Cooperativity between the Silver(I) and Iodine(III) Centers in Electrophilic Activation of Organic Substrates

Abstract

Kinetic data and computational study indicate that in the solution, pyrazole-containing iodolium salts and silver(I) center bind each other, and such interplay significantly affect the total catalytic activity of mixture of these Lewis acids compared with separate catalysis of the reactions required electrophilic activation of carbonyl, imino group, or triple CC bond. Moreover, the kinetic data and 1H NMR monitoring indicate that such cooperation results in prevention of decomposition of the organocatalysts by the silver(I) center during the reaction progress. XRD study indicates that in the solid state, the iodolium triflates and silver(I) triflate associate each other to give the complex species featuring triflate-bridged iodine(III) and silver(I) centers: a rare example of square-planar silver(I) complex and pentacoordinated trigonal bipyramidal dinuclear silver(I) complex.

Cooperative Catalysis Involving Hydrogen and Halogen Bond Donors: A Computational Study on the Thiourea–Iodonium System

“…This route has been casually mentioned in ref. 22 and recently observed by us 44 for the case of silver(I)-iodolium triflate mixture. On the other hand, HB donor can bind the counter-ion of the XB donating species leading to higher concentration of the dissociated (and catalytically active) form of the latter.…”

Computational Study on the Route of Cooperative Organocatalysis Utilizing Thiourea and Halogen Bond Donor Mixture

“…On the one hand, the thiourea can stabilize the catalytically active XB donor (potentially unstable under the reaction conditions), thus prolonging its action during the reaction. This route has been briefly mentioned in reference 22, recently observed by us 48 for the case of silver(I) triflate-iodolium triflate mixture, and suggested 49 for iodopyridinium-based XB-donating catalysts. On the other hand, the HB donor can bind the counter-ion of the XB donating species leading to a higher concentration of the dissociated (and catalytically active) form of the latter.…”

Halogen bonded associates of iodonium salts with 18-crown-6: does structural flexibility or structural rigidity of the σ-hole donor provide efficient substrate ligation?

“…Although both cyclic and acyclic iodonium salts previously exhibited excellent titration curves during the study of their binding with a series of simple nucleophiles in protic and aprotic solvents, 4,5,7,8 the titration of 18-crown-6 with 1 OTf or 2 OTf exhibited some peculiarities. Thus, in CD 3 CN, the titration of 18-crown-6 with cyclic 2 OTf showed points excellently fitted by the approximation curve (Fig.…”