Generation and reactions of halodifluoromethide ions

Wheaton, Gregory A.; Burton, Donald J.

doi:10.1021/jo00407a018

Cited by 45 publications

(6 citation statements)

References 8 publications

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“…Thus, by choosing a different solvent mixture during electroreduction, the reaction could be funneled through a predominantly anionic or radical pathway. We believe that the solvent TDA-1 increases the lifetime of the radical cage formed during the first electron transfer step of the reduction, permitting the dominance of the radical-derived product 3 , whereas HMPA, well known for its great stabilizing effect on the anionic species, favors the formation of anion-derived product 2 …”

Section: Resultsmentioning

confidence: 99%

“…Alternatively to the anionic pathway, reaction 1 can be considered to be due to difluoromethylene insertion into the silicon−chlorine bond (generation of the CF 2 carbene via α-elimination from the CF 2 Cl - anion is regarded as a facile process ). However, this possibility was ruled out when Me 3 SiBr was used instead of Me 3 SiCl as an electrophile.…”

Section: Resultsmentioning

confidence: 99%

“…This suggests that the reaction does not follow the carbene insertion pathway. Considering the high propensity of the CF 2 Cl - for an α-chloride elimination, the cationic aluminum species formed during the oxidation of aluminum in the system must efficiently stabilize the intermediate chlorodifluoromethyl anion CF 2 Cl - .…”

Section: Resultsmentioning

confidence: 99%

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Preparation of and Fluoroalkylation with (Chlorodifluoromethyl)trimethylsilane, Difluorobis(trimethylsilyl)methane, and 1,1,2,2-Tetrafluoro-1,2-bis(trimethylsilyl)ethane

et al. 1997

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CF2BrCl reacts with aluminum/N-methylpyrrolidinone in the presence of chlorotrimethylsilane to give Me3SiCF2Cl in high yield. Similarly, CF2Br2 gives Me3SiCF2Br with bromotrimethylsilane. Chlorodifluoromethylation of aldehydes using Me3SiCF2Cl and a catalytic amount of TBAF in polar solvents occurs at room temperature, providing difluoromethylated alcohols in two steps. Electroreduction of Me3SiCF2Cl in the presence of chlorotrimethylsilane gives Me3SiCF2SiMe3 (anion-derived product) and Me3SiCF2CF2SiMe3 (radical-derived product). Using THF/HMPA strongly favors the former, whereas THF/TDA-1 (tris(3,6-dioxaheptyl)amine) the latter. Me3SiCF2SiMe3 difluoromethylates aldehydes acting as a difluoromethylene dianion (“CF2 2-” equivalent), whereas Me3SiCF2CF2SiMe3 acts at room temperature as an in situ source for the perfluorovinyl anion (due to β-elimination of fluorotrimethylsilane). However, at low temperature the elimination pathway is suppressed and tetrafluoroethylene dianion (“-CF2CF2 -” equivalent) behavior is observed. The structure of Me3SiCF2CF2SiMe3 was analyzed by X-ray diffraction. All of the studied fluoroalkylating reagents are moisture- and air-stable and can be readily obtained from a single convenient precursor (CF2BrCl).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Preparation of and Fluoroalkylation with (Chlorodifluoromethyl)trimethylsilane, Difluorobis(trimethylsilyl)methane, and 1,1,2,2-Tetrafluoro-1,2-bis(trimethylsilyl)ethane

et al. 1997

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“…30 Such a behavior is attributed to the ability of the BrCF 2 anion to readily α-eliminate bromide to form the singlet difluoromethylene under the reaction conditions. 56,57 However, the Dilman group used excess bromide in the reaction mixture and this allowed the transient BrCF 2 anion to be available for the nucleophilic bromodifluoromethylation of aromatic and nonenolizable aldehydes (Scheme 15, A). 58 The excess bromide is proposed to combine with difluoromethylene to push the equilibrium towards the BrCF 2 anion, which was confirmed by treating the Ruppert-Prakash reagent, Me 3 SiCF 3 (1), with excess LiBr in the presence of benzaldehyde providing the bromodifluoromethylated alcohol.…”

Section: (Bromodifluoromethyl)trimethylsilane (Me 3 Sicf 2 Br)mentioning

confidence: 99%

Silicon-Based Reagents for Difluoromethylation and Difluoromethylenation Reactions

Krishnamoorthy

Prakash

2017

Synthesis

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There have been significant developments in the area of perfluoroalkyl group transfer using silicon reagents, specifically in nucleophilic trifluoromethylation. The mild and versatile activation conditions bestow significant synthetic prowess to the silicon reagents in the area of fluoroalkylations. Owing to the importance of difluoromethylene (CF2) containing compounds in pharmaceuticals, materials, and agrochemicals, several CF2 group transfer methods using related silicon reagents have been developed and studied in detail. This review summarizes the recent developments and trends in this area.1 Introduction2 Trimethyl(trifluoromethyl)silane (Me3SiCF3)3 (Difluoromethyl)trimethylsilane (Me3SiCF2H)3.1 Nucleophilic Addition3.2 Nucleophilic Substitution3.3 Nucleophilic Difluoromethylation of Electron-Deficient Heterocycles3.4 Metal-Mediated Cross Coupling3.5 Oxidative Coupling of Terminal Alkynes4 Post-functionalizable Difluoromethyl Transfer Reagents4.1 (Chlorodifluoromethyl)trimethylsilane (Me3SiCF2Cl)4.2 (Bromodifluoromethyl)trimethylsilane (Me3SiCF2Br)4.3 [Difluoro(iodo)methyl]trimethylsilane (Me3SiCF2I)4.4 [Difluoro(phenylthio)methyl]trimethylsilane (Me3SiCF2SPh)4.5 [Difluoro(phenylsulfonyl)methyl]trimethylsilane (Me3SiCF2SO2Ph)4.6 Diethyl [Difluoro(trimethylsilyl)methyl]phosphonate [Me3SiCF2P(O)(OEt)2]4.7 Ethyl Difluoro(trimethylsilyl)acetate (Me3SiCF2CO2Et)4.8 Difluoro(trimethylsilyl)acetamides (Me3SiCF2CONR2)4.9 Difluoro(trimethylsilyl)acetonitrile (Me3SiCF2CN)5 Others6 Conclusions

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“…-H,0 CHCl, + HO" -^CCl-r -:CC12 + Cl" + H,0 Geminal fluorine atoms appear to destabilize the carbanion intermediate in favor of more rapid formation of difluorocarbene, by a concerted o-elimination process (25), The haled ifluoromethide ion, CXF2_, is bypassed here but has been generated and utilized in other processes (26). Once formed the electron deficient carbene species can be trapped by an olefin or interact in an ionic chain mechanism with nucleophiles:…”

Section: Ch2i2-^ch2f1mentioning

confidence: 99%