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A new method of constructing "ArSCF2CF2Cu" from ArSCu and TMSCF2Br (TMS=trimethylsilyl) has been developed. The cross‐coupling reactions of the obtained "ArSCF2CF2Cu" with diverse aryl iodides (Ar′I) provide an efficient access to Ar′CF2CF2SAr. Mechanistic studies demonstrate that the "ArSCF2CF2Cu" species were generated through controllable double difluoromethylene insertions into ArS−Cu bonds rather than the 1,2‐addition of ArSCu to tetrafluoroethylene. [ABSTRACT FROM AUTHOR]

We have developed a new strategy for controllable single and double difluoromethylene (CF2) formal insertions into C−H bonds of aldehydes with nearly full selectivity under transition‐metal‐free conditions. The key to the success of controllable CF2 insertions lies in the well‐defined formation of 2,2‐difluoroenolsilyl ether and 2,2,3,3‐tetrafluorocyclopropanolsilyl ether intermediates using difluorocarbene reagent TMSCF2Br (TMS=trimethylsilyl). These two intermediates can react with various electrophiles including proton sources and various halogenation reagents, allowing for the access to diverse arrays of ketones containing difluoromethylene (CF2) and tetrafluoroethylene (CF2CF2) units. The first synthesis of relatively stable 2,2,3,3‐tetrafluorocyclopropanolsilyl ethers has been achieved, which offers a new platform to explore other unknown chemical space. [ABSTRACT FROM AUTHOR]

The transition‐metal‐catalyzed carbonylation reaction is a useful approach for ketone synthesis. However, it is often problematic to use exogenous carbonyl reagents, such as gaseous carbon monoxide. In this manuscript, we report a novel palladium‐catalyzed coupling reaction of gem‐difluoroalkenes and aryl boronic acids that yields bioactive indane‐type ketones with an all‐carbon α‐quaternary center. Characterization and stoichiometric reactions of the key intermediates RCF2PdII support a water‐induced defluorination and cross‐coupling cascade mechanism. The vinyl difluoromethylene motif serves as an in situ carbonyl precursor which is unprecedented in transition‐metal‐catalyzed coupling reactions. It is expected to raise broad research interest from the perspectives of ketone synthesis, fluoroalkene functionalization, and rational design of new synthetic protocols based on the unique reactivity of difluoroalkyl palladium(II) species. [ABSTRACT FROM AUTHOR]

A protocol for the modular assembly of the α‐fluoroamide motif has been developed, which provides a practical method for the efficient synthesis of structurally diverse α‐fluoroamides from easily available aldehydes and tertiary amines through a three‐component fluorination–aminocarbonylation process. The key to the success of this process is taking advantage of the multiple roles of the unique difluorocarbene reagent TMSCF2Br (TMS=trimethylsilyl). The mechanism of the process involves the 1,2‐fluorine and oxygen migrations of the in situ formed TMS‐protected α‐aminodifluoromethyl carbinol intermediates, which represents a new type of deoxyfluorination reaction. [ABSTRACT FROM AUTHOR]

A Cu‐catalyzed gem‐bis(trifluoromethyl)olefination of α‐diazo esters, using TMSCF3 as the only fluorocarbon source, has been developed and provides an exquisite method to access gem‐bis(trifluoromethyl)alkenes. This unprecedented olefination process involves a carbene migratory insertion into "CuCF3" to generate the α‐CF3‐substituted organocopper species, which then undergoes β‐fluoride elimination and two consecutive addition‐elimination processes to give the desired products. The key to this efficient one‐pot C1‐to‐C3 synthetic protocol lies in the controllable double (over single and triple) trifluoromethylations of the gem‐difluoroalkene intermediates. [ABSTRACT FROM AUTHOR]

An efficient method for the selective C‐difluoromethylation of carbon acids with the reagent TMSCF2Br has been developed. A variety of structurally diverse sp3‐ and sp‐hybridized carbon nucleophiles, including esters, amides, fluorenes, terminal alkynes, β‐ketoesters, malonates, and other activated C−H nucleophiles, could be efficiently and selectively transformed into the corresponding C‐difluoromethylated products under mild conditions. This protocol is also effective for the late‐stage difluoromethylation of pharmaceutically relevant molecules and can be readily scaled up. Moreover, ambident substrates with more than one reactive site towards difluorocarbene can be difluoromethylated orthogonally using TMSCF2Br. [ABSTRACT FROM AUTHOR]

