Trifluoromethanesulfinyl Chloride for Electrophilic Trifluoromethythiolation and Bifunctional Chlorotrifluoromethythiolation

Intramolecular Heterocyclization/Fluoromethylthiolation of Alkynes Enabled by a Multicomponent Reagent System

The BnSR_f (R_f = CF₂H or CF₃)/mCPBA/Tf₂O system was found to be an effective multicomponent reagent system for the one-pot synthesis of di/trifluoromethylthiolated heterocycles from alkynes. The reaction was postulated to proceed via a cascade sequence involving the oxidation of BnSR_f by mCPBA, activation of the in situ-generated sulfoxide by Tf₂O, and intramolecular cyclization/fluoromethylthiolation of the alkyne substrates enabled by the formed electrophilic sulfonium salt to give di/trifluoromethylthiolated heterocycles.

Deoxygenation of ClSO2CF2COOMe with Triphenylphosphine for the Metal-Free Direct Electrophilic Difluoroalkylthiolation of Various Heterocycles

A direct electrophilic difluoroalkylthiolation reaction of indole derivatives and other electron-rich heterocycles using methyl 2,2-difluoro-2-(chlorsulfonyl)acetate (ClSO₂CF₂COOMe) derived from Chen's reagent (FSO₂CF₂COOMe) is described. The ester group in the product can be further utilized in subsequent versatile transformations. The reactions provide good yields of the corresponding difluoroalkylthiolation products and exhibit high functional group compatibility. It is expected to serve as an alternative and practical protocol for difluoroalkylthiolation of various heterocycles.

A Toolbox of Reagents for Trifluoromethylthiolation: From Serendipitous Findings to Rational Design

Two types of electrophilic trifluoromethylthiolating reagents were developed in the past 10 years in our laboratory. The development of the first type of reagent, trifluoromethanesulfenate I, which is highly reactive toward a variety of nucleophiles, was based on an unexpected discovery in the initial design for the development of an electrophilic trifluoromethylthiolating reagent with a hypervalent iodine skeleton. A structure-activity study disclosed that α-cumyl trifluoromethanesulfenate (reagent II) without the iodo substituent is equally effective. Subsequent derivatization let us develop an α-cumyl bromodifluoromethanesulfenate III that could be used for the preparation of [¹⁸F]ArSCF₃. To remediate the low reactivity of the type I electrophilic trifluoromethylthiolating reagent for Friedel-Crafts trifluoromethylthiolation of electron-rich (hetero)arenes, we designed and prepared N-trifluoromethylthiosaccharin IV, which exhibits broad reactivity toward various nucleophiles, including electron-rich arenes. A comparison of the structure of N-trifluoromethylthiosaccharin IV with that of N-trifluoromethylthiophthalimide showed that the replacement of one carbonyl group in N-trifluoromethylthiophthalimide with a sulfonyl group made N-trifluoromethylthiosaccharin IV much more electrophilic. Thus, the replacement of both carbonyls with two sulfonyl groups would further increase the electrophilicity. Such a rationale prompted us to design and develop the current most electrophilic trifluoromethylthiolating reagent, N-trifluoromethylthiodibenzenesulfonimide V, and its reactivity was much higher than that of N-trifluoromethylthiosaccharin IV. We further developed an optically pure electrophilic trifluoromethylthiolating reagent, (1S)-(-)-N-trifluoromethylthio-2,10-camphorsultam VI, for the preparation of optically active trifluoromethylthio-substituted carbon stereogenic centers. Reagents I-VI now constitute a powerful toolbox for the introduction of the trifluoromethylthio group into the target molecules.

