3-Hydroxy-2-naphthoic hydrazide may be used to synthesize the following 2-(alkyl/arylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazoles:2-ethylamino-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-phenethylamino-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-phenylamino-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(p-bromophenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(p-chlorophenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(p-fluorophenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(m-fluorophenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(p-methoxyphenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(p-methylphenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazole2-(m-trifluoromethylphenylamino)-5-(3-hydroxy-2-naphthyl)-1,3,4-thiadiazoleIt may also be employed for the synthesis of 3-hydroxy-2-naphthaldehyde.