Tetrakis pentafluorophenyl

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)... 

Decomposition of diazo compounds by iron porphyrins is a convenient method for the synthesis of non-heteroatom carbene-iron porphyrins [22]. Reaction of [Fe(F2o-TPP)] [F20-TPP = meso-tetrakis(pentafluorophenyl)porphyrinato dianion] with diazo compounds N2C(Ph)R (R = Ph, C02Et, C02CH2CH=CH2) under an inert atmosphere afforded complexes [Fe(F2o-TPP)C(Ph)R] in 65-70% yields (Scheme 2). Like the halocarbene complex [Fe(TPP)(CCl2)], [Fe(F2o-TPP)CPh2] reacted with Melm to afford six-coordinate species [(MeIm)Fe(F2o-TPP)CPh2] in 65% isolated yield. 

Preparation and properties of stable salts containing mono- or bis-(pentafluorophenyl)aurate(I) and mono-, tris-, or tetrakis-(pentafluorophenyl) aurate(III) ions. Journal of the Chemical Society, Chemical Communications, (10), 353-354. 

Polar substituents have been attached to the porphyrin core in order to achieve water-solubility. (685) has been synthesized by reaction of the Ni11 complex of tetrakis(pentafluorophenyl)-porphyrin with dimethylammonium hydrochloride in DMF, followed by methylation with methyl trifluoromethanesulfonate (triflate) in trimethyl phosphate.1778 The triflate and chloride salts are... 

See related a-PHENYLAZO HYDROPEROXIDES, ORGANIC PEROXIDES 3842. Tetrakis(pentafluorophenyl)titanium... 

Table 1. Common materials used in quenched-fluorescence oxygen sensing (Ru(dpp)3(C104)2 tris(diphenylphenantroline) ruthenium(II) perchlorate PtOEPK platinum(II)-octaethyl-porphine-ketone PtPFPP platinum(II)-tetrakis(pentafluorophenyl)porphine PS.poly(styrene), PSu poly(sulfone) PSB poly(styrene-butadiene) block co-polymer PVC polyvinylchloride) APET amorphous poly(ethyleneterephthalate) PE poly(ethylene).

Subsequently, other publications have appeared involving the DA reactions of porphyrins with other dienes. For instance, the reaction of meso-tetrakis(pentafluorophenyl)porphyrin Id with the diene generated from pyrrole-fused 3-sulfolene gave rise to the isoindole-fused chlorin derivative 8 accompanied by a mixture of stereoisomeric bacteriochlorins 9 (Scheme 2) <98CC2355>. 

The authors conducted a similar investigation of precatalysts 7 and 11 using TiBA and trityl tetrakis(pentafluorophenyl)borate as the cocatalyst. They concluded that this material contained no fraction that could be characterized as blocky. It was therefore proposed that reversible chain transfer occurred only with MAO or TMA and not with TiBA. This stands in contrast to the work of Chien et al. [20] and Przybyla and Fink [22] (vida supra), who claim reversible chain transfer with TiBA in similar catalyst systems. Lieber and Brintzinger also investigated a mixture of isospecific 11 and syndiospecific 12 in attempts to prepare iPP/sPP block copolymers. Extraction of such similar polymers was acknowledged to be difficult and even preparative temperature rising elution fractionation (TREF) [26, 27] was only partially successful. 

Rieger et al. described a heteroatom-containing C, symmetric metallocene 13 whose stereoselectivity depended on the activator [28, 29], The resulting PP contained fewer stereoerrors when activated with a combination of TiBA and trityl tetrakis(pentafluorophenyl)borate than with MAO. In addition, the molecular weight was lower with MAO. To explain this, it was proposed that some of the stereoerrors arise by reversible chain transfer to aluminum. 

Indeed, a variety of Lewis acids have been shown to effed glycosylation with hemiacetal donors. Ernst and coworkers have used 5mol% of [Rh(III)(MeCN)3 (triphos)] tris(triflate) with 4 A molecular sieves to prepare glycoconjugates 18 and 19 [26]. Mukaiyama s group has used trityl tetrakis(pentafluorophenyl)borate (3-5 mol%) with Drierite in the preparation of disaccharides 20 and 21 [27,28]. In the synthesis of 21, the a-seledivity was shown to arise from in situ anomerization of the (1-pyranoside over time. 

Tetrakis(pentafluorophenyl)borate (TPFB), in silicone network preparation,... 

More recently, Cavaleiro et al. described a new method to prepare novel glyco-dihydro- and diglycol-tetrahydroporphyrins (chlorins 116, 117, bacteriochlorins 119 and isobacteriochlorins 118), through CuCl-catalyzed cyclopropanation reactions of a-diazoacetates derived from di-acetonides of several glycosides 113bA-bD with meso-tetrakis(pentafluorophenyl)-porphyrinatozinc(n) 115 (Scheme 16).10... 

