Synthesis and Antidepressant Activity of Some New Coumarin Derivatives

The coumarin-3-cinnamoyl derivatives 2a-d were prepared via Claisen-Schmidt condensation of 3-acetylcoumarin 1 with different aromatic aldehydes. Cycloaddition reaction of 2b,e with guanidine and thiourea yielded the corresponding aminopyrmimidine 3a,b and thioxypyrimidine derivatives 4a,b, respectively. Compounds 4a,b were condensed with chloroacetic acid or 3-bromopropionic acid to yield coumarin 3-thiazolo-pyrimidine 5a,b and thiazinopyrimidine 6a,b derivatives, respectively. Compounds 4a,b were condensed with chloroacetic acid and aromatic aldehyde to yield the aryl methylene derivatives 7a,b which could be prepared directly by condensation of compounds 5a,b with aromatic aldehydes. Compounds 2a-e were condensed with malononitrile or ethyl cyano acetate in presence of ammonium acetate to yield cyanopyridine 8a,b and cyanopyridone 9a-d derivatives, respectively, which were prepared by condensation of 3-acetylcoumarin 1, malononitrile or ethylcyanoacetate and aromatic aldehydes in presence of ammonium acetate. Condensation of compounds 2a,b,e with o-phenylenediamine in refluxing ethanol led to the formation of 10a-c as intermediate, followed by cleavage by thermolysis to benzimidazole derivative 11 along with compounds 12a-c as mixture, which were obtained directly by fusion of a,&unsaturated ketones 2 with ophenylene diamine at 200-220°C, while compound 11 could be prepared in pure form by fusion of 1 with o-phenylene diamine at the same temperature. The pharmacological screening showed that many of these obtained compounds have good antidepressant activity comparable to Tranylcypromine® as reference drugs.