Pentafluorophenylmagnesium chloride

During this period of time we, and a number of other research groups, have been investigating the reactions of highly halogenated aiynes and hetarynes with aromatic hydrocarbons, for the reasons outlined in the introduction. In a reaction of pentafluorophenylmagnesium chloride with ethylene oxide in the presence of benzene, it was shown that, as well as 3-pentafluorophenylethanol (23) a by-product of molecular formula C12H6F4 was produced 43>. 

Five products were obtained in the reactions of tetrafluorobenzyne with AT,Ahdimethylaniline 134>. When we generated tetrafluorobenzyne by heating pentafluorophenylmagnesium chloride with an excess of Af.AAdimethylaniline at 80° we obtained only three of the products. These were shown to result from the attack of tetrafluorobenzyne on the aromatic residue of the arylamine. 

In the third step an ethereal solution of the step 2 product was added to a solution of either 2.3 ml methyllithium (1.4 M in diethyl ether), 1.75 ml phenylmagnesium chloride (2 M in THF), or 7 ml of pentafluorophenylmagnesium chloride (0.5 M in diethyl ether). The reaction mixture was then slowly warmed to ambient temperature and stirred for 4 hours. The salt that formed was filtered and the filtrate concentrated. The residue was recrystallized from ether/pentane and the catalyst isolated from between 60 and 70% yield. 

Competition between the formation of Diels-Alder and ene-reaction products also occurs in the reaction of tetrafluorobenzyne (generated from pentafluorophenyl-lithium) with 7-dehydrocholesteryl methyl ether (21) as found in the reaction involving cyclohexa-1,3-diene (see above), and in keeping with the enhanced dienophilic character of tetrafluorobenzyne, the ratio of the Diels-Alder adduct (22) (22 % yield) to ene products [only (23) (51 %) was isolated] is much higher than that found with benzyne itself. Attack of tetrafluorobenzyne (from pentafluorophenylmagnesium chloride) on hex-l-ene and cis- or rraK5-hex-3-ene is claimed to yield the ene-reaction product (24) and a mixture of adduct (25) and ene-reaction product (26), respectively benzyne attacks the hex-3-enes less readily than tetrafluoro-... 

A number of substituted styrenes of the type C F3CR CR R e.g. CaFe CH CHEt, C,F5-CH CMe2) have been synthesized by dehydration with phosphorus pentoxide of alcohols [CeFj CRXOHj-CHR R ] obtained by the action of pentafluorophenylmagnesium chloride on appropriate carbonyl compounds. The kinetics of the thermal and AZBN-initiated polymerization of 2,3,4,5,6-pentafluorostyrene have been studied, and nucleophilic attack on this monomer by sodium methoxide, methylamine, dimethylamine, and lithium anilide has been shown to cause preferential displacement of the fluorine para to the vinyl group. ... 

The reaction of pentafluorophenylmagnesium chloride with aldehydes and ketones has been used to prepare pentafluorostyrenes via dehydration with PjOs of the intermediate alcohols. 2-Hydroxy-2-pentafluorophenyl-... 

Pentafluorophenylmagnesium bromide or lithium can be converted to other pentafluorophenyl organometabics by reaction with the corresponding metal chloride (237). Bis(pentafluorophenyl)phenylphosphine [5074-71-5] (Ultramark 443), (CgF )2CgH P, is offered commercially as a marker for mass spectral standardi2ation (238). 

In contrast to the extensive investigation of fluorovinylzinc reagents and their synthetic utility, only limited literature exists on fluorinated arylzinc reagents. Bis(pentafluorophenyl) zinc can be prepared by the reaction of zinc chloride with either pentafluorophenyllithium or pentafluorophenylmagnesium bromide (equation 70)64,65. An alternative route is via decarboxylation of zinc bis(pentafluorobenzoate) (equation 71)65. 

The nature of organocopper reagents appears to be dependent on the method of preparation and the stoichiometry. Specific examples are methylcopper (76, 310), phenylcopper 73), and pentafluorophenyl-copper 34, 37, 147). The best method of preparing pentafluorophenyl-copper of composition CeFsCu appears to be via the addition of copper(I) bromide to pentafluorophenylmagnesium bromide 34, 37), since the lithium reagent and copper iodide gives an ate complex 147). An ate complex was also obtained from pentafluorophenyllithium and silver chloride in equimolar proportions 265). As shown in Table III, many of the isolated copper compounds gave somewhat incorrect or irreproducible analyses, and others contain metal halide and solvent molecules. 

An attempt to prepare tetrakis(pentafluorophenyl)lead analogously from lead dichloride, pentafluorophenyllithium, and pentafluoroiodobenzene failed, although the action of pentafluorophenylmagnesium bromide on lead dichloride in the presence of benzyl chloride gave the mixed organolead compound ... 

Pentafluorophenylethanol, obtained by the established route from pentafluorophenylmagnesium bromide and acetaldehyde or from penta-fluorophenylmagnesium chloride and ethylene oxide in hydrocarbon solvents, has been converted by conventional methods into 2-pentafluorophenyl-n-propylamine [ROH RBr RCN RCH, NH, (R = C,Fs CHMe)). Cyclization of the amine (KF-DMF) gives the dihydroindoie (203), converted by dehydrogenation (Pd/Q into 4,5,6,7-tetrafluoro-3-methylindole... 

Preparation by demethylation of 2,3,4,5,6-penta-fluoro-2 -methoxybenzophenone (SM) in methylene chloride in the presence of aluminium chloride at 20 for 3-6 h (68%) [570], SM was obtained in two steps first, preparation of 2 -methoxy-2,3,4,5,6-pentafluorobenzhydrolby condensation of o-methoxyben-zaldehyde with pentafluorophenylmagnesium bromide in boiling ethyl ether for 2 h (96%). Then, this benzhydrol was oxidized with chromium trioxide in acetic acid at 20 for 20 h (95%) [570]. 

Pentafluorophenylmagnesium bromide reacts readily with mercury(II) chloride to give bis(pentafluorophenyl)mercury, which may be recrystallized from carbon tetrachloride as white crystals. The thermal stability of the mercurial is high a sample heated at 250° C for 5 hours in vacuo was unaffected. Apparently fluorine migration from the pentafluorophenyl group to mercury, thereby affording tetrafluorobenzyne, does not occur readily. Bis(pentafluorophenyl)mercury resists decomposition by protonic acids. It may be recrystallized from concentrated sulfuric acid. In carbon tetrachloride equimolar quantities of bromine and bis(pentafluorophenyl)-mercury at 60° C yield pentafluorophenylmercuric bromide and pentafluoro-bromobenzene. Bis(pentafluorophenyl)mercury is unusual in its ability to react with bipyridyl and with l,2-bis(diphenylphosphino)ethane to form... 

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