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3-Dimethyl-1-[3-methyl-(4H)-5-phenylimidazol[2,1-b]thiazol-2-yl]prop-2-enone 4 couples smoothly with benzenediazonium chloride to yield propanal 5 which is a key intermediate for the synthesis of pyridazinones 9–13, 16 and pyridazine-6-imine 8, 19. Pentadienonitrile 18 was converted into pyridine-3-carbonitrile 20 on refluxing in ethanolic sodium ethoxide solution. Pyrazole 24 was synthesized from the reaction of 5 with 1-chloro-2-phenylhydrazono propan-2-one 22.

5-arylidene-2-thiohydantoins 1a–c react with ethyl α -chloroacetate 2 and monochloroacetone to give the respective 2-imidazolinones 3a–c and 2-acetonylmercaptohydantoins 9a–c . Compounds 3a–c react with benzenediazonium chloride to afford hydrazones 5a–c . The reaction of 1a–c with ethylene bromide and with α,α -dichloroacetone gives the respective alkyl mercapto-derivatives 13a–c and 14a–c . The reaction of polyphosphoric acid with 3a–c , 9a–c , 13a–c and 14a–c yields the respective thiazolones 7a–c , imidazothioles 10a–c , imidazo-thiazoles 15a–c and imidazothiazines 16a–c . The mercapto-hydantoins 17a–d react with anthranilic acid to give quinazolin-3,5-diones 19a,b and/or 21a , b . Structural elucidation for the new products are based on compatible elementary and spectroscopic evidences.

Reaction of benzenediazonium chloride with active [1,2,4]triazin-3-ylthio-methylene compounds 3 afforded the azo coupling products 5, which yielded [1,2,4]triazolo[4,3-b][1,2,4]triazin-7(1H)-ones 8 upon treatment with sodium ethoxide in ethanol. The latter products 8 were characterized on the basis of alternate synthesis and spectral data. The mechanism of formation of 8 and the regiochemistry of the studied reactions are discussed.

Thiazole 1, when reacted with chloroacetyl chloride, afforded N-(5-acetyl-4-methylthiazol-2-yl) chloroacetamide 2. It has been found that compound 2 reacted with α-cyanocinnamonitrile derivatives 6a–c to afford reaction products 8a–c. Also, compound 2 coupled smoothly with benzenediazonium chloride afforded the phenylhydrazone 14. Coupling of the sulfonium bromide 17 with diazotized aromatic amines or N-nitrosoacetanilides afforded the arylhydrazones 20a,b. Treatment of 16 with 2-cyanoethanethioamide afforded [4-(2-amino-4-methylthiazol-5-yl) thiazol-2-yl] acetonitrile 22. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:362–369, 2000

A novel one-pot synthesis of 3-bromomethylbenzo [d] isoxazole (3) utilizing o-hydroxy-α-bromoacetophenone is reported. Coupling of 3 with benzenediazonium chloride afforded, the first reported, C-(3-benzo [d] isoxazolyl)-N-(phenyl) formohydrazidoyl bromide (13). The chemical behaviour of 3 and 13 towards a variety of chemical reagents has been investigated

When the diazonium salt (I) is heated in dichloroethane in the presence of propylene oxide, the tetra(benzyloxy)azobenzene (II) is obtained in the form of orange crystals.

Ethyl (5-cyanomethyl-1,3,4-oxadiazol-2-yl)acetate (4) could be prepared by condensing cyanoacetohydrazide (2) with diethyl monoimidic malonate (1). The reactivity of 4 towards a variety of electrophilic reagents is reported. The reaction of 1 with 2-amino-1-propene-1,1,3-tricarbonitrile gives the pyridine 12 which is converted into pyridopyridazine 13 on coupling with benzenediazonium chloride.