Application of Aromatic Substituted 2,2,2-Trifluoro Diazoethanes in Organic Reactions

Abstract:

This review provides an overview of metal-, nonmetal-, light-, or catalyst free-promoting reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with organic molecules for the synthesis of trifluoromethyl-substituted compounds. Several approaches will be reviewed and divided into (i) copper-, iron-, Trop(BF4)-, B(C6F5)3-, light-, or rhodium-promoted reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with silanes, amines, mercaptans, phosphonates, p-cyanophenol, benzoic acid, diphenylphosphinic acid, boranes and nBu3SnH, (ii) rhodium-catalyzed reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with amides and phenylhydroxylamine, (iii) copper-, rhodium-, silver-, and light-catalyzed reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with alkynes, (iv) palladium-, copper-, rhodium- and iron-catalyzed reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with alkenes, (v) BF3·OEt2-, copper-, tin- or TBAB-catalyzed reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with HF·Py, (difluoroiodo)toluene (p-TolIF2), TMSCF3, AgSCF3, TMSCF2Br or 1,3-dicarbonyl compounds, (vi) palladium-, copper-, gold/silver- or rhodium-catalyzed reactions of aromatic substituted 2,2,2-trifluoro diazoethanes with indoles, benzene compounds or pyridines, and (vii) palladium-catalyzed reaction of aromatic substituted 2,2,2-trifluoro diazoethanes with benzyl or allyl bromides.

Palladium-Catalyzed Regio- and Diastereoselective Olefinic C-H Difluoromethylthiolation at Room Temperature

Herein, we developed palladium-catalyzed regio- and diastereoselective difluoromethylthiolation of acrylamides to form the Z-isomer product at room temperature. Using 8-aminoquinoline as a directing group, this protocol resulted in a high efficiency under mild reaction conditions and showed good functional group tolerances, which opens a novel synthetic methodology for accessing SCF₂H-containing skeletons. Moreover, mechanistic studies were conducted to obtain insights into the reaction mechanism, and post-functionalization of the product reactions was performed.

S-triggered Schmidt-type rearrangement of vinyl azides to access N-aryl-(trifluoromethylsulfinyl)acetamides

A novel S-induced Schmidt-type rearrangement of vinyl azides with CF3SO2Na is developed for synthesis of N-arylated 2-(trifluoromethylsulfinyl)acetamieds, which is mediated by triphosgene (BTC) under mild reaction conditions.

Aerobic copper-mediated domino process for the synthesis of 3-(trifluoromethylseleno)indoles

An aerobic copper-mediated domino reaction for the synthesis of 3-(trifluoromethylseleno)indoles from trifluoromethylselenolation of N-Ts 2-alkynylaniline with [(bpy)CuSeCF3]2 is reported. This reaction proceeds through a sequential oxidation, alkyne coordination, and deprotonation...

Synergistic Effect of Squaric Acid in Bromine-Catalyzed Deoxygenation of Sulfonyl Derivatives: Mechanistic Investigations and Synthetic Applications in Electrophilic (Fluoroalkyl)sulfenylation

A method for electrophilic (fluoroalkyl)sulfenylation of nucleophiles by collaborative CTAB- and squaric acid-promoted deoxygenation of sulfonyl derivatives is reported. Mechanistic studies indicate that squaric acid dramatically decreased the energy barrier in the first step of deoxygenation. The mild deoxygenation process enables the reduction of a wide range of functionalized sulfonyl chlorides as well as sulfonic anhydrides. The novel method represents an operationally simple protocol using readily available reagents and exhibits broad functional group tolerance.

Recent Advances in Transition-Metal-Catalyzed Selective C–H Alkoxycarbonyldifluoromethylation Reactions of Aromatic Substrates

Fluorine is well-known as a very special element. Approximately 30% of agrochemicals and 20% of all drugs contain fluorine; most of those compounds have unique functions in biochemistry, pharmacy, and bioscience and those containing alkoxycarbonyldifluoromethyl functional groups often have irreplaceable roles. Therefore, the selective introduction of alkoxycarbonyldifluoromethylated functional groups into various aromatic substrates has significant practical application. This review describes recent advances in selective alkoxycarbonyldifluoromethylation of aromatic substrates by using different catalytic strategies (cyclometalated ruthenium complex, transient regulating and visible-light-induced strategies).

