Electrolytic partial fluorination of organic compounds.71. Highly diastereoselective anodic fluorination of sulfides having oxygen-containing heterocyclic groups

Diastereoselective anodic fluorination of sulfides having various oxygen-containing heterocyclic substituents such as 2-furanyl, 1,3-dioxolanyl, 2,2-dimethyl-1,3-dioxolanyl, 2-spirocyclohexyl-1,3-dioxolanyl, 2-spiroadamantyl-1,3-dixolanyl, and 1,3-dioxolanonyl groups at the beta-position was comparatively studied. Among the oxygen-containing heterocyclic substituents, the 2-spirocyclohexyl-1,3-dioxolanyl group gave the best diastereoselectivity (80% de). The diastereoselectivity was also affected by supporting fluoride salts and solvents. Chemical fluorination using selectfluor resulted in much lower diastereoselectivity and extremely poor yield. The fluorinated products were readily converted into the corresponding fluorinated diol in good yields by acidic hydrolysis.     

Electrolytic partial fluorination of organic compounds 84: Anodic mono- and difluorination of benzylphosphonate derivatives

Anodic fluorination of benzylphosphonate derivatives was carried out under various electrolytic conditions to provide the corresponding α-mono- and/or α,α-difluoro-products in moderate to good yields. It was found that the selectivity of fluorinated products was depending on the molecular structures of the starting substrates and the electrolytic conditions.     

Electrolytic partial fluorination of organic compounds. 64.(1) Anodic mono- and difluorination of thiazolyl sulfides

The anodic fluorination of 2-thiazolyl methyl sulfide, 2-thiazolyl propargyl sulfide, and 2-thiazolyl acetonyl sulfide was successfully carried out to provide the corresponding 5-fluorothiazole and 2,5,5-trifluorothiazoline derivatives. The latter products were readily hydrolyzed to give isolable 5,5-difluoro-2-hydroxythiazoline derivatives. On the other hand, anodic fluorination of 2-thiazolyl cyanomethyl sulfide afforded 5-fluorothiazole and alpha-fluorinated thiazole derivatives. Thus, the product selectivity was found to be greatly changed by the electron-withdrawing ability of substituents at the side chain of the thiazole ring. This is the first report of a successful anodic fluorination of a thiazole ring.     

Electrolytic partial fluorination of organic compounds. 79. Anodic fluorination of spiropyrazoline-5,3'-chroman-4-ones and thiochromanone analogues. A route to aroyl fluoride derivatives

[reaction: see text] Anodic fluorination of spiropyrazole-5,3'-chroman-4-ones and their thiochromanone analogues in dimethoxyethane containing Et4NF x 4HF resulted in ring opening of spiroheterocycles, which led to the formation of (5-pyrazolyl)methyl o-carbomethoxyphenyl ethers and their thioether analogues via benzoyl fluoride derivatives.     

Electrolytic partial fluorination of organic compounds. Part 78: Regioselective anodic fluorination of 2-oxazolidinones

Various 2-oxazolidinones were galvanostatically electrooxidized in the presence of various fluoride salts. It was found that a fluorine atom was introduced to the α-position of the nitrogen atom of N-acyl- and N-alkoxycarbonyl-2-oxazolidinones to provide the corresponding α-fluorinated products in moderate to good yields. In the case of N-phenoxycarbonyl derivative, fluorination took place on the phenyl group selectively.     

Electrolytic partial fluorination of organic compounds. 54. Anodic mono- and trifluorination of thiochroman-4-one derivatives and the factors affecting product selectivity

Anodic fluorination of (E)-3-benzylidene-2,3-dihydrothiochroman-4-one and 3-benzyl-1-thiochromone derivatives under a variety of electrolytic conditions was found to provide selectively or exclusively the same fluorinated products: (E)-3-benzylidene-2,3-dihydro-2-fluorothiochroman-4-ones. In addition, di- and trifluorinated derivatives were also obtained depending on the starting heterocycles and electrolytic conditions. The factors affecting the product selectivity were also examined.     

