Facile Aromatic Nucleophilic Substitutioins Observed for the Triarylcarbenium Ions, +

Article abstract of DOI:10.1246/bcsj.68.3233

Triarylmethanols of type (4-YC6H4)Φ2COH <Φ=2,6-(MeO)2C6H3; Y=MeO, Cl, Me2N> were prepared.The methanol, (4-MeOC6H4)Φ2COH, reacted with acids in a variety of solvents to give the triarylcarbenium salts, <(4-MeOC6H4)Φ2C>X or <(4-HOC6H4)Φ2C>X, or 4-bis(2,6-dimethoxyphenyl)methylene-2,5-cyclohexadienone, O=C6H4=CΦ2, depending on the conditions.These carbenium salts further reacted in alcohols, ROH, to give the triarylmethanes, (4-ROC6H4)Φ2CH (R=Me, Et), where the para-substituent, MeO or HO, was substituted by the solvent, accompanied by a reduction at the central c arbon.The methanol, (4-ClC6H4)Φ2COH, also reacted with acid to give the carbenium salt or the triarylmethane, depending on the conditions.While the methanol, (4-Me2NC6H4)Φ2COH, also gave the carbenium salt, <(4-Me2NC6H4)Φ2C>-X, it was inert against the formation of the triarylmethane under analogous conditions.It reacted with aqueous sodium hydroxide to give O=C6H4=CΦ2 rather than the original methanol.The para-substituent of <(4-MeOC6H4)Φ2C>X was substituted by di- and monoalkylamines, RR'NH, to give <(4-RR'NC6H4)Φ2C>X (R,R'=Me,Me; Et,Et; Me,H; Et,H; Bu,H).While <(4-ClC6H4)Φ2C>X reacted with the dialkylamines to give <(4-RR'NC6H4)Φ2C>X, it reacted with monoalkylamines, RNH2, to give <(4-ClC6H4)Φ2C-NRH2>X. <(4-Me2NC6H4)Φ2C>X was hydrolyzed in the presence of diethylamine to give O=C6H4=CΦ2, but reacted with monoalkylamines to give RN=C6H4=CΦ2.