Diphenyliodonium bromide

An interesting dichlorodiazomethane complex [WBr(NNCCl2)(dppe)2]Br has been obtained by reaction of [WBr(NNH2)(dppe)2]Br with chloroform in the presence of base and diphenyliodonium bromide.487 A mechanism involving free radicals has been postulated. If the reaction is carried out in organic solvents organonitrogen species are formed by attack of solvent radicals on the coordinated dinitrogen.487... 

To a stirred solution of methyl magnesium iodide (748 mg, 4.5 mmol) in ether (15 ml), diphenyliodonium bromide (722 mg, 2 mmol) and anhydrous nickel chloride (15 mg) were added all at once at room temperature, under nitrogen. The mixture was stirred for 20 min, unreacted methyl magnesium iodide was decomposed by addition of water, the reaction mixture was neutralized with 10% hydrochloric acid, washed with water, and the ether layer dried and concentrated. The residue was chromatographed (silica, petroleum ether) to give the pure biaryls. 

Diaryliodonium salts react more or less easily with carbonyl compounds to afford the C-arylated derivatives. Depending upon the nature of the substrate, different experimental conditions have been used. These reactions are generally performed in alcoholic solvents (r-BuOH, r-AmOH.) or in DMF, at temperatures ranging from low (- 78°C) to reflux of the solvent. Arylation of simple ketones has been obtained either by reaction of the ketone enolates with an appropriate diaryliodonium salt, i or by reaction of the ketone enol silyl ether with diaryliodonium fluoride. Phenylation of the potassium enolate of acetone (13) with diphenyliodonium bromide (14) afforded a modest yield of the monophenylation product, but the stimulation with solvated electrons led to overreaction due to the subsequent reaction of the iodobenzene, a good SrnI arylating agent under these conditions. 9... 

Diphenyliodonium tosylate (25) reacted with the sodium salt of nitroalkanes to afford relatively good yields of exclusively the C-phenyl products. The reaction took place at room temperature in DMF, but required a higher temperature for the less reactive ethyl a-nitrocaproate (55°C). Lower yields were obtained when the reaction was performed with diphenyliodonium bromide in methanol. 

Nitrobenzyl halides are reduced in a 1 e-process to radical anions, which rapidly lose halide ion to form the neutral nitrobenzyl radical. The rates for this dissociation were calculated from cyclic voltammetry data to be k = 2,5 for m-nitrobenzyl chloride and k = 2 109 secfor o-nitrobenzyl bromide. The nitrobenzyl radicals predominantly dimerize (90%), whereas a small amount yields nitrotoluenes (< 10%) by hydrogen abstraction 4541. From a series of substituted benzyl bromides those with the more positive reduction potential form bibenzyl in 25—74% yield, whereas from the less easily reducible ones dibenzyl-mercury derivatives are obtained (50—60%) 485). Reduction of benzyl chloride at the plateau of the first wave yields dibenzylmercury 4 By reduction of diphenyliodonium hydroxide at -1,6 V 51% diphenylmercury is obtained 488 ... 

Diphenyliodonium chloride, bromide, and iodide Aldrich, Lancaster Perfluoroalkyl phenyliodonium salts TCI America... 

Pyridine was also phenylated at nitrogen by diphenyliodonium tetrafluoroborate, to jY-phenylpyridinium tetrafluoroborate (88%) [68]. The less polar bromide did not react, whereas the chloride in aqueous pyridine led to the formation of C-phenylated pyridines [69]. 

Phenyl arenedithiocarboxylates. These esters can be prepared by reaction of diphenyliodonium chloride or bromide with sodium arenedithiocarboxylates. 

Phenylation Diphenylidonium bromide. Diphenyliodonium chloride. lodobenzene. p-Tohi-enesulfonic acid. 

The arylsulfonium metal halide complex salts are not readily available. Triphenylsulfoniurn hexafluorophosphate can be prepared from diphenyliodonium hexafluorophosphate by heating with phenyl sulfide, as described by Knapczyk and McEwen ( ), or by reaction of phenyl magnesium bromide with diphenyl sulfoxide followed by reaction with hexafluorophosphoric acid according to the procedure of Wildi, Taylor and Potratz (60). 

Synthesis. Diphenyliodonium hexafluorophosphate, Ph2lPF6, and triphenylsulfonium hexafluoroantimonate, PhaSSbFe, were synthesized using literature procedures (25). Tetra-n-butylammonium hexafluorophosphate, TBAPFe, was obtained by direct metathesis between tetra-n-butylammonium bromide (99%) and potassium hexafluorophosphate (tech.), KPFe. 

Single-crystal X-ray structures have been reported for the following aryl- and heteroaryliodo-nium salts diphenyliodonium triiodide [412], (2-methylphenyl)(2-methoxyphenyl)iodonium chloride [413], (2-methoxy-5-methylphenyl)(4-methoxy-2-methylphenyl)iodonium trifluoroacetate [414], (2-methoxy-5-methylphenyl)(4-methoxyphenyl)iodonium trifluoroacetate [415], a complex of diphenyliodonium tetrafluoroborate with pyridine [416], a complex of diphenyliodonium tetrafluoroborate with 1,10-phenanthroline [417], a complex of diphenyliodonium tetrafluoroborate with 18-crown-6 [418], 1-naphthylphenyliodonium tetrafluoroborate [419], 3,10-dimethyl-10//-dibenzo[, e]iodinium tetrafluoroborate [420], aryl(pentafluorophenyl)iodonium tetrafluoroborates [421], 4,4 -[bis(phenyliodonium)]-diphenylmethane ditriflate [422], [bis(4-methoxyphenyl)](diethylaminocarbodithioato)iodine(in) [423], di(p-tolyl)iodonium bromide [424], diphenyliodonium chloride, bromide and iodide [425,426], diphenyliodonium nitrate [427], diphenyliodonium tetrafluoroborate [428], thienyl(phenyl)iodonium salts [401], (anft-dimethanoanthracenyl)phenyliodonium tosylate and hexafluorophosphate [429] and 3-mesityl-5-phenylisoxazol-4-yl(phenyl)iodonium p-toluenesulfonate [409]. 

Alcock. N.W. Countryman. R.M. Secondary bonding. Part 1. Crystal and molecular structures of diphenyliodonium chloride, bromide and iodide. J. Chem. Soc.. Dalton Trans. 1977. 217. 

Examples of additives are the following EA = iodonium salt, e.g. diphenyliodonium hexafluorophosphate (more rarely, a sulfonium salt) and related derivatives [113], alkyl halide, e.g. phenacyl bromide [1.14] and triazine, e.g. 2,4,6-tris(trichloromethyl)-l,3,5-triazine ED = borate disulfide, group IVb dimetal [1.15] HD = alcohol, THE, thiol, benzoxazine, aldehyde, acetal, silane (e.g. tris(trime1hylsilyl)silane = (TMS)3Si-H) [1.16]), germane, borane, stannane, alkoxyamine, silyloxyamine, polymer substrate, etc. EPD = amine [1.17], thiol, etc. The generated radicals (e.g. Ph, R, RsSi, RR C R R in [1.13]-[1.17] ) are the initiating species. Efficient novel or newly modified dye structures in the Dye/amine, Dye/iodonium salt or Dye/silane two-component PISs have been proposed within the last 4 years (see section 1.3.5). 

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