Ultrasound‐Assisted Synthesis and Antioxidant Activity of 3‐Selanyl‐1 H‐indole and 3‐Selanylimidazo[1,2‐a]pyridine Derivatives

Abstract

As imple and rapid methodf or the selective synthesis of 3-(organylselanyl)-1 H-indoles and3 -(organylselanyl)imidazo[1,2-a]pyridines catalyzed by CuI/SeO 2 under ultrasound irradiation was developed. This protocol employs adiverse range of 1 H-indoles or imidazo[1,2-a]pyridines and diorganyl diselenides to afford the corresponding products selectively in good to excellent yields. Moreover,t he antioxidant activity of these compounds was evaluated by using aw ider ange of in vitro assays,s uch as 2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1picrylhydrazyl (DPPH) radical, ferric ion reducing antioxidant power (FRAP), and inhibition of reactive speciesf ormation in mice cortex. The bioassays revealed thatb oth classes of the newly synthesized organoselenium compounds present antioxidanta ctivity,w ith emphasis on the 3-(organylselanyl)-1 Hindoles.T his pharmacological activity opens aw ide range of biological applications where the reduction of oxidative stress is essential.[a] B. Results and DiscussionAc omparatives tudy on the use of microwaves, US, and conventional heating in the copper-catalyzed selenylation of indoles in DMSO was recently reported by us. [18b] In this reaction, Figure 1. 3-Arylselanylindoles A and B and 3-thioimidazo[1,2-a]pyridines C and D with similar effects to Combretastatin A-4a nd Enviroxime.Scheme1.Generalscheme of the present work.

Dichalcogenides/Oxone®‐Mediated Cyclization of (Z)‐Chalcogenoenynes under Ultrasound Irradiation

“…Thus, based on the above observations and on previous reports involving electrophilic cyclization reactions, [70][71][72] the reactivity of Oxone ® [40,43,81] and reactions under ultrasonic irradiation, [77][78][79][80][81] a plausible mechanism for the formation of chalcogenophenes 7-9 from 1-3 is presented in Scheme 4.…”

“…When the reaction mixture was refluxed for 8 h, the expected product 7 a was isolated in 77 % yield. Then, encouraged by recent positive results described by our research group, [77][78][79][80][81] and interested in reducing the reaction time, the mixture was sonicated at 60 % of amplitude for 60 min, using an ultrasonic probe, obtaining the desired product 7 a in 78 % yield (Table 1, entry 1). Considering this yield as satisfactory, the influence of the solvent on the performance of the cyclization was investigated ( Table 1, entries 2-12).…”

Ultrasound‐Assisted Multicomponent Reactions, Organometallic and Organochalcogen Chemistry

“…Recently, Lenardão and co‐workers reported the synthesis of selenium‐containing N ‐heterocyclic derivatives, in particular 1 H ‐indoles 80 and imidazo[1,2‐ a ]pyridines 81 . These privileged scaffolds, were reacted with diphenyl diselenide in the presence of SeO 2 through an US‐assisted Cu(I)‐catalyzed electrophilic aromatic substitution, affording products 82 and 83 , respectively (Scheme ).…”

Photocatalytic Synthesis of 3‐Sulfanyl‐ and 1,3‐Bis(sulfanyl)indolizines Mediated by Visible Light

“…Because of the potential of 3‐sulfanylindolizines in medicinal chemistry, and considering the drawbacks of the current protocols to access this class of compounds (use of strong oxidants, heating for several hours), the development of new routes to access these compounds is yet required. Thus, in continuation to our efforts in the development of efficient and selective methods to access chalcogen‐substituted heterocycles, we describe herein a photocatalyzed C–H/S–H oxidative coupling approach for the synthesis of 3‐sulfanylindolizines ( 3 ) and 1,3‐bis‐sulfanylindolizines ( 4 ), mediated by blue LED visible light and using atmospheric oxygen as a mild oxidant, as shown in Scheme .…”