A Facile Solvent-Free Route for One-Pot Multicomponent Synthesis of Benzylpyrazolyl Coumarins Derivatives in Presence of Effective Synergetic Catalytic System

Abstract

A combinatorial library of benzylpyrazolyl coumarin derivatives have been synthesized by a green one-pot four-component reaction between aryl hydrazine/hydrazine hydrate (1), ethyl acetoacetate (2), aromatic aldehydes (3) and 4-hydroxycoumarin (4) catalyzed by niobium pentachloride with silver salt under solvent-free conditions has been developed. Experimental simplicity, simple work-up procedure and solvent-free reaction condition at room temperature are important features of the present protocol.

Versatile and Sustainable Approach to Access Biologically Relevant Chromeno[2,3-b]pyridine and Benzylpyrazolyl Coumarin Derivatives Using Graphitic Carbon Nitride as a Reusable Heterogeneous Catalyst

“…To date, only a few methodologies have been reported for the development of such benzylpyrazolyl coumarin derivatives. However, the major disadvantages of these protocols are the use of corrosive and unrecyclable homogeneous acid catalysts like glacial acetic acid, 42 2-aminoethanesulfonic acid, 43 Ca-(OTf) 2 , 44 and NbCl 5 45 and the use of expensive heterogeneous catalysts like ZrO 2 nanoparticles 28 and Nb-Zr/KIT-6. 46 Therefore, the synthesis of such aforementioned biologically relevant heterocyclic compounds by the combination of MCR and carbon-based metal-free catalysts would be highly desirable.…”

“…To date, only a few methodologies have been reported for the development of such benzylpyrazolyl coumarin derivatives. However, the major disadvantages of these protocols are the use of corrosive and unrecyclable homogeneous acid catalysts like glacial acetic acid, 2-aminoethanesulfonic acid, Ca­(OTf) 2 , and NbCl 5 and the use of expensive heterogeneous catalysts like ZrO 2 nanoparticles and Nb-Zr/KIT-6 …”