Chalcogen‐Bonding Catalysis with Telluronium Cations

Abstract

Chalcogen bonding results from non‐covalent interactions occurring between electrodeficient chalcogen atoms and Lewis bases. Among the chalcogens, tellurium is the strongest Lewis acid, but Te‐based compounds are scarcely used as organocatalysts. For the first time, telluronium cations demonstrated impressive catalytic properties at low loadings in three benchmark reactions: the Friedel–Crafts bromination of anisole, the bromolactonization of ω‐unsaturated carboxylic acids and the aza‐Diels–Alder between Danishefsky's diene and imines. The ability of telluronium cations to interact with a Lewis base through chalcogen bonding was demonstrated on the basis of multi‐nuclear (17O, 31P, and 125Te) NMR analysis and DFT calculations.

Alkynyl Sulfonium Salts Can Be Employed as Chalcogen‐Bonding Catalysts and Generate Alkynyl Radicals under Blue‐Light Irradiation

“…In comparison, Matile and co‐workers reported that 30 mol% of dithieno[3,2‐b;2′,3′‐d]thiophenes catalyzed this type of reaction, giving 96 % yield within 12 days [4a] . Next, the bromination of anisole with NBS was examined [6a, 9] . The reaction went well in the presence of 5 mol% of 1 at room temperature, affording the desired product in 77 % yield within 2 h (Scheme 2b).…”

“…The reaction went well in the presence of 5 mol% of 1 at room temperature, affording the desired product in 77 % yield within 2 h (Scheme 2b). Its ChB catalysis was also explored in the bromolactonization of the unsaturated carboxylic acid with NBS [6a, 9] . This reaction afforded the expected bromolactone in 69 % yield (Scheme 2c).…”

“…[1] Recently, there has been an increasing interest in harnessing their Lewis acid catalysis under metal-free conditions to discover new activation modes. [2,3] Several elegant ChB-catalyzed ionic transformations have been developed with various chalcogen compounds by the research groups of Matile, [4] Huber, [5] Yeung, [6] Wang, [7] Gabbaï, [8] Pale, Mamane [9] and others (Figure 1b). [3] On the other hand, readily available sulfonium salts have historically been utilized to form sulfur ylides [10] or undergo sigmatropic rearrangements.…”

On the Importance of Pnictogen and Chalcogen Bonding Interactions in Supramolecular Catalysis

“…Several studies available in the literature are focused on direct applications of ChB in catalysis [112][113][114][115][116][117][118][119][120][121][122][123][124][125][126], showing interesting and clever ways of the use of ChBs to stabilize negatively charged transition states.…”

“…The second benchmark reaction used was the bromolactonization of ω-unsaturated carboxylic acids (Figure 20b). Concretely, a series of ω-unsaturated carboxylic acids was As the final example, Weiss and collaborators [117] designed and synthesized a Tellurium organocatalyst (compound 27, Figure 19a), able to efficiently catalyze three different reactions: the Friedel-Crafts bromination of anisole, the bromolactonization of ω-unsaturated carboxylic acids and the aza-Diels-Alder reaction between Danisehfsky's diene and imines. In Figure 19b the MEP surface of compound 27 is shown, which involves CF 3 substitution in both benzene rings.…”