Reactions of linear conjugated dienone structures with arenes under superelectrophilic activation conditions. An experimental and theoretical study of intermediate multicentered electrophilic species

Reactions of linear conjugated dienone structures ArCH=CHCH=CHC(=O)X, 1,5-diarylpenta-2,4-dien-1-ones (X = Ar'), 5-phenylpenta-2,4-dienoic acid (Ar = Ph, X = OH) and its methyl ester (Ar = Ph, X = OMe), with arenes under superelectrophilic activation conditions by Bronsted superacids (CF3SO3H and FSO3H) or strong Lewis acid (AlCl3) result in the formation of various compounds, such as conjugated enones, indanes, and carbocyclic derivatives. The formation of the reaction products depends on the structures of starting compounds (dienone and arene) and on the reaction conditions (temperature, time, and medium acidity). In these transformations, starting dienones are precursors of di- and tricentered electrophilic synthons leading to target products. A NMR study and DFT calculations have shown that the most probable reactive intermediates should be O,C-diprotonated species Ar+CHCH2CH=CHC(=O+H)X derived from the protonation of starting dienones. Plausible mechanisms of electrophilic transformations are discussed.

Automated summary

Reactions of compounds with linear conjugated dienone structures with arenes under superelectrophilic activation conditions result in the formation of various compounds. The formation of the reaction products depends on the structures of the starting compounds and the reaction conditions. The starting dienones act as precursors of electrophilic synthesis intermediates, leading to the formation of target products.