Fluorine carbon coupling

Fluorine-carbon coupling constants, measured for 2-, 3-, and 4-fluoropyridine and pyridinium ions, (155) have been compared with values calculated assuming only the Fermi contact mechanism. Many of the experimental trends are paralleled by those for V(C-H) values observed in pyridine and fluorobenzene. The INDO calculations qualitatively reproduce the experimental trends. 

Table 7.59 Carbon-Fluorine Spin Coupling Constants 7.109...

The same research group additionally presented further investigations on fluor-ous-phase palladium-catalyzed carbon-carbon couplings [93]. Fluorinated aryl octyl-sulfonates were reacted in slight excess with arylboronic acids under microwave con-... 

The magnitude of carbon-fluorine coupling attenuates with coupling distance in alkyl and cycloalkyl fluorides, as shown in Tables 4.20(b) and 4.21. Analogously to vicinal proton-proton, carbon-proton and carbon-carbon coupling (Sections 3.2.2.4, 3.2.4.2), 37cf depends on the dihedral angle enclosed by the C—C—C —F connection, and Karplus cosine relations such as eq. (4.7) have been derived empirically [266] and theoretically [267],... 

Table 6.49 Carbon-Fluorine Spin Coupling Constants. 6.94...

Newmark, R.A. and Hill, J.R., Carbon-13-fluorine-19 coupling constants in benzotrifluorides, Org. Magn. Reson., 9, 589, 1977. 

Another principal method is the fluorovinylation of suitable precursors by transition metal-catalyzed carbon-carbon coupling reactions [13]. Activated fluorovinyl species can be conveniently generated in situ from commonly used hydrofluorocarbons, for example HFC-134a [14] (Scheme 2.192). Fluorinated vinyl zinc halides are often used for the coupling reactions, but other activated species, for example stannanes [15] or boronates [16], have also been applied successfully. 

The anodic oxidation of carboxylic acids has also been carried out using a solid-supported base in methanol. Non-Kolbe-type electrolysis takes place to give the corresponding methoxylated product (Equation 12.7). The acid-base reaction between a carboxylic acid and a solid-supported base seems to reduce the cell voltage and makes the electrochemical reaction possible. Kolbe-type carbon-carbon coupling using aliphatic and benzylic carboxylic acids has also been accomplished using this method [26]. Based on a similar concept, anodic fluorination by an alkali metal... 

Figure 14.2 shows the quantitative NMR spectrum of the same monomer. The terminal vinylic carbon signals (Cl, CF=CF2) are represented as a fluorine-coupled distinct ddd pattern from 144 to 150 ppm with a strong 1-bond fluorine to carbon coupling constant Jp c of 275 Hz. The internal vinylic carbon (C2, CF=Cp2) also exhibited a ddd pattern from 132 to 135 ppm, which however, appears partially overlapped with a strong aromatic carbon signal (C4). 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

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