Substituents perfluoro

Trapping of carbanions by reactive fluorinated aromatic compounds gives a very simple method of introducing bulky perfluoro substituents (Scheme 28), and the more recent use of TDAE (43) to initiate these processes is discussed in the next section (see Scheme 32). 

Carbocarbonylation [216] of alkyl halide with a perfluoro substituent leads directly to the analogous carboxylic acids and esters, provided the ) -hydride elimination is slower than CO insertion. The use of PdCl2(dppf) in the esterification of 68 gives... 

The examples previously presented have featured ANRORC reactions on 6-membered rings. More recently, ANRORC-type rearrangements have been observed in dieir five-membered counterparts, although most examples feature oxadiazoles with bidentate nucleophiles. Spinelli has shown that oxadiazoles with perfluoro-substituents (46) undergo reaction with hydroxylamine to form oxadiazoles (47) with a net reversal in substitution pattern. A perfluoro-group is required at the 5-position for reactivity, as the product 3-perfluoro-oxadiazole (47) is inert to the reaction conditions (preventing reversibility). Hydrazine also efficiently reacts with oxadiazoles to form 1,2,4-triazines. 

Fluorinated indolizines remained relatively rare class of compounds. In contrast to indolizines substituted at pyrrole fragment the structures having a perfluoro-substituent in the pyridine ring are less available. This is caused by the fact that 3... 

Under flash vacuum thermolysis (FVT) the 1,2,3-triazine (32) was readily thermolyzed to an alkyne, a nitrile, and nitrogen in high yields. For unsymmetrically substituted 1,2,3-triazines as FVT substrates, fragmentation proceeded selectively a bulky substituent at C-4(6) made the adjacent C—N bond break more easily than the opposite C—N bond. The FVT method was applied to the synthesis of the fluorinated alkynes, perfluoro-3-methyl-l-butyne and difluoroethyne [(33), R = (CF3)2CF, F] (Equation (1)) (89CC1657, 91CC456). It has been claimed, however, that tris(dimethylamino)-1,2,3-triazine forms the monocyclic azete. 

When there is a hydrogen or perfluoroalkyl substituent on the alk-l-ene chain, Lewis acid catalyzed migration of the C = C bond to the 3-position can proceed to minimize the number of alkenic fluorine atoms,3 as illustrated by the isomerizations of 4//-perfluorobut-l-ene (3),8 4//-perfluoro(5-methylhex-l -enc) (5),18 perfluoro(4-methylpent-2-ene) (7),14 and perfluoro(3-methylcyclopentene) (9).2 3... 

The prefix per, as in perdeuterio- or perfluoro-, means that all the hydrogens have been replaced with the named substituent, D or F. Perhydro means saturated or fully hydrogenated. 

The He(l) photoelectron spectrum of trithiadiazepin 5 was assigned by Koopmans correlation with PM3 eigenvalues based on the structural data, and by the 7i-perfluoro effect observed. The 7i-system can be rationalized by heteroatom first-order perturbation, which reduces the cyclic Jt-delocalization. Replacement of the four F substituents by FI affected neither the long-wavelength absorption band in the UV/Vis (Vis = visible) spectrum nor the S1SN shift in the 15N NMR <1997CBR247>. 

All aspects of the structure, reactivity and chemistry of fluorine-containing, carbon-based free radicals in solution are presented. The influence of fluorine substituents on the structure, the stability and the electronegativity of free radicals is discussed. The methods of generation of fluorinated radicals are summarized. A critical analysis of the reactivities of perfluoro-n-alkyl, branched chain perfluoroalkyl and partially-fluorinated free radicals towards alkene addition, H-atom abstraction, and towards intramolecular rearrangement reactions is presented. Lastly, a summary of the synthetically-useful chemistry of fluorinated radicals is presented. 

To summarize the considerable available structural data with respect to fluorine substitution, one can conclude that non-conjugated carbon radicals bearing at least two fluorine substituents will be strongly pyramidal, a-radicals, while //-fluorine substituents appear to have little influence on the geometry of a radical. The strong a-character of CF3, CHF2, and perfluoro-n-alkyl radicals has a considerable influence on their reactivity. 

Fig. 3. Plot of the log of the rate constants for addition of perfluoro-n-octyl radicals to some para-substituted styrenes Hammett a values of the substituents...

The type of chemistry outlined here should also be extended to other elements, e.g., B, Si, Ge, Sn, etc., by attempting to prepare compounds like R3 nB(NSO)n, R4 nE(NSO)n, E = Si, Ge, Sn, and R2Te(NSO)2 with R = halogen, organo, or perfluoro-organo substituents. 

In the reaction of perfluoro-5-azanon-4-ene with 2,6-dimethylaniline, the attack at the carbon atom of the new N=C bond forms a six-membered heterocycle derived from dihydroquinazoline (00JFC(104)263). If the 2,6-positions of the benzene ring of aniline contain electron-donor substituents... 

Monoethanolamine reacts with perfluoro-2-methylpent-2-ene in the presence of triethylamine, forming 7-fluoro-5-pentafluoroethyl-6-trifluoro-methyl-2,3-dihydro[l,4]oxazepin 135 (OlJFC(llO)l 1). If the compound has bulky substituents in the -position relative to the amino group, attack at the internal double bond is sterically hindered, and the internal olefin isomerizes in the presence of the base to the terminal olefin. The attack of the N-nucleophilic center of monoethanolamine occurs at the carbon atom of the terminal double bond, giving 5-fhioro-3,3-dimethyl-7-pentafluoroethyl-6-trifhioromethyl-2,3-dihydro[l,4]-oxazepin 136 or 137 as the major product. 

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