A facile, practical and metal-free microwave-assisted protocol for mono- and bis-[1,2,4]triazolo[1,5-a]pyridines synthesis utilizing 1-amino-2-imino-pyridine derivatives as versatile precursors

Abstract

A novel and highly efficient, protocol for synthesizing mono- and bis-[1,2,4]triazolo[1,5-a]pyridines has been established utilizing the readily attainable 1-amino-2-imino-pyridines and microwave irradiation as green energy source.

A Review on The Chemistry of Nicotinonitriles and Their applications

“…Moreover, when the diethyl oxalate allowed to react with 1amino-2-iminopyridines 37 using 5 equiv. of acetic acid in ethanol under microwave irradiation, the products 160 were received in excellent yields [50] (Scheme 48). Furthermore, compounds 51a,b, 52a, 53b, and 54b showed good anticancer activities against cell culture of HepG-2, PC-3 and HCT116 cell lines [56] (Scheme 54).…”

Green Protocol for the Novel Synthesis of Thiochromeno[4,3-b]pyridine and Chromeno[4,3-b]pyridine Derivatives Utilizing a High-Pressure System

“…A little attention has been paid toward the biologically active thiochromeno­[2,3- b ]­pyridine derivatives , where few synthetic routes for some examples of thiochromeno­[2,3- b ]­pyridines were published. − Apart from this, only one publication for the synthesis of the thiochromeno­[4,3- b ]­pyridine skeleton was reported via a multicomponent reaction of thiochromanone with dimethylformamide-dimethylacetal and ethyl acetoacetate in the presence of ammonium acetate . In continuation to our work which aimed at developing new synthetic routes for new heterocyclic compounds, − herein the Q-tube reactor was used in this study. In comparison with conventional heating, the Q-tube reactor has several characteristics and features − including (1) better yield and performance, (2) a cleaner product profile that means light color and less impurities and byproducts, (3) energy savings, lower reaction time, and higher reproducibility, and (4) cheaper and safer because the sealing and pressing are easy.…”

TFA-catalyzed Q-Tube Reactor-Assisted Strategy for the Synthesis of Pyrido[1,2-b][1,2,4]triazine and Pyrido[1′,2′:2,3][1,2,4]triazino[5,6-b]indole Derivatives

“…It is important to note that when the reaction between 1-amino-2-imino-4arylpyridines and 1,2-dioxo compounds was carried out in AcOH as described in the previous procedures, the desired pyrido-triazine was not produced. The formed product was identified as the corresponding triazolo [1,5-a]pyridine derivatives, 34,36 and no products are produced. After much effort, we were able to carry out the desired reactions in the current work by employing the conditions stated in Scheme 1 to produce the corresponding pyrido-triazine derivatives in high yield, as shown later.…”

“…As shown in Scheme , the majority of the reported methods , used 1,6-diamino-4-aryl-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile as a precursor. Following our efforts to synthesize new heterocyclic compounds through eco-friendly green approaches − and after thorough literature survey, it was noted that the use of 1-amino-2-imino-4-arylpyridine-3-carbonitrile derivatives as precursors to synthesize pyrido­[1′,2′:2,3]­[1,2,4]­triazino­[5,6- b ]­indole and pyrido­[1,2- b ]­[1,2,4]­triazine derivatives has not been reported to date. The current research involves the reaction of 1-amino-2-imino-4-arylpyridines with indoline-2,3-dione (isatin) and α-keto acids such as pyruvic acid and phenylglyoxylic acid, under high-pressure conditions, using a Q-tube reactor.…”