Electroytic partial fluorination of organic compounds. 52. Regio- and diastereoselective anodic fluorination of thiazolidines

Anodic fluorination of N-benzoyl, N-acethyl-, and N-formylthiazolidine derived from L-cysteine was carried out in dimethoxyethane (DME) and acetonitrile containing various supporting fluoride salts using an undivided cell. Highly regioselective fluorination proceeded to provide the corresponding 5-monofluorinated thiazolidine derivatives in good yields in DME, and the diastereoselectivitiy was moderate to high regardless of the supporting fluoride salts. The diastereoselectivitiy of the fluorination was greatly affected by the bulkyness of the subsitituent on the nitrogen atom, and N-benzoylthiazolidine gave much higher diastereoselectivity compared with N-formyl derivative. The fluorination of the thiazolidines was not achieved by commercially available fluorinating reagents such as N-fluoropyridinium salts.     

Electrolytic partial fluorination of organic compounds. 55. Highly regio- and stereoselective anodic monofluorination of 2,3-dihydrochroman-4-one and chromone derivatives.

Anodic monofluorination at the position alpha to the oxygen atom of the (E)-3-benzylidene-2,3-dihydrochroman-4-one derivatives was successfully carried out to provide the corresponding 2-fluorochromanones selectively. This is the first regioselective electrochemical fluorination of fused-type, oxygen-containing heterocyclic compounds. Anodic fluorination of a chromone derivative also gave a similar fluorinated chromanone stereoselectively.     

Electrochemical partial fluorination of organic compounds. 80. Synthesis of cyclic alpha-arylthio-alpha-monofluorophosphonate esters

[Reaction: see text]. Seven-membered cyclic alpha-monofluorophosphonate esters such as 2-allyloxy-3-fluoro-3-phenylthio-4,7-dihydro-[1, 2]-oxaphosphinine-2-oxide were successfully synthesized in moderate total yield as 41% from open-chain allyl phosphonates having an alpha-arylthio group as an electroauxiliary using an alternative sequence of anodic fluorination and ring-closing olefin metathesis (RCM). On the other hand, in an attempt to synthesize an eight-membered analogue, a different type of seven-membered fluorinated cyclic product was formed predominantly by the RCM reaction between the allyloxy groups.     

Electrolytic partial fluorination of organic compounds. 42.(1) marked solvent effects on regioselective anodic monofluorination of 4-oxo-2-pyrimidyl sulfides

Regioselective anodic monofluorination of 4-oxo-2-pyrimidyl sulfides was investigated under various electrolytic conditions. Anodic fluorination was successfully carried out using Et(4)NF.4HF in dimethoxyethane (DME) to provide the corresponding alpha-fluorinated products in good yields. In contrast, acetonitrile (MeCN) was not suitable for the anodic fluorination due to the severe anode passivation during the electrolysis. A mixed solvent of DME and MeCN was found to be also effective for the fluorination, and the product yield increased with an increase of the ratio of DME to MeCN. The superiority of DME can be explained mainly in terms of the suppression of the anode passivation and enhancement of the nucleophilicity of the fluoride ions. Such marked solvent effects on the anodic fluorination were discussed in detail.     

Electrolytic partial fluorination of organic compounds: 89: Regioselective anodic fluorination of tetrazolyl sulfides

Anodic fluorination of five-membered nitrogen-containing heterocyclic sulfides like tetrazolyl sulfides was comparatively studied. The anodic fluorination of tetrazolyl sulfides having α-electron-withdrawing groups was successfully carried out to provide α-monofluorinated tetrazolyl derivatives in moderate yields. This is in sharp contrast to the low efficient anodic fluorination of triazolyl sulfides. Thus, it was found that the efficiency of anodic fluorination is greatly affected by the basicity of the heterocyclic groups of the starting heterocyclic sulfides.     

