A new reagent for direct difluoromethylation

Copper-Catalyzed Radical Selenodifluoromethylation of Alkenes: Access to CF2-Containing γ-Lactams

Herein, a practical Cu-catalyzed selenodifluoromethylation protocol was developed, using readily available diselenides as the selenium source under external-oxidant-free conditions. Various structurally diverse 4-seleno-substituted α,α-difluoro-γ-lactams were obtained in moderate to excellent yields. Easy scaleup and the potential for product derivatization make this method attractive for the preparation of other valuable fIuorinated γ-lactams. Mechanistic studies suggest that the catalytic system may involve a radical pathway.

Electrochemical fluoromethylation triggered lactonizations of alkenes under semi-aqueous conditions

An electrochemical difluoromethylation triggered lactonization of alkenes was developed for the first time. This protocol employs readily prepared CF2HSO2Na as the difluoromethylating reagent, affording unprecedented CF2H-containing lactones in moderate yields. Moreover, with CF3SO2Na as the trifluoromethylating reagent, a wide array of CF3-containing lactones were obtained under additional supporting electrolyte- and catalyst-free conditions.

Synthesis of 18F-difluoromethylarenes using aryl boronic acids, ethyl bromofluoroacetate and [18F]fluoride

Herein, we report the radiosynthesis of 18F-difluoromethylarenes via the assembly of three components, a boron reagent, ethyl bromofluoroacetate, and cyclotron-produced non-carrier added [18F]fluoride. The two key steps are a copper-catalysed cross-coupling reaction, and a Mn-mediated 18F-fluorodecarboxylation.

Pd-Catalyzed Selective Carbonylation of gem-Difluoroalkenes: A Practical Synthesis of Difluoromethylated Esters

The first catalyst for the alkoxycarbonylation of gem-difluoroalkenes is described. This novel catalytic transformation proceeds in the presence of Pd(acac)₂ /1,2-bis((di-tert-butylphosphan-yl)methyl)benzene (btbpx) (L4) and allows for an efficient and straightforward access to a range of difluoromethylated esters in high yields and regioselectivities. The synthetic utility of the protocol is showcased in the practical synthesis of a Cyclandelate analogue using this methodology as the key step.

Cinchona Alkaloids-Derivatives and Applications

Major Cinchona alkaloids quinine, quinidine, cinchonine, and cinchonidine are available chiral natural compounds (chiral pool). Unlike many other natural products, these alkaloids are available in multiple diastereomeric forms which are separated on an industrial scale. The introduction discusses in short conformational equilibria, traditional separation scheme, biosynthesis, and de novo chemical syntheses. The second section concerns useful chemical applications of the alkaloids as chiral recognition agents and effective chiral catalysts. Besides the Sharpless ethers and quaternary ammonium salts (chiral PTC), the most successful bifunctional organocatalysts are based on 9-amino derivatives: thioureas and squaramides. The third section reports the main transformations of Cinchona alkaloids. This covers reactions of the 9-hydroxyl group with the retention or inversion of configuration. Specific Cinchona rearrangements enlarging [2.2.2]bicycle of quinuclidine to [3.2.2] products are connected to the 9-OH substitution. The syntheses of numerous esterification and etherification products are described, including many examples of bi-Cinchona alkaloid ethers. Further derivatives comprise 9-N-substituted compounds. The amino group is introduced via an azido function with the inversion of configuration at the stereogenic center C9. The 9-epi-amino-alkaloids provide imines, amides, imides, thioureas, and squaramides. The syntheses of 9-carbon-, 9-sulfur-, and 9-selenium-substituted derivatives are discussed. Oxidation of the hydroxyl group of any alkaloid gives ketones, which can be selectively reduced, reacted with Grignard reagents, or subjected to the Corey-Chaykovsky reaction. The alkaloids were also partially degraded by splitting C4'-C9 or N1-C8 bonds. In order to immobilize Cinchona alkaloids the transformations of the 3-vinyl group were often exploited. Finally, miscellaneous functionalizations of quinuclidine, quinoline, and examples of various metal complexes of the alkaloids are considered.

Palladium-Catalyzed Difluoromethylation of Aryl Chlorides and Bromides with TMSCF2H

A palladium-catalyzed cross-coupling of aryl chlorides/bromides with TMSCF₂H is described. Two different catalysts, Pd(dba)₂/BrettPhos and Pd(P ^tBu₃)₂, are demonstrated and provide a variety of difluoromethylated arenes in good yields.

Exploration of new reaction tools for late-stage functionalization of complex chemicals

Chemistry has always had as a target the conversion of molecules into valuable materials. Nevertheless, the aim of past synthesis has primarily focused on achieving a given transformation, regardless of the environmental impact of the synthetic route. Given the current global situation, the demand for sustainable alternatives has substantially increased. Our group focuses on developing selective chemical transformations that benefit from mild conditions, improved atom economy, and that can make use of renewable feedstocks as starting materials. This account summarizes our work over the past two decades specifically regarding the selective removal, conversion, and addition of functional groups that can, later on, be applied at a late stage for the modification of complex molecules.

