The immense acidifying effect of the supersubstituent NSO2CF3 on the acidity of amides and amidines of benzoic acids in acetonitrile

摘要

The pKa values of acidic dissociation of the conjugate acids of derivatives of benzoate anions, where one or twonoxygen atoms are replaced by an u0001u0001NSO2CF3 group, N-aroyltrifluoromethanesulfonamides 1a–f and previouslynunreported N,Nu0003-bis(trifluoromethylsulfonyl)benzamidines 4a–f, were measured in acetonitrile. In the case of thenparent compound, the incorporation of the first u0001u0001NSO2CF3 group instead of the oxygen atom leads to a sharpn(by 9.6 pKa units) increase in the acidity, whereas the replacement of the second oxygen atom results in a furthernhuge increase in the acidity by 4.9 powers of ten. It was found that the sensitivity of the reaction series undernconsideration towards substituent effects (in the benzene ring) decreases in the following order: benzoicnacids > benzamides (1a–f ) > benzamidines (4a–f ). The results of this work carry potentially importantnimplications for the design of new types of superacids and catalytic materials.