Sodium toluene‐4‐sulfonate as a reusable and ecofriendly catalyst for greener synthesis of 5‐aminopyrazole‐4‐carbonitrile in aqueous medium

Abstract

In these environmentally conscious days there is need to use eco-friendly greener technologies, such as solvent free, microwave, ultrasound and use of room temperature. Here report an efficient and green protocol for the synthesis of 5-aminopyrazole-4-carbonitrile from three component condensation of phenyl hydrazine, aldehyde, and malononitrile using NaPTS as catalyst in aqueous medium. Use of water has emerged as a versatile solvent for organic reaction; it is readily available, inexpensive, environmentally benign, neutral and natural solvent. Multicomponent reactions in water are of outstanding value in organic synthesis and green chemistry. The significant features of this article are short reaction time, provide excellent yield, removal of toxic solvent and use of water as green solvent.

Recent Advances in Synthesis and Properties of Pyrazoles

“…A year later, Elnagdy and Sarma [30] reported a homogenous catalytic system using FeCl3/PVP and green solvent water/PEG-400 to synthesize 4-amino-1-aryl-1Hpyrazole-4-carbonitriles 17a-q using a cyclocondensation reaction of arylhydrazines 9af with malononitrile derivatives 16a-c. A mixture of FeCl3 and polyvinyl pyrrolidine (PVP) was used to accelerate the addition of 9a-f to the double bond of 16a-c; then, an intramolecular cyclization allows the formation of products 17a-q in up to 97% yield with reaction times of 2-4 h (Scheme 4b). In 2020, Sapkal and Kamble [31] obtained 5-aminopyrazole-4-carbonitriles 20a-m using a green protocol based on a three-component cyclocondensation of phenylhydrazine 9a, aldehyde derivatives 18a-m, and malononitrile (19) adding sodium p-toluenesulfonate (NaPTS) as a catalyst in aqueous media (Scheme 5a). The authors mentioned that NaPTS was used as a hydrotrope that helps increase the solubility of poorly soluble organic compounds in water.…”

Greener and Environmentally Benign Methodology for the Synthesis of Pyrazole Derivatives

“…Hydrotrope are surface active agent which are increases solubility of sparingly soluble compounds in water those are insoluble in aqueous medium. Therefore, hydrotropes are widely used in organic transformation, Aboli Sapkal et al [88] . synthesize 2‐aminopyrazole (76) in presence of NaPTS‐ hydrotrope in aqueous medium.…”

“…Hydrotrope are surface active agent which are increases solubility of sparingly soluble compounds in water those are insoluble in aqueous medium. Therefore, hydrotropes are widely used in organic transformation, Aboli Sapkal et al [88] synthesize 2-aminopyrazole (76) in presence of NaPTS-hydrotrope in aqueous medium. One pot multicomponent condensation of aldehyde, malononitrile and phenyl hydrazine at room temperature within 30 min, solid product is form which is filtered, recrystallized and yield is above 90 %.…”