A dual catalytic protocol for the direct arylation of non‐activated C(sp3)−H bonds has been developed. Upon photochemical excitation, the excited triplet state of a diaryl ketone photosensitizer abstracts a hydrogen atom from an aliphatic C−H bond. This inherent reactivity was exploited for the generation of benzylic radicals which subsequently enter a nickel catalytic cycle, accomplishing the benzylic arylation.

Visible-light induced, palladium catalyzeda lkylations of a,b-unsaturated acids with unactivated alkyl bromides are described. Av ariety of primary,s econdary,a nd tertiary alkylb romides are activated by the photoexcited palladium metal catalyst to provide aseries of olefins at room temperature under mild reaction conditions.Mechanistic investigations and density functional theory (DFT) studies suggest that ap hotoinduced inner-sphere mechanism is operative in whichabarrierless,single-electron transfer oxidative addition of the alkyl halide to Pd 0 is key for the efficient transformation.Cross-coupling reactions are one of the most important synthesis tools for the formation of C À Co rC-heteroatom bonds.C onventionally,t hree key steps are involved in the cross-coupling reaction:o xidative addition, transmetalation, and reductive elimination. Often challenges arise in the individual steps,d epending on the coupling partners,m etal catalysts or reaction conditions employed. In recent decades, numerous catalysts,aswell as ligands,have been developed in order to reduce the energy barrier in the bond-forming and breaking steps.More recently,ithas been shown that visiblelight enhances cross-couplings employing radicals. [1] This methodology allows single-electron transfer (SET) to replace the conventional two electron transfer process by using photoredox and transition metal dual-catalytic systems,t hus significantly reducing the barrier for each step in crosscoupling reactions. [2] Despite developments made in crosscoupling chemistry,t he conventional oxidative addition of alkyl electrophiles to Pd 0 remains sluggish, even at elevated temperature,o wing to the electron-rich nature of the alkyl halide bond. [3] In fact, computational studies have revealed that the alkyl bromide oxidative addition to Pd 0 is endothermic with ah igh energy barrier of 41.6 kcal mol À1 .F urther, alkyl-palladium(II) species that are formed through at wo-electron transfer are considerably less stable because of the lack of p-electrons interacting with the empty d-orbitals of the metal. This results in fast b-hydride (b-H) elimination from salkyl-palladium(II) intermediates which outcompetes the required olefin insertion in decarboxylative alkylation crosscoupling reactions. [3,4] In contrast to the photoredox dual-catalysis strategy which promotes cross-coupling by lowering the energy barrier, we now report the use of am echanistically distinct, SET barrierless oxidative addition strategy for alkylation of vinylic acids,using Pd complexes as both photosensitizer and cross-coupling catalyst. [5] This lowers the oxidative addition barrier resulting in an alkyl radical and aP d I intermediate (Figure 1) which can add to an a,b-unsaturated acids. Subsequent carbon dioxide elimination provides the akylated olefin and the regenerated catalyst. To the best of our knowledge,avisible light-induced palladium catalyzed decarboxylative C(sp 3 ) À C(sp 2 )c ross-coupling alkylation has not been reported.Vinylic acids are readily available and stable,...

A chiral iodoarene organocatalyst for the catalytic asymmetric fluorination has been developed. The catalyst was used in the asymmetric fluorination of carbonyl compounds providing the products with a quaternary stereocenter with high enantioselectivities. Chiral hypervalent iodine difluoride intermediates were generated in situ by treatment of the catalyst with an oxidant and hydrogen fluoride as fluoride source. As such the -fluorination of a carbonyl compound was achieved with a nucleophilic fluorine source. A combined computational and experimental approach provided insight into the reaction mechanism and the origin of enantioselectivity.

The photochemical reactivity of benzophenone is utilized for direct benzylic C–H bond acylation of methylbenzenes via H-atom abstraction as a key step. The reaction offers a robust method for synthesizing ketones using acid chlorides and anhydrides.