The Synthesis of Azulene Derivatives Condensed with Several Heterocycles

The reactions of ethyl 1,2-diaminoazulene-3-carboxylate with formic acid, nitrous acid, glyoxal sodium bisulfite, diacetyl, and benzil afforded the corresponding azulene derivatives condensed at the 1,2-position with nitrogen-containing heterocycles, namely, imidazole, triazole, and pyrazine rings. 2-Amino-1-formylazulene reacted with guanidine or thiourea to give 2-aminoazuleno[2,1-d]pyrimidine. The ultraviolet and visible absorption spectra of these azulenes are presented.