A series of 2-substituted-4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)imidazoles was synthesized and evaluated to optimize a prototype inhibitor of TGF-β type I receptor kinase (ALK5), 6. Combination of replacement of a quinoxalin-6-yl moiety of 6 with a [1,2,4]triazolo[1,5-a]pyridin-6-yl moiety, insertion of a methyleneamino linker, and a o-F substituent in the phenyl ring markedly increased ALK5 inhibitory activity, kinase selectivity, and oral bioavailability. The 12b (EW-7197) inhibited ALK5 with IC50 value of 0.013 μM in a kinase assay and with IC50 values of 0.0165 and 0.0121 μM in HaCaT (3TP-luc) stable cells and 4T1 (3TP-luc) stable cells, respectively, in a luciferase assay. Selectivity profiling of 12b using a panel of 320 protein kinases revealed that it is a highly selective ALK5/ALK4 inhibitor. Pharmacokinetic study with 12b·HCl in rats showed an oral bioavailability of 51% with high systemic exposure (AUC) of 1426 ng × h/mL and maximum plasma concentration (Cmax) of 1620 ng/mL. Rational optimization of 6 has led to the identification of a highly potent, selective, and orally bioavailable ALK5 inhibitor 12b.

6-Aryl substituted phenanthridines were synthesized via a visible-light-catalyzed cyclization of 2-isocyanobiphenyls with arylsulfonyl chlorides under oxidant-free and transition-metal-free conditions. This transformation represents an efficient and attractive synthetic utilization of arylsulfonyl chlorides.

A visible-light-catalyzed synthesis of aryl ketones from aryldiazonium salts, CO and (hetero)arenes at room temperature is discovered. This transformation represents an efficient and attractive synthetic utilization of aryl diazonium salts.Scheme 1 Synthesis of aryl ketones via redox carbonylation. † Electronic supplementary information (ESI) available. See

A visible-light-catalyzed synthesis of 3-acylindoles from simple indoles and α-oxo acids at room temperature has been discovered. This method offers rapid access to 3-acylindoles through C–C and C–H bond activation.

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