Iodide, potassium reaction with aryl halides

Acceleration by KI in the substitution reaction of aryl halides with potassium diethyl phosphite or with the 2-naphthoxide ion has also been explained on the basis of an ET through the exciplex of the charge-transfer complex formed between the aryl halide and the iodide ions34a. It has also been reported that iodide ions catalysed the photostimulated reaction of bromoarenes with diethyl phosphite ion34b. 

Additionally, the Pd-C catalysed SM reactions with aryl iodides can be accomplished at room temperature. The reactions were alternatively carried out in water if aryl halides, e.g. iodophenols 274-276, are soluble in aqueous potassium carbonate to afford the biaryls 277-279 in good to excellent yields [26], Scheme 21. 

The palladium-catalyzed cross-coupling of secondary phosphine oxides with aryl halides in water has also been reported using discrete paUadacycles as catalysts (Scheme 4.204) [340], No added ligands were needed for the metal center in this reaction although several additives were added to the reaction mixture including potassium fluoride and added TBAB. Aryl bromides, chlorides, and iodides were successfully converted into phosphine oxides using this approach, but aryl chlorides were sluggish. 

Thallium(III), particularly as the trifluoroacetate salt, is also a reactive electrophilic metallating species, and a variety of synthetic schemes based on arylthallium intermediates have been devised.75 Arylthallium compounds are converted to chlorides or bromides by reaction with the appropriate cupric halide.76 Reaction with potassium iodide gives aryl iodides.77 Fluorides are prepared by successive treatment with potassium fluoride and boron trifluoride.78 Procedures for converting arylthallium compounds to nitriles and phenols have also been described.79... 

Reaction of organic halides with alkenes catalyzed by palladium compounds (Heck-type reaction) is known to be a useful method for carbon-carbon bond formation at unsubstituted vinyl positions. The first report on the application of microwave methodology to this type of reaction was published by Hallberg et al. in 1996 [86], Recently, the palladium catalyzed Heck coupling reaction induced by microwave irradiation was reported under solventless liquid-liquid phase-transfer catalytic conditions in the presence of potassium carbonate and a small amount of [Pd(PPh3)2Cl2]-TBAB as a catalyst [87]. The arylation of alkenes with aryl iodides proceeded smoothly to afford exclusively trans product in high yields (86-93%) (Eq. 61). 

The reaction with ammonia or amines, which undoubtedly proceeds by the SNAr mechanism, is catalyzed by copper8" and nickel105 salts, though these are normally used only with rather unreactive halides.106 This reaction, with phase transfer catalysis, has been used to synthesize triarylamines.107 Copper ion catalysts (especially cuprous oxide or iodide) also permit the Gabriel synthesis (0-58) to be applied to aromatic substrates. Aryl bromides or iodides are refluxed with potassium phthalimide and Cu 0 or Cul in dimethylacetamide to give N-aryl phthalimides, which can be hydrolyzed to primary aryl amines.108... 

A second method for preparing aryl halides is the Sandmeyer reaction. During a Sandmeyer reaction, a diazonium salt reacts with copper (I) bromide, copper (I) chloride, or potassium iodide to form the respective aryl halide. The diazonium salt is prepared from aniline by reaction with nitrous acid at cold temperatures. 

Halide exchange has been extended to vinylic halides with excellent stereospecificity. Thus, under the above conditions, cw- -bromostyrene is converted to d.s-/ -chlorostyrene and trans-fi-bvomostyrene is transformed into trans-fi-chlorostyrene in high yields. Recently, Cheng and colleagues211 reported the catalytic activity of nickel powder in the exchange reaction of potassium iodide with aryl bromides at 150 °C in DMF. Zinc powder, combined with nickel bromide, is also known to promote this exchange212. 

Aryl halides reaction with metal cyanides, often with another transition metal catalyst, to give aryl nitriles (aryl cyanides). Aryl halides react with Zn(CN)2 and a palladium catalyst, for example, to give the aryl nitrile. Similarly, aryl iodides react with CuCN and a palladium catalyst to give the aryl nitrile. Potassium cyanide (KCN) reacts in a similar manner with a palladium catalyst. " Sodium cyanide has been used with a copper catalyst and 20% The reaction of aryl iodides... 

Halogen exchange reactions may be used to prepare tetrahalotellurates(IV) that are not accessible through reactions of aryl tellurium trihalides and onium halides. Treatment of tetrachloro- or bromotrichlorotellurates with dilute hydrobromic acid produces the tetrabromotellurates. The conversion of bromotellurates to tetrachlorotellurates requires concentrated hydrochloric acid. Chlorine and bromine are easily replaced by iodine when the tellurates are reacted with excess potassium iodide in dilute hydrochloric acid. The iodotellurates cannot be converted to the bromo- or chlorotellurates ... 

Generally, the reaction rates of aryl halides follow the order iodides > bromides > chlorides > fluorides. This fact can be used for the selective substimtion in polyhalogenated systems. For instance, 2-bromo -chlorotoluene gives 76% of 5-chloro-2-methylphenol by treatment with sodium hydroxide at 200 °C. Nevertheless, polyhalogenated systems which contain fluorides have a variable behaviour depending on the reaction temperature. At lower temperatures preferential hydrolysis of the fluoride takes place and at >200 °C the usual reactivity order iodides > bromides > chlorides > fluorides is observed. For instance, l,2-dibromo-3,4,5,6-tetrafluorobenzene affords 2,3-dibromo-4,5,6-trifluorophenol in 87% yield by treatment with potassium hydroxide at 85 °C. Under the same conditions, 1,4-dibromo-2,3,5,6-tetrafluorobenzene produces a 78% yield of 2,5-dibromo-3,4,6-trifluorophenol. However, 4-fluorobromobenzene with NaOH at 200 °C gives 4-fluorophenol in 70-79% yield. ... 

