Preparation Of Adapalene

The thesis mainly studied the process of preparation for intermediates of Adapalene: methyl 6-bromo-2-naphthoate and 2-(1-adamantyl)-4-bromophenol.Two new synthetic routes were designed for methyl 6-bromo-2-naphthoate. Starting from the cheap 6-methoxy-2-acetonaphthone 6-bromo-2-naphthoic acid was prepared in 26% total yield through demethylation, Bucherer reaction, diazotization, bromo-substituted reaction and haloform reaction. Additionally, the Baylis-Hillman reaction adduct of 2,4-dichlorobenzaldehyde with methyl acrylate followed by the acetylation reaction, conjugated addition of nitromethane in the presence of K2CO3 and intramolecular ring-closing in the base at 140℃afforded methyl 6-bromo-2-naphthoate in 10% yield.Instead of using conventional acid catalyst of concentrated sulfuric acid, a environmentally friendly catalyst, strong ion exchange resins, was adopted in the preparation of 2-(1-adamantyl)-4-bromophenol. The optimal condition was set after screening the parameters:1 mmol reactants with the amount of catalyst(H+ form, D001) 0.34g, affording the product in more than 95% yields at 100℃. The resin catalyst D001 has been reused for at least 10 times without significant loss of activity. Scope of the resin catalyzed adamantylation of activated aromatics with adamantanols was further explored, developing a green procedure promoted by the strongly acidic cross-linked polystyrene type sulfonic acid resins for synthesis of 2-adamantylphenol derivatives.