- CYCLIZATION REACTIONS OF SOME o-ACYLPHENYLHYDRAZONES
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The hydrazones Ia-Id and IIa-IId have been prepared by azo coupling of ethyl cyanacetylcarbamate and cyanacetamide, respectively, with diazotized o-aminoacetophenone, o-aminobenzophenone, 2-(2-aminobenzoyl)benzoic acid and 1-amino-9,10-antraquinone.The hydrazones Ia-Id have been alkaline or thermally cyclized to 2-aryl-4,5-dioxo-2,3,4,5-tetrahydro-1,2,4-triazine-6-carbonitriles IIIa-IIId.On boiling in strongly acidic medium the hydrazones I and II are cyclized to the corresponding 3-substituted indazoles Va-Vc and 2,6-dihydronaphthoindazol-6-one (Vd).Three hours boiling in 20percent hydrochloric acid does not affect the 1,2,4-triazine cycle of nitriles IIIa-IIId, the nitrile groups being only hydrolyzed to give the corresponding carboxylic acids IVa-IVd.On contrary, boiling in aqueous pyridine causes splitting of the 1,2,4-triazine cycle and formation of arylhydrazonocyanacetamides IIa-IId.IR and NMR spectroscopy has been used to study the possibility of simultaneous hydrogen bond to the both carbonyl groups in hydrazones I and II.
- Slouka, Jan,Bekarek, Vojtech,Lycka, Antonin
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p. 1746 - 1756
(2007/10/02)
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