Alkylation represents an important organic transformation in molecular science to develop privileged alkylated arenes and heteroarenes. Especially, the direct C−H bond alkylation using unactivated alkyl halides is a straightforward and attractive approach from both the step-economy and chemoselectivity perspectives. Substantial progress has been made in the direct alkylation using primary, secondary, and tertiary alkyl halides along with the methylation and fluoroalkylation. This Review broadly summarizes the transition-metal-catalyzed alkylations of C−H bonds on various arenes and heteroarenes with unactivated alkyl halides until October 2020. On the basis of the substrates utilized for alkylation, the Review is divided into two major sections: alkylation of arenes and alkylation of heteroarenes.

C−H/C−H oxidative coupling has emerged as a straightforward and powerful technique for the construction of (hetero)biaryls, with substantial application to drug discovery, agrochemicals, biology, and material sciences. Mainly aryl‐aryl, aryl‐heteroaryl, and heteroaryl‐heteroaryl couplings via double C(sp2)−H activation using 4d or 5d noble transition metal catalysts have been extensively studied. Considering the earth‐abundant and inexpensive nature of 3d transition metals, the sustainable development of C(sp2)−H/C(sp2)−H oxidative coupling employing such metal catalysts has gained significant attention. In this review, we present a comprehensive overview of C(sp2)−H/C(sp2)−H oxidative coupling of (hetero)arenes catalyzed by 3d transition metals.

Chemoselective hydrogenation of C=C, C=O and C=N bonds in α,β-unsaturated ketones, aldehydes and imines is accomplished at room temperature (27 oC) using the well-defined Mn(I) catalyst and 5.0 bar H2....