Synthesis of CF3-containing oxazolines via trifluoromethylation of allylamides with Togni reagent in the presence of alkali metal iodides

Ligand-Controlled Copper-Catalyzed Halo-Halodifluoromethylation of Alkenes and Alkynes Using Fluorinated Carboxylic Anhydrides

Polyhalogenated molecules are often found as bioactive compounds in nature and are used as synthetic building blocks. Fluoroalkyl compounds hold promise for the development of novel pharmaceuticals and agrochemicals, as the introduction of fluoroalkyl groups is known to improve lipophilicity, membrane permeability, and metabolic stability. Three-component 1,2-halo-halodifluoromethylation reactions of alkenes are useful for their synthesis. However, general methods enabling the introduction of halodifluoromethyl (CF2X) and halogen (X') groups in the desired combination of X and X' are lacking. To address this gap, for the first time, we report a three-component halo-halodifluoromethylation of alkenes and alkynes using combinations of commercially available fluorinated carboxylic anhydrides ((CF2XCO)2O, X=Cl and Br) and alkali metal halides (X'=Cl and Br). In situ prepared fluorinated diacyl peroxides were identified as important intermediates, and the use of appropriate bipyridyl-based ligands and a copper catalyst was essential for achieving high product selectivity. The synthetic utility of the polyhalogenated products was demonstrated by exploiting differences in the reactivities of their C-X and C-X' bonds to achieve selective derivatization. Finally, the reaction mechanism and ligand effect were investigated using experimental and theoretical methods to provide important insights for the further development of catalytic reactions.

Understanding and Controlling Fluorinated Diacyl Peroxides and Fluoroalkyl Radicals in Alkene Fluoroalkylations

The demand for practical methods for the synthesis of novel fluoroalkyl molecules is increasing owing to their diverse applications. Our group has achieved efficient difunctionalizing fluoroalkylations of alkenes using fluorinated carboxylic anhydrides as user-friendly fluoroalkyl sources. Fluorinated diacyl peroxide, prepared in situ from carboxylic anhydrides, enables the development of novel reactions when used as a radical fluoroalkylating reagent. In this account, we aim to provide an in-depth understanding of the structure, bonding, and reactivity of fluorinated diacyl peroxides and radicals as well as their control in fluoroalkylation reactions. In the first part of this account, the physical properties and reactivity of diacyl peroxides and fluoroalkyl radicals are described. In the subsequent part, we categorize the reactions into copper-catalyzed and metal-free methods utilizing the oxidizing properties of fluorinated diacyl peroxides. We also outline examples and mechanisms.

Electrochemical Trifluoromethylation and Sulfonylation of N-Allylamides: Synthesis of Oxazoline Derivatives

We report a new method for the synthesis of trifluoromethylated and sulfonylated oxazolines by electrochemical radical cascade cyclizations of N-allylamides with sodium trifluoromethanesulfinate or sulfonylhydrazines. This protocol provides a green and useful strategy to synthesize trifluoromethylated and sulfonylated oxazolines with a broad substrate scope under ambient conditions.

Photoredox-catalyzed synthesis of sulfonated oxazolines from N-allylamides through the insertion of sulfur dioxide

Photoredox-catalyzed generation of sulfonated oxazolines starting from N-allylamides, DABCO·(SO2)2, and aryldiazonium salts has been developed and a range of sulfonated oxazolines were obtained in moderate to good yields.

Recent Advances on the Halo- and Cyano-Trifluoromethylation of Alkenes and Alkynes

Incorporation of fluorine into organic molecules is a well-established strategy in the design of advanced materials, agrochemicals, and pharmaceuticals. Among numerous modern synthetic approaches, functionalization of unsaturated bonds with simultaneous addition of trifluoromethyl group along with other substituents is currently one of the most attractive methods undergoing wide-ranging development. In this review article, we discuss the most significant contributions made in this area during the last decade (2012−2021). The reactions reviewed in this work include chloro-, bromo-, iodo-, fluoro- and cyano-trifluoromethylation of alkenes and alkynes.

