Pentafluorophenyl compounds from

The ability of fluoro-2 -phosphanes to transform silyl ethers into fluorides was first observed during a study of the reactions of phosphorus pentafluoride and its derivatives R PF5 (n = 1, 2, 3 R = hydrocarbon group) with trimethylsilyl ethers. Subsequently, this reaction was proposed as a new method for the preparation of C-F compounds from silyl ethers or silicic acid esters with fluoro-A -phosphanes. Pentafluorophenyl-substituted fluoro-A -phos-phanes were found to react similarily, Other workers found that tctrafluoro(phenyl)-A -phos-phane. which was chosen as the most convenient reagent with regard to reactivity and stability, gave considerable amounts of elimination products, especially with primary and cyclic alcohols. Good yields of fluorinated products are obtained when stable carbocations can be formed at the site of substitution, such as in tertiary alcohols, but 2-phcnylethanol. benzyl alcohol and diphcnylmethanol, on the other hand, give only poor yields of fluorinated products ethers and polymers are the main products. ... 

Reaction of bis(cyclopentadienyl)diphenyltitanium(iv) with acetylenes affords a general route to titana-indenes. The products from the reactions with phenyl-(trimethylsilyl)ethyne and bis(pentafluorophenyl)ethyne were both characterized by single crystal Z-ray studies, and the structure of the former is shown in (6). The structure is drawn with the one double bond, because, unlike metallocyclo-pentadienes in general, the Ci—Ca bond in (6) is significantly shorter than C3—C4, which is typically aromatic. The two Ti—C bonds in (6) are similar in length but the Ti—Cx bond length in the pentafluorophenyl compound is longer, which the authors attribute to steric factors. ... 

There has been a preliminary report (57a) of the synthesis of pentafluorophenylboron halides by cleavage of pentafluorophenyl groups from penta-fluorophenyltin compounds by boron halides. This synthesis is analogous to that used to obtain perfluorovinylboron compounds, described above. 

Xenon difluoride has been used to oxidize a number of antimony compounds [102, 109] in yields ranging from 73 to 98%. Elemental fluorine oxidized tris(pen-tafluorophenyl)stibine to tris(pentafluorophenyl)stibine difluoride in 98% yield [706]. Oxidative fluonnation of stibines has also been accomplished with iodine pentafluoride [707]. 

A method for generating a perfluoroarylmagnesium compound is the cleavage of a pentafluorophenyl-metal bond by a nucleophile such as ethyltnagnesium bromide As an example, tetrakis(pentafluorophenyl)tin on reaction with ethyl-magnesium bromide gives a series of products, one of which may result from pentafluorophenylmagnesium bromide [27] (equation 7)... 

The first asymmetric intramolecular Stetter reactions were reported by Enders and co-workers utilising triazolium salt pre-catalyst 125. Treatment of substrate 123 generated 1,4-dicarbonyl compound 124 in good yield and enantioselectivity [56]. These salicylaldehyde-derived substrates 123 have since become the standard test substrates for the development of new catalysts for the asymmetric intramolecular Stetter reaction. Bach and co-workers have achieved moderate enantioselectivities using axially-chiral thiazolium pre-catalyst 126 [41], whilst Miller and co-workers have developed peptidic thiazolium pre-catalyst 127 [57]. In 2005, Rovis and coworkers showed that the NHCs derived from triazolium salts 128-130 were excellent catalysts for the asymmetric intramolecular Stetter reaction of a wide range of substrates, giving typically excellent yields and enantioselectivities [58]. The iV-pentafluorophenyl catalyst 129 currently represents the state of the art in asymmetric Stetter reactions (Scheme 12.24) [59]. 

Clearly, Greek or Latin numeral roots in conjunction with numerical locants can be used to indicate the number and positions of fluorine substituents in any type of organo-fluorine compound or group, ranging from monofluorinated systems, e.g. 2-fluorobutane (1), to perfluorinated entities, e.g. l,l,l,2.2,3,4,4,4-nonafluoro-3-iodobutane(2). Fluorine locants may be omitted, and often are in non-indexing situations when naming simple and therefore easily visualized fully fluorinated aliphatic/cycloaliphatic or monocyclic aromatic compounds or groups, e.g. octafluoropropane (3), hexafluorocyclopropane (4), pentafluoropropanoic acid, (5). pentafluorophenyl (6). 

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