反应详情

Key building block 2-(5-bromo-pyridin-2-yl)-5-chloro-pentanoic acid (XII) can be prepared according to Scheme 8. Starting with commercially available 5-bromo-2-iodo-pyridine (XXXV), copper-catalyzed reaction with malonic acid diethyl ester furnishes 2-(5-bromo-pyridin-2-yl)-malonic acid diethyl ester (XXXVI). Hydrolysis and decarboxylation under basic conditions gives (5-bromo-pyridin-2-yl)-acetic acid (XXXVII), which subsequently can undergo nucleophilic acyl substitution with thionyl chloride in methanol to provide (5-bromo-pyridin-2-yl)-acetic acid methyl ester (XXXVIII). Deprotonation of XXXVIII with strong base followed by alkylation with 1-bromo-3-chloropropane gives 2-(5-bromo-pyridin-2-yl)-5-chloro-pentanoic acid methyl ester (XXXIX), which can then be hydrolyzed under aqueous basic conditions to furnish key building block 2-(5-bromo-pyridin-2-yl)-5-chloro-pentanoic acid (XII).