A novel approach for the synthesis of imidazo and triazolopyridines from dithioesters

Abstract

Various imidazo- and triazolo-pyridines were synthesised by the intramolecular cyclization of pyridine 2-methylamine and dithioesters under mild conditions.

Recent synthetic methodologies for imidazo[1,5-a]pyridines and related heterocycles

“…28 Ramesha et al described a simple and convenient procedure for obtaining imidazo[1,5-a]pyridines 52 from commercially available dithioesters 51 and 2-methylaminopyridines 50 using T 3 P in THF (Scheme 12). 29 Screening of various catalysts, solvents, and additives revealed that the optimal reaction conditions were 2-methylaminopyridine (1.1 equiv. ), T 3 P (1.0 equiv., 50% in EtOAc), and DMSO (2.0 equiv.)…”

Applications of Oxone® in Organic Synthesis: An Emerging Green Reagent of Modern Era

“…Even though, a range of methods are already reported for the generation of these valuable molecules but they have some limitations for instance involvement of toxic reagents, prolonged reaction times, limited substrate scopes, harsh reaction conditions, and tedious work-up procedures as well. [287][288][289] In order to overcome some of the above mentioned critical problems, Ravinder's group in 2016 reported an efficient and expedient way for the synthesis of a varied 3aryl [1,2,4]triazolo [4,3-α]pyridines 347 a-g from the oxidative cyclization of 2-(2-arylidenehydrazinyl)pyridines 346 utilizing RuCl 3 /oxone in 1,2-dichloroethane (DCE) as a solvent in a chemoselective manner (Scheme 114). [290] A detailed possible mechanism reported by the authors is stated in the Scheme 115.…”

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

“…Most synthetic approaches rely on various cyclocondensations of nucleophilic (2-aminomethyl)pyridine precursors, introducing a new five-membered ring. Typically, carboxylic acids [16][17][18][19][20], acyl anhydrides [21][22][23], acyl chlorides [24][25][26][27], esters [28], thioamides [29][30][31], dithionates [32,33], or thiocarbamates [34] are employed as electrophilic components, but oxidative cyclocondensations with aldehydes have also been showcased [35][36][37]. However, given the importance of these targets, new preparative methods are still in high demand.…”