Design and biological evaluation of imidazo[1,2-a]pyridines as novel and potent ASK1 inhibitors.

Imidazo[1,2-a]pyridine derivatives were designed, synthesized, and evaluated as inhibitors of the apoptosis signal-regulating kinase 1 (ASK1). These were based on a benzothiazole derivative that was discovered from high-throughput screening of our compound library. As a result, we identified potent, selective, and orally bioavailable ASK1 inhibitors for wide range of therapeutic targets.

Palladium-catalyzed dehydroarylation of triarylmethanols and their coupling with unsaturated compounds accompanied by C-C bond cleavage.

Triarylmethanols are effectively dehydroarylated and reacted with some unsaturated compounds by using an appropriate palladium catalyst system such as Pd(OAc)2-P(1-Nap)3 (1-Nap = 1-naphthyl) to give the corresponding arenes and hydroarylation products, respectively, along with diaryl ketones.

Palladium-catalyzed arylation of alpha,alpha-disubstituted arylmethanols via cleavage of a C-C or a C-H bond to give biaryls.

The palladium-catalyzed arylation of alpha,alpha-disubstituted arylmethanols with aryl halides proceeds not only via C-H bond cleavage at the ortho-position, but also via cleavage of the sp(2)-sp(3) C-C bond with the liberation of ketones (beta-carbon elimination) to give the corresponding biaryls. Both reactions appear to occur through common arylpalladium(II) alcoholate intermediates. The results of systematic studies with respect to which C-C or C-H bond is preferentially cleaved in the arylation are reported. Among the important findings is the selective elimination of ortho-substituted aryl groups even from aryl(diphenyl)methanols due to steric reasons. Thus, various biaryls having ortho-substituents can be produced efficiently by treatment of the corresponding aryl(diphenyl or dimethyl)methanols with aryl bromides and chlorides.