The Synthesis of a Novel Inhibitor of B-Raf Kinase

A scaleable synthetic route to [4,7']bis-isoquinolinyl-1-yl-(2-tert-butyl-pyrimidine-5-yl)amine (1), an inhibitor of B-Raf kinase is described. The key step in the synthesis is the Pd-catalyzed Negishi coupling of 4-bromo-1-chloroisoquinoline with trifluoromethanesulfonic acid isoquinoline-7-yl ester to yield 1-chloro[4,7']bis-isoquinolinyl. This intermediate is transformed to the desired drug substance in one additional step, by reaction with 2-tert-butyl-5-aminopyrimidine in the presence of NaH. A special focus was put on the finally successful removal of traces of Zn and Pd in the drug substance, which came from the Negishi coupling.