Fluorine elimination

Heptafluoro-2-naphthyllithiuni prepared by metalation reaction can thermally decompose to a hexafluoro-l,2-naphlhalyne by elimination of lithium fluoride [36, 37] In this organolithium compound, fluorine elimination can occur from either position 1 or 3, however, no evidence for fluorine elimination from position 3 IS observed... 

These results provide extra evidence for the hypothesis of simultaneous chain growth polymerization and fluorine elimination via interaction with energetic species in the formation of plasma polytetrafluorethylene. This is also consistent with the observation that for a plasma of C2F4 confined in a closed system the pressure decreases initially to a minimum (polymerization) and then increases (fluorine elimination) producing a non-condensible gas ° . 

Carbonyl complexes of nickel and perfluoroketonesin donor solvents are thermally stable against fluorine elimination. However, in the presence of iodobenzene loss of fluorine has been observed with a concomitant benzoylation at the carbonyl oxygen.213... 

Partial Substitution of Fluorine Elimination of One Fluorine Atom... 

Perfluoronaphthalene undergoes multiple fluorine elimination by sulfur nucleophiles under similar conditions.3 Whereas the 2.6-bis(alkylsulfanyl)hexafluoronaphthalenes (alkyl = Me, Et, i-Pr) can be obtained in good yields (< 53%), tetra- and penta-substituted products are accessible in very poor yields. However, moderate yields of hexakis(alkylsulfanyl)-substituted products can be obtained in hexamethylphosphoric triamide, i.e. under conditions suitable for complete replacement of all fluorine atoms.3... 

Finally, the metal-perfluoroalkyl linkage also appears to be less susceptible to facile decomposition by the a- or -elimination pathways that dominate much of the chemistry of hydrocarbon alkyls and lead to metal hydrides. The absence of these reaction pathways, at least for the later transition metals, may reflect the relative strength of the C—F bond versus the M—F bond compared to C—H/M—H analogues (32). However, a-fluoride abstraction reactions can be accomplished with exogenous fluoride acceptors to give fluorinated carbene complexes (see Section III,B,1). One example of an apparent -fluorine elimination reaction is shown in Eq. (2) (33) and presumably is driven by the stronger bond to fluorine formed by early transition... 

Although fluorinated triazolines exhibit unusual thermal stability,145 fluorine elimination can be effected under the influence of tetrakisdimethyl-aminoethylene as a catalyst (Scheme 141).14 ... 

The polymers from this group show excellent thermal stability when they do not contain hydrogens, for example, when they are perfluorinated. Compounds having both hydrogen and a halogen (such as fluorine) eliminate the hydrohalogenated acid (HF, HCI, etc.) at lower temperatures. Some literature reports on thermal decomposition for this group of compounds are indicated in Table 8.2.1 [1]. 

Burke (1970) found that fluorine inhibited the sodium-potassium pump and resulted in dysfunction of the iodine pump indirectly, as well as low iodine uptake, thus decreasing serum thyroid hormone levels. KendaU-Taylor (1972) proved that fluorine decreased the production of 3 —5 -cyclic adenosine monophosphate by inhibiting adenylcyclase in the thyroid fluorine also blocked stimulation by TSH. It was also reported that fluorine eliminated 1 from the thyroid in the form of iodized protein. Few studies were reported on synergistic action of iodine and fluorine. 

Schlosser developed a fluorine sacrihcial route to 5-fluoropyrazoles.Treatment of methyl 3-methoxy-2-trifluoromethyl-2-propenoate with aryl or heteroaryl hydrazines resulted in nucleophilic displacement of the methoxy group. Under weakly basic conditions, cyclization occurred with fluorine elimination to give 1-(het)aryl-4-carboxymethyl-5-fluoropyrazoles 126 in moderate yields. The reaction with alkyl hydrazines resulted in no heterocychzation (Fig. 3.72). 

These reactions have also been studied by DFT. When the set of four ruthenium isomers is considered (Scheme 51), it becomes clear that the [Ru(H)F(PH3)2(GO)(=GF2)] is almost equienergetic with [RuH(GF3)(PH3)2(GO)]. However, the fluorocarbene complex, [RuF2(PH3)2(GO)(=GFH)], is substantially more stable, and the difluoromethyl complex, [Ru(GF2H)F(PH3)2(GO)], is the most stable of all in accord with experiment. The calculated structure of [RuH(GF3)(PH3)2(GO)] shows a remarkable distortion of the GF3 group in which one fluorine is brought close to the metal (2.626 A) while extending its G-F bond (Scheme 51). This structure resembles that of an agostic alkyl, and clearly assists the a-fluorine elimination. " ... 

PCP)Ir(H)(F)(olefin) (Fig. 4.17). Presumably, ethylene is lost from this six-coordinate species to afford the hydrido fluoride product the free ethylene then displaces NBE from (PCP)F(NBE) to form the (PCP)Ir(ethylene). For 2-fluoropropane, the same general mechanism applies, but the propylene formed from j8-fluorine elimination binds less strongly than ethylene to (PCP)Ir, thus eventually allowing quantitative conversion to (PCP)Ir(H)(F). 

---