GOQDs and GOQDs-NS-doped carbocatalysts: A concise study on production and use in one-pot green MCRs

Nowadays, the catalysts' usage in chemical reactions is unavoidable, and this has led scientists to look for producing and using catalysts which not only cause pollution and toxicity in the reactions and products, but also generate economical benefits.Our goal in this paper is to produce a fully biocompatible, non-toxic and inexpensive carbocatalyst with a graphene oxide structure for use in multi-component reactions as a heterogeneous catalyst.The research has been carried out to simplify the method of preparing carbocatalysts. In this article, we heated citric acid and thiourea in the simple bottom-up method in which nitrogen and sulfur were atomically inserted into a carbon-carbon bond of graphene oxide.The results have been obtained by comparing graphene oxide quantum dots (GOQDs) and functional graphene oxide quantum dots (GOQDs) and functional nitrogen and sulfur-doped graphene oxide quantum dots (NS-doped-GOQDS) using the produced carbocatalyst in the synthesis of spiro indoline pyrano pyrazoles and highly substituted pyridine derivatives with chemical and pharmacological properties.A simple and affordable bottom-up method has been developed to synthesize fluorescent NS-doped-GOQDS by the condensation of CA in the presence of thiourea with water elimination at 185 ℃. After the production of NS-doped-GOQDS, the carbocatalyst is used in the synthesis of spiro[indoline-3,4'-pyrano [2, 3-c]pyrazole] derivatives in four-component reactions and pyridine derivatives in five-component reactions.