Halogenation of Imidazo[1,2‐α]pyridines with DXDMH (X=Cl, Br and I) Using DMSO as a Solvent and an Oxidant

Abstract

A simple and inexpensive methodology is reported for the conversion of imidazo[1,2‐α]pyridines to 3‐halo imidazo[1,2‐α]pyridines via oxidative halogenation using DXDMH (X=Cl, Br and I) paired with dimethyl sulfoxide, which serves as the oxidants as well as cosolvent.

Ultrasound-Assisted Iodination of Imidazo[1,2-α]pyridines Via C–H Functionalization Mediated by tert-Butyl Hydroperoxide

“…Based on the abovementioned results from the control experiments and previous reports studies, ,,, we proposed a plausible mechanism for this transformation in Scheme . Initially, molecular iodine reacted with TBHP to form t BuOI and HOI.…”

“…Chancharunee et al and Gámez-Montaño et al discovered an efficient USI-assisted green direct synthesis of imidazo­[1,2-α]­pyridines, respectively (Scheme c,d). , Although these advances have been made in recent years, development on the functionalization of imidazo­[1,2-α]­pyridines is still highly desirable. In this context, there has been an increasing interest in the use of ultrasonic irradiation for halogenation reactions as tools for green chemistry. − On the basis of the abovementioned points, our group continued ongoing research on sustainable organic synthesis and halogenation of imidazo­[1,2-α]­pyridines. − Herein, we report the first example of the oxidative iodination of imidazo­[1,2-α]­pyridines with molecular I 2 in an innocuous solvent accelerated by ultrasonic irradiation, which produced 3-iodinated products in very high yields within a short time (Scheme e).…”

Diethylaminosulfur Trifluoride: A Novel, Low-Cost, Stable Double Thiolation Reagent for Imidazo[1,2-α]pyridines

“…Based on these preliminary mechanistic studies and relevant reports, − we proposed a reaction mechanism, as depicted in Scheme . Initially, 2-arylimidazo­[1,2-α]­pyridines ( 1a ) could exist as the resonance structure A , which reacts with DAST to furnish intermediate B with the elimination of HF.…”

“…Diethylaminosulfur trifluoride (DAST), as commercially available organic synthons, has usually been utilized as a fluorinated reagent and trifluoromethylthiolation reagent. [41][42][43][44][45][46]50,51 Based on our research interest in the C−H bond functionalization strategies to manipulate various imidazopyridines, 47,48 we herein report a metal-free, nucleophilic strategy for the synthesis of bis(imidazo [1,2- DAST efficiently to afford the desired products 3b−3d in good yields. Meanwhile, the presence of an electron-donating substituent like the methyl, methoxy, or phenyl group was able to give products 3e−3g in up to 92% isolated yield.…”

“…Diethylaminosulfur trifluoride (DAST), as commercially available organic synthons, has usually been utilized as a fluorinated reagent and trifluoromethylthiolation reagent. − ,, Based on our research interest in the C–H bond functionalization strategies to manipulate various imidazopyridines, , we herein report a metal-free, nucleophilic strategy for the synthesis of bis­(imidazo­[1,2-α]­pyridine-3-yl)­sulfanes using DAST as a sulfur source, which shows good scope and functional group tolerance (Scheme d). Moreover, our aim was to explore new chemical transformation of DAST and ascertain its use as a novel sulfur reagent.…”