Microwave-assisted and conventional synthesis of benzothieno [3,2-e] [1,3,4] triazolo[4,3-c]pyrimidines: A comparative study

Benzothieno[2,3-d]pyrimidines (2,3,4) and benzothieno[3,2-e][1,3,4] triazolo[4,3-c] pyrimidines (5a-c) were synthesized from the precursor 2-amino-7-oxo-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile 1 by employing the conventional method as well as the microwave irradiation technique. The precursor 2-amino-3-cyanothiophene analogue 1 was synthesized by employing the well-known Gewald reaction. In the present work it has been found that the microwave supported syntheses are more efficient than the conventional classical heating methods. The structures of all the compounds were ascertained by spectral and analytical data.