Quantitative Analyses and Control of Catalytic Organic Transformations

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Asymmetric hydrogenation of a-(acylamino)acrylic esters with Ru(CH_3COO)_2 [(S)-binap] (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) has been revealed to proceed via monohydride-unsaturate mechanism. The enantioselectivity that is opposite to the (S)-BINANP-Rh case has been interpreted in terms of stereo-complementary models of the enamide/metal chelate complexes. The detailed analysis of the isotopomer ratios has proved that the major S and minor R enantiomers are produced via the same mechanism involving diastereomeric intermediates. With (Z)-3-phenyl-2-butenoic acid, however, the minor enantiomer is formed mostly by mechanisms that differ from the major one. The observed enantioselectivity has generally been interpreted to result from competing diastereomorphic catalytic cycles caused by a single chiral catalyst; however, this supposition has not been substantiated. Our study calls into question such a generalized treatment. Furthermore, in this research project, we have found two new catalyses 1. Cp^*Rh(III)-catalyzed Leuckart-Wallach (LW)-type reductive amination of ketones and 2. catalytic allyl ether cleavage and formation using [CpRu(CH_3CN)_3]PF_6 and 2-pyridinecarboxylic acid derivatives. Both process are very clean and operational simple. In particular, the new salt waste-free allyl ether synthesis has overcome the long-pending problems in Williamson's ether synthesis.