1.2- diphenylethylenediamine DPEN

Noyori-type Ru-complexes, prepared by the combination of polar phosphonic acid-derived 10 and 11 with (R,R)-DPEN (1,2-diphenylethylenediamine), were also used to catalyze the asymmetric hydrogenation of aromatic ketones in an ionic liquid/iPrOH biphasic system (Scheme 7.3) [20]. The conversions and enantioselectivities were quite comparable to those obtained from homogeneous reaction in iPrOH. The Ru complex 10-DPEN immobilized in the ionic liquid layer could be recycled six times without any significant loss of enantioselectivity, albeit with a dramatic drop in activity after the third run. 

Incorporation of DPEN (1,2-diphenylethylenediamine) in the same skeleton of Zr-phosphonates improves both catalytic activity and enantioselectivity to almost quantitative value [85], The syntheses involved the same sequence of reactions as in the previous work and TGA and microanalysis suggested their formulae as... 

The discovery by the recent Nobel-laureate, Ryoji Noyori, of asymmetric hydrogenation of simple ketones to alcohols catalyzed by raras-RuCl2[(S)-binap][(S,S)-dpen] (binap = [l,l -binaphthalene-2,2/-diyl-bis(diphenylphosphane)] dpen = diphenylethylenediamine) is remarkable in several respects (91). The reaction is quantitative within hours, gives enantiomeric excesses (ee) up to 99%, shows high chemoselecti-vity for carbonyl over olefin reduction, and the substrate-to-catalyst ratio is >100,000. Moreover, the non-classical metal-ligand bifunctional catalytic cycle is mechanistically novel and involves heterolytic... 

Moreover, when (lR,4.S)-(—)-menthone (105), equilibrating with isomenthone, the 4R isomer, is hydrogenated with (/ )-BINAP and (S,5)-l,2-diphenylethylenediamine (abbreviated as DPEN), (+)-neomenthol (106) is formed exclusively. 

In a related approach, Fan et al. synthesized a series of dendritic BINAP-Ru/chiral diamine ((R,R)-l,2-diphenylethylenediamine DPEN) catalysts for the asymmetric hydrogenation of various simple aryl ketones (Fig. 15) [42]. The resulting systems displayed high catalytic activity and enantioselectivity and allowed facile catalyst recycling. In the case of 1-acetonaphthone and... 

The confined space of the pores can be tailored to optimize catalytic performance. One example of this behavior is the study by Thomas and coworkers [8] who found that anchoring the chiral ligand (R,R)-diphenylethylenediamine (dpen) to the inner... 

Close to polymer boimd-BINAP/diamine ruthenium precatalyst [11], complexes of BINAP or their derivatives in the presence of polymer bound diamine have been employed. These catalytic systems have been mainly studied by Itsuno with immobilized diphenylethylenediamine (DPEN). As the use of A-substituted 1,2-diamine ligands decreased the catalytic activity of hydrogenation of simple ketones contrary to free diamine ligands, they have been less employed. However, A-substitnted 1,2-diamine ligands are rather effective in the hydrogenation of a-snbstitnted ketone, snch as a-amido ketones. Thus, two types of immobilized DPEN have been performed. Fnnctionalized DPEN for subsequent grafting onto polymer or eopolymerization are presented (Scheme 3). 

After rigorous optimization study, the Ru-based catalyst 103 with /)-cymene and 2,4,6-triisopropylphenylsulfonyl-diphenylethylenediamine (DPEN) ligands was found to be the best for this purpose. While performing a detailed kinetic study, it was found that the reaction was inhibited by in situ formation of carbon dioxide from the formic acid. It has been further observed that the active Ru-hydride... 

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