Heteroannulation of chromene derivatives. Synthesis of chromeno[4,3- e ] indazolone chromeno[4,3- f ]quinazoline and pyrano[3,2- c ]chromene derivatives

Abstract

Pentane-2,4-dione and 3-ethoxycarbonylcoumarin react in the presence of sodium ethoxide to form 10-acetyl-7,9-dihydroxy-6H-benzo[c]chromen-6-one (2). Compound 2 reacted with aromatic aldehydes and ethyl cyanoacetate to give the chromeno-chromenediones 3 and 4 respectively, with hydrazine hydrate to form the azine 5, with phenyl hydrazine giving the chromeno-indazole 6, with primary amines to form the imines 7a–f, and with thiourea to give the chromeno-quinazoline 8. Methyl 2-amino-4-(4-methoxyphenyl)-5-oxo-4,5-dihydro-pyrano[3,2-c]chromene-3-carboxylate (9a) and the corresponding 3-carbonitrile 9b were prepared, and the reactions of the ester 9a with phenacyl chloride, furoyl chloride, and hydrazine hydrate were investigated.