Pd(ii)-Catalyzed decarboxylative meta-C–H difluoromethylation

Palladium(ii)-catalyzed decarboxylative meta-C–H difluoromethylation reactions have been developed. Initial mechanistic studies disclosed that a migratory insertion would be involved in this meta-selective C–H functionalization.

Visible-light-induced radical hydrodifluoromethylation of alkenes

Visible-light-induced radical hydrodifluoromethylation of alkenes with the phosphonium salt [Ph₃P⁺CF₂H Br⁻] under transition-metal-free conditions is described.

Organic electrosynthesis: electrochemical alkyne functionalization

We outline examples of electrochemical alkyne functionalization reactions in connection with green and sustainable chemistry that proceed with excellent atom economy.

Discovery of Orally Active Inhibitors of Brahma Homolog (BRM)/SMARCA2 ATPase Activity for the Treatment of Brahma Related Gene 1 (BRG1)/SMARCA4-Mutant Cancers

SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin subfamily A member 2 (SMARCA2), also known as Brahma homologue (BRM), is a Snf2-family DNA-dependent ATPase. BRM and its close homologue Brahma-related gene 1 (BRG1), also known as SMARCA4, are mutually exclusive ATPases of the large ATP-dependent SWI/SNF chromatin-remodeling complexes involved in transcriptional regulation of gene expression. No small molecules have been reported that modulate SWI/SNF chromatin-remodeling activity via inhibition of its ATPase activity, an important goal given the well-established dependence of BRG1-deficient cancers on BRM. Here, we describe allosteric dual BRM and BRG1 inhibitors that downregulate BRM-dependent gene expression and show antiproliferative activity in a BRG1-mutant-lung-tumor xenograft model upon oral administration. These compounds represent useful tools for understanding the functions of BRM in BRG1-loss-of-function settings and should enable probing the role of SWI/SNF functions more broadly in different cancer contexts and those of other diseases.

Potassium Iodide-Promoted One-Pot Synthesis of Fluoroalkylated Quinoxalines via a Tandem Michael Addition/Azidation/Cycloamination Approach

Fluoroalkylated quinoxlines with various groups were efficiently synthesized via a one-pot tandem Michael addition/azidation/cycloamination process. Under the mild and metal-free conditions, a bis-imine intermediate (4a) was detected and isolated for the first time. KI played a crucial role in this reaction. The mechanism was described.

Copper-Mediated Trifluoromethylation of Benzylic Csp3 -H Bonds

Trifluoromethyl-containing compounds play a significant role in medicinal chemistry, materials and fine chemistry. Although direct C-H trifluoromethylation has been achieved on Csp² -H bonds, direct conversion of Csp³ -H bonds to Csp³ -CF₃ remains challenging. We report herein an efficient protocol for the selective trifluoromethylation of benzylic C-H bonds. This process is mediated by a combination Cu^III -CF₃ species and persulfate salts. A wide range of methylarenes can be selectively trifluoromethylated at the benzylic positions. A combination of experimental and theoretical mechanistic studies suggests that the reaction involves a radical intermediate and a Cu^III -CF₃ species as the CF₃ transfer reagent.

Radical difluoromethylthiolation of aromatics enabled by visible light

Direct introduction of a difluoromethylthio group (-SCF2H) to arenes represents an efficient route to access a valuable catalogue of organofluorines; however, to realize this transformation under metal-free and mild conditions still remains challenging and rarely reported. Herein, a metal-catalyst-free and redox-neutral innate difluoromethylthiolation method with a shelf-stable and readily available reagent, PhSO2SCF2H, under visible light irradiation is described. This light-mediated protocol successfully converts a broad spectrum of arenes and heteroarenes to difluoromethylthioethers in the absence of noble metals and stoichiometric amounts of additives.

Direct heterobenzylic fluorination, difluorination and trifluoromethylthiolation with dibenzenesulfonamide derivatives

Functionalization of heterocyclic scaffolds with mono- or difluoroalkyl groups provides unique opportunities to modulate drug pKa, influence potency and membrane permeability, and attenuate metabolism. While advances in the addition of fluoroalkyl radicals to heterocycles have been made, direct C(sp3)-H heterobenzylic fluorination is comparatively unexplored. Here we demonstrate both mono- and difluorination of a range of alkyl heterocycles using a convenient process that relies on transient sulfonylation by the electrophilic fluorinating agent N-fluorobenzenesulfonimide. We also report heterobenzylic trifluoromethylthiolation and 18F-fluorination, providing a suite of reactions for late-stage C(sp3)-H functionalization of drug leads and radiotracer discovery.

Radical Chlorodifluoromethylation: Providing a Motif for (Hetero)arene Diversification

A method for the radical chlorodifluoromethylation of (hetero)arenes using chlorodifluoroacetic anhydride is reported. This operationally simple protocol proceeds under mild photochemical conditions with high functional group compatibility and complements the large body of literature for the trifluoromethylation of (hetero)arenes. Introduction of the chlorodifluoromethyl motif enables rapid diversification to a wide array of aromatic scaffolds. This work showcases the chlorodifluoromethyl group as an attractive entryway to otherwise synthetically challenging electron-rich difluoromethyl(hetero)arenes. Furthermore, facile conversion of the CF2Cl moiety into the corresponding aryl esters, gem-difluoroenones, and β-keto-esters is demonstrated.