synthesis method | 3-bromoisonicotinic acid and methanol under the catalysis of solid superacid, methyl 3-bromoisonicotinate was obtained by esterification, and the conversion rate of 3-bromoisonicotinic acid was increased by keeping the excess of methanol, therefore, the halogen atom in the structural formula of the product is easily protonated, and the halogen atom is a strong electron-withdrawing group after protonation, the bromine substituent attached to the halogen atom is also a strong electron-withdrawing group, the carbon atom attached to the bromine substituent shows strong electropositivity. At this time, the methanol oxygen atom in the reaction system shows strong electronegativity due to the lone pair of electrons, the nucleophilic addition reaction takes place on the carbon atom which is easily attacked and attached to the bromine substituent, and then the hydrogen bromide and the proton are removed respectively under the weak alkaline condition to obtain the by-product. |