Gabriel reaction. Review.1 The Gabriel reaction is ordinarily not applicable to aryl halides however, under catalysis with cuprous bromide or iodide and in boiling DMA (dimethylacetamide) as solvent, aryl bromides or iodides (but not chlorides) react with potassium phthalimide to give phthalimido compounds in >5-95% yield.2... 

Treatment of diazonium salts with cuprous, Cu(I), salts generates aryl halides. When 398 reacts with CuCl (cuprous chloride) or CuBr (cuprous bromide), the products are chlorobenzene or bromobenzene via what is probably a radical reaction.29l jhis conversion is known as the Sandmeyer reaction. 2 The use of copper powder rather than cuprous salts for this transformation is often called the Gattermann reaction. 93,292b,c Aryl iodides are also produced from diazonium salts by reaction with potassium iodide (KI) but the actual reactive species may be l3-.294,295 Treatment of aniline derivative 403 with sodium nitrite and HCl followed by treatment with KI, for example, gave a 89% yield of 404.Aryl nitriles are generated under Sandmeyer conditions using cuprous cyanide (CuCN), as in the conversion of 405 to benzonitrile derivative 407 via diazonium chloride, 406. 

Preparation of Phosphines from Metallated Phosphines. - Alkali metal-free phosphide anions have been shown to be formed under synthetically useful conditions in the equilibria between primary or secondary phosphines with the Schwesinger bases (23). Techniques have been developed for the preparation of alkali metal diphenylphosphide reagents in high purity, as evidenced by P nmr studies. The same paper reports a study of the course of the reactions between potassium diphenylphosphide and a series of aryl-, n-alkyl- and neopentyl-halides. The results provide the first evidence of the involvement of single electron transfer (SET) processes in the reactions of alkyl halides. This pathway is dominant in the case of neopentyl-type iodides, but plays only a minor role in the related reactions of neopentyl-type bromides and chlorides. No evidence was adduced of the involvement of SET processes in the reactions of unhindered... 

This reaction was initially reported by Finkelstein in 1910. It is a preparation of alkyl iodide from alkyl bromide or chloride with potassium or sodium iodide in acetone. Therefore, this reaction is generally known as the Finkelstein reaction. Occasionally, it is also referred to as the Finkelstein halide exchange, Finkelstein displacement, or Conant-Finkelstein reaction. Mechanistically, this reaction is a simple nucleophilic substitution (often via Sn2), as iodide is a stronger nucleophile than bromide or chloride. The yield of this reaction is very high and can be quantitative if occurs in DMF. It was found that the trifluoromethyl group retards the displacement of bromide when it presents as an a- or /3-substituent but accelerates the reaction as a substituent in an allylic chloride. Under normal conditions, this type of halide displacement does not occur for aryl halides. For dihalides, unsaturated or cyclic compounds may form via carbocation intermediates, which form transient covalent iodides or are reduced directly by iodide to free radicals. However, the aromatic halide exchange reacts smoothly when 10% Cul is present in the reaction... 

The reaction of 1,3-dinitrobenzenes with aryl iodides can be accomplished by using copper(I) tert-butoxide in situ prepared from CuCl and potassium rert-butoxide in dry DME. In this case, the reaction can be realized under essentially milder reaction conditions, at 70-110 C in the presence of pyridine as the base with respective yields. For instance, the biaryl 40 was produced from compounds 38 and 39 after 20 h at 67 C in DME / pyridine as the reaction solvent in 95% yield, respectively [38]. Dehalogenation products were isolated from many Ullmann reactions performed with the (relatively acidic) nitro-aryl halides, even when exclusion of water or acidic (protic) substances was provided. Furthermore, nitro-aryl halides are partially converted to triarylamines by reduction and subsequent exhaustive A -arylation [44,45]. Finnaly, it can be concluded that the Ullmann and related reactions are still valuable tools in the preparative organic chemistry providing a simple and usually efficient approach to simple symmetrical and certain classes of unsymmetrical biaryls. 

In 1970 Hashimoto published a report on the reaction of potassium hexacy-anodinickelate with organic halides in aqueous solutions [295]. Benzyl bromides were transformed into dibenzyl ketones in the presence of CO in a water-acetone solution. If the reaction was carried out in a water-methanol solution, trans-fi-bromostyrene was transformed into methyl trani-cinnamat. Surprisingly, cinna-maldehyde was also formed in a 10 % yield (Scheme 2.47). The reaction of nickel carbonyl [Ni(CO)4l with organic halides was studied by Bauld in 1963 [296]. Aryl iodides were reacted with Ni(CO)4 in methanol and produced the corresponding methyl benzoate in good yields. If the reaction was carried out in THF, arils were formed. The reaction of allyl halides with Ni(CO)4 in the presence of MgO will produce but-3-enylsuccinic acid [297]. 

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