Carbonyl Activation by Selenium‐ and Tellurium‐Based Chalcogen Bonding in a Michael Addition Reaction

Abstract

In the last years the use of chalcogen bonding-the noncovalent interaction involving electrophilic chalcogen centers-in noncovalentorganocatalysis has received increasedi nterest, particularly regarding the use of intermolecularL ewisa cids. Herein, we present the first use of tellurium-based catalysts for the activation of ac arbonyl compound (and only the second such activation by chalcogen bondingi ng eneral). As benchmark reaction, the Michael-typea ddition between trans-crotonophenone and 1-methylindole (and its derivatives) was investigated in the presence of various catalyst candidates. Whereas non-chalcogen-bonding reference compounds werei nactive, strong rate accelerations of up to 1000c ould be achieved by bidentate triazolium-basedc halcogen bond donors, with product yields of > 90 %w ithin 2h of reaction time. Organotellurium derivatives were markedly more active than their seleniuma nd sulphur analogues and non-coordinatingc ounterions like BAr F 4 provide the strongest dicationic catalysts.Chalcogen bonding [1] denotes the attractive interaction between electrophilicc halcogen centers and Lewis bases.

σ‐Hole Interactions in Catalysis

“…The same catalyst system was subsequently also applied in the Michael addition of indoles to trans ‐crotonophenone . Again, the tellurium‐based chalcogen‐bond donor showed the highest catalytic activity.…”

Zero-, one-, two- and three-dimensional supramolecular architectures sustained by Se…O chalcogen bonding: A crystallographic survey

“…It is stressed that the focus of the present review is upon the role of intermolecular Se … O contacts and upon the supramolecular aggregation patterns they sustain. In general terms, chalcogen interactions find very practical applications in a range of contexts beyond biology and medicine [16] , [17] , [18] , such as in molecular/anion recognition [19] , [20] , [21] , [22] , catalysts [23] , [24] and materials science [25] , [26] . With this level of activity, it is not surprising there are several authoritative reviews of chalcogen bonding [27] , [28] , [29] , [30] , including reviews of different physiochemical procedures for their detection in phases other than in crystals [31] , [32] , [33] , the primary importance of X-ray crystallographic investigations notwithstanding.…”

The Nature of Strong Chalcogen Bonds Involving Chalcogen‐Containing Heterocycles

“…[9][10][11] It could be shown that this bond type can also be used for crystal engineering, [12][13][14] molecular recognition in solution [15][16][17][18][19][20][21] and catalysis. [11,20,[22][23][24][25][26][27][28] Very strong and promising chalcogen bonds are found in electron-poor tellurium compounds such as isotellurazole oxides [21,29] or telluradiazole. [18,30,31] These tellurium-containing systems form strongly associating dimers and oligomers [21] in solution and can therefore be used as recognition units in supramolecular chemistry.…”