New electrophilic difluoromethylating reagent

Copper-Catalyzed Synthesis of Difluoromethylated/C-4- and C-5-Functionalized Polycyclic Coumarin Derivatives

A facile and novel synthetic method for the synthesis of functionalized polycyclic coumarins at the C-4 and C-5 positions is proposed for the first time, which employs copper-catalyzed addition reactions of undiscovered alkenes with difluoromethyl radicals to construct polycyclic coumarins. This strategy is characterized by high regioselectivity, easy availability of raw materials, and simple operation. Additionally, such undiscovered coumarin alkenes can be reacted with a variety of difluoromethyl precursors to obtain a wide range of valuable C-4 and C-5 position functionalized/difluoromethylated polycyclic coumarins. More importantly, some of the products showed significant inhibition of proliferation in vitro against melanoma B16-F10 and lung cancer A549 cell lines with optimal IC50 values of 8.57 and 16.04 μM, respectively.

Synthesis of N-Difluoromethyl Carbonyl Compounds from N-Difluoromethylcarbamoyl Fluorides

Fluorinated small molecules are commonly used in functional small-molecule chemistry, and N-difluoromethyl (N-CF2H) compounds are particularly intriguing due to their unique and unexplored physiochemical properties. However, despite limited progress, a general methodological approach to the synthesis of N-CF2H compounds remains elusive. Here, guided by computation, we present a simple and practical protocol to access N-CF2H amides and related carbonyl derivatives. The protocol involves a one-pot conversion of thioformamides through desulfurization-fluorination and acylation, providing N-difluoromethylcarbamoyl fluoride building blocks that can be further diversified to a variety of unexplored N-CF2H carbonyl compounds with rich functionality. Additionally, preliminary studies on their properties and stability showcased their potential application in pharmaceuticals and agrochemicals.

Phototriggered Fluoroalkylation/Cyclization of Unactivated 1-Acryloyl-2-cyanoindoles: Synthesis of RCOCF2-Substituted Pyrrolo[1,2-a]indolediones

A photochemical approach toward RCOCF2-substituted pyrrolo[1,2-a]indolediones was developed by the radical cascade difluoroalkylation/cyclization reaction of unactivated 1-acryloyl-2-cyanoindoles with ethyl iododifluoroacetate or iododifluoramides under visible-light irradiation. This transition-metal- and photosensitizer-free protocol afforded diverse difluoroalkylated pyrrolo[1,2-a]indolediones in moderate to good yields under mild reaction conditions. Most appealingly, the reaction can proceed smoothly under sunlight irradiation, which opens a new avenue toward difluoroalkylated pyrrolo[1,2-a]indolediones.

Synthesis of Partially Fluorinated Alkyl Triflates by Electrochemical Fluorination (Simons Process)

A scalable straightforward synthesis of monofluoro- and difluoromethyl triflate CF3 SO2 OCH2 F (MH2F ) and CF3 SO2 OCHF2 (MHF2 ) through electrochemical fluorination (ECF, Simons process) of methyl triflate MH3 in anhydrous hydrogen fluoride at nickel anodes is presented. The ECF method is also feasible for the preparation of the deuterated analogues CF3 SO2 OCD2 F (MD2F ) and CF3 SO2 OCDF2 (MD2F ). Surprisingly, no H/D exchange occurs during ECF of CF3 SO2 OCD3 (MD3 ); this provides further evidence for a NiF3 /NiF4 -mediated ECF mechanism. The ECF of selected partially fluorinated ethyl triflates is described, and electrochemical fluorination of CF3 SO2 OCH2 CF3 (EH2F3 ) leads to the until now unknown chiral CF3 SO2 OCHFCF3 (EHFF3 ). The analogous fluoromethyl and fluoroethyl nonaflates are also accessible by ECF. This study contains detailed spectroscopic, structural, and thermal data on (fluoro)methyl and fluoro(ethyl) triflates.

[(SIPr)Ag(CF2 H)]: A Shelf-Stable, Versatile Difluoromethylation Reagent

Due to its unique physical and electrophilic properties, the difluoromethyl group (-CF2 H) has been playing an irreplaceable role in the field of pharmaceutical and agrochemical industry. Methods that could efficiently incorporate the difluoromethyl group into the target molecules are increasing in the recent years. Developing a stable and efficient difluoromethylating reagent is thus highly attractive. In this review, we describe the development of a nucleophilic difluoromethylation reagent [(SIPr)Ag(CF2 H)], including its elemental reaction, difluoromethylation reaction with different types of electrophiles, and its application in the synthesis of a nucleophilic and an electrophilic difluoromethylthiolating reagent.

Visible-Light-Promoted bis(Difluoromethylation)/Cyclization of 2-Vinyloxy Arylalkynes to Prepare Benzofuran Derivatives

A visible-light-promoted difluoromethylation/cyclization of 2-vinyloxy arylalkynes was developed, providing a variety of bis(difluoromethyl)-substituted benzofurans in moderate to good yields. A plausible mechanism involving difluoromethyl radical cascade cyclization and solvent-promoted ionic addition was proposed. This protocol has the advantages of having mild reaction conditions, simple operation, and good functional group tolerance.

