions, one of the precatalysts, RuCl2[(-R)-Tolbinap)(DMF)n], is selectively... 

Preparation of the JST class (see Section 12.3.4) of the ruthenium-diphosphine-diamine complex, [(PhanePhos)Ru(diamine)Cl2], produced highly active and enantioselective catalysts in the reduction of aryl methyl ketones (128, R = Me), as well as a,P-unsaturated ketones.162-163 Higher... 

In comparison, Ru-diphosphine/diamino complexes react readily with H2. The authors investigated the activity of the catalyst formed from RuCp and the 1,2-diamine ligand 56 (Fig. 14) used for the hydrogenation of ketones with H2 and that it can be enhanced by quinuclinide-based ligands. 

Abdur-Rashid, K. Faatz, M. Lough, A. J. Morris, R. H. Catalytic cycle for the asymmetric hydrogenation of prochiral ketones to chiral alcohols Direct hydride and proton transfer from chiral catalysts trans-Ru(H)2(diphosphine) (diamine) to ketones and direct addition of dihydrogen to the resulting hydridoamido complexes. ]. Am. Chem. Soc. 2001,123, 7473-7474. 

SCHEME 30.1. Mechanism of asymmetric reduction of ketones with molecular hydrogen in the presence of Ru(diphosphine)(l,2-diamine)Cl2 complex. 

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