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.