Synthesis and reactivity of cationic iridium(I) complexes of cycloocta-1,5-diene and chiral dithioether ligands. Application as catalyst precursors in asymmetric hydrogenation †

Abstract

New chiral dithioether compounds (–)-2,2-dimethyl-4,5-bis(isopropylsulfanylmethyl)-1,3-dioxolane (–)-diospr and (+)-2,2-dimethyl-4,5-bis(phenylsulfanylmethyl)-1,3-dioxolane (+)-diosph were prepared from diethyl (+)-L-tartrate. An alternative synthetic method for preparing the previously described bis(methylsulfanylmethyl) dithioether (–)-diosme was devised. By co-ordinating of the dithioethers to different (cycloocta-1,5-diene)iridium(I) compounds chiral cationic complexes [Ir(cod){(–)-diosme}]BF₄ 1, [Ir(cod){(–)-diospr}]BF₄·CH₂Cl₂ 2 and [Ir(cod){(+)-diosph}]BF₄ 3 were synthesized and then studied by ¹H, ¹³C NMR and FAB mass spectrometry. The complexes reacted with CO to give the corresponding binuclear tetracarbonyls [Ir₂(µ-L)₂(CO)₄][BF]₂ 4-6. The dithioether ligands were replaced by PPh₃ in 1–3 providing [Ir(cod)(PPh₃)₂]BF₄. The addition of H₂ to complexes 1 and 2 at –70 °C gave cis-dihydridoiridium(III) complexes [IrH₂(cod){(–)-L}]BF₄ 7 and 8 which are in equilibrium in solution with the parent complexes, depending on the temperature. Two possible diastereomers were distinguished for 8 at low temperatures. Complexes 1–3 were active precursors in the asymmetric hydrogenation of different prochiral dehydroamino acid derivatives and itaconic acid, at room temperature under an atmospheric pressure of H₂, and the highest enantiomeric excess obtained was 47%.

