engleski

Effect of Different Additives on the Rates of Mechanochemical C–H Bond Activation

C–H bond activation with palladium compounds remains a challenge not only as the most convenient approach for the synthesis of palladacycles explored in various areas of material science and biological chemistry1 but also due to its exceptional importance in the organic synthetic chemistry.2 Namely, the C–H bond activation presents the crucial step in many organic reactions promoted by palladium catalysts.1 Due to the rapid evolution of the mechanochemical methods and their application in the organic catalytic reactions, 2 a better understanding of factors influencing the solid- state C–H bond activation is essential. Herein we report the study of regioselective solid- state C–H bond activation in asymmetric azobenzene substrate (AZB) with PdCl2 precursor using various ball-milling methods, neat grinding (NG), liquid-assisted grinding (LAG), ion-assisted grinding (IAG) and ion-and-liquid- assisted grinding (ILAG). Detailed mechanistic insight obtained by in situ Raman monitoring in combination with stepwise ex situ NMR, IR and PXRD studies supports the electrophilic process which proceeds via a coordination complex (adduct) undergoing deprotonation by an external base, Scheme 1. In situ and ex situ spectroscopic monitoring also revealed how liquids of different acid-base properties and proticity as well as selected solids used as additives modify precursor and its reactivity as well as the activation rates of C–H bonds.

paladij ; organometali ; aktivacija C-H veze ; mehanokemija

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