Enzyme catalysis has always been an inspiration and an unattainable goal for chemists due to features such as high specificity,selectivity,and efficiency.Here,wedisclose afeature neither common in enzymes nor ever described for enzyme mimics,b ut one that could prove crucial for the catalytic performance of the latter,n amely the ability to catalyze and inhibit two different reactions at the same time.R emarkably, this can be realized by two identical, spatially resolved catalytic sites.Inthe future,such asynchronized catalyst action could be used not only for controlling chemoselectivity,asinthe present case,but also for regulating other types of chemical reactivity.
Acetals of the cyanohydrins of aromatic aldehydes were deprotonated to generate carbanions, which were used in the vicarious nucleophilic substitution of the hydrogen atom of aromatic and heteroaromatic nitro compounds to form p‐nitro‐substituted diarylacetonitriles. The reaction selectively occurred para to the nitro group. The anion of the hemiacetal of acetaldehyde was shown to be an efficient leaving group in the base‐induced β‐elimination step.
Pillar[n]arenes constitute the most recognizable macrocyclic compounds discovered recently. So far, research has been focused on their binding properties, while the catalytic properties were poorly explored. Herein we present the study of the binding as well as the catalytic properties of pillar[5]-and pillar [6]arenes functionalized with carboxylic groups in water. We show that electrostatic stabilization is not the main driving force during the binding, however, it is crucial for catalysis. The macrocycles promote the hydrolysis of a wide variety of hydrazones, and their catalytic activity, in essence, is determined by the barrier of the passage of the substrate through the macrocyclic cavity. This opens up new perspectives for these macrocycles that could make a strong competition to traditional supramolecular catalysts such as cyclodextrins or cucurbiturils.
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