Yankun Hou

Electrolytic Partial Fluorination of Organic Compounds XL. Solvent Effects on Anodic Fluorination of Heterocyclic Sulfides

Solvent effects on electrolytic partial fluorination of α-(2-benzoxazolylthio)-, α-(2-benzothiazolylthio)-, and α-(2-pyrimidylthio)acetates were investigated systematically using acetontrile (MeCN) and 1,2-dimethoxyethane (DME) containing Et 4 NF.nHF (n = 3, 4) as a supporting electrolyte and a fluoride ion source. MeCN was not suitable for the fluorination of these heterocyclic sulfides since formation of nonconductive polymers on the anode took place to result in low yields or no fluorination of fluorinated products. In contrast, the use of DME did not cause such polymer film formation and provided much better or excellent fluorinated product yields. The superiority of DME can be explained in terms of its ability to solvate the cationic part of the fluoride salt in which a reactive fluoride ion is left for easy attack on the anodically generated cationic intermediate. It is noted that addition of DME into MeCN electrolytic solution markedly increased the product yield and current efficiency since the polymer film formation on the anode and overoxidation of the fluorinated products were effectively suppressed.

Electrolytic Partial Fluorination of Organic Compounds. Part 41: Highly Selective Electrolytic Fluorination of Dimethoxyethane, its Homologues, and Crown Ethers

Abstract The anodic fluorination of dimethyoxyethane (DME), and diethylene glycol dimethyl ether in acetonitrile containing a fluoride salt as a supporting electrolyte and a fluoride ion source using an undivided cell provided the corresponding monofluoromethyl ethers as a main product in good yields. On the other hand, anodic fluorination of crown ethers resulted in carbon–carbon bond cleavage which led to the selective production of α,ω-difluoro products with high yields. A carbon anode as well as a platinum anode was found to be effective for the electrolytic fluorination when Et 3 N·5HF was used as the supporting electrolyte.

ELECTROLYTIC PARTIAL FLUORINATION OF ORGANIC COMPOUNDS. PART 29. ANODIC MONO- AND DIFLUORINATION OF 2-BENZOXAZOLYL SULFIDES

Abstract Anodic fluorination of 2-benzoxazolyl sulfides using various fluoride salts and dimethoxyethane as a supporting electrolyte and a solvent, respectively, resulted in the formation of the corresponding mono- and difluorinated products in reasonable yields. The monofluorination took place selectively at the position α to the sulfur atom while the difluorination resulted at both the α -position and the benzene ring while the expected α , α -difluorination did not take place at all. Moreover, anodic fluorination of the electrolytic solvent, DME, which has never been reported so far, was also observed as a side-reaction and this fluorination was further confirmed by carrying out anodic fluorination of DME itself in the absence of a substrate sulfide.

Electrolytic partial fluorination of organic compounds. Part 37: Selective electrolytic fluorination of dimethoxyethane, diethylene glycol dimethyl ether, and crown ethers☆

Abstract The anodic fluorination of dimethoxythane (DME) and diethylene glycol dimethyl ether in acetonitrile containing a fluoride salt provided moderate yields of the corresponding monofluoromethyl ethers. The anodic fluorination of crown ethers resulted in carboncarbon bond cleavage which led to the selective production of α,ω-difluoro products with high yields.

Electrolytic partial fluorination of organic compounds: 38. Solvent effects on electrolytic fluorination of ethyl α-(2-pyrimidylthio)acetate

Electrolytic partial fluorination of ethyl α-2-(pyrimidylthio)acetate was comparatively studied in acetonitrile and 1,2-dimethoxyethane (DME) containing Et4NF·4HF as a supporting electrolyte and a fluoride ion source. Acetontrile was not suitable for the fluorination due to the severe anode passivation. In contrast, use of DME provided the corresponding α-monofluorinated product in quantitative yield. A mixed electrolytic solvent of DME and acetonitrile was also effective for the fluorination and the product yield increased with an increase of the ratio of DME to acetonitrile. The superiority of DME can be explained mainly in terms of both the suppression of the anode passivation and enhancement of the nucleophilicity of fluoride ions.

Electrolytic partial fluorination of organic compounds. Part 34. Regioselective anodic fluorination of benzyl thiocyanate and its derivatives

Abstract Highly regioselective anodic monofluorination of benzyl thiocyanate and its derivatives was successfully carried out at a platinum anode in acetonitrile using Et3N·5HF as a supporting electrolyte and a fluorine source to provide the corresponding α-fluorinated products in moderate to good yields. It was also found that the fluorinated product yield was affected significantly by supporting fluoride salts and temperature.