A Novel Route to 4-Aminopyrazoles and Aminopyrazolo[4,3-b]pyridines

Abstract

3-Oxo-2-arylhydrazononitriles 6 are readily converted into 4-aminopyrazoles 1 via reaction with α-haloketones, chloroacetonitrile and ethyl chloroacetate. The aminopyrazoles are readily converted into aminopyrazolo[4,3-b]pyridines upon treatment with malononitrile. Compounds are readily diazotized to yield unstable diazonium salts that readily cyclized into pyrazolo[4,3-c]pyridazines.

Enaminonitriles in Heterocyclic Synthesis: A Route to 1,3-Diaryl-4-aminopyrazole Derivatives

“…In conjunction to our interest in chemistry of pyrazoles [15,16,17] and condensed pyrazoles [18,19,20] we decided to develop an efficient route to the title compounds. A logical route to these compounds would be the reaction of hydrazones 1a , f with functionally substituted alkyl halides to yield targeted compounds 3 via intermediate 2 .…”

Studies with 2‐arylhydrazononitriles: Further investigations on reactivity of 2‐arylhydrazononitriles towards hydroxylamine

“…Arylhydrazononitriles are versatile reagents that have already been extensively utilized as precursors to polyfunctional substituted heteroaromatics [1][2][3][4]. Recently it has been found that whereas the arylhydrazononitriles (1a-g) [5,6] reacted with hydroxylamine hydrochloride in refluxing DMF in presence of sodium acetate to yield 1,2,3-triazoles 3a-g (Scheme 1), treatment of (1h-k) [7] under the same conditions afforded 1,2,4-triazol-5-amine 4h-k. Amidoximes are isolable intermediates in these reactions.…”

3-Aminopyrroles and their application in the synthesis of pyrrolo[3,2-d]pyrimidine (9-deazapurine) derivatives

“…[5][6][7][8][9] Recently we described several efficient approaches to heteroaromatic systems using functionally substituted enamine precursors. [10][11][12][13][14] In continuation to our interest in the chemistry of β,β-enaminonitriles we report here the results of our work aimed at exploring the potential utility of 3-anilino-2-cyanoacrylonitrile in the heterocyclic synthesis. The synthesized β,β-enaminonitriles 2 are converted into the corresponding 3-aminopyrrole derivatives by reaction with α-haloketones under basic conditions, a Thorpe-Ziegler cyclization.…”