Transition-metal-catalyzed C-H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

Borate-mediated aryl polyfluoroalkoxylation under transition-metal-free conditions

We describe the transition-metal-free coupling for polyfluoroalkoxy arenes using polyfluoroalkoxy borates, which serve as counterions to diaryliodonium salts and transferring mediators of polyfluoroalkoxy groups. This strategy demonstrates high functional group compatibility owing to the low nucleophilicity of the borate mediator, thus offering a practical approach for synthesizing diverse polyfluoroalkoxy arenes.

Rh(III)-Catalyzed Sequential ortho-C-H Bond Annulation and Desulfonylation of 3-Aryl-2H-benzo[e][1,2,4]thiadiazine-1,1-dioxides: Access to 1-Aminoisoquinolines

An efficient Rh(III)-catalyzed C-H functionalization of 3-aryl-2H-benzo[e][1,2,4]thiadiazine-1,1-dioxides with diaryl and dialkyl alkynes has been developed for the first time to the synthesis of 1-aminoisoquinoline derivatives in a single step. This method involves through the formation of one C-C bond and one C-N bond followed by desulfonylation to generate a novel series of isoquinolines in good to excellent yields. This is a direct method to produce pharmaceutically more relevant scaffolds with a high functional diversity.

Site-Selective Ortho/Ipso C-H Difunctionalizations of Arenes using Thianthrene as a Leaving Group

Site-selective ortho/ipso C-H difunctionalizations of aromatic compounds were designed to afford polyfunctionalized arenes including challenging 1,2,3,4-tetrasubstituted ones (62 examples, up to 97 % yields). To ensure the excellent regioselectivity of the process while keeping high efficiency, an original strategy based on a "C-H thianthenation/Catellani-type reaction" sequence was developed starting from simple arenes. Non-prefunctionalized arenes were first regioselectively converted into the corresponding thianthrenium salts. Then, a palladium-catalyzed, norbornene (NBE)-mediated process allowed the synthesis of ipso-olefinated/ortho-alkylated polyfunctionalized arenes using a thianthrene as a leaving group (revisited Catellani reaction). Pleasingly, using a commercially available norbornene (NBE) and a unique catalytic system, synthetic challenges known for the Catellani reaction with aryl iodides were smoothly and successfully tackled with the "thianthrenium" approach. The protocol was robust (gram-scale reaction) and was widely applied to the two-fold functionalization of various arenes including bio-active compounds. Moreover, a panel of olefins and alkyl halides as coupling partners was suitable. Pleasingly, the "thianthrenium" strategy was successfully further applied to the incorporation of other groups at the ipso (CN/alkyl/H, aryl) and ortho (alkyl, aryl, amine, thiol) positions, showcasing the generality of the process.

Copper-Catalyzed C-H (Phenylsulfonyl)difluoromethylation of Acrylamides: Scope, Mechanism, and Critical Role of Additives

Herein, we report the Cu-complex catalyzed, native functional group-assisted, and TFA/NMF additives promoted (phenylsulfonyl)difluoromethylation of vinylic C(sp2 )-H bond of acrylamides. Using our in-home designed reagent, this reaction enables the construction of the C(sp2 )-CF2 SO2 Ph bond from simple C-H bond activation by copper catalysis under mild reaction conditions with total Z-selectivity. The versatility of utilized fluorinated group was illustrated by its conversion into value-added CF2 moieties as well as the remarkable =CHF residue. The performed experimental and computational mechanistic studies enabled to identify the true nature of active catalyst and substrate, as well as establish critical roles of TFA and NMF additives. In this reaction, the TFA acts as a promoter of the much-needed CuII /CuII →CuIII /CuI disproportionation, while the NMF facilitates the following ligand exchange and C-C coupling processes. We ruled out the generation of radical intermediates and established the C-H activation to be irreversible and the rate-determining step of the entire process.