Condensation of 3-methyl/ethyl-5-mercapto-s-triazole with 3-acetylcoumarinand its derivatives

3-Methyl/ethyl-5-mercapto-s-triazoles 2 on condensation with either 3-(2-br omoacetyl)coumarins or with substituted 3-acetyl comarins using bromine in the presence of trichloro-(N,N'-ethylene-bis-aminobenzamide) lanthanum and samarium as a catalyst, followed by cyclization of the intermediate 3-alkyl -5-coumarinacyl-thio-s-triazole 3 using PPA furnish 3-alkyl-5-coumarinylthi azolo[3,2-b]-s-triazoles 4 and not the isomeric 3-alkyl-5-coumarinylthiazol o[2,3-c]-s-triazoles 6. 2-Acetyl- or 2-propanoylhydrazino-4-coumarinyl-thia zolo hydrobromides 5, obtained from the reaction of acetyl/propanoyl thiose micarbazides 1 with either substituted 3-(2-bromoacetyl) coumarins or with bromine and substituted 3-acetylcoumarin using trichloro-(N,N'-ethylene-bis -aminobenzamide)lanthanum (III) and samarium (III) as a catalyst, on treatm ent with phosphoryl chloride undergo facile cyclization yielding 5-alkyl-5- coumarinylthiazolo[2,3-c]-s-triazole 6.