Metal-assisted reactions. Part 27.1 3-Benzyloxy-1,2-benzisothiazole 1,1-dioxide: an unusual ether linkage that does not permit heterogeneous catalytic hydrogenolysis

Abstract

Aryl or allyl ethers of some heterocyclic systems can be readily hydrogenolysed or cross-coupled catalytically with transition metals to give arenes, alkenes or alkanes. Unexpectedly for transition metals, the corresponding alkyl and, particularly, benzyl ethers are totally inert. An X-ray structure determination on 3-benzyloxy-1,2-benzisothiazole 1,1-dioxide 1 has shown that there is no inherent structural reason for this major difference, apart from the absence of a suitable p-orbital in the benzyl ethers.

References

1. Part 26. J. A. C. Alves, J. V. Barkley, A. F. Brigas and R. A. W. Johnstone, J. Chem. Soc., Perkin Trans. 2, 1997, 669.
2. R. N. Butler, in Comprehensive Heterocyclic Chemistry, vol. 5, Part 4A, ed., K. T. Potts, Pergamon Press, Oxford, 1984, pp. 834–838 and in Comprehensive Heterocyclic Chemistry II, vol. 4, ed., R. C. Storr, Pergamon Press, Oxford, 1996, pp. 672–678; M. L. Carmellino, M. Montagelo, G. Pagani, F. Pastoni, M. Pregnolato and M. Terrini, J. Med. Chem., 1996, 31, 919.
3. A. F. Brigas and R. A. W. Johnstone, Tetrahedron Lett., 1990, 31, 5789; R. A. W. Johnstone and P. J. Price, Tetrahedron, 1985, 41, 2483.
4. A. F. Brigas and R. A. W. Johnstone, J. Chem. Soc., Chem. Commun., 1994, 1923.
5. A. F. Brigas and R. A. W. Johnstone, Acta Crystallogr., Sect. C, 1996, 52, 1293.
6. J. A. C. Alves, A. F. Brigas and R. A. W. Johnstone, Acta Crystallogr., Sect. C, 1996, 52, 1576.
7. M. L. S. Cristiano, R. A. W. Johnstone and P. J. Price, J. Chem. Soc., Perkin Trans. 1, 1996, 1453.
8. See, for example, P. A. Chaloner, Handbook of Coordination Catalysis in Organic Chemistry, Butterworths, London, 1986, pp. 266–268, 851; H. M. Colquoun, J. Holton, D. J. Thompson and M. V. Twigg, New Pathways for Organic Synthesis, Plenum Press, New York, 1984, pp. 18–19, 202–203, 234; P. Knochel, Synlett., 1995, 393; R. Vanasselt and C. J. Elsevier, Organometallics, 1994, 13, 1972; V. Galamb, G. Palyi, F. Ungvary, L. Marko, R. Boese and G. Schmid, J. Am. Chem. Soc., 1986, 108, 3344; and see ref. 11, pp. 160–161.
9. F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and R. Taylor, J. Chem. Soc., Trans. Perkin 2, 1987, S1–S19.
10. For C–O bonds, the bond order n is related to bond length r_n by the expression, r_n=r₁– 0.28ln n, in which r₁ is an average length for an aliphatic single C–O bond. Thus, bond order can be estimated from bond length. It has been shown that the equation, D_n=D₁×n^p, relates the bond strength (D_n) for any C–O bond of order n with that of a single C–O bond (D₁); the exponent p is very close to 1 and so, D_n=D₁×n. See ref. 1 and other leading references therein.
11. R. A. W. Johnstone, A. H. Wilby and I. D. Entwistle, Chem. Rev., 1985, 85, 129; 164–165.
12. Molecular Structure Corporation ( 1995), TEXSAN. Single Crystal Structure Analysis Software, Version 1.7. MSC, 3200 Research Forest Drive, The Woodlands, TX 77381, USA.
13. For details of the deposition scheme, see ‘Instructions for Authors’, J. Chem. Soc., Perkin Trans. 1, 1997, Issue 1. Any request to the CCDC should quote the full literature citation and the reference number 207/131.