Transition metal-catalyzed C-H bond functionalizations have been the focus of intensive research over the last decades for the formation of C-C bonds from unfunctionalized arenes, heteroarenes, alkenes. These direct transformations provide new approaches in synthesis with high atom- and step-economy compared to the traditional catalytic cross-coupling reactions. However, such methods still suffer from several limitations including functional group tolerance and the lack of regioselectivity. In addition, they often require harsh reaction conditions and some of them need the use of strong oxidant, in a stoichiometric amount, avoiding these processes to be truly eco-friendly. The use of photoredox catalysis has contributed to a significant expansion of the scope of C(sp)-H bond functionalizations which include the direct arylations, (perfluoro)alkylations, acylations, and even cyanations. Most of these transformations involve the photochemical induced generation of a radical followed by its regioselective addition to arenes, heteroarenes, or alkenes, leading to the building of a new C(sp)-C bond. The use of photoredox catalysis plays crucial roles in these reactions promoting electron transfer, enabling the generation of radical species and single electron either oxidation or reduction. Such reactions operating at room temperature allow the building of C-C bonds with high chemo-, regio-, or stereoselectivity. This review surveys the formation of C(sp)-C bonds initiated by photoredox catalysis which involves a C(sp)-H bond functionalization step, describes the advantages compared to traditional C(sp)-H bond functionalizations, and presents mechanistic insights into the role played by the photoredox catalysts.

Considering the importance of the development of powerful green catalysts and the omnipresence of amide bonds in natural and synthetic compounds, we report here on reactions between alcohols and amines for amide bond formation in which heterogeneous gold and gold/iron, -nickel, or -cobalt nanoparticles are used as catalysts and molecular oxygen is used as terminal oxidant. Two catalysts show excellent activity and selectivity, depending on the type of alcohols used. A wide variety of alcohols and amines, including aqueous ammonia and amino acids, can be used for the amide synthesis. Furthermore, the catalysts can be recovered and reused several times without loss of activity.

International audienceIn recent years, palladium-catalyzed arylation of heteroaroms. via C-H bond activation has become a popular method for generating carbon-carbon bonds. For this reaction, a wide variety of heteroaroms. such as (benzo)furans, (benzo)thiophenes, pyrroles, indoles, thiazoles, oxazoles, imidazoles, pyrazoles or triazoles can be employed. In most of these heterocycles, several reactive C-H bonds are present. If specific C-H bonds of such heteroarenes can be coupled with arenes, this becomes one of the most simple methods to access bi(hetero)arenes. In the past few years, several results using modified and improved catalysts and new reaction conditions have been reported permitting better control of the regioselectivity of such arylations. For example, initially only C2- or C5-arylated thiophenes were accessible via palladium-catalyzed direct arylation, whereas now regioselective C3- or C4-arylations are possible when appropriate reaction conditions are used. In this review, the influence of the reactants, catalysts and reaction conditions on the regioselectivity of palladium-catalyzed arylation of heteroaroms. is reported. The recent progress in the regioselectivity control now allows the synthesis of a wide variety of complex mols. using only a few steps, and will certainly provide simpler access to new heteroaryl derivs. in the next years