Figure 2.
Synthetic schemes for the syntheses of PDE4D inhibitors. (A) Inhibitors were synthesized through the Suzuki coupling reactions of alkyl bromide and arylboronic esters/acids. (B) Inhibitors were synthesized through the substitution reactions of alkyl halide. (C) Inhibitors were synthesized through the palladium-mediated coupling of anilines/phenols (ArNH2/ArOH) with aryl chloride. (D) Inhibitor 23 was synthesized as a side product from the reaction of palladium-mediated coupling of α-fluorinated 2-picolinyl triflones with arylboronic acids.