Generation of carbon centered radicals from organic halides represents a powerful tool in modern organic chemistry, especially in the context of photoredox catalysis. However, activation of carbon–halogen bonds is usually promoted by toxic and hazardous tin reagents. Alternatively, α‐aminoalkyl radicals have emerged as a cheap and efficient halogen atom transfer (XAT) reagents, although the activation mechanism is still underexplored with respect to hydrogen atom transfer (HAT) chemistry. Herein, we report a computational systematic evaluation of four different α‐aminoalkyl radicals on the Halogen Atom Transfer (XAT) mechanism. We have evaluated up to 32 reactions, including two different types of substrates (Ph−X and Cy−X). This systematic study aims to provide a big picture on the key effects in this reactivity including the hybridization of carbon, the nature of the halogen, and the electronics/sterics of the α‐aminoalkyl radical.

Although considerable advances have been made in developing chemoselective transformations of ubiquitous carboxylic acid groups, many challenges still exist. For instance, their selective reduction is problematic if both more nucleophilic and more electrophilic groups are present in the starting material. Here, we address this problem with a simple and mild protocol using bench‐stable reagents at ambient temperatures. This platform is able to tolerate a diverse range of functionality, leaving ketones, esters, nitro‐groups, olefins, nitriles and amides untouched. A combination of experimental and computational mechanistic experiments demonstrate that this reaction proceeds via hidden borane catalysis with small quantities of in situ generated BH₃playing a key role in the exquisite selectivity that is observed.

Formation of carbon‐carbon bonds through cross‐coupling reactions using readily available substrates, like alcohols, is crucial for modern organic chemistry. Recently, direct alkyl alcohol functionalization has been achieved by the use of N‐Heterocyclic Carbene (NHC) salts via in situ formation of an alcohol‐NHC adduct and its activation by a photoredox catalyst to generate carbon‐centered alkyl radicals. Experimentally, only electron deficient NHC activators work but the reasons of this behavior remain underexplored. Herein, a DFT computational study of the mechanism of alcohol activation using up to seven NHC salts is performed to shed light into the influence of their electronic properties in the alkyl radical formation. This study demonstrates that four reaction steps are involved in the transformation and characterizes how the electronic properties of the NHC salt affect each step. A fine balance of the NHC electron‐richness is proved to be determinant for this transformation.

Although considerable advances have been made in developing chemoselective transformations of ubiquitous carboxylic acid groups, many challenges still exist. For instance, their selective reduction is problematic if both more nucleophilic and more electrophilic groups are present in the starting material. Here, we address this problem with a simple and mild protocol using bench‐stable reagents at ambient temperatures. This platform is able to tolerate a diverse range of functionality, leaving ketones, esters, nitro‐groups, olefins, nitriles and amides untouched. A combination of experimental and computational mechanistic experiments demonstrate that this reaction proceeds via hidden borane catalysis with small quantities of in situ generated BH₃playing a key role in the exquisite selectivity that is observed.

A density functional theory (DFT) study was performed to evaluate the reaction mechanism of the C–N bond formation under an integrated hydrogen atom transfer/radical-polar crossover photoredox catalytic cycle. The regioselective activation of a model substrate, including three reactive positions (3° benzylic C–H bond, 2° benzylic C–H bond, and primary C–Cl bond) was addressed to distinguish among the radical C–H activation mechanism and the standard SN2 reaction. We demonstrated that activation of tertiary benzylic C–H bond is the most favored and forms exclusively the experimentally observed product. In addition, the whole photoredox catalytic cycle, including the outer-sphere electron-transfer steps, was characterized computationally.