Abstract
The application of enantioselective catalytic methods for the technical preparation of chiral agrochemicals is illustrated for three active ingredients of the acylanilide type. The key step for the technical synthesis of the herbicide (S)–metolachlor (trade name DUAL MAGNUM®) is the enantioselective hydrogenation of an imine intermediate using a novel iridium ferrocenyl–diphosphine catalyst that exhibited an unprecedented high activity (average turnover frequency up to 350,000 h-1) with an enantioselectivity of 80%. (R)–metalaxyl and clozylacon were synthesized with > 95% and 99% enantiomeric purity, respectively. The enantioselective hydrogenation of the corresponding enamides with Rh or Ru/binap catalysts was the key step in both cases. Some conclusions regarding the development of the catalyst system are made and important prerequisites for the use of enantioselective catalysts for the production of agrochemicals are discussed.
Similar content being viewed by others
References
G.M. Ramos Tombo and D. Bellus, Angew. Chem. 103 (1991) 1219; H.P. Fischer, H.P. Buser, P. Chemla, P. Huxley, W. Lutz, S. Mirza, G.M. Ramos Tombo, G. Van Lommen and V. Sipido, Bull. Soc. Chim. Belg. 103 (1994) 565.
For background information see R.A. Sheldon, Chirotechnology (Marcel Decker, Inc., New York, 1993); J. Crosby, in: Chirality in Industry, eds. A.N. Collins, G.N. Sheldrake and J. Crosby (John Wiley, Chichester, 1992) p. 1; J. Crosby, Tetrahedron 47 (1991) 4789.
H.U. Blaser, B. Pugin and F. Spindler, in: Applied Homogeneous Catalysis by Organometallic Complexes, eds. B. Cornils and W.A. Herrmann (VCH, Weinheim, 1996) pp. 992–1009.
C. Vogel and R. Aebi, DP 23 28 340 (Ciba-Geigy AG, 1972).
H. Moser, G. Ryhs and H. Sauter, Z. Naturforsch. 37b (1982) 451.
For a more detailed case history see: F. Spindler, B. Pugin, H.P. Jalett, H.P. Buser, U. Pittelkow and H.U. Blaser, in: Catalysis of Organic Reactions, Vol. 68, ed. R.E. Malz (Marcel Dekker Inc., New York, 1996) p. 153.
D. Vineyard, W. Knowles, M. Sabacky, G. Bachmann and D. Weinkauf, J. Amer. Chem. Soc. 99 (1977) 5946.
For recent overviews on enantioselective imine hydrogenations see: H.U. Blaser and F. Spindler, Chimica Oggi (1995 June) p. 11; H.U. Blaser and F. Spindler, in: Proceedings of Chiral Europe'94 Symposium, Spring Innovations (Stockport, UK, 1994) p. 69.
W.R. Cullen, M.D. Fryzuk, B.R. James, G. Kang, J.P. Kutney, R. Spogliarich and I.S. Thorburn, US 4,996,361 (Ciba-Geigy AG, 1987); W.R. Cullen, M.D. Fryzuk, B.R. James, J.P. Kutney, G.-J. Kang, G. Herb, I.S. Thorburn and R. Spogliarich, J. Mol. Catal. 62 (1990) 243.
R. Crabtree, H. Felkin, T. Fellebeen-Khan and G. Morris, J. Organometal. Chem. 168 (1979) 183.
N. Alcock, J.M. Brown, A. Derome and A. Lucy, J. Chem. Soc., Chem. Commun. (1985) 575.
F. Spindler and B. Pugin, EP Patent 0256982 (Ciba-Geigy AG, 1988); F. Spindler, B. Pugin and H.U. Blaser, Angew. Chem. Int. Ed. Engl. 29 (1990) 558.
A. Togni, C. Breutel, A. Schnyder, F. Spindler, H. Landert and A. Tijani, J. Am. Chem. Soc. 116 (1994) 4061.
H.P. Buser, B. Pugin, F. Spindler and M. Sutter, Tetrahedron 47 (1991) 5709 and references therein.
S.C. Stinson, C&EN October 9 (1995) 45.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Blaser, H., Spindler, F. Enantioselective catalysis for agrochemicals. The case histories of (S)–metolachlor, (R)–metalaxyl and clozylacon. Topics in Catalysis 4, 275–282 (1997). https://doi.org/10.1023/A:1019164928084
Issue Date:
DOI: https://doi.org/10.1023/A:1019164928084