Convenient access to trifluoromethanol

Synthesis of Partially Fluorinated Alkyl Triflates by Electrochemical Fluorination (Simons Process)

A scalable straightforward synthesis of monofluoro- and difluoromethyl triflate CF3 SO2 OCH2 F (MH2F ) and CF3 SO2 OCHF2 (MHF2 ) through electrochemical fluorination (ECF, Simons process) of methyl triflate MH3 in anhydrous hydrogen fluoride at nickel anodes is presented. The ECF method is also feasible for the preparation of the deuterated analogues CF3 SO2 OCD2 F (MD2F ) and CF3 SO2 OCDF2 (MD2F ). Surprisingly, no H/D exchange occurs during ECF of CF3 SO2 OCD3 (MD3 ); this provides further evidence for a NiF3 /NiF4 -mediated ECF mechanism. The ECF of selected partially fluorinated ethyl triflates is described, and electrochemical fluorination of CF3 SO2 OCH2 CF3 (EH2F3 ) leads to the until now unknown chiral CF3 SO2 OCHFCF3 (EHFF3 ). The analogous fluoromethyl and fluoroethyl nonaflates are also accessible by ECF. This study contains detailed spectroscopic, structural, and thermal data on (fluoro)methyl and fluoro(ethyl) triflates.

Comprehensive Study and Development of a Metal-Free and Mild Nucleophilic Trifluoromethoxylation

Among the general interest in fluorinated compounds, trifluoromethoxylated molecules play a specific role. However, despite this interest, the development of efficient reagents to perform trifluoromethoxylation reactions remains a challenge. Here, 2,4-dinitro-trifluoromethoxybenzene (DNTFB) is used as a trifluoromethoxylating reagent to perform nucleophilic substitution under mild metal-free conditions with different leaving groups, including direct dehydroxytrifluoromethoxylation. A mechanistic study rationalized the reaction and subsequently proposed only three reaction conditions, depending on the reactivity of the starting substrates.

Degradation of Perfluoroalkyl Ether Carboxylic Acids with Hydrated Electrons: Structure-Reactivity Relationships and Environmental Implications

This study explores structure-reactivity relationships for the degradation of emerging perfluoroalkyl ether carboxylic acid (PFECA) pollutants with ultraviolet-generated hydrated electrons (e_aq^-). The rate and extent of PFECA degradation depend on both the branching extent and the chain length of oxygen-segregated fluoroalkyl moieties. Kinetic measurements, theoretical calculations, and transformation product analyses provide a comprehensive understanding of the PFECA degradation mechanisms and pathways. In comparison to traditional full-carbon-chain perfluorocarboxylic acids, the distinct degradation behavior of PFECAs is attributed to their ether structures. The ether oxygen atoms increase the bond dissociation energy of the C-F bonds on the adjacent -CF₂- moieties. This impact reduces the formation of H/F-exchanged polyfluorinated products that are recalcitrant to reductive defluorination. Instead, the cleavage of ether C-O bonds generates unstable perfluoroalcohols and thus promotes deep defluorination of short fluoroalkyl moieties. In comparison to linear PFECAs, branched PFECAs have a higher tendency of H/F exchange on the tertiary carbon and thus lower percentages of defluorination. These findings provide mechanistic insights for an improved design and efficient degradation of fluorochemicals.

Synthesis of Tri- and Difluoromethoxylated Compounds by Visible-Light Photoredox Catalysis

Trifluoromethoxy (OCF3 ) and difluoromethoxy (OCF2 H) groups are fluorinated structural motifs that exhibit unique physicochemical characteristics. Incorporation of these substituents into organic molecules is a highly desirable approach used in medicinal chemistry and drug discovery processes to alter the properties of a parent compound. Recently, tri- and difluoromethyl ethers have received increasing attention and several innovative strategies to access these valuable functional groups have been developed. The focus of this Minireview is the use of visible-light photoredox catalysis in the synthesis of tri- and difluoromethyl ethers. Recent photocatalytic strategies for the formation of O-CF3 , C-OCF3, O-CF2 H, and C-OCF2 H bonds as well as other transformations leading to the construction of ORF groups are discussed herein.

Perfluoroalcohols: The Preparation and Crystal Structures of Heptafluorocyclobutanol and Hexafluorocyclobutane-1,1-diol

The first X-ray crystal structure of an α-fluoroalcohol is reported. Heptafluorocyclobutanol was obtained in quantitative yield from hexafluorocyclobutanone by HF addition in anhydrous hydrogen fluoride. The compound was characterized by its X-ray single crystal structure. Heptafluorocyclobutanol readily undergoes hydrolysis to hexafluorocyclobutane-1,1-diol, which was also structurally characterized by X-ray diffraction.

The perfluorinated alcohols c-C6F11OH, c-C6F10-1,1-(OH)2 and c-C6F10-1-(CF3)OH

The thermally unstable α-fluoroalcohol undecafluorocyclohexanol (c-C₆F₁₁OH) was prepared by addition of hydrogen fluoride to the corresponding ketone.

Mechanistic studies on intramolecular C-H trifluoromethoxylation of (hetero)arenes via OCF3-migration

The one-pot two-step intramolecular aryl and heteroaryl C-H trifluoromethoxylation recently reported by our group has provided a general, scalable, and operationally simple approach to access a wide range of unprecedented and valuable OCF3-containing building blocks. Herein we describe our investigations to elucidate its reaction mechanism. Experimental data indicate that the O-trifluoromethylation of N-(hetero)aryl-N-hydroxylamine derivatives is a radical process, whereas the OCF3-migration step proceeds via a heterolytic cleavage of the N-OCF3 bond followed by rapid recombination of a short-lived ion pair. Computational studies further support the proposed ion pair reaction pathway for the OCF3-migration process. We hope that the current study would provide useful insights for the development of new transformations using versatile N-(hetero)aryl-N-hydroxylamine synthons.

Probing the Reactivity of the Potent AgF2 Oxidizer. Part 1: Organic Compounds

The reactivity of Ag(II)F2 towards a variety of organic compounds of a high degree of fluorination has been investigated. AgF2 readily fluorinates P(C6F5)3 to PF2(C6F5)3, and attacks the isothiocyanate functional group, -NCS, yielding Ag2S. Perfluorinated aliphatic nitriles resist the action of AgF2, but aromatic C6F5CN undergoes a radical-initiated oligomerization; byproducts include C6F6CN• and C6F5N2• (after intramolecular rearrangement following the bimolecular reaction). AgF2 oxidizes higher fluorosulfonic acids (C4F9SO3H, C8F17SO3H) at or close to the room temperature and triflic acid (CF3SO3H) at its boiling point to the corresponding peroxides. CF3COOH and CF3CONH2 are also decomposed in redox reactions, but the gaseous products have not been identified. Surprisingly, AgF2 is kinetically inert to perfluorinated aromatic hydrocarbons and to CCl4, but it decomposes CBr4 with vigorous elimination of Br2. CI4 decomposes explosively in the presence of AgF2. C6F5OH and CF3COOH are readily oxidized with AgF2 but, surprisingly, t-C4F9OH is kinetically resistant under similar conditions. Coordination complexes of perfluorinated aza and oxa Lewis bases (including perfluorinated 15-crown-5 ether) and AgF2 are not formed under the experimental conditions.