Chlorophenyllithium, 2139 4-Fluorophenyllithium, 2166 Pentafluorophenylaluminium dibromide, 2053 Pentafluorophenyllithium, 2059 Tetrakis(pentafluorophenyl)titanium, 3842... 

After extensive experimentation, a simple solution for avoiding catalyst deactivation was discovered, when testing an Ir-PHOX catalyst with tetrakis[3,5-bis (trifluoromethyl)phenyl]borate (BArp ) as counterion [5]. Iridium complexes with this bulky, apolar, and extremely weakly coordinating anion [18] did not suffer from deactivation, and full conversion could be routinely obtained with catalyst loadings as low as 0.02 mol% [19]. In addition, the BArp salts proved to be much less sensitive to moisture than the corresponding hexafluorophosphates. Tetrakis (pentafluorophenyl)borate and tetrakis(perfluoro-tert-butoxy)aluminate were equally effective with very high turnover frequency, whereas catalysts with hexafluorophosphate and tetrafluoroborate gave only low conversion while reactions with triflate were completely ineffective (Fig. 1). 

These researchers found that the nucleophilicity of the complex depended on the electronic nature of the porphyrin. While a [(TPFPP)Fe (02)] (TPFPP equals the dianion of me5 o-tetrakis(pentafluorophenyl)porphyrin) complex did not epoxidize alkenes, adding dimethylsulfoxide (DMSO) as an axial ligand restored the complexes nucleophilicity and ability to epoxidize alkenes. The authors ascribed this restored capability to push the side-on peroxo into a more open, end-on, nucleophilic conformation. Watanabe and co-workers... 

Other examples of oxidant-iron(III) adducts as intermediates in iron porphyrin-catalyzed reactions have been published as listed in references 54a-k. Competitive alkene epoxidation experiments catalyzed by iron porphyrins with peroxy acids, RC(0)00F1, or idosylarenes as oxidants have been proposed to have various intermediates such as [(porphyrin)Fe (0-0-C(0)R] or [(porphyrin)Fe (0-I-Ar)]. Alkane hydroxylation experiments catalyzed by iron porphyrins with oxidant 3-chloroperoxybenzoic acid, m-CPBA, have been proposed to operate through the [(porphyrin)Fe (0-0-C(0)R] intermediate. J. P. CoUman and co-workers postulated multiple oxidizing species, [(TPFPP )Fe =0] and/or [(TPFPP)Fe (0-I-Ar)] in alkane hydroxylations carried out with various iodosylarenes in the presence of Fe(TPFPP)Cl, where TPFPP is the dianion of me50-tetrakis(pentafluorophenyl)porphyrin. ... 

In 1998 the groups of Jprgensen and Helmchen reported the preparation of the chiral silyl cationic salt 2 (Scheme 3) [30]. This was the first time that a chiral silyl cation was used as a catalyst in an enantioselective reaction, hi order to ensure that the silyl salt had a high reactivity, the almost chemically inert and non-coordinating anions tetrakis[pentafluorophenyl]borate [TPFPB] and tetrakis[3,5-bis (trifluor-omethyl)phenyl]borate [TFPB] were chosen as counter anions. 

Since silyl cations are highly reactive and moisture sensitive, the salts (S)-2a and (S)-2b were prepared in situ from the air and moisture stable precursor (S)-5 via a hydride transfer [34, 35] with trityl tetrakis[3,5-bis(trifluoromethyl)phenyl]borate [Tr][TFPB] or trityl tetrakis[pentafluorophenyl]borate [Tr][TPFPB], The authors showed by Si-NMR studies that the desired salts were formed. The silyl salt (5)-2a was then tested in the Diels-Alder reaction as shown in Scheme 5. A good reactivity was found, and the product was obtained in 95% yield with higher than 95% endo selectivity at -40 °C in 1 h. However, only 10% ee was achieved. 

The catalytic activity of the oxoisoindolium salt 54 and 55 was compared to that of trityl tetrakis[pentafluorophenyl]borate salts in the addition reaction of enol acetate to benzaldehyde and glycosylation reaction (Scheme 59) [151, 152]. 

The utilization of compound 54 in the aldolization showed higher yield of the product (92%) after 30 min, compared to that (73%) of a trityl catalyzed reaction. The similar results were obtained in the glycosylation reaction 85% (o/p ratio 9 91) and 72% (cx/p ratio 10 90) respectively. The application of the highly hindered tetrakis[pentafluorophenyl]borate anion is remarkably advantageous for the stabilization of the positive charge in the carbocation 54 and at the same time promotion of its accessibility to the interaction with a carbonyl species. 

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