Reactions of Alkyltropylium Ions with a Base

Abstract

On the reaction with a base (e.g., aqueous sodium hydroxide), isopropyl- and methyl-tropylium ions afforded cycloheptatrienyl polymers with an alkylene bridge, such as IIIa and IIIb, while the t-butyltropylium ion gave a mixture of 3- and 4-t-butyltropone, which was then transformed to 4-and 5-t-butyltropolone (VIIIa and IX). The bromination of VIIIa with 3 mol of bromine in methanol gave 3,7-dibromo-4-t-butyl-2-methoxy-2,3-dihydrotropolone (XIIa). On the heating of the adduct (XIIa) at 130°C, 7-bromo-4-t-butyltropolone (XIa) was formed.