Multistep synthesis of thiazoloquinazolines under microwave irradiation in solution

Thiazolo[5,4-f]quinazolines are synthesised in six or seven steps from 2-amino-5-nitrobenzonitrile. Both heterocyclic rings are fused onto the central benzene ring via imino-1,2,3-dithiazoles which are readily obtained from primary aromatic amines and 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt). Four of the steps were improved in yield or reaction time or both, compared to conventional heating, by microwave irradiation of solutions of the reactants in a focused open microwave oven.