One of the major aims in chemistry is to influence a chemical reaction in order to obtain the required products at the best possible yield. One of the tools is catalysis. A new class of catalysts bases on 2,2′-bipyridyl N,N’-dioxide skeleton was developed in the group of Prof. Kotora. It is assumed that the catalysts act as bases, hence they bind to protons or other positively charged species or groups. Based on the investigation of the properties of the catalysts, we have found that they belong to extremely basic compounds, so-called superbases. Most of the known superbases are derived from nitrogen-containing compounds, where nitrogen serves as the binding site for a proton. Our catalysts are first experimentally studied oxygen superbases (i.e. proton is bound to oxygen). Investigation of mechanisms of reactions, which are catalyzed by these superbases, brought surprising results. Oxygen atoms of the catalysts do not bind directly to an electrophilic site of a reactant. Instead the catalyst acts as a sort of a minienzyme, which contains a structurally well defined, highly polar binding site for a substrate and at the same time has a hydrophobic envelope. Thus, in nonpolar solvents polar reactants tend to hide inside the polar pockets of the catalysts, which firstly brings the reactants together and secondly influences their mutual interaction. The result is a selective reaction, which leads to the required products with high yields.
Fig. 1. Illustration of a “polar pocket” of an organocatalyst. The molecule is depicted using an electrostatic potential color-coded on electron-density surface.
MORE INFORMATION CAN BE FOUND IN PUBLICATION:
- L. Ducháčková, A. Kadlčíková, M. Kotora, J. Roithová, .J. Am. Chem. Soc. 2010, 132, 12660.