18-C-6H3O+]: an in-situ generated macrocyclic complex and an efficient, novel catalyst for synthesis of pyrano[2,3-c]pyrazole derivatives

Manisha Mishra,Aatika Nizam,V R Sriram Krishnan,K J Jomon

doi:10.1038/s41598-020-70665-z

Manisha Mishra, Aatika Nizam + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-70665-z

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Journal: Scientific Reports	Publication Date: Aug 31, 2020
Citations: 11	License type: open-access

Affiliation: Christ University

Abstract

Synthesis of small aromatic heterocycles is of greater importance in the organic chemistry due to their vibrant applications in pharmaceuticals, agrochemicals and veterinary products. Pyranopyrazoles are one such class of heterocycles associated with numerous applications. Hence herein we report a multicomponent crown ether catalyzed, ultrasound irradiated methodology to make different functionalized pyranopyrazoles in a single step. This technique involves the in-situ generation of [18-C-6H3O+][OH−] complex, which in turn activates the aromatic aldehyde and aids in the facile nucleophilic addition.

Highlights

Synthesis of small aromatic heterocycles is of greater importance in the organic chemistry due to their vibrant applications in pharmaceuticals, agrochemicals and veterinary products
In continuation of our work on the development of new and simple catalyst for the synthesis of bioactive compounds[14,15,16,17], taking inspiration from K Nikoofar’s work on the preparation of Spiro[indoline-3,2′-quinoline] substrates using [DB-18-C-6K+][OH−]nIL18 and noting the fact that very little is explored in this, we report the in-situ generation of crown ether hydronium ion complex ([18-C-6H3O+][OH−]) and it’s catalytic activity in four-component synthesis of pypys under sonication (Fig. 1)
We began our investigation by performing a model reaction using benzaldehyde (1a), 2a, 3 and 4a as substrates, and 2 mol% of 18-crown-[6]-ether/H2O in methanol under ultrasound irradiation for 10 min

Summary

Introduction

Synthesis of small aromatic heterocycles is of greater importance in the organic chemistry due to their vibrant applications in pharmaceuticals, agrochemicals and veterinary products. Pyranopyrazoles are one such class of heterocycles associated with numerous applications. We report a multicomponent crown ether catalyzed, ultrasound irradiated methodology to make different functionalized pyranopyrazoles in a single step This technique involves the in-situ generation of [18-C-6H3O+][OH−] complex, which in turn activates the aromatic aldehyde and aids in the facile nucleophilic addition. The key to the success of this method is the synthesis of bis-pypys, which was established using the developed catalytic system (Fig. 2)

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Conclusion