2,3,3‐Trimethylindolenine and 5‐chloro‐2,3,3‐trimethylindolenine were converted into β‐diformyl compounds by the action of the Vilsmeier reagent at 50°C. The dialdehydes reacted with various arylhydrazines and 2‐pyridylhydrazine to produce mono‐hydrazones as mixtures of cis and trans isomers. Heating the hydrazones in refluxing ethanol produced 3,3‐dimethyl‐2‐(1‐aryl‐1H‐pyrazol‐4‐yl)‐3H‐indoles in excellent yields. Reaction of the β‐diformyl compounds with hydrazine itself led directly to 3,3‐dimethyl‐2‐(pyrazol‐4‐yl)‐3H‐indoles.

in Wiley InterScience (www.interscience.wiley.com).5-Hydrazinoquinoline and 8-hydrazinoquinoline were converted via Fischer syntheses with 3-methylbutan-2-one into pyrido-indolenines 2,3,3-trimethyl-3H-pyrrolo[2,3-f]quinoline 7 and 2,3,3-trimethyl-3H-pyrrolo[3,2-h]quinoline 11, respectively. Exposure of the indolenines to the Vilsmeier reagent produced aminomethylene-malondialdehydes 8 and 12, which reacted with hydrazine or arylhydrazines to give 4-(3H-pyrrolo[2,3-f]quinolin-2-yl)-and 4-(3H-pyrrolo[3,2-h]quinolin-2-yl)-pyrazoles, 9 and 13.

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2-(5-Chloro-2-phenoxyphenyl)hydrazine was converted to corresponding 3H-indole by Fischer method utilizing the isopropyl methyl ketone in acetic acid. The reaction of 3H-indole with Vilsmeier-Haack reagent furnished aminomethylene malonaldehyde in excellent yield while the reactions of malonaldehyde with hydrazine, arylhydrazines, amines, cyanoacetamide and hydroxylamine hydrochloride, led to the corresponding pyrazole derivatives, enamines, cyanopyridone, and cyanoacetamide derivatives respectively.