Jan-Feb 2007 Flash Vacuum Pyrolysis of 1-Azolyl- 1-phenylhydrazono-2-propanones 219 Osman M. E. El-Dusouqui, a Mervat M. Abdelkhalik, b Alya M. Al-Etaibi, c Hicham H. Dib, a Nouria A. Al-Awadi a a Chemistry Department, Kuwait University, P.O. Box 5969 Safat, 13060 Kuwait b Applied Science Department, College of Technological Studies, Public Authority for Applied Education and Training, Kuwait c Science Department, College of Nursing, Public Authority for Applied Education and Training, Kuwait Received February 15, 2006 G H N N N N G CH 3 N N R= 1,2,4-triazole G H N O CH 3 R N H O H 3 C G N N R = benzimidazole + Flash vacuum pyrolysis (FVP) of 1-(2-arylhydrazono)-1-(1H-1,2,4-triazol-1-yl)acetone 8a-c at 650°C and 2.67 Pa yielded 5-substituted 1-(1H-indazol-3-yl)ethanone 14a-c and 4,6-disubstituted cinnoline 18a-c. Similarly FVP of 1-(1H-benzo[d]imidazol-1-yl)-1-(2-phenylhydrazono)acetone 9a-c gave 8H- benzo[4',5']imidazo[2',1':5,1]pyrrolo[2,3-c]cinnoline derivatives 23a-c. A plausible mechanism is suggested to account for their transformation based on the kinetics and products of reaction. J. Heterocyclic Chem., 44, 219 (2007). INTRODUCTION We have recently reported efficient procedures for the synthesis of 3-acylcinnolines starting with 3-oxo-3-aryl-2- arylhydrazonopropanal 1, where it underwent preferential cyclization in acid medium to give only the corresponding 3-acylcinnolines 2 (Scheme 1) [1]. Scheme 1 G O Ar N N reaction acid catalysed G H H Ar O N N 2 1 We have also reported the result of efficient utilization of the preparative power of FVP in synthesis of benzimidazo[1,2-b]cinnoline derivatives 4 and several novel condensed heterocycles (Scheme 2) [2-4]. RESULTS AND DISCUSSION In the present work we describe our results on the FVP of 8a-c and 9a-c prepared via coupling of 6 and 7 with aromatic diazonium salts following literature procedures (Scheme 3) [5,6]. Scheme 2 H 2 O N 2 CH 3 R H O N Ar N G CH 3 Bt O N H N G NHCOCH 3 G CH 3 N N N 5 Products Bt = 1-benzotriazole + 4 3 Scheme 3 CH 3 N N O NCl - ArN + NCl - ArN + CH 3 N N N O G CH 3 N N O N H N G CH 3 N N N O N H N 8-9a, G = H b, G = CH 3 c, G = Cl 7 6 8 9