Phenyliodonium chloride

The first alkynyliodonium salt, (phenylethynyl)phenyliodonium chloride, synthesized in low yields from (dichloroiodo)benzene (3) and lithium phenylacetylide (equation 1), was reported in 196526. This chloride salt is unstable and readily decomposes to a 1 1 mixture of chloro(phenyl)acetylene and iodobenzene. It was not until the 1980s, however, that alkynyliodonium salts became generally available. This was made possible by the introduction of sulfonyloxy-/l3-iodanes as synthetic reagents46 and by the recognition that iodosylbenzene (4) can be activated either with boron trifluoride etherate or with triethy-loxonium tetrafluoroborate31. These reagents are now widely employed for the conversion of terminal alkynes and their 1-silyl and 1-stannyl derivatives to alkynyliodonium salts (equations 2 and 3). A more exhaustive survey of iodine(III) reagents that have been... 

Apart from copper(I)-mediated reactions, few studies of the treatment of vinyliodonium salts with carbanions have appeared. The vinylations of the 2-phenyl- and 2- -hexyl-l,3-indandionate ions shown in equations 222 and 223 are the only reported examples of vinyliodonium-enolate reactions known to this author26,126. ( ,)-l-Dichloroiodo-2-chloroethene has been employed with aryl- and heteroarvllithium reagents for the synthesis of symmetrical diaryliodonium salts (equation 224)149,150. These transformations are thought to occur via the sequential displacement of both chloride ions with ArLi to give diaryl (/ -chlorovinyl)iodanes which then decompose with loss of acetylene (equation 225). That aryl(/ -chlorovinyl)iodonium chlorides are viable intermediates in such reactions has been shown by the conversion of ( )-(/ chlorovinyl)phenyliodonium chloride to diaryliodonium salts with 2-naphthyl- and 2-thienyllithium (equation 226)149,150. 

Side-chain chlorination to 2,3-dichloromethylpyridine with JV-chloro-succinimide followed by ring-closure with sodium sulphide, oxidation to the sulphoxide with phenyliodonium chloride, and dehydration on AI2O3 according to the method of Cava gave (540). Curiously, attempts to prepare the benzo-analogue (541) by the same method were unsuccessful. However, the transient existence of (541) could be demonstrated by trapping with A -phenylmaleimide. ... 

Pyridine has been phenylated with the following free-radical sources benzenediazonium chloride with aluminum trichloride the Gomberg reaction " phenylhydrazine and metal oxides A -nitroso-acetanilide dibenzoyl peroxide phenylazotriphenylmethane di-phenyliodonium hydroxide and electrolysis of benzoic acid. ° Although 2-phenylpyridine usually accounts for over 50% of the total phenylated product, each of the three phenyl derivatives can be obtained from the reaction by fractional recrystallization of the... 

Tetrahydrobenzyl alcohol (( )3-cyclohexenene-l-methanol) and 30% aqueous hydrogen peroxide were purchased from Fluka, AG. 3-Cyclohexene-1-carboxylic acid and cis-4-cyclohexene-l,2-dicarboxylic acid were used as purchased from Lancaster Chemical Co. Methyl iodide, acetic anhydride, Oxone (potassium peroxymonosulfate), Aliquot 336 (methyl tri-n-octylammonium chloride), sodium tungstate dihydrate and N,N-dimethylaminopyridine (DMAP) were purchased from Aldrich Chemical Co. and used as received. 3,4-Epoxycyclohexylmethyl 3, 4 -epoxycyclohexane carboxylate (ERL 4221) and 4-vinylcyclohexene dioxide were used as purchased from the Union Carbide Corp. (4-n-Octyloxyphenyl)phenyliodonium hexafluoroantimonate used as a photoinitiator was prepared by a procedure described previously (4). 

E-(P-Alkylvinyl)phenyliodonium salts react with tetra-n-butylammonium halides to yield the correspondingly substituted Z-haloethenes (80-100% for chloro-, bromo- and iodo-derivatives) [41], In contrast, in the corresponding reaction with Z-(2-benzenesulphonyl-ethenyl)phenyliodonium salts, nucleophilic substitution occurs with retention of configuration to yield the Z-2-benzenesulphonyl-l-haloethenes [42], The ammonium fluorides fail to yield the fluoroethenes, but produce the ethynes by simple elimination [41]. Where carboxylic acids have low solubility in organic solvents, their conversion into the acid chlorides is frequently difficult. Phase-transfer catalysis not only allows the conversion to be effected rapidly, it also results in high yields of a wide range of acid chlorides [43]. 

