1.2.3.4.5- pentakis benzene

Stmcturally novel pyrazole derivatives include the propellene 2,3,4,5,6-pentakis(pyrazol-r-yl)pyridine 1 and the corresponding 3 ,5 -dimethylpyrazole derivative 2<96T11075>. Poly(pyrazol-l-ylmethyl)benzenes, such as 3, have been prepared as multidentate ligands <95AJC1587>. Solid phase synthesis of structurally diverse 1-phenylpyrazolones was reported, with application to combinatorial synthesis <96SL667>. 

When benzene reacts with a six-fold excess of Ic in the presence of aluminum chloride at room temperature, the peralkylated product, hexakis[2-(di-chloromethylsilyl)ethyl]benzene is obtained as the major component along with other lower polyalkylated products pentakis-, tetrakis-, tris-, and bis[2-(di-chloromethylsilyl)ethyl]benzene. 

The reaction of ethylbenzene with five equivalents of Ic under the same alkylation conditions used for toluene, gives pentakis- (25%), tetrakis- (9%), tris- (4%), and bis[2-(dichloromethylsilyl)ethyl]ethylbenzene (1%) as well as a mixture of many transalkylated products (44%). It is of interest that longer alkyl-substituted benzenes exhibited different behavior in peralkylations with Ic. The transalkylation of ethylbenzene is responsible for the significantly low yield (25%) of peralkylation product in comparison with yields obtained from the alkylation of benzene " or toluene. Peralkylation of K-propylbenzene and K-butylbenzene gives similar results to those of ethylbenzene. 

Fluorine NMR data for the three bis-(trifluoromethyl)benzenes are given in Scheme 5.51, while such data for the tris(trifluoromethyl)-, tetrakis(trifluoromethyl)-, pentakis(trifluoromethyl)-, and hexakis (trifluoromethyl)benzenes are given in Scheme 5.52.3 In the bis(trifluoromethyl)benzene series, one will notice that adding a second trifluoromethyl group meta or para does not have much effect upon the fluorine chemical shifts, but when vicinal, as in the ortho compound, considerable deshielding is observed. 

However, the results of a 125Te-NMR spectroscopic investigation of a mixture containing tellurium tetrakis[trifluoroethoxide] and potassium trifluoroethoxide in benzene suggested that only the pentakis[trifluoroethoxy]tellurate(IV) anion is formed3. 

Tellurium tetrakis[trifluoroethoxide] and an excess of potassium trifluoroethoxide reacted in benzene in the presence of 18-crown-6. According to results from the Te-NMR spQcivii, potassium pentakis[tnfluoroethoxo]tellurate(IV) was the only compound formed. ... 

Pentakis(methoxycarbonyl)cyclopentadiene, which is a strong protic acid, reacts with bistributyltin oxide in benzene at room temperature to give a salt between the diaquotri-butyltin cation and the cyclopentadienide anion as shown in equation 9-48.109 The cation has a trigonal bipyramidal structure, with the water molecules in the apical positions, and these can be replaced by other ligating molecules such as HMPT and DMF. 

A. Kiitt, V. Movchun, T. Rodima, T. Dansauer, E.B. Rusanov, 1. Leito, 1. Kaljurand, J. Koppel, V. Pihl, 1. Koppel, G. Ovsjannikov, L. Toom, M. Mishima, M. Medebielle, E. Lork, G.-V. Roschenthaler, I.A. Koppel, and A.A. Kolomeitsev, Pentakis(trifluoromethyl)phenyl, a sterically crowded and electron-withdrawing group Synthesis and acidity of pentakis(trifluoromethyl)benzene, -toluene, -phenol, and -aniline, J. Org. Chem. 73 (2008), pp. 2607-2620. 

C9 7H8lOaPsRha, M CarbonatO pentakis(triphenylphosphine)dirhodium -benzene, 42B, 1003... 

The photochemistry of six-membered Af-heterocycles has been much less extensively investigated. That of pentakis(pentafluoroethyl)pyridine resembles that of hexakis(pentafluoroethyl)benzene. U.v. irradiation at longer wavelengths produces the para-bonded isomer (146), which isomerizes to the aza-prismane (147) upon excitation at shorter wavelengths ... 

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