References

1. C. S. Chin and B. Lee, J. Chem. Soc., Dalton Trans., 1991, 1323 and refs. therein.
2. C. Claver and A. M. Masdeu, Trends Organomet. Chem., 1994, 1, 549 and refs. therein.
3. B. R. James and R. S. McMillan, Can. J. Chem., 1977, 55, 3927.
4. J. Solé, C. Bo, C. Claver and A. Ruiz, J. Mol. Catal., 1990, 61, 163; C. K. Lai, A. A. Naiini and C. H. Brubaker, jun., Inorg. Chim. Acta, 1989, 164, 205; A. A. Naiini, H. M. Ali and C. H. Brubaker, jun., J. Mol. Catal., 1991, 67, 47 and refs. therein.
5. (a) Ph. Kalck, R. Poilblanc, R. P. Martin, A. Rovera and A. Gaset, J. Organomet. Chem., 1980, 195, C9; (b) H. Schumann, H. Hemling, N. Goren and J. Blum, J. Organomet. Chem., 1995, 485, 209; (c) M. Eisen, P. Weitz, S. Shtelzer, J. Blum, H. Schumann, B. Gorella and F. H. Görlitz, Inorg. Chim. Acta, 1991, 188, 167; (d) H. Schumann, B. Gorella, M. Eisen and J. Blum, J. Organomet. Chem., 1991, 412, 251; (e) M. Eisen, J. Blum, H. Schumann and B. Gorella, J. Mol. Catal., 1989, 56, 329.
6. (a) Ph. Kalck, in Organometallics in Organic Synthesis, eds. A. de Meijere and H. tom Dieck, Springer, Heidelberg, 1987, pp. 297–320; (b) S. Gladiali, J. C. Bayón and C. Claver, Tetrahedron Asymmetry, 1995, 6, 1453 and refs. therein; (c) F. Agbossou, J. F. Carpentier and A. Mortreux, Chem. Rev., 1995, 85, 2485; (d) C. Claver, S. Castillón, N. Ruiz, G. Delogu, D. Fabbri and S. Gladiali, J. Chem. Soc., Chem. Commun., 1993, 1833; (e) A. M. Masdeu, A. Orejón, A. Ruiz, S. Castillón and C. Claver, J. Mol. Catal., 1994, 94, 149; (f) A. Castellanos-Paéz, S. Castillón and C. Claver, J. Organomet. Chem., 1997, 539, 1; (g) A. Aaliti, N. Ruiz, J. Forniés, A. Ruiz, C. Claver, C. J. Cardin, D. Fabbri and S. Gladiali, J. Organomet. Chem., in the press.
7. F. Fache, P. Gamez, F. Nour and M. Lemaire, J. Mol. Catal., 1993, 85, 131.
8. H. B. Kagan, in Comprehensive Organometallic Chemistry, eds. G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon, Oxford, 1982, vol. 8, ch. 53; H. Takaya, T. Onta and R. Noyori, in Catalytic Asymmetric Synthesis, ed. I. Ojima, VCH, New York, 1993, ch. 1; R. Noyori, in Asymmetric Catalysis in Organic Synthesis, Wiley, New York, 1994, ch. 2, p. 16; J. M. Brown, Chem. Soc. Rev., 1993, 25; H. Brunner, in Top. Stereochem., 1988, 18, 129; J. M. Brown, in Insights into Speciality Inorganic Chemicals, ed. D. Thompson, The Royal Society of Chemistry, Cambridge, 1995, ch. 6.
9. (a) S. Akutagawa, in Asymmetric Hydrogenation with Ru–BINAP: Chirality in Industry, eds. A. N. Collins, G. N. Sheldrake and J. Crosby, Wiley, Chichester, 1992, p. 325; (b) S. Akutagawa, in Asymmetric Hydrogenation with Ru–BINAP: Catalysis of Organic Reactions, eds. M. Scaros and M. L. Prunier, Marcel Dekker, New York, 1994, p. 135; (c) S. Akutagawa, Appl. Catal. A, Gen., 1995, 128, 171.
10. Asymmetric Synthesis, ed. J. D. Morrison, Academic Press, New York, 1985, vol. 5; R. Noyori, Science, 1990, 245, 1194; W. S. Knowles, Acc. Chem. Res., 1983, 16, 106; Asymmetric Catalysis, Maryinus Nijhoff, Boston, MA, 1984; J. M. Brown, Nature (London), 1991, 350, 191.
11. W. S. Knowles, J. Chem. Educ., 1986, 63, 222.
12. W. A. Nugent, T. V. RajanBabu and M. J. Burk, Science, 1993, 259, 479; G. M. Ramos Tombo and D. Bellus, Angew Chem., Int. Ed. Engl., 1991, 30, 1193; J. Alberecht and U. Nagel, Angew. Chem., Int. Ed. Engl., 1996, 35, 407.
13. M. J. Burk, J. E. Feaster and R. L. Harlow, Organometallics, 1990, 9, 2653; M. J. Burk, J. E. Feaster, W. A. Nugent and R. L. Harlow, J. Am. Chem. Soc., 1993, 115, 10 125.
14. T. V. RajanBabu, T. A. Ayers and A. L. Caslnuovo, J. Am. Chem. Soc., 1994, 116, 4101.
15. T. Ohta, H. Takaya, M. Kitamura, K. Nagai and R. Noyori, J. Org. Chem., 1987, 52, 3174.
16. (a) P. A. Chaloner, M. A. Esteruelas, F. Joó and L. A. Oro, in Homogeneous Hydrogenation, Kluwer, Dordrecht, 1994, ch. 4; (b) L. A. Oro, J. A. Cabeza, C. Cativiela, M. D. Díaz de Villegas and E. Meléndez, J. Chem. Soc., Chem. Commun., 1983, 1383; (c) J. A. Cabeza, C. Cativiela, M. D. Díaz de Villegas and L. A. Oro, J. Chem. Soc., Perkin Trans. 1, 1988, 1881.
17. H. B. Kagan and T. P. Dang, J. Am. Chem. Soc., 1972, 94, 6429.
18. M. Carmack and C. J. Kelley, J. Org. Chem., 1969, 33, 2171.
19. R. D. Feltham and R. G. Hayter, J. Chem. Soc., 1964, 4587; R. Uson, J. Gimeno, J. Fornies and F. Martínez, Inorg. Chim. Acta, 1981, 50, 173; A. Ruiz, C. Claver, J. C. Rodríguez, M. Aguiló, X. Solans and M. Font-Altaba, J. Chem. Soc., Dalton Trans., 1984, 2665.
20. W. J. Hälg, L. R. Öhrström, H. Rüeggh, L. M. Venanzi, T. Gerfin and V. Gramlich, Helv. Chim. Acta, 1993, 76, 788.
21. Ph. Kalck and R. Poilblanc, Inorg. Chem., 1975, 14, 2779; J. C. Rodriguez, A. Ruiz and C. Claver, Transition Met. Chem., 1984, 9, 237.
22. M. Green, T. A. Kuc and H. Taylor, J. Chem. Soc. A, 1971, 2334.
23. J. C. Rodriguez, C. Claver and A. Ruiz, J. Organomet Chem., 1985, 293, 115.
24. D. Sellmann, H.-P. Neumer and F. Knoch, Inorg. Chim. Acta, 1991, 190, 61.
25. R. H. Crabtree, H. Felkin, T. Fillebeen-Khan and G. E. Morris, J. Organomet. Chem., 1979, 168, 183.
26. (a) D. G. Hamilton and R. H. Crabtree, J. Am. Chem. Soc., 1988, 110, 4126; (b) J. C. Lee, jun., W. Yao and R. H. Crabtree, Inorg. Chem., 1996, 35, 695.
27. K. Nakamoto, in Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley, New York, 1978.
28. I. Ojima, T. Kogure and N. Yoda, J. Org. Chem., 1980, 45, 4728.
29. J. L. Herde, J. C. Lambert and C. V. Senoff, Inorg. Synth., 1974, 15, 18.
30. J. Chatt and J. M. Davidson, J. Chem. Soc. A, 1965, 843.
31. C. Cativiela, J. Fernandez, J. A. Mayoral, E. Melendez, R. Usón, L. A. Oro and M. J. Fernandez, J. Mol. Catal., 1992, 16, 19.
32. H. Frank, C. J. Nickolson and E. Bayer, J. Chromatogr. Sci., 1977, 15, 174.