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Die anodische Oxidation von 15 tert‐butyl‐substituierten Phenolen 1a–o in wasserfreiem Acetonitril oder in Acetonitril/Perchlorsäure führt zu den entsprechenden 7‐tert‐Butyl‐2‐methylbenzoxazolen 3a–o. Der Strukturbeweis wurde durch unabhängige Synthese von 3k und 13C‐NMR‐Spektroskopie sowie durch Röntgenstrukturanalyse von 7‐tert‐Butyl‐2‐methyl‐5‐benzoxazolcarbaldehyd (3i) geführt. Der Einfluß des Elektrolytsystems auf die Produktbildung wird diskutiert.

3-Amino-4-cyanopyrazole I reacts with hydroxylamine and with hydrazine to yield 1H,6H-3-aminopyrazolo[3,4-c]pyrazole (III and IV). Diazotized IV couples with 2-naphthol to give the arylazo derivative VI which cyclizes to 9H-naphthol[2,1-e]pyrazolo[3',4':3,4]pyrazolo[5,1-c]-[1,2,4]triazine VII by means of acetic acid. The pyrazol-5-ylthiourea obtained from I and phenyl isothiocyanate undergoes base-catalyzed cyclization to give pyrazolo[3,4-d]pyrimidinethione derivative IX. Compound I reacts with cyclohexane in the presence of zinc chloride to give the tetrahydropyrazolo[3,4-b]quinoline derivative XI. The reaction of I with pyridine 1-oxide affords 4H,5H-pyrazolo[5',1':2,3] [1,2,4]triazolo[1,5-a]pyridine-3-carbonitrile XII.

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in Wiley InterScience (www.interscience.wiley.com).Synthesis of new heterocyclic compounds containing the pyridazinone moiety, which have a valuable biological activities, has been achieved through the nucleophilic addition of benzylamine to 4-(p-substituted phenyl)-4-oxo-2-butenoic acid 1a,b, followed by cyclocondensation of the adducts 2a,b to the corresponding pyridazin-3-one derivatives 3a,b. The behavior of the latter compounds toward different nucleophilic and electrophilic reagents was investigated. The structures of the newly synthesized compounds were elucidated by elemental analysis and spectroscopic data.

a y p t . f&smct Condensation of 3-amino4cyanopyrazole (1) with ethylacetoacetate, ethyl cyanoacetate, diethy1 malonate and acetylacetone afforded pyrazolo[l,5-a]pyrimidine derivatives (2-8a). Other cqmpounds (Sb-b) of this ring system were obtained by treatment of 1 with arylidenemalononitrile and ethylarylidenecyanoacetate. And the reaction of compound (1) with activated acetylenes yeilded pyrazolo[l,5-~~pyrimidine derivatives (lla-b).A solution of 1 (1.08 g, 0.01 mole) and activated acetylenes (namely, methyl propiolate, ethyl propiolate and / or dimethyl acetylenedicarboxylate, 0.01 mole) in dioxane (20 mL) was refluxed for 10 h, the solvent was evaporated in vacuum and the residue was crystallized from suitable solvent to give lla, b.The characterization of these new compound are given in Table 1.

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