Synthesis of 1,4-Disubstituted Pyrido[1′,2′:1,5]pyrazolo[3,4-d]pyridazines by Means of SNAr and Palladium-Catalysed Reactions

Design of new disubstituted imidazo[1,2-b]pyridazine derivatives as selective Haspin inhibitors. Synthesis, binding mode and anticancer biological evaluation

Haspin is a mitotic protein kinase required for proper cell division by modulating Aurora B kinase localisation and activity as well as histone phosphorylation. Here a series of imidazopyridazines based on the CHR-6494 and Structure Activity Relationship was established. An assessment of the inhibitory activity of the lead structures on human Haspin and several other protein kinases is presented. The lead structure was rapidly optimised using a combination of crystal structures and effective docking models, with the best inhibitors exhibiting potent inhibitory activity on Haspin with IC₅₀ between 6 and 100 nM in vitro. The developed inhibitors displayed anti-proliferative properties against various human cancer cell lines in 2D and spheroid cultures and significantly inhibited the migration ability of osteosarcoma U-2 OS cells. Notably, we show that our lead compounds are powerful Haspin inhibitors in human cells, and did not block G2/M cell cycle transition due to improved selectivity against CDK1/CyclinB.

Three successive and regiocontroled palladium cross-coupling reactions to easily synthesize novel series of 2,4,6-tris(het)aryl pyrido[1',2':1,5]pyrazolo[3,4-d]pyrimidines

The first access to tris(het)arylated pyrido[1',2':1,5]pyrazolo[3,4-d]pyrimidine derivatives is reported. The series were generated from 4-chloroaminopyridinium, which afforded the key intermediate bearing three leaving groups, i.e. a C-2 methylsulfanyl, a lactame carbonyl group in C-4 and a chlorine atom in C-6. The regioselective reactions led to the tris(het)aryl derivatives with satisfying to high yields. The three successive cross-coupling reactions occurred first in C-6 by the displacement of chlorine, next in C-4 position by a sequential Pd-catalyzed phosphonium coupling and finally in C-2 under a Pd/Cu-catalyzed desulfitative cross-coupling reaction. The optimization and scope of each reaction are discussed and the original compounds characterized.

Controlled Dimroth Rearrangement in the Suzuki-Miyaura Cross Coupling of Triazolopyridopyrimidines

Polynitrogen heterocycles are often subject to Dimroth rearrangement which consists of ring opening, bond rotation, and ring closure. In this note, we report a synthesis of two new families of triazolopyridopyrimidines. Successful functionalization via a Suzuki-Miyaura coupling was performed with total control of triazole (Dimroth) isomerization based on the judicious choice of reaction conditions.