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

The thermolysis of iodonium salts in which their counteranion is a halide may be performed in the molten state or in solution the products are an iodoarene and a haloarene. The reaction which is a nucleophilic aromatic substitution is, however, not preparatively useful an exception was 3-indolyl phenyliodonium trifluoroace-tate which on heating with various chlorides and bromides in DMSO afforded variable mixtures of 2- and 3-haloindoles. By contrast, the jV-methyl and N-benzyl analogues gave only 2-chloro derivatives [58], Sometimes useful products may be obtained from the thermolysis of dibenziodolium or other heterocyclic salts, as exemplified in the preparation of l-iodo-2-(2-iodophenyl)naphthalene [59] ... 

Attempts to prepare a (/ -fiuorovinyl)iodonium salt from l-decynyl(phenyl)iodonium tetrafluoroborate by the procedures employed for / -chloro- and (/ -bromovinyl)iodonium halides have been unsuccessful103. Admixture of the decynyliodonium salt and lithium fluoride in acetic acid ultimately (2 days, rt) leads to l-acetoxy-2-decanone103. (Z )-(/ -Fluoro-jS-perfluoroalkylvinyl)iodonium triflates, on the other hand, can be made by the treatment of (1H, li/-perfluoroalkyl)phenyliodonium triflates with sodium hydride (equation 178)136. Apart from 2-fluoro-l-hexadecenyl(phenyl)iodonium chloride (synthesis not described)104, these are the only reported examples of (/ -fluorovinyl)iodonium salts. 

The production of the (Z)-haloalkenes is thought to proceed via initial exchange of the tetrafluoroborate and halide ions and collapse of the resulting vinyliodonium halides by the addition-elimination (Ad-E) mechanism (equations 203 and 204)84. As with Ad-E reactions of moderately activated vinyl halides (X = Cl, Br), which typically occur with configurational retention (> 95%)143 145, the intermediate carbanions apparently prefer a least motion rotation of 60° prior to the expulsion of iodobenzene. It has been demonstrated by an NMR study that anion exchange between (Z)-(2)-phenylsulfonyl-l-decenyl)-phenyliodonium tetrafluoroborate and tetrabutylammonium chloride occurs instantaneously in deuteriochloroform84. Furthermore, when authentic halide salts of the... 

Coupling of a benzoic acid derivative under basic conditions is achieved with alkyl iodides," alkyl chlorides,dimethyl sulfate, or (l,1-dihydroperfluoroalkyl)phenyliodonium triflates. Common bases used arc potassium carbonate or sodium hydroxide (with phase-transfer catalyst). " Again, employing acid chlorides " - or anhydrides, " is the method of choice. The reaction can be performed without further activation, " " but in most cases the transformation takes place in the presence of the usual bases, triethylamine - " or pyridine " " " " " [in some cases 4-(dimethylamino)pyridine is added " ]. In a similar manner carbamates. thiocarbamates, " or thiocarbonates are synthesized. Perfluoropropcn-2-ol... 

The chlorination of norbornadiene with copper(II) chloride, " " chlorine, phenyliodonium dichloride, gold(III) chloride, and molybdenum(V) chloride have been reported to yield predominantly 3,5-dichlorobicyclo[2.2.1.0 ]heptanes 11 and The results of the reaction with other chlorinating agents are summarized in Table 3. 

In the case of unsyimnetrical diaryliodonium salts (the anisyl, tolyl or nitrophenyl derivatives of phenyliodonium salts - or some thienyl aiyliodonium salts ), the product composition is always in favour of the ligand coupling product involving the less electron-rich arene group. A good yield of 3-methoxyindole (60%) was obtained in the reaction of phenyl 3-indolyliodonium chloride with methanol in the presence of boron trifluoride-etherate. ... 

A third type of derivatives of iodonium salts, the perfluoroalkyl phenyliodonium (dfluoromethane sulfonates (FITS), showed an enhanced reactivity compared to the chloride and the tetrafluoroborate salts. In a series of papers, Umemoto et al have extensively studied the synthesis of these compounds and their reactivity towards a wide range of more or less powerful nucleophiles. 206 Different mechanistic pathways have been demonstrated to occur in these reactions. Ligand coupling appears to be involved in a number of nucleophilic displacements implying various types of carbanions, thiols and other nucleophilic substrates. 

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]. 

The acylation of arenes with alcohols has been shown to be possible using a palladium chloride catalyst in the presence of f-butylhydroperoxide. In 2-arylpyridines, substitution is directed to the ortho-position and, after initial paUadation, the formation of intermediate (59) is likely before reductive elimination yields the acylated product. The regioselective acetoxylation of indoles, at the 3-position, has been achieved using the palladium-catalysed reaction with phenyliodonium acetate. 3-Acyl indoles may also be prepared using acetyl chlorides with zirconium tetrachloride as a Lewis acid catalyst. 

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