Four component synthesis of highly functionalized pyrano[2,3-c]pyrazoles from benzyl halides

Abstract

N-methylmorpholine N-oxide and silver oxide (Ag 2 O) oxidized four component reaction for the preparation of pyranopyrazole with different substituted pattern have been developed which provides rapid access to a library of compounds in good to excellent yields by using benzyl halide, malanonitrile/ethyl cyanoacetate, diethylacetylenedicarboxylate/ethyl acetoacetate and hydrazine hydrate as reactants. This transformation involves the breaking of one CO bond and formation of 2 CC , 2 C-N, and a CO bond leading to the formation of a five and six membered ring in one pot operation.

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

“…The results were satisfying giving good yield of the products (5o-5q). The formation of products (5o-5q) were confirmed by comparing their melting points with reported melting points [5][6][7] . Next, we were interested in the synthesis of bis-pypys with the established conditions by using bis-aldehyde functionalities (Fig.…”

“…The physical properties of pyranopyrazoles (pypys) have rendered them as highly efficient pharmacophores, for the treatment of cancer, diabetic, pyretic, HIV, etc 1 . The existing synthetic methods for the generation of pypys requires long reaction time, tedious purification and tough conditions [2][3][4][5][6][7][8][9][10][11] , therefore the development of a straightforward method is sought for. Among macrocycles, crown ethers are of great value in synthetic chemistry field as phase transfer catalyst.…”

Synthesis of pyrano[2,3‐c]pyrazoles: A review

“…First report on the preparation of dihydropyrano[2,3‐c]pyrazoles from benzyl halides in the presence of silver oxide (Ag 2 O) and N ‐methylmorpholine N ‐oxide (NMO) as oxidizing agents was published by Beerappa and Shivashankar in 2018. [ 102 ] Diethyl acetylenedicarboxylate (DEAD) 123 and malononitrile 23 were more reactive in the multicomponent reaction as compared to ethyl acetoacetate 22 and ethyl cyanoacetate 77 . Benzyl halides bearing both electron releasing and withdrawing substituents equally participated in the reaction but the highest yield (92%) was obtained with 4‐nitrobenzyl bromide 122 (Scheme 26).…”

Visible Light‐Induced Synthesis of Biscoumarin Analogs under Catalyst‐Free Conditions

“…However, these methods suffer from the limitations such as use of expensive, toxic, greater loading of catalysts, incomplete conversion, and lower yields. Prompted by the previous points and our continuous efforts for preparing heterocyclic derivatives , we envisioned the catalyst‐free synthesis of biscoumarin derivatives using visible light (CFL bulb) system at ambient temperature.…”