Indoles copper® trifluoroacetate

The synthesis of 7-methoxyindole was accomplished starting from 1-acetylindoline (34). Regioselec-tive intr uction of iodine was achieved using thallium trifluoroacetate, then potassium iodide. Deacetylation and oxidation to the indole (35), followed by reaction with sodium methoxide in DMF, gave the 7-methoxyindole (36) in 48% overall yield (Scheme 13). More recently, Somei et al have reported that treating the intermediate thallium species with copper(II) sulfate pentahydrate gives directly the l-acetyl-2,3-dihydro-7-hydroxyindole (37) in 42% yield (Scheme 14). It remains to be seen whether this is a general process. 

The aryl chlorides and aryl bromides are easily prepared by treatment of the arylthallium(III) bis(trifluoroacetates) with the corresponding copper(I) or copper(II) halides. The best yields were obtained with the copper(II) halides in dioxane under reflux. 2 These reactions have been successfully applied by Somei et al to the synthesis of indole derivatives by reaction of the arylthallium compounds with copper(II) salts in DMF. 127,133,134... 

Thallation of benzanilides with thallium tris(trifluoroacetate) in a mixture of trifluoroacetic acid and ether gave the c rr/to-thallated products. Reaction of these products with copper(I) acetylide in acetonitrile led to the 2-benzamidotolanes (119), which were eventually elaborated into the 2-phenyl-indole derivatives. 111 ... 

Itami has reported that electron-rich arenes can be arylated by arylboronic acids in the presence of stoichiometric copper(II) trifluoroacetate [ 103 ]. Trimethoxybenzene, indole, and pyrrole were shown to be reactive. Reactions proceed in dichloromethane in the presence of trifluoroacetic acid. 

Arylation. Copper(II) trifluoroacetate was used to perform the arylation of indoles with triphenylbismuth bis-trifluoroacetate. Products bearing a C3 phenyl group were obtained with Cs-unsubstituted indoles (eq4) and IV-phenyl derivative with carbazole. 

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