Catalytic Access to Functionalized Allylic gem ‐Difluorides via Fluorinative Meyer–Schuster‐Like Rearrangement

Electrochemical Reductive Cross-Coupling of Vinyl Bromides for the Synthesis of 1,3-Dienes

An electroreductive cross-electrophile coupling protocol was developed for the construction of valuable 1,3-dienes from vinyl bromides. Furthermore, this scalable method can also be used to forge complex [4 + 2] cycloadducts in a one-pot manner. One of the most important advantages of this green and sustainable protocol is the in situ release of nickel catalyst from the inexpensive electrodes without the addition of extra harmful metal catalysts and reductant.

A metal-free strategy to construct fluoroalkyl-olefin linkages using fluoroalkanes

We present a metal-free strategy to access fluoroalkyl-olefin linkages from fluoroalkane precursors and vinyl-pinacol boronic ester (BPin) reagents. This reaction sequence is templated by the boron reagent, which induces C-C bond formation upon oxidation. We developed this strategy into a one-pot synthetic protocol using RCF2H precursors directly with vinyl-BPin reagents in the presence of a Brønsted base, which tolerated oxygen- and nitrogen-containing heterocycles, and aryl halogens. We also found that HCF3 (HCF-23; a byproduct of the Teflon industry) and CH2F2 (HCF-32; a low-cost refrigerant) are amenable to this protocol, representing distinct strategies to generate RCF2H and RCF3 molecules. Finally, we demonstrate that the vinyldifluoromethylene products can be readily derivatized, representing an avenue for late-stage modification after installing the fluoroalkyl unit.

Synthetic Advantages of Defluorinative C-F Bond Functionalization

Much progress has been made in the development of methods to both create compounds that contain C-F bonds and to functionalize C-F bonds. As such, C-F bonds are becoming common and versatile synthetic functional handles. This review summarizes the advantages of defluorinative functionalization reactions for small molecule synthesis. The coverage is organized by the type of carbon framework the fluorine is attached to for mono- and polyfluorinated motifs. The main challenges, opportunities and advances of defluorinative functionalization are discussed for each class of organofluorine. Most of the text focuses on case studies that illustrate how defluorofunctionalization can improve routes to synthetic targets or how the properties of C-F bonds enable unique mechanisms and reactions. The broader goal is to showcase the opportunities for incorporating and exploiting C-F bonds in the design of synthetic routes, improvement of specific reactions and advent of new methods.

Defluorinative 1,3-Dienylation of Fluoroalkyl N-Triftosylhydrazones with Homoallenols

A silver-catalyzed regioselective defluorinative 1,3-dienylation of trifluoromethyl phenyl N-triftosylhydrazones using homoallenols as 1,3-dienyl sources provides a variety of α-(di)fluoro-β-vinyl allyl ketones with excellent functional group tolerance in moderate to good yields. The reaction proceeds through a silver carbene-initiated sequential etherification and Claisen type [3,3]-sigmatropic rearrangement cascade. The synthetic utility of this protocol was demonstrated through the downstream synthetic elaboration toward diverse synthetically useful building blocks.

Dual Photoredox/Nickel-Catalyzed Dehydrative Difluoroalkylation of Benzyl Alcohols for the Synthesis of Allylic gem-Difluorides

A photoredox/Lewis acid cooperative catalytic system has been developed for the construction of Cvinyl-CRf bonds through the dehydrative difluoroalkylation of benzyl alcohols. A variety of allylic gem-difluorides could be obtained in moderate yields with good to excellent E/Z selectivity. In addition, several control experiments have been explored, and a possible mechanism was proposed for this process.

Synthesis of Chiral Tertiary Allylic- and Propargylic Fluorides from Nonaflates of Chiral α-Fluorinated β-Keto Dicarbonyl Compounds

The acetyl group of chiral α-fluorinated dicarbonyl compounds was transformed to nonaflates through a reaction with perfluorobutanesulfonyl fluoride in the presence of DBU in 82-95% yield. These nonaflates were used in Suzuki and Sonogashira coupling reactions to afford chiral tertiary allylic fluorides bearing gem-disubstituted terminal alkenes with excellent optical purities (45-91%, ≥94% ee). In addition, chiral tertiary propargylic fluorides were obtained from the reaction of nonaflates with DBU (73-86%, ≥94% ee).