1 Introduction

2 para-C–H Alkoxycarbonyldifluoromethylation of Aromatic Derivatives

2.1 Ruthenium Catalysis

2.2 Palladium Catalysis

2.3 Visible-Light Catalysis

2.4 Iron Catalysis

3 meta-C–H Alkoxycarbonyldifluoromethylation of Aromatic Derivatives

3.1 Ruthenium Catalysis

3.2 Palladium Catalysis

4 The Influence of Transition Metals and Directing Groups on Site Selectivity of Alkoxycarbonyldifluoromethylation

4.1 The Influence of Directing Groups on the Site Selectivity of Alkoxycarbonyldifluoromethylation

4.2 The Influence of Transition Metals on the Site Selectivity of Alkoxycarbonyldifluoromethylation

5 Conclusions

A three-component iodine-catalyzed oxidative coupling reaction: a heterodifunctionalization of 3-methylindoles

A metal-free method for the synthesis of heterodifunctional indole derivatives is developed through TBHP/KI-mediated oxidative coupling. The reaction constructs C-O and C-C bonds in succession with the help of tert-butyl peroxy radicals generated by the TBHP/KI catalytic system, enabling the direct realization of the heterodifunctionalization of indole in one pot. The product of this reaction is a novel heterodifunctional compound. This work might provide a new effective method for the synthesis of polycyclic indole compounds.

Synthesis of difluoromethyl and deuterium-labeled difluoromethyl thioethers from aliphatic electrophiles

A one-pot difluoromethylthiolation of alkyl electrophiles with thiourea and diethyl bromodifluoromethylphosphonate is described. The transition-metal-free approach, readily available reagents, and mild conditions provide a practical way for the synthesis of difluoromethyl thioethers. By changing the "H" source to the most commonly used "D" sources CD₃OD and D₂O, this strategy enables efficient synthesis of SCF₂D-substituted molecules in good yields with high levels of D incorporation.

Electrophilic Hypervalent Trifluoromethylthio-Iodine(III) Reagent

Herein we report the design and synthesis of hypervalent trifluoromethylthio-iodine(III) reagent 1 and the elucidation of its structure by NMR spectroscopy and X-ray crystallography. The trifluoromethylthiolation reactions of 1 with various nucleophiles were explored, and this compound was found to be a versatile electrophilic reagent for the transfer of a trifluoromethylthio group (-SCF₃). The hydrogen-bonding mode responsible for the activation of 1 by the solvent 1,1,1,3,3,3-hexafluoro-2-propanol was investigated both experimentally and computationally.

Practical and regioselective halo-trifluoromethylthiolation of sulfur ylides

A H2O mediated practical and highly regioselective chloro- and bromo-trifluoromethylthiolation of sulfur ylides is reported using a difunctionalization strategy. In the reaction sequence, sulfur ylides presumably react with an electrophilic trifluoromethylthiolating reagent to generate an α-SCF3 substituted sulfonium salt intermediate, which then undergoes a substitution with nucleophilic halogens.

Novel usage of 2-BTSO2CF2H for metal-free electrophilic difluoroalkanethiolation of indoles

2-BTSO₂CF₂H was used as an efficient electrophilic –SCF₂H synthon for the first time for the metal-free electrophilic difluoromethylthiolation of indoles.

Novel Bifunctionalization of Activated Methylene: Base-Promoted Trifluoromethylthiolation of β-Diketones with Trifluoromethanesulfinyl Chloride

A novel bifunctionalization of activated methylene was achieved successfully through the base-promoted trifluoromethylthiolation of β-diketones or β-ketoesters with trifluoromethanesulfinyl chloride. A series of α-trifluoromethylthiolated α-chloro-β-diketones and α-chloro-β-ketoesters were obtained in moderate to good yields under mild conditions. When β-diketones containing a phenyl group with a hydroxyl or amino substituent at the ortho position were used as substrates, intramolecular trifluoromethylthiolation/cyclization reaction took place to give the corresponding cyclic products. Furthermore, the protocol could be extended to perfluoroalkylthiolation with the sodium perfluoroalkanesulfinate/POCl₃ system. On the basis of experimental results, plausible mechanisms are proposed.

Metal- and phosphine-free electrophilic vicinal chloro-alkylthiolation and trifluoromethylthiolation of indoles using sodium sulfinate in the presence of triphosgene

Efficient chloro-alkylthiolation and trifluoromethylthiolation of indole derivatives were developed.