Perfluoroalkyl-phenyl

Aryl-A3-iodanes bearing an electron-deficient alkyl ligand such as aryl(sul-fonylmethyl)-A3-iodanes (Section 3.2.7) and aryl(perfluoroalkyl)-A3-iodanes are relatively stable. A series of (perfluoroalkyl)phenyl-A3-iodanes 96 were synthesized in good yields by treating bis(trifluoroacetoxy)-A3-iodanes with benzene in the presence of triflic acid [47]. The AModanes 96 transfer the perfluoroalkyl groups to a variety of nucleophiles with reductive elimination of iodobenzene. The nucleophiles involve Grignard reagents, alkyllithiums, enolate anions, alkenes, alkynes, trimethylsilyl enol ethers, arenes, phenols, and thiols. In these reactions, the AModane 96 serves as a source of the perfluoroalkyl cation and, in... 

A variety of perfluoroalkyl(phenyl)iodonium salts were obtained from precursors such as RFI(OH)OTf, RfI(OOCCF3)2 and others when coupled with benzene or arenes, as reported in a recent review article [143]. Similarly, a trifluo-roethyl group attached to iodine(III) can also be coupled to the phenyl ring upon reaction with PhSiMe3 as outlined in Scheme 47 [144]. 

Perfluoroalkyl(phenyl)iodonium sulfonates 42 (also known as FITS reagents), as well as lFf,lff-perfluoroalkyl(aryl)iodonium triflates 44, have found practical application as electrophilic fluoro alkylating reagents toward a... 

Fluoroalkyl(aryl)iodonium salts are the most stable and practically important class of alkyl(aryl)iodonium derivatives. The application of such salts as electrophilic fiuoroalkylating reagents was reviewed in 1996 by Umemoto [1017]. Perfluoroalkyl(phenyl)iodonium trifiates (FITS reagents) 764 are efficient perfluoroalky-lating reagents toward various nucleophiUe substrates, sueh as arenes, carbanions, alkynes, alkenes, carbonyl compounds, amines, phosphines and sulfides [1017]. Scheme 3.300 shows several representative examples of electrophilic perfluoroalkylations using FITS reagents. 

Other perfluoroalkyl-phenyl analogues 561 proved difficult to prepare and handle, but 3,5-bis(perfluorooctyl)phenyl butyl selenide 562 was accessible as precursor for the identical active species 563. The catalyst 562 showed higher activity (turn over frequency) compared to diselenide 553 in the oxidation of aldehydes and ketones with aqueous hydrogen peroxide. Furthermore, 562 could be used to oxidize substrates under fluorous monophasic, biphasic, and triphasic conditions (Fig. 7.29) [360]. 

Rate constants and Arrhenius parameters for the reaction of Et3Si radicals with various carbonyl compounds are available. Some data are collected in Table 5.2 [49]. The ease of addition of EtsSi radicals was found to decrease in the order 1,4-benzoquinone > cyclic diaryl ketones, benzaldehyde, benzil, perfluoro propionic anhydride > benzophenone alkyl aryl ketone, alkyl aldehyde > oxalate > benzoate, trifluoroacetate, anhydride > cyclic dialkyl ketone > acyclic dialkyl ketone > formate > acetate [49,50]. This order of reactivity was rationalized in terms of bond energy differences, stabilization of the radical formed, polar effects, and steric factors. Thus, a phenyl or acyl group adjacent to the carbonyl will stabilize the radical adduct whereas a perfluoroalkyl or acyloxy group next to the carbonyl moiety will enhance the contribution given by the canonical structure with a charge separation to the transition state (Equation 5.24). 

The exchange reaction of perfluoroalkyl iodides and iodopentafluorobenzene with dialkylzinc in the presence of Lewis base, such as diglyme or pyridine, afforded the corresponding bis(trifluoromethyl)zinc and bis(pentafluoro-phenyl)zinc in high yield [41] (Scheme 12). 

The benzimidoyl thiocarbodihydrazide (237) was cyclized by Soviet chemists to yield 3-phenyl-l,4-dihydro-l,2,4,5-triazine-6(5//)-thione (238). But since (237) was prepared by reaction of ethyl benzimidate and thiocarbodihydrazide this reaction can also be classified as a synthesis by a [5 + 1] atom fragment method (77KGS564). When the perfluoroalkyl hydrazidines (239) were heated with anhydrous iron(III) chloride, cyclization occurred with... 

Progress in the areas of photoscrambling and valence bond isomerization reactions in aromatic156 and heteroaromatic compounds157 has led to the study of new cyclic systems with strained olefinic double bonds.158 Dewar benzene, Dewar thiophene, benzvalene, and their heteroaromatic counterparts substituted with fluoro and/or perfluoroalkyl substituents have been synthesized and their reactions with phenyl azide have been investigated. 

