Organocatalytic Asymmetric Synthesis and Use of Organoselenium Compounds

Abstract

Abstract:In the last ten years organocatalysis has emerged as an efficient and sustainable strategy for the asymmetric synthesis of chiral molecules. Optically active intermediates for novel interesting transformations are generated under mild and operationally simple conditions when selenium-containing compounds are used as reaction partners. The peculiar reactivity of organoselenium compounds has been exploited in practical one-pot sequences for the asymmetric construction of densely functionalized compounds starting from simple precursors. IntroductionIn the last few decades organoselenium compounds, because of their high structural diversity, rich chemistry, ready availability, and easy handling, have become very popular in synthetic chemistry. 1 In some respects the structure and reactivity of organoselenium compounds are similar to those of the better-known sulfur analogues, but certain features make selenium derivatives particularly valuable. For example, selenium forms weaker σ-bonds than sulfur, hence, reactions which involve cleavage of C-Se, O-Se, and N-Se bonds occur at a faster rate and under milder conditions. A selenium group is usually introduced in high yield into a target molecule through electrophilic or nucleophilic reagents with a predictable chemo-, regio-, and stereoselectivity. In many cases the insertion is concomitant with the introduction of vicinal functional groups or with the formation of rings and stereocenters. The selenium group can also be used for further elaborations such as ionic or radical substitutions and elimination processes. One of the most attractive aspects of selenium chemistry is the wide applicability in asymmetric synthesis, a topical area of modern organic chemistry. 1,2 Many compounds have been prepared in the optically active form by asymmetric versions of common selenium-based methodologies. In this field our research group has made several contributions such as asymmetric cyclofunctionalizations of alkenes with optically active diselenides 3 and short synthetic sequences for access to heterocycles with achiral selenium reagents and compounds from the chiral pool. 4 However, with the exception of selenofunctionalization and deselenylation sequences with chiral diselenides and metal-catalyzed reactions in which the organoselenium compound acts as a chiral ligand, 1,2 catalytic asymmetric methods based on selenium chemistry are poorly investigated. This is surprising since the field of asymmetric organocatalysis has recently emerged as a robust and powerful strategy for the enantioselective construction of building blocks, natural products, and molecules of pharmaceutical interest. Pioneering cinchonidine-catalyzed 1,4-additions of benzeneselenol to cyclohexenones 5 and L-prolinamide-catalyzed α-selenenylations of carbonyl compounds 6 gave products with poor enantioselectivity. Very recently, Denmark et al. reported the first catalytic selenoetherification reactions of alkenes by using a BINAM-derived thiophosphoroamide catalyst. 7 In this Account we illustrat...

Ruthenium-Catalyzed [2+2+2] Cycloaddition of α,ω-Diynes and Selenocyanates: An Entry to Selenopyridine Derivatives

“…Furthermore, the gram-scale synthesis of 3h by using this reaction allowed access to the desired cycloadduct in 90% yield (see the Supporting Information). Cycloaddition in the presence of 2,2difluoro-5-selenocyanatobenzo[d] [1,3]dioxole 2i furnished heterocyclic derivative 3i with good yield (63%).…”

“…Organoselenium compounds are attractive target molecules because of their use in asymmetric catalysis 1 or in ionic liquids for electrophilic substitutions. 2,3 Moreover, interest in heterocyclic chalcogenic molecules has increased over the last decades, thanks to their pharmacological and biological activities.…”

Recent advances in selenium promoted or catalyzed electrophilic aminations of alkenes and alkynes

“…Very recently, nitrogen containing functional groups have been also incorporated onto C-C triple bonds for a convenient and stereo-controlled access to synthetically valuable vinyl selenides. [35][36][37][38] In 2016 the first highly regio-and stereo-selective functionalization of alkynes with diphenyldiselenide and Nfluorobenzenesulfonimide (NFSI) has appeared in the literature (Scheme 13). 39 Scheme 13.…”

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

“…The synthesis of organoselenium compounds and their biological activity have attracted considerable attention in research fields directed to drug discovery [1][2][3][4][5][6][7][8][9][10][11][12][13]. Among these compounds, heteroaryl selenides and heteroaryl diselenides have been synthesized by a variety of methods [14,15], and many of the targets exhibited biological activity (Figure 1).…”