AlCl3-Mediated CHF2 Transfer and Cyclocondensation of Difluoromethoxy Functionalized o-Phenylenediamines to Access N-Substituted Benzimidazoles

Herein, we report for the first time a transition-metal-free frustrated Lewis pair (FLP) catalyzed CHF₂ group migration from an oxygen atom to the neighboring nitrogen atom, which led to the synthesis of N-substituted benzimidazoles at room temperature with excellent yields, broad functional group tolerance, and a short reaction time. The oxygen-attached difluoromethane acted as a C1 source in the synthesis of N-substituted benzimidazoles in the presence of AlCl₃ by cleaving one C-O bond and two C-F bonds, resulting in formation of two new C-N bonds.

C-H Electrophilic (phenylsulfonyl)difluoromethylation of (hetero)arenes with a newly designed reagent

The synthesis of an original electrophilic difluoromethylating reagent was successfully achieved upon a straightforward protocol (3 steps). Like a Swiss army knife, this bench-stable reagent allowed the functionalization of various classes of compounds under mild and transition metal-free conditions. Hence, an efficient and operationally simple tool for the construction of C(sp2)-, C(sp3)- and S-CF2SO2Ph bonds was provided, expanding the chemical space of PhSO2CF2-containing molecules. Late-stage functionalization of bioactive molecules and the synthesis of PhSO2CF2- and HCF2-analogs of Lidocaine were also successfully achieved.

Direct Synthesis of N-Difluoromethyl-2-pyridones from Pyridines

A novel method for the synthesis of N-difluoromethyl-2-pyridones was described. This protocol enables the synthesis of N-difluoromethyl-2-pyridones from readily available pyridines using mild reaction conditions that are compatible with a wide range of functional groups. The preliminary mechanistic study revealed that N-difluoromethylpyridinium salts were the key intermediates to complete this conversion.

Synthesis of Difluoromethanesulfinate Esters by the Difluoromethanesulfinylation of Alcohols

Herein, we report the first synthesis of difluoromethanesulfinate esters via the direct difluoromethanesulfinylation of alcohols with HCF₂SO₂Na/Ph₂P(O)Cl. Primary, secondary, and tertiary alcohols were converted to the corresponding difluoromethanesulfinate esters in good to excellent yields under mild conditions. The late-stage functionalization of complexed biologically active natural products was also demonstrated. The method was extended to the trifluoromethanesulfinylation of alcohols using CF₃SO₂Na in the presence of a catalytic amount of Me₃SiCl to provide trifluoromethanesulfinate esters.

Metal-Free Difunctionalization of Pyridines: Selective Construction of N-CF2H and N-CHO Dihydropyridines

The reactivity of N-difluoromethylpyridinium salts is seldom explored because of their instability and low availability. Here we present a novel nucleophilic addition of N-difluoromethylpyridinium salts with nitroalkanes to synthesize N-CF₂H-dihydropyridines and N-CHO-dihydropyridines in a highly efficient and regioselective pathway. This protocol exhibits good functional group tolerance and good to excellent yields.

Stereoselective synthetic strategies of stereogenic carbon centers featuring a difluoromethyl group

The scope of this review is to summarize routine asymmetric synthetic methods which enable the effective and selective introduction of difluoromethyl groups into the desired compounds, providing a general introduction to this important research area.

Recent progress in photochemical radical di- and mono-fluoromethylation

Recently, photoinduced radical difluoromethylation has emerged as a step-economical synthetic method of CHF2-containing compounds. In this article, difluoromethylation of alkenes, isonitriles and aryl bromides promoted by photoredox catalysis is described together with a non-catalytic photoinduced system. Representative reactions will be discussed for each highlighted difluoromethylating reagent. In addition, related monofluoromethylation with their corresponding monofluoromethylating reagents is also discussed.

Pummerer Synthesis of Chromanes Reveals a Competition between Cyclization and Reductive Chlorination

The competition between an unprecedented reductive chlorination and the Pummerer reaction was studied and applied to the synthesis of benzofused oxygen heterocycles including 3-aminochromanes and in the intramolecular chlorination of activated aromatic rings. The use of (COCl)₂ as a Pummerer activator showed substantial activity, producing α-chlorinated sulfides that can undergo Pummerer-Friedel-Crafts cyclization. If the aromatic ring has electron-donating groups in position three, then the reaction follows a different pathway, yielding the reductive chlorination products, where the chlorine atom comes from a sulfonium salt.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

General, Practical and Selective Oxidation Protocol for CF₃S into CF₃S(O) Group

A simple and efficient protocol for the oxidation of trifluoromethyl, mono- and difluoromethyl sulfides to the corresponding sulfoxides without over-oxidation to sulfones, using TFPAA prepared in situ from trifluoroacetic acid and 15% H₂O₂ aqueous solution was developed. The methodology is suitable for a wide range of aromatic and aliphatic substrates in milligram and multigram scales.

