Chemo-selective Suzuki-Miyaura reactions: Synthesis of highly substituted [1,6]-naphthyridines

The Suzuki-Miyaura reaction of methyl-5-bromo-8-(tosyloxy)-1,6-naphthyridine-7-carboxylate (5), with 2 equiv. of arylboronic acids gave diarylated product, 5,8-diaryl-1,6-naphthyridine-7-carboxylate (7), whereas 1 equiv. of arylboronic acid resulted in site-selective formation of 5-aryl-8-(tosyloxy)-1,6-naphthyridine-7-carboxylate (8). The reactions proceeded with excellent chemo-selectivity in favor of the bromide group. Likewise, one-pot reaction with completely different boronic acids by sequential addition produced 1,6-naphthyridine-7-carboxylates, (10) containing two different aryl groups at 5 and 8 positions. (C) 2017 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.