Electrolytic partial fluorination of organic compounds. Part 51: Electrochemical fluorination of 1-methylpyrroles having electron-withdrawing groups at the 2-position: Effect of supporting fluoride salts on the fluorinated product selectivity

Anodic fluorination of 1-methylpyrroles having electron-withdrawing groups at the 2-position was comparatively studied using Et₃N•3HF and Et₃N•2HF as a supporting electrolyte and a fluorine source. The use of Et₃N•3HF gave trifluorinated products predominantly or selectively depending on solvents used while the use of Et₃N•2HF provided the corresponding monofluorinated pyrrole derivatives in considerable amount along with the trifluorinated products regardless of the solvents. This is the first successful example of selective anodic fluorination of pyrroles. The effects of supporting electrolyte on product selectivity are discussed.     

Surface ionization of organic compounds and its applications

Surface ionization of organic compounds in a weak external electric field involving the formation of many-atomic positive ions is considered (including specific features of the phenomenon, its major characteristics, experimental techniques used and possible applications).

Information is presented on the adsorption of compounds of complex composition which was obtained in studying the phenomenon. A detailed analysis is made of the reactions of particles in the adsorbed layer, as well as of the methods of determining the binding energies of the particles undergoing ionization (primary molecules and many-atomic radicals and complexes produced on the surface) to the surface, and of their lifetimes on the surface against thermal desorption in the charged and neutral states.

Vast possibilities are shown to open up by using the thermally equilibrium processes of many-atomic particle ionization occurring on the surface for the determination of the properties of molecules, radicals and complexes (e.g. thermal stability, the weakest bond energies in ions, ionization potentials of the particles analyzed).

The physicochemical aspects of the surface ionization-based detection of organic compounds and of its applications to analytical mass spectrometry, gas chromatography and analytical chemistry of the atmosphere are considered. Attention is focused upon the fact that the high ionization coefficients observed for a number of compounds ensure a record-high sensitivity when using surface ionization-based detection.     

Electrochemical partial fluorination of organic compounds. 74. Efficient anodic synthesis of 2-fluoro- and 2,3-difluoro-2,3-dihydrobenzofuran derivatives

Anodic fluorination of 3-substituted benzofuran derivatives in a variety of fluoride salts resulted in the formation of three fluorinated products; two stereoisomers of 2,3-difluoro-2,3-dihydrobenzofuran (cis and trans) and cis-2-fluoro-3-hydroxy-2,3-dihydrobenzofuran derivatives. Dehydrofluorination of the main products, cis-difluoro derivatives, furnished the nonaromatic 2-fluoro-3-benzofuranyledene derivatives instead of the aromatic 2-fluorobenzofuran derivatives.     

Application of aza-transfer to organic compounds : Reactions between heterocyclic diazo compounds and hydrazines

Aza-transfer reactions between heterocyclic hydrazines and diazonium salts or between heterocyclic diazo compounds and substituted hydrazines have been investigated. The reaction proceeds via intermediate tetrazenes and labelled compounds have been used to elucidate the reaction mechanism.     

Electrolytic transformation of functional groups of fluoroorganic compounds. I. Anodic methoxylation and acetoxylation of trifluoroethyl sulfide

Anodic methoxylation and acetoxylation of phenyl trifluoroethyl sulfide were successfully performed to give the corresponding α-methoxy and α-acetoxy sulfides in good to excellent yields, respectively. These products were found to be useful building blocks for the synthesis of fluoroorganic compounds.     

Recent advance in heterocyclic organozinc and organomanganese compounds; direct synthetic routes and application in organic synthesis

A practical synthetic route for the preparation of 2-pyridyl and 3-pyridyl derivatives has been accomplished by utilizing a simple coupling reaction of stable 2-pyridylzinc bromides and 3-pyridylzinc bromides. The organozincs used in this study were easily prepared via the direct insertion of active zinc into the corresponding bromopyridines. The subsequent coupling reactions with a variety of different electrophiles have afforded the corresponding coupling products. Using highly active manganese, a variety of Grignard-type organomanganese reagents have been obtained. The subsequent coupling reactions of the resulting organomanganese reagents with several electrophiles have also been accomplished under mild conditions.