Abstract: A highly efficient copper‐mediated aromatic pentafluoroethylation method using TMSCF3 as the sole fluoroalkyl source is described. The reaction proceeds by a key C1 to C2 process, that is, the generation of CuCF3 from TMSCF3, followed by a subsequent spontaneous transformation into CuC2F5. Various aryl iodides were pentafluoroethylated with the TMSCF3‐derived CuC2F5. This method represents the first practical and efficient method for pentafluoroethylation of aryl iodides using commercially available TMSCF3 as a pentafluoroethyl precursor. [ABSTRACT FROM AUTHOR]

A new method for the on-site preparation of tetrafluoroethylene (TFE) and a procedure for its efficient use in pentafluoroethylation by fluoride addition were developed by using a simple two-chamber system. The on-site preparation of TFE was accomplished by dimerization of difluorocarbene derived from (trifluoromethyl)trimethylsilane (TMSCF3) under mild conditions. Other fluoroalkylation reactions, such as (aryloxy)tetrafluoroethylation and tetrafluoroethylation processes, were also achieved using a similar approach. This work not only demonstrates a convenient and safe approach for the generation and use of TFE in academic laboratories, but also provides a new strategy for pentafluoroethylation. [ABSTRACT FROM AUTHOR]

A general method for the efficient difluoromethylation of alcohols using commercially available TMSCF2Br (TMS=trimethylsilyl) as a unique and practical difluorocarbene source is developed. This method allows primary, secondary, and even tertiary alkyl difluoromethyl ethers to be synthesized under weakly basic or acidic conditions. The reaction mainly proceeds through the direct interaction between a neutral alcohol and difluorocarbene, which is different from the difluoromethylation of phenols. Moreover, alcohols containing other moieties that are also reactive toward difluorocarbene can be transformed divergently by using TMSCF2Br. This research not only solves the synthetic problem of difluorocarbene-mediated difluoromethylation of alcohols, it also provides new insights into the different reaction mechanisms of alcohol difluoromethylation and phenol difluoromethylation with difluorocarbene species. [ABSTRACT FROM AUTHOR]

Terminal monofluoroalkenes are important structural motifs in the design of bioactive compounds, such as homeostasis regulators and mechanism-based enzyme inhibitors. However, it is difficult to control the stereoselectivity of known carbonyl olefination reactions, and olefin metathesis is limited to disubstituted terminal monofluoroalkenes. Although sulfoximines have been used extensively in organic synthesis, reports on their use in carbonyl olefination reactions have not appeared to date. Herein, we report highly stereoselective carbonyl monofluoroolefination with a fluorosulfoximine reagent. The potential of this method is demonstrated by the synthesis of MDL 72161 and by the late-stage monofluoromethylenation of complex molecules, such as haloperidol and steroid derivatives. [ABSTRACT FROM AUTHOR]

A pentacoordinate bis(difluoromethyl)silicate anion, [Me3Si(CF2H)2]−, is observed for the first time by the activation of Me3SiCF2H with a nucleophilic alkali-metal salt and 18-crown-6. Further study on its reactivity by tuning the countercation effect led to the discovery and development of an efficient, catalytic nucleophilic difluoromethylation of enolizable ketones with Me3SiCF2H by using a combination of CsF and 18-crown-6 as the initiation system. Mechanistic investigations demonstrate that [(18-crown-6)Cs]+[Me3Si(CF2H)2]− is a key intermediate in this catalytic reaction. [ABSTRACT FROM AUTHOR]

A AgF-mediated fluorination with a concomitant cross-coupling between a gem-difluoroolefin and a non-fluorinated olefin is reported. This highly efficient method provides facile access to both α-CF3 alkenes and β-CF3 ketones, which otherwise remain challenging to be directly prepared. The application of this method is further demonstrated by the synthesis of bioactive isoxazoline derivatives. This approach represents a conceptually novel route to trifluoromethylated compounds that combines the in situ generation of the CF3 moiety and a CH functionalization in a single reaction system. [ABSTRACT FROM AUTHOR]

Although many methods are available for the synthesis of optically enriched monofluoromethyl secondary alcohols, synthesizing optically enriched monofluoromethyl tertiary alcohols remains a challenge. An efficient and easy-to-handle nucleophilic fluoromethylation protocol was developed. The current monofluoromethylation showed much higher facial selectivity than the corresponding difluoromethylation and proceeded via a different type of transition state. Excellent stereoselective control at the fluorinated carbon chiral center was found, an effect believed to be facilitated by the dynamic kinetic resolution of the chiral α-fluoro carbanions. [ABSTRACT FROM AUTHOR]