Indane-Based Chiral Aryl Chalcogenide Catalysts: Development and Applications in Asymmetric Electrophilic Reactions

Asymmetric electrophilic reactions provide an ideal method for the construction of chiral molecules by incorporating one or more functional groups into the parent substrates under mild conditions. However, due to the issues of the reactivities of electrophilic species and the possible racemization of chiral intermediates as well as the restriction of the chiral scaffolds of chiral catalysts, many limitations remain in this field, such as the narrow scopes of substrates and electrophiles as well as the limited types of nucleophiles and reactions. To overcome the limitations in the synthesis of diversified chiral molecules, we developed a series of indane-based chiral amino aryl chalcogenide catalysts. These catalysts are easily prepared based on the privileged chiral indane scaffold. They can provide an appropriate H-bonding effect by varying the amino protecting groups as well as offer a proper Lewis basicity and steric hindrance by adjusting different substituents on the aryl chalcogenide motifs. These features allow for them to meet the requirements of reactivity and the chiral environment of the reactions. Notably, they have been successfully applied to various asymmetric electrophilic reactions of alkenes, alkynes, and arenes, expanding the field of electrophilic reactions.Using these catalysts, we realized the enantioselective CF₃S-lactonization of olefinic carboxylic acids, enantioselective CF₃S-aminocyclization of olefinic sulfonamides, desymmetrizing enantioselective CF₃S-carbocyclization of gem-diaryl-tethered alkenes, enantioselective CF₃S-oxycyclization of N-allylamides, enantioselective intermolecular trifluoromethylthiolating difunctionalization and allylic C-H trifluoromethylthiolation of trisubstituted alkenes, formally the intermolecular CF₃S-oxyfunctionalization of aliphatic internal alkenes, intermolecular azidothiolation, oxythiolation, thioarylation of N-allyl sulfonamides, desymmetrizing enantioselective chlorocarbocyclization of aryl-tethered diolefins, enantioselective Friedel-Crafts-type electrophilic chlorination of N-allyl anilides, and enantioselective chlorocarbocyclization and dearomatization of N-allyl 1-naphthanilides. Additionally, the enantioselective electrophilic carbothiolation of alkynes to construct enantiopure carbon chirality center-containing molecules and axially chiral amino sulfide vinyl arenes and the electrophilic aromatic halogenation to produce P-chirogenic compounds can be accomplished. In these reactions, a bifunctional binding mode is proposed in the catalytic cycles, in which an acid-derived anion-binding interaction might exist and account for the high enantioselectivities of the reactions.In this Account, we demonstrate our achievements in asymmetric electrophilic reactions and share our thoughts on catalyst design, our understanding of asymmetric electrophilic reactions, and our perspectives in the field of chiral chalcogenide-catalyzed asymmetric electrophilic reactions. We hope that the experience we share will promote the design and development of other novel organocatalysts and new challenging reactions.

Halocyclobutanol Dehydration En Route to Halocyclobutenes

A new method for the preparation of halocyclobutenes is described. The developed process involves the dehydration of halocyclobutanols by using tetrafluoroboric acid–diethyl ether complex in dichloromethane at room temperature. The process allows for high yields of halocyclobutenes to be achieved by using alcohols that do not trigger the formation of isomeric allylic halides.

Direct Synthesis of Disubstituted Trifluoromethylthiolated Alkenes

In the field of organofluorine chemistry, the quest for emergent fluorinated groups is in high demand. In particular, the scientific community has shown special interest in the SCF3 residue thanks to its unique properties. Indeed, over the last decade, the SCF3 group has become a pivotal fluorinated moiety, as demonstrated by several SCF3-containing compounds of interest, and, related to that, the steadily increasing number of synthetic methods that are available to access such molecules. In this Short Review, the main advances made for the synthesis of trifluoromethylthiolated disubstituted alkenes will be discussed and highlighted.

