Synthesis of isocyanates from carbamate esters employing boron trichloride

Abstract

The conversion of carbamate esters to isocyanates and diisocyanates of industrial importance is possible using BCl₃ in the presence of Et₃N; the reaction is simple in execution and work-up, occurring under mild conditions and affording isocyanates in excellent yields.

References

1. P. Braunstein, Chem. Rev., 1989, 89, 1927; G. Ortel, Polyurethane Handbook, Hanser, Munich, 1985; H. Twichett, Chem. Rev., 1974, 74, 209.
2. Kirk-Othmer, Encyclopaedia of Chemical Technology, 4th edn., Wiley, New York, 1995, vol. 14, p. 902.
3. (a) S. J. Skoog and W. L. Gladfelter, J. Am. Chem. Soc., 1997, 119, 11 049; (b) A. M. Tafesh and J. Weiguny, Chem. Rev., 1996, 96, 2035; (c) P. Wehman, P. C. J. Kamer and P. W. N. M. van Leeuwen, Chem. Commun., 1996, 217; (d) I. Pri-Bar and J. Schwartz, J. Org. Chem., 1995, 60, 8124; (e) V. L. K. Valli and H. Alper, J. Am. Chem. Soc., 1993, 115, 3778 and references cited therein.
4. V. L. K. Valli and H. Alper, Organometallics, 1995, 14, 80; T. W. Leung and B. D. Dombek, J. Chem. Soc., Chem. Commun., 1992, 205; S. Cenini, M. Pizzotti and C. Crotti, in Aspects of Homogeneous Catalysis, ed. R. Ugo, Reidel, Dordrecht, The Netherlands, 1988, vol. 6, p. 97 and references cited therein.
5. V. L. K. Valli and H. Alper, J. Org. Chem., 1995, 60, 257.
6. H. Alper, H. Hamel, D. J. H. Smith and J. B. Woell, Tetrahedron Lett., 1985, 26, 2273; K. E. Hashem, J. B. Woell and H. Alper, Tetrahedron Lett., 1984, 25, 4879; J. B. Woell and H. Alper, Tetrahedron Lett., 1984, 25, 3791.
7. L. A. Paquette, Encyclopaedia of Reactants for Organic Synthesis, Wiley, Chichester, 1995, p 645.
8. Kirk-Othmer, Encyclopaedia of Chemical Technology, 4th edn., Wiley, New York, 1997, vol. 24, p. 695.
9. D. Riley, W. D. McGhee and T. Waldman, ACS Symp. Ser., 1994, 577, 122.