Expanding the scope of fused pyrimidines as kinase inhibitor scaffolds: synthesis and modification of pyrido[3,4-d]pyrimidines

Fused pyrimidine cores are privileged kinase scaffolds, yet few examples of the 2-amino-pyrido[3,4-d]pyrimidine chemotype have been disclosed in the context of kinase inhibitor programs. Furthermore, no general synthetic route has been reported to access 2-amino-pyrido[3,4-d]pyrimidine derivatives. Here we report a versatile and efficient chemical approach to this class of molecules. Our strategy involves the concise preparation of 8-chloro-2-(methylthio)pyrido[3,4-d]pyrimidine intermediates and their efficient derivatisation to give novel compounds with potential as kinase inhibitors.