Predicting the catalytic activity of azolium-based halogen bond donors: an experimentally-verified theoretical study

Abstract

The most promising types of iodoazolium compounds exhibiting high catalytic activity toward halogen abstraction and carbonyl activation are highlighted.

The mechanism and impact of mono/bis(iodoimidazolium) halogen bond donor catalysts on Michael addition of indole with trans-crotonophenone: DFT calculations

“…As seen from Table 1, the minimum value of the electrostatic potentials ( V S,min ) of trans -crotonophenone (the Michael acceptor) is −46.40 kcal mol −1 . The V S,max value of C 5 H 8 N 2 I + (cat1) is 103.84 kcal mol −1 , which is similar to the cations of the studied azolium types calculated by Bolotin et al 72 For the bis(iodoimidazolium) halogen bond donors, due to the different substituents connecting the two 2-iodoimidazolium, the V S,max values increase in the order of –C 6 H 6 –, –C 3 H 6 –, and –C 6 H 3 CF 3 –.…”

“…The ESP distribution analysis demonstrated the strong correlation between the σ-hole on the halogen atom of halogen bond donors and the Gibbs free energy of the activation of the considered reactions. 72 In our work, it is worth noting that the V S,max values of bis(iodoimidazolium) halogen bond donors are about 41 kcal mol −1 higher than cat1, which predicts the catalytic superiority of bis(iodoimidazolium) halogen bond donors relative to the mono(iodoimidazolium) halogen bond donor.…”

Magnesium Complexes with Isomeric Pyrazol‐4‐ylidene and Imidazol‐2‐ylidene Ligands

“…[21] 2 a: 1 H NMR (499.9 MHz, C 6 D 6 ): δ = 1.16 (d, J = 6.9 Hz, 24H, ArCH(CH 3 ) 2 ), 1.21 (d, J = 6.9 Hz, 24H, ArCH(CH 3 ) 2 ), 1.71 (s, 12H, NCCH 3 ), 3.20 (sept, J = 6.9 Hz, 8H, ArCH(CH 3 ) 2 ), 4.98 (s, 2H, NCCH), 6.82 (dd, 5H, J = 6.2, 3.0 Hz, 5H, ArH), 7.04 (dd, J = 4.9, 1.8 Hz, 10H, ArH), 7.06-7.23 (m, 12H, ArH) ppm. [{( Dip nacnac)MgI} 2 ] [22] 3 a: 1 Iodopyrazoles and iodopyrazolium salts [9,10,25] were prepared in analogy to previously published methods. 4-Iodo-1,3,5-trimethylpyrazole.…”

“…[16] As suitable starting materials towards pyrazol-4-ylidene complexes, we prepared two small 1,2,3,5-tetraalkyl-4-iodopyrazolium iodide salts from the respective 4-iodopyrazole and iodomethane, as described previously. [9,10,25] The reactions of these salts [ Me PZI]I 5 a (4-iodo-1,2,3,5-tetramethylpyrazolium iodide) and [ Et PZI]I 5 b (3,5-diethyl-4-iodo-1,2-dimethylpyrazolium iodide), see Scheme 2, with one equivalent of dimagnesium(I) complexes [{( Ar nacnac)Mg} 2 ] 1 a, b in toluene, benzene or hexane proceeded slowly at room temperature. The reaction mixtures are suspensions, due to the poor solubility of the salts, that slowly lose the yellow colour of the magnesium complexes and form product mixtures dominated by [{( Ar nacnac)MgI} 2 ] 3 a, b and other magnesium iodide species, see Scheme 2.…”

Ionic Liquids as Organocatalysts for Nucleophilic Fluorination: Concepts and Perspectives

“…Significantly enhanced reactivity and selectivity have also been observed in concerted reactions such as nucleophilic substitution reactions in ionic liquids [ 14 , 15 , 16 ]. By combining a variety of cations and anions with characteristic structures, it is possible to tailor-make task-specific ILs with desirable properties for specific chemical reactions [ 15 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ].…”