Iron-Catalyzed Preparation of Trifluoromethyl Substituted Vinyl- and Alkynylcyclopropanes

Fluoroalkyl-Substituted Diazomethanes and Their Application in a General Synthesis of Pyrazoles and Pyrazolines

A novel continuous-flow approach for the synthesis of fluoroalkyl-substituted diazomethanes has been developed. Utilizing a cheap, self-made microreactor fluoroalkyl-substituted amines were transformed into the corresponding diazomethanes using tert-butyl nitrite and acetic acid as catalyst. These diazomethanes were employed in [2+3] cycloaddition reactions with olefins and alkynes, yielding valuable pyrazolines and pyrazoles in good to excellent yields.

Diastereoselective Johnson-Corey-Chaykovsky trifluoroethylidenation

(2,2,2-Trifluoroethyl)diphenylsulfonium triflate was found to be an efficient ylide reagent for the Johnson-Corey-Chaykovsky reaction to afford trifluoromethyl epoxides, cyclopropanes and aziridines. Interestingly, excellent but different diastereoselectivity was observed for these transformations. Both trifluoromethyl epoxides and cyclopropanes were obtained with trans-selectivity, whereas aziridines were obtained with cis-selectivity.

Generation and Synthetic Application of Trifluoromethyl Diazomethane Utilizing Continuous Flow Technologies

A continuous process for the synthesis and inline separation of anhydrous trifluoromethyl diazomethane in a single continuous flow process is presented. The diazo building block is generated from the corresponding amine and NaNO2 under acidic, aqueous conditions and subsequently diffuses through a gas-permeable membrane into an organic stream. To avoid storage and transportation of the hazardous compound, a representative downstream process in a packed-bed reactor yielding highly functionalized building blocks was developed.

Fluorinated diazoalkanes – a versatile class of reagents for the synthesis of fluorinated compounds

Fluorinated diazo compounds were long neglected in organic synthesis. This review discusses the flourishing chemistry of these reagents, ranging from C–H activation to cycloadditions for the synthesis of fluorinated compounds.

Rhodium catalyzed synthesis of difluoromethyl cyclopropanes

Difluoromethyl-substituted cyclopropanes still remain one of the most challenging class of substrates.

In Situ generation of difluoromethyl diazomethane for [3+2] cycloadditions with alkynes

A novel approach to agrochemically important difluoromethyl-substituted pyrazoles has been developed based on the elusive reagent CF2 HCHN2 , which was synthesized (generated in situ) for the first time and employed in [3+2] cycloaddition reactions with alkynes. The reaction is extremely practical as it is a one-pot process, does not require a catalyst or the isolation of the potentially toxic and explosive gaseous intermediate, and proceeds in a common solvent, namely chloroform, in air. The reaction is also scalable and allows for the preparation of the target pyrazoles on gram scale.

Copper-triggered three-component reaction of CF3CHN2, nitriles, and aldehydes: highly diastereoselective synthesis of CF3-substituted oxazolines and vicinal amino alcohols

A novel, catalytic, three-component C–C, C–N and C–O bond forming reaction to afford CF₃-substituted oxazolines is realized.

The asymmetric synthesis of CF3-containing spiro[pyrrolidin-3,2′-oxindole] through the organocatalytic 1,3-dipolar cycloaddition reaction

A new strategy for the construction of optically active 5′-CF₃ spiro[pyrrolidin-3,2′-oxindole] was described by using CF₃CH₂NH₂ as a building block.

Metal-free radical perfluoroalkylation of (hetero)arenes

We report a metal-free radical perfluoroalkylation method which uses inexpensive and commercially available perfluorocarboxylic anhydrides as an easy to use source of perfluoroalkyl radicals.

Iron-catalyzed transformations of diazo compounds

Although iron-promoted diazo transformations were only discovered during the 1990s, iron can undergo facile changes in its oxidation state and possesses distinct Lewis acid character, and these properties have afforded iron a privileged position as a catalyst in the transformations of diazo compounds. In this review, we have provided an overview of the iron-catalyzed diazo transformation reactions reported in the literature by the end of 2013 with the aim of stimulating further interest in this area of research.

Synthesis of trifluoromethylated isoxazolidines: 1,3-dipolar cycloaddition of nitrosoarenes, (trifluoromethyl)diazomethane, and alkenes

Isoxazolidines have proven to be important substrates in synthetic organic chemistry. Limited examples in the literature that provide trifluoromethylated versions of these compounds have prompted us to investigate a 1,3-dipolar cycloaddition route providing access to N-functionalized isoxazolidines containing a trifluoromethyl group. Thus, a 1,3-dipolar cycloaddition of nitrosoarenes, (trifluoromethyl)diazomethane, and alkenes was developed. The starting materials can be synthesized from easy to handle and accessible reagents. The reaction proved to be tolerant of a variety of electron-deficient alkenes and nitrosoarenes.

Photocatalytic synthesis of allylic trifluoromethyl substituted styrene derivatives in batch and flow

A cobalt-catalyzed photochemical synthesis of allylic trifluoromethanes from styrene derivatives using 2,2,2-trifluoroethyl iodide is described. The method complements existing approaches, providing an alternative bond construction strategy to access these compounds. The process may be conducted in continuous mode in a novel photochemical flow reactor, resulting in a notable productivity increase.

Synthesis of trifluoromethyl-substituted cyclopropanes via sequential Kharasch-dehalogenation reactions

A two-step process for the synthesis of trifluoromethyl-substituted cyclopropanes is described. Halothane, an anesthetic agent, is added to olefins in a ruthenium-catalyzed Kharasch reaction. The resulting 1,3-dihalides are converted into cyclopropanes by dehalogenation with magnesium. This procedure represents an alternative to metal-catalyzed cyclopropanations involving trifluoromethyl diazomethane.