Reaction chemistry of tri-substituted mesitylene derivatives and the synthesis of sterically buttressed 1,3,5-triaminocyclohexyl ligands

Abstract

The sterically buttressed triamine cis,cis-2,4,6-trimethyl-1,3,5-triaminocyclohexane is weakly basic in aqueous solution (pK_a: 7.83, 6.73, 5.15; 298 K) because of steric inhibition to solvation. As a result of intramolecular hydrogen-bonding and stabilising σ_C–H–σ*_C–N interactions, the free amine and its monoprotonated salt adopt a conformation in which the three amino groups are axially disposed. It possesses a reduced reactivity in S_N2 reactions and may be converted via selective alkylation or condensation to polydentate ligands incorporating carboxylate, hydroxyphenyl or phosphinate groups. An intramolecular hydride transfer mechanism accounts for the formation of a stable bicyclic amidine formed during acidic hydrolysis of a tricyclic bis-aminal derived from the parent triamine by a phosphinoxymethylation. The crystal structures of two of the mesitylene derivatives have been determined.

References

1. M. Goodall, K. Gloe, P. M. Kelly, D. Parker and H. Stephan, J. Chem. Soc., Perkin Trans. 2, 1997, 59.
2. (a) E. Swarzenbach, Helv. Chim. Acta, 1952, 35, 2344; (b) H. Stetter, D. Thiesen and G. J. Steffens, Chem. Ber., 1970, 103, 200; L. Fabbrizzi, M. Micheloni and P. Paoletti, J. Chem. Soc., Dalton Trans., 1980, 1055.
3. (a) R. F. Childers, R. A. D. Wentworth and L. J. Zompa, Inorg. Chem., 1971, 10, 302; (b) L. J. Zompa, Inorg. Chem., 1971, 10, 2647; (c) E. B. Heisher, A. E. Gebala, A. Levey and P. A. Tasker, J. Org. Chem., 1971, 36, 3042.
4. (a) J. E. Bollinger, J. T. Mague, C. J. O'Connor, W. A. Banks and D. M. Roundhill, J. Chem. Soc., Dalton Trans., 1995, 1677; J. E. Bollinger, J. T. Mague, W. A. Banks, A. J. Kastin and D. M. Roundhill, Inorg. Chem., 1995, 34, 2143; (b) K. Hegetschweiler, M. Ghisletta, T. F. Fassler, R. Nesper, H. W. Schmalle and G. Rihs, Inorg. Chem., 1993, 32, 2032; K. Hegetschweiler, A. Egli, R. Alberto and H. W. Schmalle, Inorg. Chem., 1992, 31, 4027.
5. R. D. Hancock, Chem. Rev., 1989, 89, 1893.
6. K. Hegetschweiler, M. Ghisletta, L. Hausherr-Primo, T. Kradolfer, H. W. Schmalle and V. Gramlich, Inorg. Chem., 1995, 34, 1950.
7. S. de Angelis, A. Batsanov, T. J. Norman, D. Parker, K. Senanayake and J. Vepsalainen, J. Chem. Soc., Chem. Commun., 1995, 2361.
8. E. L. Eliel and S. H. Wilen, Stereochemistry of Organic Compounds, Wiley–Interscience, New York, 1994, p. 696.
9. D. S. Kemp and K. S. Petrakis, J. Org. Chem., 1981, 46, 5140; K. Williams, B. Askew, P. Ballester, C. Buhr, K. S. Jeong, S. Jones and J. Rebek Jr., J. Am. Chem. Soc., 1989, 111, 1070.
10. A. Cahours, Ann. Chim. (Paris), 1849, 25, 40; A. W. Hoffmann, Annalen, 1849, 71, 129; N. A. Kholevo, Zh. Prokl. Khim (Leningrad), 1930, 3, 251.
11. P. Deslongchamps, Stereoelectronic Effects in Organic Chemistry, Pergamon Press, Oxford, 1983; A. J. Kirby, The Anomeric Effect and Related Stereoelectronic Effects at Oxygen, Springer-Verlag, Berlin, Heidelberg and New York, 1983.
12. D. Hofner, S. A. Lesko and G. Binsch, Org. Magn. Reson., 1978, 11, 179.
13. E. Cole, C. J. Broan, K. J. Jankowski, D. Parker, K. Pulukkody, B. A. Boyce, N. R. A. Beeley, K. Millar and A. T. Millican, Synthesis, 1992, 63.
14. K. Hegetschweiler, V. Gramlich, M. Ghisletta and H. Samaras, Inorg. Chem., 1992, 31, 2341.
15. C. H. Rochester and B. Russell, J. Chem. Soc. B, 1967, 743; H. Maskill, The Physical Basis of Organic Chemistry, Oxford University Press, Oxford, 1989, p. 201.
16. G. B. Bates and D. Parker, J. Chem. Soc., Perkin Trans. 2, 1996, 1109.
17. TEXSAN, Version 5.0, TEXRAY Structure Analysis Package, Molecular Structure Corporation, The Woodlands, TX77381, USA, 1989.
18. G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
19. G. M. Sheldrick, SHELXL-93, Program for the Refinement of Crystal Structures, University of Göttingen, Germany, 1993.