Mechanism and Origin of Site Selectivity and Regioselectivity of Scandium-Catalyzed Benzylic C-H Alkylation of Tertiary Anilines with Alkenes

Benzylic C(sp³)-H alkylation of tertiary anilines with alkenes by an anilido-oxazoline-ligated scandium alkyl catalyst was recently reported with C-H site selectivity and alkene-dependent regioselectivity. Revealing the mechanism and origin of selectivity is undoubtedly of great importance for understanding experimental observations and developing new reactions. Herein, density functional theory (DFT) calculations have been carried out on the model reaction of Sc-catalyzed benzylic C(sp³)-H alkylation of N,N-dimethyl-o-toluidine with allylbenzene. The reaction generally undergoes the generation of active species, alkene insertion, and protonation steps. The difference of the distortion energy of the aniline moiety in transition states, which is related to the ring size of the forming metallacycles, accounts for the site selectivity of C-H activation. Benzylic C(sp³)-H activation possessing less strained five-membered metallacycle compared to the ortho-C(sp²)-H and α-methyl C(sp³)-H activation results in benzylic C(sp³)-H alkylation observed experimentally. Both steric and electronic factors are responsible for the 1,2-insertion regioselectivity for alkyl-substituted alkenes, while electronic factors control the 2,1-insertion manner for vinylsilanes. The analysis of original alkene substrates further strengthens the understanding of the alkene-dependent regioselectivity. These results help us to obtain the mechanistic understanding and are expected to be conducive to the development of new C-H functionalization reactions.

Diversification of aliphatic C-H bonds in small molecules and polyolefins through radical chain transfer

The ability to selectively introduce diverse functionality onto hydrocarbons is of substantial value in the synthesis of both small molecules and polymers. Herein, we report an approach to aliphatic carbon-hydrogen bond diversification using radical chain transfer featuring an easily prepared O-alkenylhydroxamate reagent, which upon mild heating facilitates a range of challenging or previously undeveloped aliphatic carbon-hydrogen bond functionalizations of small molecules and polyolefins. This broad reaction platform enabled the functionalization of postconsumer polyolefins in infrastructure used to process plastic waste. Furthermore, the chemoselective placement of ionic functionality onto a branched polyolefin using carbon-hydrogen bond functionalization upcycled the material from a thermoplastic into a tough elastomer with the tensile properties of high-value polyolefin ionomers.

Palladium-Catalyzed Multistep Tandem Carbonylation/N-Dealkylation/Carbonylation Reaction: Access to Isatoic Anhydrides

A novel and efficient synthesis of isatoic anhydride derivatives was developed via palladium-catalyzed multistep tandem carbonylation/N-dealkylation/carbonylation reaction with alkyl as the leaving group and tertiary anilines as nitrogen nucleophiles. This approach features good functional group compatibility and readily available starting materials. Furthermore, it provided a convenient approach for the synthesis of biologically and medicinally useful evodiamine.

Pd/Cu-Catalyzed aerobic oxidative aromatic C–H bond activation/N-dealkylative carbonylation towards the synthesis of phenanthridinones

A straightforward Pd/Cu-catalyzed oxidative C–H bond activation/N-dealkylative carbonylation of tertiary [1,1′-biphenyl]-2-anilines towards the synthesis of various biologically important phenanthridin-6(5H)-ones has been developed. A wide range of functional groups are well tolerated in this transformation.

Hydroperfluoroalkylation of electron-deficient olefins with perfluoroalkyl iodides promoted by zinc/viologen

The hydroperfluoroalkylation of electron-deficient olefins with perfluoroalkyl iodides promoted by a zinc/viologen system is described. Interestingly, no iodoperfluoroalkylation product was observed without the presence of a radical H-donor.