The chemistry of the triazolopyridines: an update

Enantioselective Aza‐Michael Addition of Imides by Using an Integrated Strategy Involving the Synthesis of a Family of Multifunctional Catalysts, Usage of Multiple Catalysis, and Rational Design of Experiment

“…The amide and ester functionalities of compound 4 b were cleaved to afford biologically interesting cyclic hydroxy amino acid 5, see the Supporting Information for details. [17] We are unaware if compound 1 f has been employed in any other asymmetric transformation. [17] We are unaware if compound 1 f has been employed in any other asymmetric transformation.…”

Synthesis of 1,2,4‐Triazolo[4,3‐a]pyridines and Related Heterocycles by Sequential Condensation and Iodine‐Mediated Oxidative Cyclization

“…Treatment of 4a with moleculari odine in the presence of K 2 CO 3 in 1,4-dioxane at 80 8Cr esulted in the desired triazolopyridine (1a)i n9 1% yield ( With the optimal reaction conditions ( Table 1, entry 8) in hand, we soughtt oe xamine the scope and generality of this sequential synthesis. Condensation of 2a with substituted benzaldehydes 3,f ollowed by I 2 -mediated oxidative cyclization, produced as eries of 3-aryl [1,2,4]triazolo[4, 3-a]pyridines (1b-m) in good to excellent yields (Scheme 2). This synthetic method is compatible with both electron-donatinga nd -withdrawing groups (EDGs and EWGs, respectively)a tt he para, meta,a nd ortho positions of the benzene ring of the aldehydes (3b-m).…”

“…Triazolopyridines are an important class of fused-ring heterocyclic compounds. [1] Amongt he various triazolopyridine derivatives, the 1,2,4-triazolo[4,3-a]pyridine skeleton widely exists in many compounds with diversep harmaceutical properties, such as anti-inflammatory, [2] antithrombotic, [3] antiproliferative, [4] antidepressant/antipsychotic, [5] antibacterial, [6] and antiviral activities. [7] For example, selective p38a inhibitor 5 exhibited significanta nti-inflammatory activity in ar at model of arthritis (Figure 1).…”

“…[2c] As ap ositive allostericm odulator (PAM) of the metabotropic glutamate 2r eceptor,c ompound 6 showed good antipsychotic activity in mice. [5a] 1,2,quinoline 7 was demonstrated to have good inhibitory activity against severalb acterials trains. [6a] Moreover, 1 ,2,4-triazolo[4,3a]pyridines can also be used as herbicidala gents in agriculture.…”

“…[6a] Moreover, 1 ,2,4-triazolo[4,3a]pyridines can also be used as herbicidala gents in agriculture. [8] Owing to their excellent deep-blue emission and stability properties, 3-aryl [1,2,4]triazolo[4, 3-a]pyridines could be potential candidatesf or applicationsi nh igh-performance organic light-emitting diodes (OLEDs). [9] As urvey of the literature indicated that 1,2,4-triazolo[4,3a]pyridines could be prepared by the following strategies (Scheme 1): a) cyclodehydration of acylated 2-hydrazinopyridines in acetic acid under microwavei rradiation [10] or by using Lawesson'sr eagent; [11] b) tandem/one-pot reactiono f2 -hydrazinopyridines with carboxylic acids in the presence of reagents such as POCl 3 /PCl 5 , [12] polystyrene-bound triphenylphosphine (PS-PPh 3 )/CCl 3 CN, [13] and 1,1'-carbonyldiimidazole (CDI); [14] with isothiocyanates promoted by polymer-supported Mukaiyama's reagent; [15] or with aryl iodides through[ Mo(CO) 6 ]-mediated carbonylation; [16] c) oxidative cyclization of 2-pyridylhydrazones with oxidants such as hypervalent iodine reagents, [17] N-bromosuccinimide( NBS), [18] chloramine T, [19] ceric ammonium nitrate (CAN), [20] and CuCl 2 ; [21] and d) Cu-catalyzed direct CÀH( hetero)arylation of preformed1 ,2,4-triazolo[4, 3-a]pyridines.…”