Precise Introduction of Small Functional Group (NH2, OH, CH3, CN, F, CF3) in Organic Molecules via Direct C-H Activation.

Small functional groups are responsible for the characteristic chemical reactivity and biological properties of molecules. These functional groups in some way, express the overall characteristic of the molecule. Currently, various methodologies and noble reagents are being explored for the direct introduction of small functional groups such as amine, hydroxyl, fluorine, and methyl into valuable molecules without any further deprotection. Among several synthetic methodologies, the direct C-H activation approach offers a straightforward pathway for the incorporation of small functional groups, connecting the realm of modern organic chemistry with sustainability and versatility. A variety of transition metal catalysts and noble reagents can be used to facilitate such chemical transformations. In the current review, small group functionalization via direct C-H activation is discussed in the following five sections: (i) importance of small functional groups in drug discovery, (ii) amination, (iii) hydroxylation, (iv) methylation, (v) cyanation, (vi) fluorination and trifluoromethylation and the application in late-stage functionalization.