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

Abstract

The kinetics of the ring‐into‐ring conversion of some new (Z)‐phenylhydrazones of 3‐benzoyl‐1,2,4‐oxadiazole containing different nitrogen‐substituents at C‐5 (3b–d; X = NHMe, NMe2, and NHCOMe) into the relevant triazoles 4b–d have been examined in a wide range of pS+ (0.1–11.9) in 1:1 (v/v) dioxane/water solution. The obtained results have been compared with previous data concerning the (Z)‐phenylhydrazone of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole (3a; X = NH2). All of the studied (Z)‐phenylhydrazones rearrange through three different pathways (specific acid‐catalysed, uncatalysed and general base‐catalysed). The different effects of the substituents on the course of the rearrangement in the three pathways have been examined.

Synthesis of 1,2,3-triazoles containing an allomaltol moiety from substituted pyrano[2,3-d]isoxazolones via base-promoted Boulton–Katritzky rearrangement

“…So, the well-known Boulton-Katritzky reaction of hydrazones of 1,2,4-oxadiazoles leads to the corresponding 1,2,3-triazoles containing an amide fragment. Generally, the considered rearrangement proceeds under action of acidic or basic reagents [3][4][5][6][7]. Other options for this process are based on the application of copper salts or ionic liquids [8,9].…”

Tandem C–N coupling/Boulton–Katritzky rearrangement reactions of 3-aminoisoxazoles or 1,2,4-oxadiazol-3-amines with 2-pyridyl trifluoromethanesulfonate: a rapid access to [1,2,4]triazolo[1,5-a]pyridines

“…A range of nucleophilic side chains (X = Y–H, NCC, NNC and CNC) have been investigated during the last few decades. 7–9 However, the preinstallation of nucleophilic side chains during BK rearrangement reactions is a limitation which needs to be overcome. Herein, we'd like to report a palladium catalyzed tandem C–N coupling/Boulton–Katritzky rearrangement process of 3-aminoisoxazoles or 1,2,4-oxadiazol-3-amines with 2-pyridyl trifluoromethanesulfonate for the facile syntheses of functionalized [1,2,4]triazolo[1,5- a ]pyridines (Scheme 1d).…”

Iron Nitrate-Mediated Selective Synthesis of 3-Acyl-1,2,4-oxadiazoles from Alkynes and Nitriles: The Dual Roles of Iron Nitrate

“…Interest in 3-acyl-1,2,4-oxadiazoles has widely expanded due to their biological and pharmacological activities (Figure ). However, the methods for the direct synthesis of 3-acyl-1,2,4-oxadiazoles from readily available substrates remain very rare and most of them require using substrates as solvents. Moreover, nitriles are readily available and stable compounds containing carbon–nitrogen triple bonds.…”