Abstract
5-Amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile, prepared by reaction of malononitrile dimer with hydrazine, smoothly reacts with chloroacetyl chloride to form 2-chloro-N-(4-cyano-3-(cyanomethyl)-1H-pyrazol-5-yl)acetamide in good yield. The latter easily reacts with 3-cyanopyridine-2-thiolates to give hybrid molecules bearing nicotinonitrile and pyrazole units.
1. Introduction
3(5)-Aminopyrazoles have been extensively used as easily accessible reagents in designing and building of a number of ring-fused pyrazoles of potential synthetic and medicinal interest such as pyrazolo[3-b]pyridines, pyrazolo[1,5-a]pyrimidines, pyrazolo[3,4-d]pyrimidines, pyrazolo[3,4-b]pyrazines, etc. [,,,].
In 1959, Taylor and Hartke reported [] the synthesis of 5-amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile 1 by reaction of malononitrile dimer with hydrazine (Scheme 1).
Scheme 1.
Synthesis of 5-amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile 1.
This polyfunctionalized pyrazole have been reported to be widely used in organic synthesis for preparation of pyrazolo[3,4-d]pyridazine 2 [], pyrazolo[4,3-c]pyridine 3 [], pyrazolo[1,5-a]pyrimidine 4 [], pyrazolo[1,5-a]quinazoline 5 [], pyrazolo[1,5-a]pyridine 6 [,], pyrazolo[3,4-dlpyrimidine 7 [], pyrazolo-1,3-thiazine 8 [], 3,4-diamino-1H-thieno[3,4-c]pyrazole-6-carbonitrile 9 [], etc. (Scheme 2).
Scheme 2.
The diversity of heterocyclic products derived from 5-amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile 1.
2. Results and Discussion
In continuation of our studies on the chemistry of functionalized pyridines [,,,], we decided to prepare hybrid molecules bearing both nicotinonitrile and 3(50-aminopyrazole moieties. First, we prepared chloroacetamide 10 through reaction of 5-amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile 1 with chloroacetyl chloride (Scheme 3).
Scheme 3.
Synthesis of chloroacetamide 10.
2-Chloro-N-(4-cyano-3-(cyanomethyl)-1H-pyrazol-5-yl)acetamide 10 was found to be reactive towards various S-nucleophiles such as 3-cyanopyridine-2-thiolates, easily available from corresponding 3-cyanopyridine-2(1H)-thione 12 (Scheme 4). Compound 11 is a useful intermediate for preparation of thieno[2,3-b]pyridines by the Thorpe–Ziegler reaction.
Scheme 4.
Synthesis of compound 11.
3. Experimental
3.1. Preparation of 2-Chloro-N-(4-Cyano-3-(Cyanomethyl)-1H-Pyrazol-5-yl)Acetamide 10
Equimolar amounts of 5-amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile 1 and chloroacetyl chloride were dissolved in PhMe and refluxed for 5–7 h. The reaction mixture was left to stand at r.t. for 24–72 h and the precipitate was filtered off and to give 10 in 65–70% yield.
3.2. Preparation of Compound 11
3-Cyanopyridine-2(1H)-thione 12 (0.01 mol) was suspended or dissolved in 15 mL of DMF, and the mixture was treated with 10% aq. KOH (0.01 mol). After 10 min, the reaction mixture was treated with 2-chloro-N-(4-cyano-3-(cyanomethyl)-1H-pyrazol-5-yl)acetamide 10 (0.01 mol). The mixture was stirred for 2 h, and the precipitated solid was filtered off and washed with EtOH to afford compound 11 in 75–90% yields.
Funding
The reported study was funded by RFBR and Krasnodar region according to research project No. 19-43-230007.
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