Synthesis of novel 3-hetaryl-substituted 6- and 8-hydroxybenzo[f]coumarin derivatives

Eight novel 3-hetaryl-substituted 6- and 8-hydroxybenzo[f]iminocoumarin compounds were synthesised by the reaction of 2,5-dihydroxynaphthaldehydes or 2,7-dihydroxynaphthaldehydes with 2-cyanomethylbenzo-thiazole, 2-cyanomethylbenzoimidazole, 1-methyl-2-cyanomethylbenzoimidazole and 2-cyanomethyl-4-phenylthiazole. The iminocompounds obtained were hydrolysed with hydrochloric acid to the benzo[f]coumarins. Becaue of the high reactivity of the iminocoumarins, only mixtures which also contained the corresponding coumarin compounds were isolated. The absorption and steady-state fluorescence characteristics of the benzo[f]coumarins (benzo[f]chromen-2-ones) synthesised were studied in ethanol and in toluene.