A Shorter Synthesis of Dithienopyridines Through Pd(0)-Catalyzed Coupling of 2-(2-Trimethylstannyl-3-thienyl)-1,3-dioxolane with<i>tert</i>- Butyl<i>N</i>-(<i>ortho</i>-Halothienyl)carbamates
Less sterically crowded 2-(2-trimethylstannyl-3-thienyl)-1,3-dioxolane (4) was prepared and coupled with tert-butyl N-(ortho-halothienyl) carbamates, catalyzed by Pd(0) complex, to give dithieno[3,2-b; 2′,3′-d] pyridine (5), dithieno[3,4-b; 2′,3′-d]pyridine (6), and dithieno[2,3-b; 2′,3′-d]pyridine (7) in good yields.