Syntheses of Substituted Phenyl-2-thienyliodonium Halides and Their Pyrolysis Reactions

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Abstract
Various substituted phenyl-2-thienyliodonium halides were prepared by the reaction of thiophene with substituted phenyliodoso acetates in acetic anhydride–concentrated sulfuric acid. In the pyrolysis reaction of substituted phenyl-2-thienyliodonium chlorides it was found that the chloride ion selectively attacked the 1-carbon of the phenyl group. The product ratios in the pyrolysis reaction of substituted phenyl-2-thienyliodonium bromides can be explained on the basis of a bimolecular aromatic nucleophilic substitution except for p-chlorophenyl-2-thienyliodonium bromide. In the case of p-chloro substituted derivative an interesting effect of p-chloro group was observed. The pyrolysis reaction of substituted phenyl-2-thienyliodonium iodides gave substituted phenyl iodides and 2-iodothiophene. The solution reaction of phenyl-2-thienyliodonium halides in N,N-dimethylformamide gave halobenzene and 2-iodothiophene. These results suggest that the reaction proceeds via an interaction between the halide ion and the phenyl group in a trigonal-bipyramidal structure.