One-Pot NBS-Promoted Synthesis of Imidazoles and Thiazoles from Ethylarenes in Water

Abstract

A facile and eco-friendly method has been developed for the synthesis of imidazoles and thiazoles from ethylarenes in water. The reaction proceeds via in situ formation of α-bromoketone using NBS as a bromine source as well as an oxidant, followed by trapping with suitable nucleophiles to provide the corresponding products in good yields under metal-free conditions.

A multi pathway coupled domino strategy: I2/TBHP-promoted synthesis of imidazopyridines and thiazoles via sp3, sp2 and sp C–H functionalization

“… 5 In recent years, some new synthetic methods have been developed. For instance, when ethylbenzene 6 and styrene 7 act as starting materials, α-halo acetophenone is synthesized by adding an oxidant and a halogenating reagent ( Scheme 2c and d ). In addition, transition metal-catalyzed C–H bond activation methods for phenylacetylene 8 have been reported ( Scheme 2e ).…”

Recent Advances in the Synthesis of Imidazo[1,2‐a]pyridines: A Brief Review

“…reported a direct transformation of ethylarenes into primary aromatic amides in presence of N‐bromosuccinimide (NBS) as the key intermediate with a mixture of ethyl acetate and water. Motivated by this work, Chen et al [252] . in 2019 demonstrated a facile, eco‐friendly and one‐pot approach for the synthesis of various imidazo[1,2‐ a ]pyridines 337 from ethylarenes 335 in water in good yields.…”

“…Keeping in mind these limitations, Roslan et al [250] in 2019 In 2016, Shimokawa et al [251] reported a direct transformation of ethylarenes into primary aromatic amides in presence of N-bromosuccinimide (NBS) as the key intermediate with a mixture of ethyl acetate and water. Motivated by this work, Chen et al [252] in 2019 demonstrated a facile, eco-friendly and one-pot approach for the synthesis of various imidazo[1,2a]pyridines 337 from ethylarenes 335 in water in good yields. The authors reported that all reactions were metal-free and carried out in the water as the solvent.…”

Crystal structure of 4-(1-phenylimidazo[1,5-a]pyridin-3-yl)benzoic acid (C20H14N2O2)

“…One is the Vilsmeier-type cyclization reaction along with the variant methods [16,17]. Other methods involve the usage of organometallic catalysts [18] or an oxidant [19] and also the one-pot condensation reactions of amines and aldehydes [20,21]. In an attempt to synthesize a Schiff base using the one-pot condensation reaction using 4-(aminomethyl)benzoic acid and 2-benzoylpyridine, imidazole[1,5-a]pyridine moiety was isolated as a product in agreement with Wang et al [20] and Volpi et al [21].…”