synthesis with nitriles synthesis of some new mercaptopyridazine, mercaptopyridazino[1,6-a]quinazoline and thiophene derivatives合成与腈合成一些新的mercaptopyridazine mercaptopyridazino[1,6]喹唑啉和噻吩衍生物.pdf

Molecules 2008, 13, 2750-2757; DOI: 10.3390/molecule OPEN ACCESS molecules ISSN 1420-3049 /journal/molecules Article Synthesis with Nitriles: Synthesis of Some New Mercapto- pyridazine, Mercaptopyridazino[1,6-a]quinazoline and Thiophene Derivatives Mariam A. Al-Sheikh Chemistry, Girls College of Education, Jeddah, P. O. Box 138016, Jeddah 21323, Kingdom of Saudi Arabia; E-mail: r1425@ Received: 17 July 2008; in revised form: 20 October 2008 / Accepted: 28 October 2008 / Published: 4 November 2008 Abstract: 2-(1-(4-Bromophenyl)-2-thiocyanatoethylidene)malononitrile (3) undergoes azo coupling with diazotized aromatic amines to afford arylhydrazone derivatives, which are readily cyclized to afford the corresponding 3(2H)-pyridazinimine derivatives upon reflux in aqueous NaOH. Under similar condition an o-cyanoarylhydrazone derivative was cyclized into 6H-pyridazino[1,6-a]quinazolin-6-imine, which in turn was easily transformed into 6H-pyridazino[1,6-a]quinazolin-6-one on reflux in ethanolic/HCl. Compound 3 afforded substituted 5-acetylthiophene derivatives upon reflux in AcOH/HCl mixtures. Keywords: Thiophene; Pyridazine; Pyridazino[1,6-a]quinazoline. Introduction During the past few decades there has been increasing interest in the synthesis and properties of pyridazines, pyridazinones and pyridopyridazinones. Pyridazines and pyridazino[1,6-a]quinazolines show diuretic [1], antihyprertensive [2,3], anticonvulsant, antispasmodic and muscle relaxant activities [3,4]. T