Development of Practical Catalytic Asymmetric Hydrogenatioh Using Methanol as a Hydrogen Source

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In this project, we studied O-H activation with late-transition metal complexes. We have found that [Ir(μn-Cl)(binap)]_2 (1) can easily activate methanol and the complex 1 and its oxidative addition complex of methanol act as efficient hydrogenation catalyst precursors of alkyne using methanol as a hydrogen source. Although these Complexes act as catalyst precursors for asymmetric hydrogenation of prochiral olefins also, their catalytic activity was not high enough and the enantio-selectivity for hydrogenation of dehydroamino acids remained as high as 50 %ee. Complex 1 can also activate various kinds of carboxylic acids very easily and (S)-1 gave quantitatively and stereoselectively, mononuclear hydrido(carboxylato) complexes (S)-OC-6-23-A-[Ir(Cl)(H)(h^2-0_2CR){(S)-binap}] (R=Me, Ar) (2), among five possible stereoisomers. Complexes 2 were found very efficient catalyst precursors for asymmetric hydrogenation of imine. Especially, for hydrogenation of cyclic imines, very high optical in … More duction over 99 %ee was realized. So-called a neutral rhodium-diphosphine catalyst, "RhCl(diphosphine)", has been prepared in situ and used in many kinds of catalysis, but its isolation is rare and the complex has not been well characterized. We have succeeded in isolation and full characterization including X-ray analysis of the rhodium analogue of complex 1, [Rh(μ-Cl){(S)-binap}]_2 (3). Complex 3 has a very similar structure to that of 1 but the properties of 3 were very much different from those of complex 1 ; Complex 1 is very sensitive against air as well as protic molecules but complex 3 was inert against these substances even at heating conditions. As complex 3 is considered to be effective for activation of dihydrogen, more detailed studies on Complex 3 will be needed. A comparative studies between complexes 1 and 3 would provide useful information about their applications. In addition, we contributed a review article about O-H activation to a book, "Catalytic Heterofunctionalization" edited by A. Togni and H. Grutzmacher and published by Wiley-VCH. Less