Metal‐Free CN‐ and NN‐Bond Formation: Synthesis of 1,2,3‐Triazoles from Ketones, N‐Tosylhydrazines, and Amines in One Pot

Abstract

A novel synthetic approach toward 1,4-disubstituted 1,2,3-triazoles by C-N- and N-N-bond formation has been established under transition-metal-free conditions. Complete control of the regioselectivity was successfully achieved. Commercially available anilines, ketones, and N-tosylhydrazine were treated with molecular iodine in one pot to allow the regioselective generation of 1,4-disubstituted 1,2,3-triazoles in high yields without the use of azides.

Iodine-DMSO mediated conversion of N-arylcyanothioformamides to N-arylcyanoformamides and the unexpected formation of 2-cyanobenzothiazoles

“…On the other hand, the iodine/DMSO oxidation system has truly revolutionized synthetic practices in a plethora of reactions involving oxidation processes. 43–56 This oxidant has been particularly used in C–N bond chemistry as a greener solution to existing conventional synthetic methodologies and to avoid employing harsh, toxic, and expensive metals and reagents. The wide and abundant availability of iodine and DMSO, ease of preparation, moisture and air stability, atom and step economy, as well as its environmentally benign nature render such system very convenient.…”

Nickel-catalyzed multicomponent reaction of dinitriles and hydrazine hydrochlorides with boronic acids: access to 1,3-diaryl-1H-pyrazol-5-amines and 4,5-dihydropyridazin-3(2H)-ones

“…This reaction is applicable to 2-benzylmalononitrile, generating the tetrasubstituted pyrazole 4x in 90% yield (Scheme 2, eqn (c)). It should be emphasized that without the isolation of 4a , by the treatment with acetophenone and TsNHNH 2 18 directly, the biologically active triazole biheteroaryl skeleton 8a was afforded favorably in a one-pot manner (Scheme 2, eqn (d)), which offers a simpler avenue to 8a compared with the reported methods. 4 In addition, the amino could react with TsCl, leading to a sulfonamide-substituted pyrazole derivative in 67% yield (Scheme 2, eqn (e)).…”

Luxury of N‐Tosylhydrazones in Transition‐Metal‐Free Transformations

“…The other approach for the one‐pot synthesis of 1,2,3‐triazoles was demonstrated by the research group of Zhang through a molecular iodine‐catalyzed three‐component reaction of ketones, N ‐tosylhydrazines and amines . Notably, two pathways have been proposed by the authors after a series of control experiments with different possible intermediates.…”