Aryl iodides silver® acetate

Regioselective functionalization of unreactive carbon-hydrogen bonds, in particular, arylation of pyridines by using aryl iodide, silver acetate, and catalytic palladium acetate 06SL3382. 

Treatment of aryl tellurium trichlorides with silver fluoride, potassium bromide, or potassium iodide causes chlorine to be exchanged for other halogens (see p. 320). The reaction of 4-ethoxyphenyl tellurium trichloride with silver acetate gave a compound of indefinite composition6. 

Using an alternative method, homoallylic iodides are efficiently transformed into cyclopropylmethyl acetates using silver acetate in anhydrous benzene (Table 1). y-Disubstituted or conjugated homoallylic iodides are particularly reactive and rearrange quantitatively. y-Monosub-stituted iodides afford mixtures of cyclopropylmethyl and homoallyl acetates in a 1 1 ratio, whereas the absence of a y-alkyl or aryl group in the homoallylic iodides leads to elimination, only. 

O/t/20-arylation of benzoic acids is often preferable to ortho-arylation of benzamides if conversion of the amide moiety to other functional groups is desired. However, only a few reports have dealt with the orf/io-functionalization of free benzoic acids due to challenges that involve such transformations. The reactions can be complicated by decarboxylation of the product and the starting material. Despite those difficulties, several methods for direct o/t/io-arylation of benzoic acids have been developed. Yu has shown that arylboronates are effective in arylation of benzoic acids under palladium catalysis [59], The reactions require the presence of palladium acetate catalyst, silver carbonate oxidant, and benzoquinone. Even more interestingly, the procedure is applicable to the arylation of unactivated sp3 C-H bonds in tertiary carboxylic acids such as pivalic acid (Scheme 13) if aryl iodide coupling partner is used. Aryl trifluoroborates can also be used [60],... 

Another method that has been developed for benzoic acid arylation by aryl iodides involves use of a combination of catalytic palladium acetate with stoichiometric silver acetate in acetic acid (Scheme 14) [61], This method is tolerant of chloride and bromide substitution and most likely proceeds through a Pd(II)-Pd(IV) coupling cycle. Moderately electron-poor to electron-rich benzoic acids are reactive,... 

The coupling of anilines with arylboronic acids has been described in a process catalysed by palladium acetate without the need for ligands, bases, or salts. The mechanism shown in Scheme 17, where S represents solvent, involves in situ formation of the dia-zonium salt from the aniline, and formation of an arylpalladium alkoxo complex which allows the transmetallation step with arylboronic acids. It has been shown that a free amine may be used as a DG in a palladium-catalysed reaction promoted by soluble silver salts. The latter aid the formation of intermediates, (136), which may undergo cyclopalladation followed by transmetallation with an arylboronic acid and reductive elimination. Related work has shown thatbiaryl-2-amines may react with aryl iodides in the presence of palladium acetate and silver acetate to give mono- or di-arylated species such as (137). 

Silver acetate promoted iodine removal and palladium-catalyzed coupling of aryl iodides and (V-acylated anilides produced ortho-aryl acylated anilides, which were then hydrolyzed to give 2-aryl or 2,6-diarylanilines. This silver-ion assisted palladium-catalyzed aryl-aryl coupling was general (53-96% yields) and showed functional group tolerance for chloride and bromide substituents in either the aryl iodides or anilides (eq 16).i ... 

Palladium/silver-catalyzed Heck reactions have usually involved vinyl or aryl halides and alkenes, but these reaction conditions were also extended to allenes. Indeed, Zenner and Larock65 showed that simple alkyl allenes readily reacted with aryl and vinyl iodide derivatives in the presence of palladium acetate or chloride and silver phosphate. Moreover, the reaction could be rendered asymmetric using chiral ligands the best one was a bisoxazolidine derivative (Scheme 10.37). 

---