Fluorination desulfurative

Partial fluorination of 4-arylthio-l,3-dioxolan-2-ones occurs preferentially at the carbon atom adjacent to the thio group [67]. However, a remarkable solvent effect is encountered. In the more polar solvent, dimethoxyethane substitution occurs, while in the less polar dichloromethane a larger portion of the desulfurization with cleavage of the phenylthio group takes place. This is attributed to the fact that the intermediate radical cation is more stable in the polar solvent and undergoes deprotonation, while in the less polar solvent, the less stabilized radical cation dissociates into a dioxolane cation and a phenylthio radical. 

Ar—O—CF3 and Ar—O—CHF2 type compounds are now accessible through the desulfurization-oxidative fluorination of dithiocarbonates and dithiianes. ° Introduction of a O—CHF2 group can also be performed by adding the corresponding difluorocarbene onto the phenolic hydroxyl (cf. Chapter 2). ° ... 

The oxidative desulfurization-fluorination of methyl A,-alkyl-A,-pyridyl(or pyrimidin-yl)dilhiocarbamates produces the corresponding (trifluoromethyl)amino-substituted pyridines (or pyrimidines) 5.69... 

Oxidative Desulfurization-Fluorination of Methyl A - Alkyl- V-heteryldithiocarbamates General Procedure 49... 

Tetrabutylammonium dihydrogen trifluoride also performs oxidative desulfurization fluorina-tion of 2-substituted l,l,l-txis(methylsulfanyl)ethanes in the presence of DBH leading to a new route to partially fluorinated alkenes. l,l,l-tris(methylsulfanyl)-5-phenylpentane (22) reacts with TBADTF in the presence of DBH to give the fluoro derivative 23, which is converted to the fluoroalkene 25 via the sulfoxide 24 followed by pyrolysis.217... 

Desulfurization-fluorination reactions of organosulfur compounds were used to synthesize organolluorine derivatives under mild conditions [255]. Hiyama et al. reported such processes for xanthates [256], dithiocarbamates [257] and arenedithiocarboxylates [258]. The procedure given here is representative. 

The same reagent combination—that is, NO+BF.4 (used in an excess of 1.2 equivalent) in conjunction with PPHF—also induces desulfurative fluorination of phenylsulfides521 (Scheme 5.51). A possible mechanism includes the intermediate cation 131, which undergoes fluorination via an SN2 or SN1 pathway. Dithiolanes,... 

Selective introduction of a fluorine atom into organic compounds is important due to the unique biological and physical properties of fluorinated compounds. One useful method for C-F bond formation is desulfurative fluorina-tion realized by a cleavage of C-S bonds of dithioacetals. Thus, 1,3-ditholane derivatives undergo a facile reaction... 

It is well known that halomethyleneiminium salts, often prepared in situ (see Section 2.1.2.2) react with ammonium salts, primary amines, secondary amides, urea and IV-substituted ureas to afrbrd amidinium salts, from which the free amidines can be obtained by addition of bases. > 4 Some recent results are given below. Dimethylformamide chloride and other 7V,iV-disubstituted formamide chlorides were reacted with acetanilides, chloroacetanilides, 6-aminopenam derivatives, 2-aminopyrimidine, 4-aminouracil, 2-amino-4-chloropyridazine, 2-aminothiazole, 2-aminobenzothiazole and thiobenzamides to give the amidines via the amidinium salts. In the reaction of MA -disubstituted formamide chlorides with thiobenzamides the solvent seems to be decisive for the course of the reaction. In tertiary formamides the thiobenzamides are desulfurized to nitriles, whereas in CHCI3 or CCI4 amidinium salts (296 Scheme 45) are formed. From trimethylsilyl isocyanate and the fluorinated amine (297) the /V-fluorocarbonylamidine (298) is accessible. ... 

The fluorination product 66 was then treated with acetic acid followed by reductive desulfurization with Raney nickel in aqueous NaOH to give defluorination product ddG, but not FddG (2). Accordingly, we tried the desulfurization of compound 66 in various solvent systems prior to deprotection with the acid. After several unsuccessful attempts, we obtained the desired Tr2-FddG 67 in 61% isolated yield when we carried out Raney-nickel reduction in toluene. This method is advantageous because fluorination can be achieved using the scalable reagent NfF. 

Deoxyschizandrin, synthesis of 1278, 1280 Deprotonation 92-105 energy of 3, 97-100 Depsides 942-944 Derivative isotherm summation 944 Derivative spectrometry 929, 984 Derivatization, pre-analysis 985-991 DesMarteau sulfonimide, as electrophilic fluorinating agent 647 Desulfurization 1079 Detoxification, of phenoUc compounds 1361-1363... 

Dithioacetales 104 have been transformed into difluoromethyl derivatives 105 a one-pot desulfurative fluorination of dithiolane led to the synthesis of difluoroalkylthiophene. Treatment of the dithioacetales 104a, b with pyridinium polyhydrogen fluoride (PPHF) and nitrosyl tetrafluoroborate at 0 °C led to 3-(l,l-difluoroheptyl) thiophene 105a (40 %) or 3-(l,l-difluorononyl)thiophene 105b (30 %) [65]. 

The first is fluorination of cyclopenta[c]thiophene-4,6-dione 106 by treatment with A-fluoro-6-(trifluoromethyl)pyridinium-2-sulfonate (MEC-04B) in ethyl acetate to give l,3-dibromo-5,5-difluorocyclopenta[c]thiophene-4,6-dione 107 in 84 % yield. Then, conversion of the two carbonyl groups to difluoromethylene groups was accomplished via formation of the bis-l,3-dithiolane derivative 108 followed by desulfurative fluorination with hydrofluoric acid-pyridine complex and dibromatin (l,3-dibromo-5,5-dimethylhydantoin) in dichloromethane to afford 1,3-dibromohe xafluorocyclopenta[c]thiophene 109 in a two-step yield of 73 % [Id, 67]. 

Hiyama [22] et al. developed the oxidative desulfurization-fluorination of dithio-carbonates (xanthogenates) by treatment with l,3-dibromo-5,5-dimethylhydantoin (DBH) or N-bromosuccinimide (NBS) and a huge excess of 70 % hydrogen fluoride-pyridine (Olah s reagent, up to 80 equivalents). The corresponding trifluoromethyl ethers are formed in moderate to excellent yields. 

Kuroboshi M, Suzuki K, Hiyama T (1992) Oxidative desulfurization-fluorination of xanthates. A convenient synthesis of trifluoromethyl ethers and difluoro(methylthio)methyl ethers. Tetrahedron Lett 33 4173 176. doi 10.1016/S0040-4039(00)74681-8... 

A review of the scope and limitations of fluoro-Pummerer rearrangements, oxidative desulfiirization-fluorination, and oxidative desulfurization-di- and tri-fluorination reactions for the synthesis of fluorinated compounds has been reported. ... 

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