Scalable and Practical Synthesis of Halo Quinolin-2(1H)-ones and Quinolines

Abstract

A practical and scalable synthesis of halo quinolin-2(1H)-ones is presented. The heterocycles are easily accessed from inexpensive halo anilines in a two-step sequence. The anilines are acylated with methyl 3,3-dimethoxypropionate under basic conditions in quantitative yields. The crude amides undergo cyclization in sulfuric acid to the desired halo quinolin-2(1H)-ones in 28–93% yield (2 steps). The synthetic sequence was successfully applied on 800 g scale. Anilines with strong electron withdrawing or electron donating groups were poor substrates for this procedure. 6-Iodoquinolin-2(1H)-one and 6-bromo-8-iodoquinolin-2(1H)-one were further functionalized to obtain quinolines substituted with various functional groups.