Access towards enantiopure α,α-difluoromethyl alcohols by means of sulfoxides as traceless chiral auxiliaries

A new methodology to access enantiopure α,α-difluoromethyl alcohols is hereby being described. The strategy relies on the use of an enantiopure aryl α,α-difluoromethyl sulfoxide employed as chiral and removable auxiliary for the stereoselective difluoromethylation of carbonyl derivatives. The obtained α,α-difluoro-β-hydroxysulfoxides displayed unprecedented diastereomeric ratios.

An electrophilic reagent for the synthesis of OCHFMe-containing molecules

Herein the synthesis of a novel and bench stable electrophilic reagent to construct the OCFHMe motif from O-nucleophiles has been described. This sulfonium salt, readily obtained in 5 steps, reacted with various phenols and alcohols. The resulting products, including complex molecules, were obtained in good yields. This reagent was also used for the functionalization of thiol derivatives.

Palladium-catalyzed Mizoroki-Heck-type reactions of [Ph2SRfn][OTf] with alkenes at room temperature

The first Pd-catalyzed Mizoroki-Heck-type reaction of [Ph₂SR_fn][OTf] with alkenes is described. The reaction of [Ph₂SR_fn][OTf] (R_fn = CF₃, CH₂CF₃) with alkenes in the presence of 10 mol% Pd[P(t-Bu)₃]₂ and TsOH at room temperature provided the corresponding phenylation products in good to high yields. The bases that benefit the traditional Mizoroki-Heck reactions severely inhibited the transformation with [Ph₂SR_fn][OTf], whereas acids significantly improved the reaction. This protocol supplies a new class of cross-coupling partners for Mizoroki-Heck-type reactions and gains important insights into the reactivity of phenylsulfonium salts either with or without fluorine-containing alkyl groups as the promising phenylation reagents in organic synthesis.

Highly C-selective difluoromethylation of β-ketoesters by using TMSCF2Br/lithium hydroxide/N,N,N-trimethylhexadecan-1-ammonium bromide

The first highly C-selective difluoromethylation of β-ketoesters was achieved by combining TMSCF₂Br/LiOH/(CH₃(CH₂)₁₅(CH₃)₃NBr).

Metal-free di- and tri-fluoromethylation of alkenes realized by visible-light-induced perylene photoredox catalysis

Regioselective amino-difluoromethylation of aromatic alkenes via C(sp³)-CF₂H and C(sp³)-N bond formation with the C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C moiety has been achieved in a single operation by visible-light photoredox catalysis. The combination of a shelf-stable and easy-to-handle sulfonium salt, S-difluoromethyl-S-di(p-xylyl)sulfonium tetrafluoroborate, and perylene catalysis is the key to the successful transformation. Furthermore, this noble metal-free protocol allows for the photocatalytic trifluoromethylation of alkenes.

Catalytic asymmetric radical aminoperfluoroalkylation and aminodifluoromethylation of alkenes to versatile enantioenriched-fluoroalkyl amines

Although great success has been achieved in asymmetric fluoroalkylation reactions via nucleophilic or electrophilic processes, the development of asymmetric radical versions of this type of reactions remains a formidable challenge because of the involvement of highly reactive radical species. Here we report a catalytic asymmetric radical aminoperfluoroalkylation and aminodifluoromethylation of alkenes with commercially available fluoroalkylsulfonyl chlorides as the radical sources, providing a versatile platform to access four types of enantioenriched α-tertiary pyrrolidines bearing β-perfluorobutanyl, trifluoromethyl, difluoroacetyl and even difluoromethyl groups in excellent yields and with excellent enantioselectivity. The key to success is not only the introduction of the CuBr/chiral phosphoric acid dual-catalytic system but also the use of silver carbonate to suppress strong background and side hydroamination reactions caused by a stoichiometric amount of the in situ generated HCl. Broad substrate scope, excellent functional group tolerance and versatile functionalization of the products make this approach very practical and attractive.

Methods for the asymmetric introduction of organofluorine groups are often limited by the lack of variability in the starting materials. Here the authors report an asymmetric radical process for the introduction of fluoroalkyl groups using readily available fluoroalkylated sulfonyl chlorides.

Transition-metal free direct difluoromethylthiolation of electron-rich aromatics with difluoromethanesulfonyl chloride

A new method for phosphine-mediated difluoromethylthiolation of indoles and other electron-rich aromatics using difluoromethanesulfonyl chloride was developed.

Direct Difluoromethylation of Alcohols with an Electrophilic Difluoromethylated Sulfonium Ylide

A general method for the formation of alkyl difluoromethylethers under mild reaction conditions and with good functional-group tolerance was developed. The development of the method was based on the invention of a stable, electrophilic, difluoromethylating reagent, difluoromethyl-(4-nitrophenyl)-bis(carbomethoxy) methylide sulfonium ylide, which was synthesized by reaction of the easily available 4-nitrophenyl (difluoromethyl)thioether and dimethyl diazomalonate in the presence of a rhodium catalyst.