Synthesis and Reactions of 2-(4-Oxochromen-3-yl) benzothiazolium and -benzoxazolium Bromides
Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2, SK-842 15 Bratislava, Slovak Republic
a Department of Chemistry, Faculty of Natural Sciences, University of St. Cyril and Methodius, Námestie Jozefa Herdu 2, Sk-917 01 Trnava, Slovak Republic
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Abstract: Benzothiazolium and benzoxazolium bromides 4, 5 were synthesized either by one-pot condensation of substituted 4-oxochromene-3-carboxaldehydes 1 with 2-methylbenzothiazole (2a) or 2-methylbenzoxazole (2b) and benzyl bromide or by condensation of 1 with 2-methylbenzothiazolium or 2-methylbenzoxazolium bromides 3 under microwave irradiation or by the classical heating. The advantage of microwave irradiation in comparison with classical reactions was reflected in the significantly reduced reaction time and increased yields. Reactions of resulting benzothiazolium salt 4b with primary and secondary amines led to 2-substituted derivatives 6 or phenylpyrazolo[3,4-b]pyridine 7.
Keywords: benzoxazolium bromides, benzothiazolium bromodes, microwave irradiation, 4-oxochromene-3-carboxaldehydes
Full paper in Portable Document Format: acs_0032.pdf
Acta Chimica Slovaca, Vol. 2, No. 1, 2009, pp. 12—24