Highly Enantioselective Lewis Acid Catalyzed Conjugate Addition of Imidazo[1,2-a]pyridines to α,ß-Unsaturated 2-Acylimidazoles under Mild Conditions.

A highly enantioselective protocol for the conjugate addition of 2-arylimidazo[1,2-a]pyridines and other imidazo derivatives to α,ß-unsaturated 2-acylimidazoles is described. The method uses a previously reported chiral-at-metal rhodium catalyst and provides the corresponding adducts in yields of 25-98% with enantioselectivities up to er > 99:1. Additionally, the transformation proceeds under mild conditions using ethanol as the solvent at room temperature.

KIO3-catalyzed selective oxidation of thiols to disulfides in water under ambient conditions.

Herein, we report a KIO3-catalyzed oxidative coupling of thiols to their corresponding disulfides in water, in a short time and at ambient temperature. The reaction has a broad scope and exhibits good functional group tolerance, resulting in the desired products in excellent yields. This approach allows the reuse of the reaction system in multiple cycles and scale-up. Furthermore, the current protocol demonstrates compatibility for in situ generation of disulfides and post application in C(sp2)-H bond sulfenylation.

Catalyst- and metal-free C(sp2)-H bond selenylation of (N-hetero)-arenes using diselenides and trichloroisocyanuric acid at room temperature.

In this paper, we report an eco-friendly approach for the C(sp2)-H bond selenylation of imidazopyridines and other N-heteroarenes as well as simple arenes at ambient temperature. This new protocol consists of the reaction between (N-hetero)-arenes and the diorganyl-diselenides and trichloroisocyanuric acid (TCCA)-ethanol reagent system. In a short reaction time, the desired selenylated products were obtained regioselectively in good yields, with tolerance for a wide range of functional groups.

Synthesis of the Brivaracetam Employing Asymmetric Photocatalysis and Continuous Flow Conditions.

An original total synthesis of the antiepileptic drug brivaracetam (BRV) is reported. The key step in the synthesis consists of an enantioselective photochemical Giese addition, promoted by visible-light and the chiral bifunctional photocatalyst Δ-RhS. Continuous flow conditions were employed to improve the efficiency and allow an easy scale-up of the enantioselective photochemical reaction step. The intermediate obtained from the photochemical step was converted into BRV by two different pathways, followed by one alkylation and amidation, thus giving the desired active pharmaceutical ingredients (API) in 44% overall yield, 9:1 diastereoisomeric ratio (dr) and >99:1 enantiomeric ratio (er).

Decarboxylative ring-opening of 2-oxazolidinones: a facile and modular synthesis of ß-chalcogen amines.

We report herein the synthesis of primary and secondary ß-chalcogen amines through the regioselective ring-opening reaction of non-activated 2-oxazolidinones promoted by in situ generated chalcogenolate anions. The developed one-step protocol enabled the preparation of ß-selenoamines, ß-telluroamines and ß-thioamines with appreciable structural diversity and in yields of up to 95%.

Photoinduced, Direct C(sp2 )-H Bond Azo Coupling of Imidazoheteroarenes and Imidazoanilines with Aryl Diazonium Salts Catalyzed by Eosin†Y.

Herein, a greener approach to the eosin Y-Na2 catalyzed, C(sp2 )-H bond azo coupling of imidazoheteroarene with aryl diazonium salts is described, under acid free conditions. This direct photoredox process resulted in the corresponding azo products in good to excellent yields. Besides, this new approach could also be applicable to anilines, which is a poorly reactive substrate by other methods. The main features of this reaction are that it provides high yields and is gram-scalable and applicable to biologically relevant imidazoheteroarenes and -anilines.

Rose Bengal catalysed photo-induced selenylation of indoles, imidazoles and arenes: a metal free approach.

In this report, the highly efficient Rose Bengal-catalysed C(sp2)-H selenylation of indoles, imidazoles and arenes was achieved using a half molar equiv. of diorganoyl diselenides. This metal-free, photo-induced protocol resulted in selenylated products in good to excellent yields. The reaction features are high yields, an atom-economic, gram-scalable and metal-free approach, and applicability to different biologically relevant (hetero)arenes.

Direct, Metal-free C(sp2 )-H Chalcogenation of Indoles and Imidazopyridines with Dichalcogenides Catalysed by KIO3.

Herein, we report a greener protocol for the synthesis of 3-Se/S-indoles and imidazo[1,2-a]pyridines through direct C(sp2 )-H bond chalcogenation of heteroarenes with half molar equivalents of different dichalcogenides, using KIO3 as a non-toxic, easy-to-handle catalyst and a stoichiometric amount of glycerol. The reaction features are high yields, based on atom economy, easy performance on gram-scale, metal- and solvent-free conditions as well as applicability to different types of N-heteroarenes.

Metal- and Solvent-Free Approach to Access 3-Se/S-Chromones from the Cyclization of Enaminones in the Presence of Dichalcogenides Catalyzed by KIO3.

Herein, we describe a greener protocol for the one-pot synthesis of 3-Se/S-4H-chromen-4-ones. The desired products were obtained in good to excellent yields using 2-hydroxyphenyl enaminones and half equivalents of various odorless diorganyl dichalcogenides (S/Se) in the presence of glycerol (5 molar equiv) and KIO3 (15 mol %) as the catalyst under solvent-free conditions.