Sodium gluconate: An efficient organocatalyst for the synthesis of dihydropyrano[2,3-c] pyrazole derivatives

A Khandebharad,S Sarda,B Agrawal,M Soni

doi:10.4314/bcse.v33i2.13

Abstract

Sodium gluconate presented as a category of biomolecule found to be a proficient and recyclable organocatalyst for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives via one-pot multicomponent reaction of aryl aldehyde, malononitrile, ethyl acetoacetate and hydrazine hydrate in water as a solvent. The catalyst is non-toxic in nature, commercially available, biodegradable and easily separated from the reaction mixture. Present protocol avoids the use of the heavy metal catalyst, harsh reaction condition and the reusability of catalyst, broad substrate scope, simple work-up procedure and excellent yield of products make this protocol greener. KEY WORDS : Pyrano[2,3-c]pyrazole, Sodium gluconate, Multicomponent reaction (MCR), Knovenagel condensation, Bio-based organocatalyst Bull. Chem. Soc. Ethiop. 2019 , 33(2), 331-340. DOI: https://dx.doi.org/10.4314/bcse.v33i2.13

Highlights

Advances in one pot multicomponent reactions (MCRs) become one of the powerful ways of synthesizing medicinally important fused heterocycles
The developments of newer catalyst which are in accordance with the principle of green chemistry are mostly used in one pot synthesis of heterocyclic compounds [8,9]
Reaction was carried out without any catalyst in aqueous media and it observed that only Knovengel product was formed in lesser amount which proves the need of catalyst for the reaction

Summary

INTRODUCTION

Advances in one pot multicomponent reactions (MCRs) become one of the powerful ways of synthesizing medicinally important fused heterocycles. The direct use of commercially available biomolecules as a catalyst makes the processes simple and efficient and gains the significance over the conventional catalytic system, since their biocompatibility and known inclusive data about non-toxic nature allow them to enter into the category of catalyst and accepted as an environmentally suitable methodology In this regard, great efforts have been performed to use different biomolecules like chitosan [10], β-cyclodextrinmonosulphonic acid [11], meglumine [12], starch [13], cellulose [14], and sodium alginates [15] as catalytic systems. The use of such molecules in pure form without post modification, as catalysts is of great importance since they are available, eliminate toxic metals, cost effective, biodegradable and eco-compatible In this context, sodium gluconate can play a major role as a natural and biodegradable salt. 6-Amino-1,4-dihydro-4-(4-methylphenyl)-3-methylpyrano[2,3-c]pyrazole-5-carbonitrile (5h). 1H NMR (DMSO-d6, 400 MHz): δ 1.78 (s, 3H, -CH3), 2.26 (s, 3H, -CH3), 4.54 (s, 1H, C-H), 6.82 (s, 2H, -NH2), 7.04 (m, 2H, Ar-H), 7.12 (m, 2H, Ar-H), 12.06 (s, 1H, -NH) ppm; 13C NMR (DMSO-d6, 100 MHz): δ 9.80, 20.67, 35.88, 57.37, 97.76, 120.88, 127.40, 129.03, 135.50, 135.75, 141.53, 154.8, 160.81; ES-MS: m/z 265.2 [M-H]+

RESULTS AND DISCUSSION

H O N NH

92 This work

CONCLUSION