One‐Pot Synthesis of 3‐Aryl‐5‐amino‐1,2,4‐thiadiazoles from Imidates and Thioureas by I₂‐Mediated Oxidative Construction of the N–S Bond

Abstract

A simple and practical method for the one‐pot synthesis of 3‐aryl‐5‐amino‐1,2,4‐thiadiazoles from imidates and thioureas has been developed. The protocol proceeds through sequential base‐mediated nucleophilic addition‐elimination reactions and an I2‐mediated oxidative coupling for the N–S bond formation. The approach employes readily available and nontoxic substrates and a simple workup to provide 3‐aryl‐5‐amino‐1,2,4‐thiadiazoles that have a free or substituted amino group.

Controllable Rh(III)-Catalyzed C–H Arylation and Dealcoholization: Access to Biphenyl-2-carbonitriles and Biphenyl-2-carbimidates

“…Rhodium (III)-catalyzed direct C–H transformation has emerged in the past few years as a powerful and versatile strategy for the construction of valuable molecules . Among them, readily available benzimidates, which act as both directing groups and synthons for cyclization, are always employed as the reaction partners . In previous works, sequential Rh­(III)-catalyzed direct C–H activations and intramolecular nucleophilic additions frequently occurred between benzimidates and the coupling reactants such as α-diazocarbonyl compounds, azides, anthranils, nitrosobenzenes, dioxazolones, alkenes, sulfur ylides, etc., thus furnishing isoquinolines, quinazolines, and other heterocycles (Scheme ).…”

Synthetic Routes to Imidates and Their Applications in Organic Transformation: Recent Progress

“…i) Cyclization reactions between the N-substituted imidates and alkenes, alkynes, amines, amides, aldehydes or azirines, were reported for the synthesis N-heterocycles such as (benz)imidazoles, [52] triazin-amines, [53] quinazolines, [54] triazoles and oxadiazoles, [55] thiadiazoles, [56] and oxadiazines. [57] In some cases, when imidates contained an alkenyl or alkynyl group in their structure, a cyclization pathway took place via an intramolecular process in the presence of the appropriate metal catalyst such as Au, Ag and Cu and the corresponding oxazolines [58] or oxazoles [59] were formed as the major products (Scheme 35).…”

Isolation of unique heterocycles formed from pyridine-thiocarboxamides as diiodine, iodide, or polyiodide salts

“…[1][2][3][4][5] Numerous methods have been developed to access these moieties, including dimerization of aryl nitriles in the presence of ammonium sulfide, as well as the cyclization reaction of nitriles or imine esters with thioamides. [6][7][8][9] Perhaps the most straightforward method developed is the oxidative cyclization of two thioamides. Techniques have been developed utilizing specialized reagents such as phosphovanadomolybdic acid or pseudocyclic benziodoxole triflate.…”