Syntheses of Trifluoroethylated N-Heterocycles from Vinyl Azides and Togni's Reagent Involving 1,n-Hydrogen-Atom Transfer Reactions

2,2,2-Trifluoroethyl-substituted 3-oxazolines, 3-thiazolines, and 5,6-dihydro-2H-1,3-oxazines have been obtained by reacting substituted vinyl azides with a combination of Togni's reagent and substoichiometric amounts of iron(II) chloride. The results of density functional theory calculations support the proposed mechanism involving 1,n-hydrogen-atom transfer reactions.

A new hypervalent iodine(iii/v) oxidant and its application to the synthesis of 2H-azirines

The reaction of o-nitroiodobenzene and mCPBA in acetic acid was found to afford a novel hypervalent iodine compound, in the structure of which both iodine(iii) and iodine(v) moieties coexist. The nitro groups at the ortho phenyl positions were found to be crucial in stabilizing this uncommon structure. This novel hypervalent iodine(iii/v) oxidant is proved to be effective in realizing the synthesis of 2-unsubstitued 2H-azirines via intramolecular oxidative azirination, which could not be efficiently achieved by the existing known hypervalent iodine reagents.

Silver-Promoted Synthesis of 5-[(Pentafluorosulfanyl)methyl]-2-oxazolines

The synthesis of 5-[(pentafluorosulfanyl)methyl]-2-oxazolines is reported. The use of a silver promoter allows the intramolecular cyclization of N-[2-chloro-3-(pentafluorosulfanyl)propyl]amide to occur without elimination of the chlorine atom, a reaction pathway typically observed for β-chloro-SF₅-alkyl compounds. The products, potentially valuable SF₅-containing heterocycles, are obtained in up to 97% yield.

Metal-free alkene oxy- and amino-perfluoroalkylations via carbocation formation by using perfluoro acid anhydrides: unique reactivity between styrenes and perfluoro diacyl peroxides

A practical metal-free perfluoroalkylation using acid anhydrides with unique reaction mode via carbocation has been developed.

We present a strategy for metal-free, alkene difunctionalization-type, oxy- and amino-perfluoroalkylations, using perfluoro acid anhydrides as practical and user-friendly perfluoroalkyl sources. This method provides efficient access to oxy-perfluoroalkylation products via carbocation formation due to the unique reactivity between styrenes and bis(perfluoroacyl) peroxides generated in situ from perfluoro acid anhydrides. This reaction is also applicable to metal-free intramolecular amino-perfluoroalkylation of styrenes bearing a pendant amino group. Synthetic utility of the oxy-trifluoromethylation products was confirmed by demonstrating derivatization via hydrolysis, elimination, and acid-catalyzed substitution with carbon nucleophiles. The mechanism of the carbocation formation was investigated experimentally and theoretically.

N-Heterocycle-Forming Amino/Carboperfluoroalkylations of Aminoalkenes by Using Perfluoro Acid Anhydrides: Mechanistic Studies and Applications Directed Toward Perfluoroalkylated Compound Libraries

This work describes a practical and efficient method for synthesizing a diverse array of perfluoroalkylated amines, including N-heterocycles, to afford perfluoroalkylated chemical libraries as potential sources of drug candidates, agrochemicals, and probe molecules for chemical-biology research. Perfluoro acid anhydrides, which are commonly used in organic synthesis, were employed as a perfluoroalkyl source for intramolecular amino- and carbo-perfluoroalkylations of aminoalkenes, affording perfluoroalkylated N-heterocycles, including: aziridines, pyrrolidines, benzothiazinane dioxides, indolines, and hydroisoquinolinones. Diacyl peroxides were generated in situ from the perfluoro acid anhydrides with urea·H₂O₂, and allowed to react with aminoalkenes in the presence of copper catalyst to control the product selectivity between amino- and carbo-perfluoroalkylations. To illustrate the synthetic utility of bench-stable trifluoromethylated aziridine, which was prepared on a gram scale, we used it to synthesize a wide variety of trifluoromethylated amines including complex molecules, such as trifluoromethylated tetrahydroharmine and spiroindolone. A mechanistic study of the role of the copper catalyst in the aminotrifluoromethylation of allylamine suggested that Cu(I) accelerates CF₃ radical formation via decomposition of diacyl peroxide, which appears to be the turnover-limiting step, while Cu(II) controls the product selectivity.