Pentafluoropyridine reaction with

This overall synthetic strategy (see Figure 11.8) was adapted to give a range of isomeric pyrido[2,3-/z]pyrazincs structures 34 by simply varying the order of reaction with appropriate mono- and difunctional nucleophiles [57, 58] (see Table 11.6). For example, reaction of sodium phenylsulfinate with pentafluoropyridine gives the... 

Substitution reactions of pentafluoropyridine occurred with nucleophiles in the presence of alkali metal fluorides in graphite (84IZV2158). Treatment... 

Tetrafluoropyridazine, 37 times more reactive than pentafluoropyridine in the reaction with ammonia, with octafluoroisobutene at high temperature gives exclusively perfluoro-3,6-di-f-butylpyridazine (184), whereas... 

Tetrafluoro-4-trifluoromethylthiopyridine 136 was prepared in high yield by the reaction of pentafluoropyridine 119 with the CF3S anion, generated from F2C=S or its trimer, and cesium fluoride at — 15°C (Scheme 6.40). 

Pentafluoropyridine Reactions of pentafluoropyridine with nucleophiles proceed very readily and, in the vast majority of cases, substitution of fluorine located at the 4-position is achieved regioselectively. Reactions involving a very wide range of oxygen, nitrogen, sulfur, and carbon-centered nucleophiles have been reported and representative examples of such processes are indicated in Table 8.2. Of... 

The order of nucleophilic substitution for the displacement of fluorine atoms in pentafluoropyridine, as outlined above, is generally in the order 4 > 2 > 3, but this reactivity can be altered by reaction with bifunctional nucleophiles. Substitution of the 4-position may be followed by attack at the adjacent 3-position due to the geometric constraints of the system as outlined in Fig. 8.9. Similarly, tetrafluor-opyridine derivatives bearing substituents at the 4-position react with appropriate difunctional nucleophiles to give poly functional annelated sy stems. 

The annelated systems described above arise from intramolecular attack by two nucleophilic centers upon the pentafluoropyridine unit. In contrast, reaction of an excess of pentafluoropyridine with similar difunctional nitrogen nucleophiles gives access to systems in which two pyridine units are linked by a bridging unit which, upon reaction with a further equivalent of difunctional nucleophile, release... 

The formation of a fluorocarbanion by deprotonation of ethyl a-H-hexafluoro-isobutyrate and its reaction with pentafluoropyridine have been reported (Scheme 66). Treatment of perfluoro-(4-isopropyIpyridine) with sodium azide gives the... 

Substitution of pentafluoropyridine with 2-bromothiphenol yields the 4-substituted derivative (54). Further treatment with butyl lithium results in lithium-bromine exchange followed by intramolecular substitution of the 3-fluorine to give the cyclized product (55). In the corresponding reaction with 2-bromophenol, the final product, (56), is likely to be formed following a Smiles rearrangement of the lithiated intermediate. There has been a detailed kinetic and computational study of the substitution of fluorine at the 6-position of 2,5,6-trifluoronicotinonitrile by... 

Dmowski W, Haas A (1985) Chimia 39 185 (b) Dmowski W, Haas A (1987) Trifluoro-methanethiolate ion. Part 2. Nucleophilic substitution in pentafluoropyridine. Synthesis and characteristics of trifluoromethylthio and trifluoromethylsulphonyl derivatives. J Chem Soc Perkin Trans 1 2119-2124. doi 10.1039/P19870002119 (c) Dmowski W, Haas A (1988) Tiifluoromethanethiolate ion. Part 3. Reactions with tetrafluoropyridazine and tetrafluoropy-limidine. J Chem Soc Perkin Trans 1 1179-1181. doi 10.1039/P19880001179... 

Tetrafluoro-4-trifluoromethylthiopyridine (240) was prepared in high yield by the reaction of pentafluoropyridine (144) with the CF3S anion, generated from F2C=S or its trimer, and cesium fluoride at -15 °C [139] (Scheme 71). When the trimer was used as a precursor of the CF3S anion compound 240 reacted further at 20 °C to give a mixture of polysubstituted pyridines 241-243 in the ratio of 4.5 2 1, respectively. When the reaction mixture was then heated at 100 °C both compounds 241 and 243 were fully converted into compound 242. Compound 242 was the only product (65 %) of the reaction which was carried out at 100-110 °C [141] (Scheme 71). 

Although photo-cycloadditions to benzene are well established, analogous reactions with pyridine, which, unlike benzene, has a non-bonding HOMO, are scarce. However, photoelectron spectroscopy shows that for perfluoropyridine the HOMO is rr-bonding, and that cyclo-adducts are to be expected. In fact, pentafluoropyridine undergoes photo-addition with ethylene to give a mixture of the 1 1 and 1 2 adducts (31) and (32). ... 

Several methods for the preparation of unsymmetrical sulfur diimides RN=S=NR have been developed. One approach involves the addition of a catalytic amount of an alkali metal to a mixture of two symmetrical sulfur diimides, RN=S=NR and RT8i=S=NR. A second method makes use of alkali-metal derivatives of [RNSN] anions.Eor example, derivatives in which one of the substituents is a fluoroheteroaryl group can be prepared by the reaction of the anionic nucleophile [RN=S=N] with pentafluoropyridine. Sulfur diimides of the type RN=S=NH (R = 2,4,6- Bu3C6H2S) have also been prepared. "... 

Raman and multinuclear NMR spectroscopy have been used to study the reaction product of pentafluoropyridine with XeF+AsF6 in anhydrous HF. Identified in the mixture was a fluoro(pentafluoropyridine)xenon(II) cation with the Xe bonded to the ring N (88CC257). 

Attempts to perform hydrodefluorination on other polyfluoroarenes using 9c met with mixed success (Table 8.4). Pentafluoropyridine proved to be highly active with a turnover number of 13.6, although the distribution of products revealed up to three hydrodefluorination reactions (Table 8.4, entry 4). Substrates with a lower fluorine content, such as CF.CH, and 1,2- or 1,4-CF,H were unreactive. 

Perfluoroarenes also undergo facile and selective monosubstitution with hydroxyl-amine. This reaction is general and proceeds with different Ai-alkylhydroxylamines and a number of perfluorinated arenes (e.g. 29, equation 19) and pentafluoropyridine. 

Perfluorotoluene and pentafluoropyridine have been proposed as reagents for protecting alcohols and phenols as perfluoroaryl ethers, a reaction which takes place under mild PTC conditions. Deprotection involves demethoxylation with NaOMe in DMF at 60 C (Scheme 18 R = phenyl, steroidal).158... 

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