Ring‐Opening Reaction of Imidazo[1,2‐a]pyridines Using (Diacetoxyiodo)benzene and NaN₃: The Synthesis of α‐Iminonitriles

Abstract

The reaction of imidazo[1,2‐a]pyridine with NaN3 in the presence of (diacetoxyiodo)benzene as an oxidant resulted in the unusual formation of α‐iminonitriles in good yields under mild conditions. This method provides access to α‐iminonitriles under cyanide‐free and metal‐free reaction conditions.

Oxidant‐Mediated Nitrogenation and Recyclization of Imidazo[1,2‐a]pyridines with Sodium Azide: Synthesis of 4H‐Pyrido[1,2‐a][1,3,5]triazin‐4‐ones

“…First, 3‐azidoimidazo‐[1,2‐ a ]pyridine C was formed between 1 a and NaN 3 in the presence of K 2 S 2 O 8 /KMnO 4 . This azidation process possibly involved a radical pathway or an oxidant‐mediated pathway, as also evidenced by the results of control experiment. The aryl azide C could undergo thermal decomposition to afford nitrene intermediate E with the exclusion of N 2 , which occurred intramolecular cyclization for the formation of strained azirine D ,.…”

“…In the past few years, substantial efforts toward the regioselective functionalization of imidazo[1,2‐ a ]pyridines were largely focused on the C3 position, such as arylation, alkenylation, carbonylation, sulfenylation, cyanation, thiocyanation, phosphonation, trifluoromethylation, trifluoroethylation and so on . On the other hand, the transformation based on the ring‐opening of imidazo[1,2‐ a ]pyridines into other valuable synthetic intermediates or more complicated heterocycles has been scarcely reported . In recent years, the N‐atom incorporation process using readily available nitrogen sources enabled the formation the useful target products with enriched structural diversity .…”

“…To gain more insight into the reaction mechanism, several control experiments were implemented as shown in Scheme . Initially, a series of possible intermediates were proposed on the basis of previous reported literatures ,. Then, the substrate 1 a was subjected into the standard reaction conditions without the addition of NaN 3 , and the reaction process was monitored by LC‐HRMS (Scheme , eq 1).…”

“…Base on the preliminary mechanistic investigation and the previous reported literatures,, a plausible reaction mechanism was proposed as depicted in Scheme . First, 3‐azidoimidazo‐[1,2‐ a ]pyridine C was formed between 1 a and NaN 3 in the presence of K 2 S 2 O 8 /KMnO 4 .…”

(Diacetoxy)iodobenzene-Mediated Oxidative C–H Amination of Imidazopyridines at Ambient Temperature

“…As a consequence, recently much attention has been paid on the direct C–H amination of C­(sp 2 )–H bond due to its straightforwardness . In this context iodine­(III)-mediated oxidative C­(sp 2 )–H amination has emerged as an important strategy . Intramolecular oxidative amination of aromatic C–H bonds using hypervalent iodine have been found to construct various heterocyclic compounds, however the intermolecular amination of arenes and heteroarenes under metal-free conditions have been less explored.…”