4-Nitrostilbene-2-carboxylic acid was treated with chlorine to obtain 7-nitro-trans-4-chloro-3-phenyl-3, 4-dihydroisocoumarin (7), mp 183484°C. 7-Nitro-3-phenylisocoumarin, mp 256257°C, obtained by dehydrochlorination of (7), could be reduced into 7-amino-3-phenylisocoumarin (5). Diazotization of (5) with subsequent coupling with β-naphthol and β-naphthyl-amine gave red-colored compounds, (9), mp 253.5254.5°C, and (10), mp 248249°C, respectively. 7-Chloro- (11), mp 181. 5, -182. 5°C, and 7-bromo-3-phenyli-socoumarins (12), mp 185. 5186°C, were synthesized from (5) by the Sandmeyer reaction. 7- (2H-Naphtho [1, 2-d] p-triazol-2-yl) -3-phenylisocoumarin (1), mp 309 310°C, was obtained by refluxing (10) with cupric sulfate in pyridine. By heating a mixture of (1), aqueous ammonia, and methyl cellosolve in the autoclave at 200220°C for 10 hrs, 7- (2H-naphtho [1, 2-d] -triazol-2-yl) -3-phenylisocarbostyril (2), mp 333.5334.5°C, was prepared. 2- (3-Carboxy-4-styrilphenyl) -2H-naphtho [1, 2-d] -triazole and 2- (p-styrilphe-ny1) -2H-naphtho [1, 2-d] -triazole were also synthesized for comparison. Their infrared, ultraviolet absorption and fluorescence spectra and that of (1) and (2) were measured and discussed.