204
CARLONI ET AL.
the linear biscarbonates become the sole reaction products
(Table 2, entries s and t).
6. (a) Crowther, H. L., and McCombie, H., J. Chem. Soc. 103, 27 (1913);
(b) Ben–Ishai, D., J. Am. Chem. Soc. 78, 4692 (1956).
7. Bigi, F., Maggi, R., and Sartori, G., Green Chem. 2, 140 (2000).
8. Inesi, A., Mucciante, V., and Rossi, L., J. Org. Chem. 63, 1337 (1998).
9. (a) McGhee, W., Riley, D., Christ, K., Pan, Y., and Parnas, B., J. Org.
Chem. 60, 2820 (1995); (b) Yoshida, M., Hara, N., and Okuyama, S.,
Chem. Commun. 151 (2000).
4. CONCLUSIONS
In conclusion, we have shown that the hybrid organic–
inorganic material prepared by anchoring TBD to MCM-41 10. Sheldon, R. A., Chem. Ind. (London) 12 (1997).
11. Vauthey, I., Valot, F., Gozzi, C., Fache, F., and Lamaire, M.,
Tetrahedron Lett. 41, 6347 (2000).
12. Ono, Y., Appl. Catal. A 155, 133 (1997).
silica can be utilized as efficient heterogeneous basic cata-
lystforthe synthesisof carbamatesandunsymmetricalalkyl
carbonates by reaction of DEC with aliphatic amines or
alcohols. Products are obtained in high yield and selectivity
and the solid catalyst can be recovered simply by filtration
and reused for different cycles without apparent lowering
of activity. A supported N-carbethoxyguanidinium active
intermediate is proposed, and some spectroscopic data are
shown to support the mechanistic hypothesis.
13. Saikh, A.-A. G., and Sivaram, S., Chem. Rev. 96, 951 (1996).
14. (a) Lindner, E., Schneller, T., Auer, F., and Mayer, H. A., Angew.
Chem. Int. Ed. Engl. 38, 2154 (1999); (b) “Chiral Catalyst Immobili-
sation and Recycling” (D. E. De Vos, I. F. J. Vankelecom, and P. A.
Jacobs, Eds.). VCH, Weinheim, 2000.
15. Subba Rao, Y. V., De Vos, D. E., and Jacobs, P. A., Angew. Chem. Int.
Ed. Engl. 36, 2661 (1997).
16. Blanc, A. C., Macquarrie, D. J., Valle, S., Renard, G., Quinn, C. R., and
Brunel, D., Green Chem. 2, 283 (2000).
17. (a) Weisel, C. A., Mosher, H. S., and Whitmore, F. C., J. Am. Chem.
Soc. 67, 1055 (1945); (b) Williams, J. L. R., Reynolds, D. D., Dunham,
K. R., and Tinker, J. F., J. Org. Chem. 24, 64 (1958).
18. Carothers, W. H., and van Natta, J., J. Am. Chem. Soc. 52, 314
(1930).
19. The loading of MCM-41–TBD catalyst is 1.04 mmol/g, the surface area
is 385 m2 g 1, and the material is thermally stable up to 200 C.
20. The loading of KG-60–TBD catalyst is 0.47 mmol/g, the surface area
is 155 m2 g 1, and the material is thermally stable up to 200 C.
21. (a) Climent, M. J., Corma, A., Guil–Lo´pez, R., Iborra, S., and Primo,
J., J. Catal. 175, 70 (1998); (b) Macquarrie, D. J., and Jackson, D. B.,
J. Chem. Soc., Chem. Commun. 1781 (1997).
ACKNOWLEDGMENTS
The authors acknowledge the support of the Ministero dell’Universita`
e della Ricerca Scientifica e Tecnologica (MURST), Italy; the Consiglio
Nazionale delle Ricerche (CNR), Italy; and the University of Parma
(National Project “Processi Puliti per la Chimica Fine”). The authors are
grateful to the Centro Interdipartimentale Misure (CIM) for the use of
NMR and mass instruments and to Mr. Pier Antonio Bonaldi (Lillo) for
technical collaboration.
REFERENCES
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lower reactivity and gave mixtures of carbamates and ureas: for ex-
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carbamate ethyl ester (28%) and diphenylurea (24%).