Improved access to thiazolo[5,4-d]thiazole and thieno[2,3-d]thiazole

Abstract

Five-membered rings are of interest as building blocks for nonlinear optical (NLO) materials. We found easy access to the title compounds: thiazolo[5,4-d]thiazole 1 has been obtained in three simple steps starting with the chlorination of ethyl isothiocyanatoacetate 8, followed by dehydrohalogenation to the diethyl 2,5-dicarboxylate of 1, which yielded 1 after saponification and decarboxylation. Thieno[2,3-d]thiazole 2 has been synthesized in two steps by reductive deamination of the easily available 2-aminothieno[2,3-d]thiazole 5.

References

1. P. Boldt, M. Blenkle, I. Cabrera, D. Lupo and W. Hickel, Nonlinear Opt., 1994, 173.
2. M. Blenkle, P. Boldt, C. Bräuchle, W. Grahn, I. Ledoux, H. Nerenz, S. Stadler, J. Wichern and J. Zyss, J. Chem. Soc., Perkin Trans. 2, 1996, 1377.
3. G. Subramanian, P. v. Rague-Schleyer and H. Jiao, Angew. Chem., 1996, 108, 2824.
4. C. W. Dirk, H. E. Katz and M. L. Schilling, Chem. Mater., 1990, 2, 700.
5. J. R. Johnson, D. H. Rotenberg and R. Ketcham, J. Am. Chem. Soc., 1970, 4046.
6. C. Paulmier and F. Outurquin, J. Heterocycl. Chem., 1983, 20, 113.
7. S. Athmani, M. F. Farhat and B. Iddon, J. Chem. Soc., Perkin Trans. 1, 1992, 973.
8. G. Beck, H. Heitzer and H. Holtschmidt, Synthesis, 1985, 586.
9. R. Bossio, S. Marcaccini, R. Pepino, T. Torroba and G. Valle, Synthesis, 1987, 1138.
10. G. Ottmann and H. Hooks, J. Org. Chem., 1966, 31, 838.