Sulfones, sulfoxides, sulfonates trifluoromethyl

Bromination of the enol ether product with two equivalents of bromine followed by dehydrobromination afforded the Z-bromoenol ether (Eq. 79) which could be converted to the zinc reagent and cross-coupled with aryl halides [242]. Dehydrobromination in the presence of thiophenol followed by bromination/dehydrobromination affords an enol thioether [243]. Oxidation to the sulfone, followed by exposure to triethylamine in ether, resulted in dehydrobromination to the unstable alkynyl sulfone which could be trapped with dienes in situ. Alternatively, dehydrobromination of the sulfide in the presence of allylic alcohols results in the formation of allyl vinyl ethers which undergo Claisen rearrangements [244]. Further oxidation followed by sulfoxide elimination results in highly unsaturated trifluoromethyl ketonic products (Eq. 80). 

E)-3-Arylidenethiochroman-4-oncs possess thioether and oi,[)-unsaturatcd ketone functionalities both of which are susceptible to oxidation by DMD. In fact, chemoselective oxidation at sulfur is observed with a separable mixture of the sulfoxide and sulfone being produced in >5 1 ratio. A similar situation holds for the related thioflavanones. Epoxidation of the alkenic double bond in the thiochromanone 1,1-dioxides alone can be achieved using methyl(trifluoromethyl)-dioxirane (Scheme 65) <1994T13113>. However, reaction of NaOCl with 3-arylidenethioflavanones gives the epoxide and subsequent oxidation with DMD then gives a mixture of the sulfoxide and sulfone <2003MRC193>. 

Trifluoromethyl-substituted sulfides, sulfoxides, and sulfones can undergo [4-F 2]-cycloaddition reactions with various dienes under thermal conditions (Table 2) sec also formation of 15 and 17. 5... 

Table 2. [4 + 2] Cycloadditions with Trifluoromethyl-Substitutcd Sulfides, Sulfoxides, and Sulfones...

Perfluorinated oxaziridine 80 oxidizes 1-trifluoromethyl vinyl sulfides 134 to the corresponding sulfoxides 135 in high yields at -50°C (Table 8) <1996S399>. However, at room temperature, sulfones are formed... 

Electrolytic desulfurization of o-aminobenzyl sulfide, sulfoxide or sulfone illustrates carbon-sulfur bond cleavage. Careful control of the reaction conditions is important to achieve chemoselectivity (Scheme 17). Trifluoromethyl substituents are not reduced under the conditions used (Cd sheet ca-... 

Scheme 2.178 Conversion of sulfonyl and sulfinyl halides to the corresponding trifluoromethyl sulfones and sulfoxides by nucleophilic trifluoromethylation [38].

Organic fluorine compounds and methods for their preparation are the central topic of the next four procedures. Much of the synthetic versatility of methyl phenyl sulfone is embodied in FLUOROMETHYL PHENYL SULFONE and the fluoro Pummerer reaction of methyl phenyl sulfoxide with DAST is a key step in its preparation. The utility of this fluoromethyl sulfone in the preparation of fluoroalkenes Is demonstrated in a companion procedure for Z-[2-(FLUOROMETHYLENE) CYCLOHEXYL]BENZENE, a procedure with several prominent stereoselective features. Geminal difluoroalkenes are featured in the following procedure. (3,3 DIFLUOROALLYL)TRIMETHYLSILANE is prepared by a method in which the radical addition of dibromodifluoromethane to alkenes and the selective reduction of a-bromoalkylsilanes are key steps. A procedure for nucleophilic introduction of the trifluoromethyl group completes this set. The key reagent, (TRIFLUOROMETHYL)-TRIMETHYLSILANE is obtained by reductive coupling of TMS chloride and bromotrifluoromethane. Liberation of a CF3- equivalent with fluoride ion in the presence of cyclohexanone affords 1-TRIFLUOROMETHYL-1-CYCLOHEXANOL. 

Nucleophilic attack of t-BuO anion on carbon, sulfur, or silicon conqiounds such as TMSCP3, 4 secondary trifluoroamides and trifluoroacetates, secondary trifluoromethanesulfinamides and trifluoromethanesulfinates, and trifluoromethyl sulfoxides and sulfones allows the transfer of a trifluoromethyl carbanion to various electrophilic acceptors, such as nonenolizable ketones and aldehydes (eq 54). ... 

TMSCF3 reacts with dimethyl sulfoxide in the presence of catalytic amount of TBAF to give Me2CF3SOTMS. Arylsul-fonyl fluorides react with TMSCF3 to give the corresponding trifluoromethyl sulfones. ... 

Sulfur, Selenium and Tellurium Derivatives. TMSCF3 reacts with elemental sulfur, selenium or tellurium in the presence of a fluoride anion, leading to trifluoromethylthiolates, seleniates or tellurates, respectively.Aryltrifluoromethyl-sulfides, sulfoxides and sulfones were obtained from the corresponding arylsulfenyl, sulfinyl and sulfonyl halides, respectively, by treatment with TMSCF3 and TASF. The reaction of disulfides and diselenides with TMSCF3 and TBAF gave trifluoromethyl thioethers and selenoethers, respectively (eq 26). The same procedure can also be carried out from thiocyanates and selenocyanates. 

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