The Diverse supramolecular synthons formed by 2-subsituted 5-morpholinomethylphenyl Triazolo[1,5-a]pyridines in solid state

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

“…1 Among them, 1,2,4-triazolo [1,5-a]pyridines which are considered as a unique category of N-bridged 5,6bicyclic compounds have received substantial consideration for either their potential utility as bioactive precursors or for other industrial applications. 2,3 For example, they exhibit several pharmaceutical behaviors including, mGlu modulation, 4 PHD-1 inhibition, 5 PDE10 inhibition, 6 and acting as an antioxidant. 7 In addition examples of these compounds have been utilized as herbicidal agents 8 and for treatment of diabetes (type-II), 9,10 cardiovascular disorders, 11 and hyperproliferative disorders.…”

“…Similarly, Zhao et al 21 described a Cu-Zn/Al-Ti reusable catalyst for the same conversion. Further, Jianguang and co-workers successfully synthesized triaryl [1,2,4]triazolo [1,5-a]pyridine derivatives via copper-catalyzed radical cyclization reaction of benzylidenmalononitriles and azines. 22 More recently, Xia et al presented the preparation of triazolopyridines through the copper-catalyzed oxidative cyclization of amidines or 2-aminopyridines with several nitriles.…”

“…23 Notwithstanding, these reactions are followed by certain drawbacks, such as using the catalysts in higher loads (5-20 mol%) and not being recyclable or reusable. Moreover, these metal catalysts could be interacted conveniently with the obtained products, since [1,2,4]triazolo [1,5-a]pyridines are reported to be coordinated effectively with transition metals producing stable complexes. 24,25 Such challenges are of particular economic and environmental concerns, limiting the utility of such protocols in large-scale productions, and hence in industrial purposes.…”

“…24,25 Such challenges are of particular economic and environmental concerns, limiting the utility of such protocols in large-scale productions, and hence in industrial purposes. Furthermore, access to [1,2,4]triazolo [1,5a]pyridines has also been documented for certain metal-free synthetic procedures. For instance, Alizadeh et al reported the synthesis of [1,2,4]triazolo [1,5-a]pyridine derivatives via iodine-catalyzed one-pot four-component reaction comprising malononitrile, dimethyl acetylenedicarboxylate, aromatic aldehydes, and benzylidenehydrazines.…”

“…Furthermore, access to [1,2,4]triazolo [1,5a]pyridines has also been documented for certain metal-free synthetic procedures. For instance, Alizadeh et al reported the synthesis of [1,2,4]triazolo [1,5-a]pyridine derivatives via iodine-catalyzed one-pot four-component reaction comprising malononitrile, dimethyl acetylenedicarboxylate, aromatic aldehydes, and benzylidenehydrazines. 26 Even though, this approach could be implemented only to alkynes with powerful electron-decient moieties.…”