Synthesis of Ethyl 2-Arylaminoimidazo[2,1-b]benzothiazole-3-carboxylates Jabbar Khalafy,* Ali Reza Molla Ebrahimlo and Karim Akbari Dilmaghani Chemistry Department, Urmia University, Urmia 57159, Iran 3-Arylamino-4-ethoxycarbonylisoxazol-5(2H)-ones, substituted on nitrogen with a benzothiazole group, reacts with triethylamine in ethanol under reflux conditions to provide a convenient synthesis of ethyl 2-aryl- aminoimidazo[2,1-b]benzothiazole-3-carboxylates. Keywords: Isoxazolones; 2-Chlorobenzothiazole; Imidazobenzothiazoles; Base induced rearrangement; Triethylamine. INTRODUCTION The synthesis of isoxazol-5(2H)-one with benzothi- azole substituted on nitrogen 1a has been reported by Prager and co-workers 1 as shown in Scheme I. It has been reported 2 that the 2-benzothiazol-2-yl iso- xazolones 1a and 2b gave the corresponding imidazobenzo- thiazoles 2a and 2b respectively on photolysis in ethyl ace- tate/trifluoroacetic acid, and the acrylate 3 was obtained from the photolysis of 1a in methanol. Base-catalysed rearrangement of isoxazolinyl hetero- cycle 1a using a solution of sublimed potassium t-butoxide in dry tetrahydrofuran at 40 °C gave ethyl 2-hydroxy-4-oxo- 4H-pyrimido[2,1-b]benzothiazole-3-carboxylate 4. 3 We have recently reported 4 that the reaction of certain 2-aryl-3-arylaminoisoxazolones 5 with triethylamine leads to the formation of indoles 6 and carbon dioxide, an outcome that is formally the same as that achieved by photolysis or py- rolysis 5 (Scheme II). We have also reported 6 that 3-(4-substituted phenyl)- aminoisoxazol-5(2H)-ones, substituted on nitrogen with a nitropyridine group, react with triethylamine to give imi- dazo[1,2-a]pyridines and indoles. With 4-bromophenyl and Journal of the Chinese Chemical Society, 2004, 51, 1347-1352 1347 * Corresponding author. Fax: (+98)441-3443442; e-mail: jkhalafi@yahoo.com; J.khalafi@mail.urmia.ac.ir N O H R EtO 2 C O S N Cl 130 o C / 15 min O R EtO 2 C O S N N 1a R=H Scheme I N S N O OH CO 2 Et 4 N O O CO 2 Et Ar NH 5 TEA / EtOH N ArHN E tO 2 C H 6 Scheme II