Noyori cause

Vedejs et al. reported catalyst inhibition during a study on the enantioselective transfer hydrogenation of dihydro-isoquinolines using Noyori s catalyst (Scheme 44.2) [27]. Here, the problem is caused by the bidentate nature of the substrate. Whereas the bromo compound 1 a could be rapidly reduced, the tosylamide-sub-stituted compound lb could not be reduced, and although the problem could be alleviated somewhat by alkylation of the sulfmamide to 1 c, hydrogenation of this was still sluggish. Although the authors propose this to be a case of product... 

Chirality is built into the catalysts by employing ligands with either chirality centers or axes (Section 7.9). Noyori s widely used BINAP has a chirality axis, and crowding prevents interconversion of enantiomers by restricting rotation around the bond connecting the naphthalene rings. The metal, usually ruthenium, is held in place by the two phosphorus atoms (yellow) in a chiral environment. The steric demands in the cavity occupied by the metal in Ru-BINAP cause reaction to occur preferentially at one face of the double bond. 

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