Heterocyclization of Functionalized Vinylic Derivatives of Imidazo[1,2-a]pyridines

Abstract

Heterocyclization of functionalized vinylic derivatives of imidazo[1,2-a]pyridines was explored experimentally and theoretically using semiempirical AM1 and ab initio methods. A range of functionalized vinylic derivatives (azido, amino, and carbodiimide groups) were prepared for conversion into pyrroloazaindoles 19-22, imidazo[1,x]-, (x = 5, 6, 7, 8), [2,6]-, and [2,7]naphthyridines 28-30, 35-38 by thermal reaction. In the case of vinylic groups in the 5 position, peri annulation also was observed. The experimental and theoretical data are compared and discussed.

Synthesis and antiviral activity of an imidazo[1,2-a]pyrrolo[2,3-c]pyridine series against the bovine viral diarrhea virus

“…Reduction of esters 3a-f in presence of lithium aluminium hydride yielded alcohols 4a-f which were oxidized with MnO 2 to afford aldehydes 5a-f. Substituents on 3-position can be easily introduced at this stage by using electrophilic substitution reactions that occur in imidazo[1,2-a]pyridine series mostly at this position [20]. Following standard procedures, selective bromination of aldehydes 6 [15] and 5a afforded respectively 3-bromo derivatives 7a and 7b, while 3-nitro compound 8 was obtained by classical nitration of 5a.…”

“…Substituted ethyl imidazo[1,2-a]pyrrolo[2,3-c]pyridine-8-carboxylates in positions 2 and 3 of the imidazole ring were easily obtained in two steps from the corresponding imidazo[1,2-a]pyridine-8-carbaldehydes according to the Chezal's procedure [15,21] (Scheme 3). Briefly, aldehydes 5a-f, 7a-b and 8 were converted into the corresponding ethyl azidopropenoate compounds 9a-i, by the addition of ethyl azidoacetate in the presence of an ethanolic sodium ethoxide solution [22], which can subsequently be cyclised in refluxing chlorobenzene to yield compounds 10a-i.…”

“…We demonstrated earlier that the imidazo[1,2-a]pyrrolo[3,2-c]pyridines 1a, b [15] (Fig. 1) selective inhibit the replication of pestiviruses by targeting a region of the finger domain of the RdRp [16].…”

Synthesis, X‐ray crystal structure and optical properties of novel 2‐aryl‐3‐ethoxycarbonyl‐4‐phenylpyrido[1,2‐a]benzimidazoles

“…Nitrogen bridge‐head heterocycles are of special interest, due to their wide variety biological activities and optical/electrical properties, and many of attractive methods have been developed for synthesizing this class of compounds. Of these heterocycles, compounds containing imidazo[1,2‐a]pyridine ring systems and related structures such as imidazo[1,2‐a]pyrimidine, imidazo[1,2‐a]quinoxaline or imidazo[2,1‐a]isoquinoline have been reported to possess a wide variety of biological and pharmacological properties. In contrast, the related pyrido[1,2‐a]benzimidazole ring system has not received much attention until the past two decades when some of its derivatives found pharmaceutical applications, based on their anti‐anxiety , anti‐tumour and antiviral activities .…”

Lead Optimization of Imidazopyrazines: A New Class of Antimalarial with Activity on Plasmodium Liver Stages

“…13 A regioselective bromination at C3 with NBS provided 3-bromo-6-carboxylate 7 as the sole product isolated. 14 Hydrolysis of 7 to the corresponding acid (8) followed by amide bond formation with an appropriate amine provided compound 9.…”