On the use of multi-parameter free energy relationships: the rearrangement of (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole into (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas

The Boulton–Katritzky Reaction: A Kinetic Study of the Effect of 5‐Nitrogen Substituents on the Rearrangement of Some (Z)‐Phenylhydrazones of 3‐Benzoyl‐1,2,4‐oxadiazoles

“…The values of ( k A,R ) 3 for general‐base and specific‐acid catalysis determination were calculated from thermodynamic parameters in a p S + range, depending on the nature of the substituent present (Tables S2–S4 of the Supporting Information) and managed as described previously 6j,6k…”

“…Indeed, in the rearrangement products, the amidic group linked at C(4) shows a “resonance‐stabilisation in the side chain”. In the last decade, we focused our study on the reactivity of several ( Z )‐arylhydrazones of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole 3 ,6f,6j,6k which are able to rearrange into the relevant (2‐aryl‐5‐phenyl‐2 H ‐1,2,3‐triazol‐4‐yl)ureas 4 , and we have collected kinetic data under a range of experimental conditions. In the absence of the 5‐amino group (substrates 5 ) rearrangement into 6 can occur by heating the solid ( Z )‐arylhydrazone above its melting point or in a solution of different solvent (polar, apolar, or dipolar aprotic), eventually in the presence of bases.…”

Chemistry of 1,2,3-triazoles

“…It should be mentioned that the concentration of base is another crucial factor for the rearrangement process. Different pathways were confirmed to exist: a proton-concentration-independent or uncatalyzed pathway, and proton-concentration-dependent or base-catalyzed one, requiring either a general or a specific base catalyst [295][296][297][298][299][300][301]. Several investigations indicated the effect of the substituents on the arylhydrazone moiety on the electronic properties of the key atoms involved in the MHR, namely the hydrogen atom bound to the N(α)-atom, and the N(2) and C (5) atoms.…”

“…This peculiar case was also described as "monocyclic rearrangement of heterocycles"(MHR) recognized by Boulton and Katritzky as a general class of ring-ring rearrangements [327]. Besides its synthetic applications, this rearrangement gets a lot of attention due to the interesting aspects of its mechanism [295][296][297][298][299][300][301][302][303][304]. The process can be depicted as an internal (intramolecular) nucleophilic substitution (S Ni ), and therefore the reactivity of substrates can be related to the main factors affecting the reactivity towards S N reactions, i.e.…”

“…There are several drugs on the market for the treatment of diseases, such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV), based on this concept. Recently, Chang and coworkers reported the classical synthesis of several new 1,2,3-1H-triazole moieties at the 4 0 -C substituted-2 0 -deoxynucleosides, based on their past experience that most of the 4 0 -C substituted-2 0 -deoxynucleosides exhibited potent anti-HIV-1 activity without significant cytotoxicity [295,296]. The evaluation of the triazole-nucleosides indicated that most of these compounds also exhibited potent anti-HIV-1 activity without significant cytotoxicity, and the best results (179a-c) are presented in Scheme 22 [297].…”