Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Patent
1998-01-22
1999-12-28
Nazario-Gonzalez, Porfirio
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
556 21, 556 28, 556136, 564485, 564500, 548402, C07F 1900, C07F 1500, C07F 1702
Patent
active
06008393&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to iridium-diphosphine complexes having ligands of oxy acids and to a process for the hydrogenation of imines in the presence of such complexes, the hydrogenation being enantioselective when the complex contains chiral diphosphines.
U.S. Pat. No. 4,994,615 describes a process for the asymmetric hydrogenation of prochiral N-arylketimines wherein iridium catalysts having chiral diphosphine ligands are used. U.S. Pat. No. 5,011,995 describes a process for the asymmetric hydrogenation of prochiral N-alkylketimines using the same catalysts. U.S. Pat. No. 5,112,999 discloses polynuclear iridium compounds and a complex salt of iridium, which contain diphosphine ligands, as catalysts for the hydrogenation of imines. U.S. Pat. No. 5,371,256 and EP-A-0 612 758 describe iridium complexes having chiral ferrocenyl diphosphine ligands for the homogeneous enantio-selective hydrogenation of imines.
Those homogeneous catalysis processes have proved valuable, although it is evident, especially in the case of relatively large batches and on an industrial scale, that, depending on the catalyst precursor, the substrate and the diphosphine ligands that are used, the catalysts frequently tend to become deactivated to a greater or lesser extent. In many cases, especially at elevated temperatures--for example at temperatures >25.degree. C., which are necessary for a short reaction time--it is therefore not possible to achieve complete conversion. For industrial applications of the hydrogenation processes, therefore, the catalyst productivity is too low from the point of view of economic viability. Nor is it possible to eliminate those disadvantages by the addition of metal halides as described in U.S. Pat. No. 4,994,615, U.S. Pat. No. 5,011,995 and U.S. Pat. No. 5,112,999.
It has now been found that iridium-diphosphine complexes having at least one ligand of an oxy acid are excellent homogeneous catalysts especially for the enantioselective hydrogenation of imines. It has also been found that the catalyst activity can be increased considerably if the reaction mixture contains a soluble halide and an acid. It has also unexpectedly been found that, with the addition of an acid, the deactivation of the catalysts can be considerably reduced or completely eliminated at the same time. It has also been found, surprisingly, that, with the addition of an acid, at the same time the enantioselectivity when asymmetric catalysts are used is high, and high optical yields even of more than 80% can be achieved, even at reaction temperatures of more than 50.degree. C. It has also unexpectedly been found that, with the addition of an acid, it is even possible at the same time to achieve higher conversions and optical yields with less catalyst, which offers very considerable economic advantages since the molar ratio of imine to iridium catalyst can be greatly increased.
The invention relates to compounds of formulae I, Ia and Ib, or mixtures of at least two of those compounds bonded to a C.sub.2 -, C.sub.3 - or C.sub.4 -carbon chain, with the result that the diphosphine forms a 5- to 7-membered ring together with the Ir atom, S(.dbd.O)O or P(.dbd.O)O in the anion.
The iridium compounds are preferably homogeneous catalysts that are substantially soluble in the reaction medium. The term "catalyst" also includes catalyst precursors that are converted into an active catalyst species at the beginning of a hydrogenation reaction. In the compounds of formulae I, Ia and Ib, DIP is preferably a ditertiary diphosphine (a) the phosphine groups of which are bonded to different carbon atoms of a carbon chain having from 2 to 4 carbon atoms, or (b) the phosphine groups of which are either bonded directly or via a bridge group --CR.sub.v R.sub.w -- in the ortho positions of one cyclopentadienyl ring or are bonded to each cyclopentadienyl ring of a ferrocenyl, or (c) one phosphine group of which is bonded to a carbon chain having 2 or 3 carbon atoms and the other phosphine group of which is bonded to an oxygen atom or a nitrogen ato
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Osborn John Anthony
Sablong Rafael
Spindler Felix
Dohmann George R.
Kalinchak Stephen G.
Lopez Gabriel
Nazario-Gonzalez Porfirio
Novartis AG
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