Photochemical Aromatic Alkylation

Article abstract of DOI:10.1021/jo00236a034

Photolysis of n-alkyl iodides (propyl, butyl, pentyl, and hexyl) in neat aromatic compounds (benzene, toluene, and anisole) produced modest amounts of the corresponding n-alkylated aromatic products.In addition, varying amounts of isomerized alkylarene were found, and extensive isomerization was noted in the recorvered alkyl iodides.All isomerization was suppressed by running the photolyses in the presence of triethylamine, an HI trapping agent.Photolysis of secondary alkyl iodides (isopropyl, sec-butyl, and 2- and 3-hexyl) led to very small amounts of the corresponding sec-alkylarene.When the photolyses were performed in solvents such as acetonitrile and methanol, solvolysis products (N-alkylacetamides, or alkyl methyl ethers) were formed at the expense of the aromatic substitution products.These results were indicative of alkyl cation intermediates, presumably formed by way of electron transfer within an initial alkyl radical-iodine atom pair.Of various model cation systems studied for comparison, the photolysis intermediates resembled poorly solvated cation models (i.e. from aprotic alkylamine deaminations) most closely.