The benzene derivatives containing the fluorinated sulfone have been prepared either by nucleophilic substitution of the 4-fluorophenyl derivative (e.g. 1) or by starting with the appropriately substituted sodium thiophenoxide and reacting with perfluoroalkyl iodide follow by oxidation with either MCPBA or chromium oxide (12. li.) The biphenyl derivatives have been prepared by palladium catalyzed cross coupling chemistry of the 4-bromophenyl derivative (e.g. 2) with substituted phenyl boronic acid (yields 37-84%) (JLH, .). Compound 16 has been prepared by palladium catalyzed cross coupling of (4-bromophenyl)perfluorohexyl sulfone with vinyl anisole in 37 % yield (JJL). The vinyl sulfones, 7 and 9, have been prepared by condensation of CH3S02Rf (JJL) with the appropriate aldehyde (yields 70,and 73%) following a literature procedure (1 ). Yields were not optimized. 

Reduction of perfluoroalkyl ketones with chiral lithium alkoxides gave chiral a-perfluoroalkyl alcohols in high enantiomeric excesses. The order of steric effects on this reaction is estimated as C7F15 > substituted phenyl > CF3.388... 

Diketones are synthesized by Claisen condensation of appropriate acetyl methyl ketone and ethyl perfluoroalkyl carboxylate. For example, 4,4/-bis(l",l,/,l//,2//,2",3//,3//-heptafluoro-4//,6//-hexanedion-6"-yl)-chlorosulfo-o-terphenyl (BHHCT) was synthesized from o-terphenyl by three step reactions (scheme 3 (Yuan et al., 1998a, 1998b)). The o-ter-phenyl are acetylated by acetyl chloride with anhydrous aluminum chloride as a Lewis acid and 4,4 -diacetyl-e>-terphcnyl is obtained. Then, the 4,4/-diacetyl-o-terphenyl is reacted with perfluoropropionic acid ethyl ester with sodium methoxide as a base. Finally, 4,4,-bis(l", 1",l//,2,2,3,/,3"-heptafluoro-4//,6"-hexanedion-6//-yl)-o-terphenyl is chloro-sulfonylatcd by chlorosulfonic acid to form BHHCT. 

Perfluoroalkyl radicals were generated according to a procedure developed by this research group, involving iodine abstraction from perfluoroalkyl iodides by phenyl radical (Equation 14.13) this latter derives from thermal decomposition of benzoyl peroxide (Equation 14.14). 

Compounds of this family are numerous, since the phenyl ring may be substituted, whereas perfluoroalkyl (Rf) groups of great diversity have been used. Actually, the preparation that follows is for compounds containing the group RfCH2 the same procedure was essentially used for other Arl+Rf salts. 

Attempts to prepare a (/ -fiuorovinyl)iodonium salt from l-decynyl(phenyl)iodonium tetrafluoroborate by the procedures employed for / -chloro- and (/ -bromovinyl)iodonium halides have been unsuccessful103. Admixture of the decynyliodonium salt and lithium fluoride in acetic acid ultimately (2 days, rt) leads to l-acetoxy-2-decanone103. (Z )-(/ -Fluoro-jS-perfluoroalkylvinyl)iodonium triflates, on the other hand, can be made by the treatment of (1H, li/-perfluoroalkyl)phenyliodonium triflates with sodium hydride (equation 178)136. Apart from 2-fluoro-l-hexadecenyl(phenyl)iodonium chloride (synthesis not described)104, these are the only reported examples of (/ -fluorovinyl)iodonium salts. 

The mass spectra of 1,3,4-oxadiazole, 2,5-diphenyl- and 2-perfluoroalkyl-l,3,4-oxadiazoles, including suggested fragmentation pathways, have been discussed (B-71MS528). The molecular ion is the base peak in the spectra of 1,3,4-oxadiazole and 2-amino-5-phenyl-... 

Benzoxazoles, 7-lithio-, 56, 221 Benzoxazoles, 2-perfluoroalkyl-, 60, 24 Benzoxazole, 2-phenyl, 2, 7-dilithio-, 56, 221... 

By reactionof a 1,1-difluoroethene with tributylphosphane in the presence of boron trifluoride-diethyl ether complex, the vinylphosphonium salt is obtained. On subsequent hydrolysis the selectivity of formation of the Z- and E-isomer is 100%, but it diminishes after the introduction into the alkene. together with the perfluoroalkyl group, of substituents such as phenyl and... 

Perfluoroalkyl halides can be converted into phenyl sulfides by treatment with aromatic or aliphatic disulfides under reductive conditions involving the presence of various precursors of the SO/ radical anion. ... 

Perfluoroalkyl anions, which form carbenes upon subsequent elimination of a-fluorine, may be generated by cleavage of the carbon-tin and carbon-mercury bonds in, for example, (trifluoromethyl)trimethyltin [56] and phenyl(trifluoromethyl)mercury [57] (Figure 6.40) under very mild conditions. Carbenes may be generated from... 

By reaction of a 1,1-difluoroethene with tributylphosphane in the presence of boron trifluoride-diethyl ether complex, the vinylphosphonium salt is obtained. On subsequent hydrolysis the selectivity of formation of the Z- and F-isomer is 100%, but it diminishes after the introduction into the alkene. together with the perfluoroalkyl group, of substituents such as phenyl and 4-methoxyphcnyl. In accordance with this methodology, a method of substitution of fluorine by hydrogen at the fluoroolefinic double bond has been developed.194,206 The first stage of this reaction includes the formation of a fluoro-/5-phosphane from the fluoroalkene and tributylphosphane. The decomposition of this /l5-phosphane in the aqueous solvent leads to a fluoroalkene, e.g. formation of l.206... 

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