1 Introduction

2 Trifluoromethylthiolation of Prefunctionalized Alkenes

3 Direct C–H Trifluoromethylthiolation of Alkenes

4 Trifluoromethylthiolation of Miscellaneous Derivatives

5 Conclusion

Hydride reduction of o-(fluorosilyl)benzodifluorides for subsequent C–F transformations

An efficient method for sequential C–F transformations of o-hydrosilyl-substituted benzotrifluorides is disclosed. A key to the success is hydride reduction of o-fluorosilyl-substituted difluoromethylenes prepared by a single C–F transformation of...

Synthesis of Aminoallenes via Selenium-π-Acid-Catalyzed Cross-Coupling of N-Fluorinated Sulfonimides with Simple Alkynes

The facile synthesis of aminoallenes, accomplished by a selenium-π-acid-catalyzed cross-coupling of an N-fluorinated sulfonimide with simple, non-activated alkynes, is reported. Until now, aminoallenes were difficult to be accessed by customary means, inasmuch as pre-activated and, in part, intricate starting materials were necessary for their synthesis. In sharp contrast, the current study shows that ordinary internal alkynes can serve as simple and readily available precursors for the construction of the aminoallene motif. The operating reaction conditions tolerate numerous functional groups such as esters, nitriles, (silyl)ethers, acetals, and halogen substituents, furnishing the target compounds in up to 86 % yield.

Modern approaches towards the synthesis of geminal difluoroalkyl groups

This review will cover the importance of and most recent approaches toward geminal difluoroalkyl groups. Transition metal-mediated, photochemical, organocatalytic, and other methods as well as their mechanistic implications will be discussed, with special emphasis on applications to biologically-relevant compounds.

Synthesis, C-H bond functionalisation and cycloadditions of 6-styryl-1,2-oxathiine 2,2-dioxides

A series of 6-styryl-1,2-oxathiine 2,2-dioxides have been efficiently obtained by a two-step protocol from readily available (1E,4E)-1-(dimethylamino)-5-arylpenta-1,4-dien-3-ones involving a regioselective sulfene addition and subsequent Cope elimination. Pd-Mediated direct C-H bond functionalisation of the 6-styryl-1,2-oxathiine 2,2-dioxides and a wider selection of 5,6-diaryl substituted 1,2-oxathiine 2,2-dioxides proceeded smoothly to afford C-3 (hetero)aryl substituted analogues and the results are contrasted with those of a complementary bromination - Suzuki cross-coupling sequence. Whilst the cycloaddition of benzyne, derived from in situ fluoride initiated decomposition of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate, to the substituted 1,2-oxathiine 2,2-dioxides resulted in low yields of substituted naphthalenes, the addition of 4-phenyl-1,2,4-triazoline-3,5-dione to the 6-styryl-1,2-oxathiine 2,2-dioxides afforded novel 5,9-dihydro-1H-[1,2]oxathiino[5,6-c][1,2,4]triazolo[1,2-a]pyridazine-1,3(2H)-dione 8,8-dioxides through a silica-mediated isomerisation of the initial [4 + 2] adducts.

Single C-F Transformations of o-Hydrosilyl Benzotrifluorides with Trityl Compounds as All-in-One Reagents

A facile method to prepare difluoromethylenes, including α,α-difluorobenzyl chlorides, by single C-F transformations of benzotrifluorides is disclosed. The C-F cleavage followed by chlorination proceeded smoothly using trityl chloride through the generation of trityl cation as an activator and chloride anion as a nucleophile. Diverse difluoromethylenes such as difluorobenzyl ethers were efficiently prepared by virtue of the good versatility of the resulting chloro and fluorosilyl groups.

Chalcogenide-Catalyzed Intermolecular Electrophilic Thio- and Halofunctionalization of gem-Difluoroalkenes: Construction of Diverse Difluoroalkyl Sulfides and Halides

Thio- and halodifluoromethylated compounds are an important class of compounds in medicinal chemistry and organic synthesis. Herein, we report a facile method for the construction of these compounds via chalcogenide-catalyzed intermolecular electrophilic thio- and halofunctionalization of gem-difluoroalkenes. Simple treatment of gem-difluoroalkenes with electrophilic sulfur/halogen reagents and various O- or N-nucleophiles affords diverse multifunctionalized thio- and halodifluoromethylated compounds. This reaction features a relatively broad substrate scope, good functional group tolerance, and mild reaction conditions.