Regioselective Nucleophilic Substitution of 5-Bromo-2-methoxytropone

The reaction of 5-bromo-2-methoxytropone with O- and N-nucleophiles, such as ethanol/potassium carbonate, sodium hydroxide, diethylamine, propylamine, p-chloroaniline/triethylamine, and p-phenylenediamine/triethylamine, gave corresponding 2-O- and 2-N-substituted troponoids. Alkyl diamines reacted with the substrate to produce bis(2-aminotropone)s. In the case of S-nucleophiles as 1-propanethiol, thiophenol, and 4-aminothiophenol with a base, the regioselective substitution at the 5-position occurred. Halogenation reagents, triphenyldibromophosphorane and its dichloro analogue, furnished 2,5-dibromo- and 2,5-dichlorotropones, respectively.