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The preparation of eight isomeric thieno[2,3‐b]‐ and [3,2‐b]‐fused naphthyridines [1] was improved through the Pd(0) catalyzed cross‐coupling of 3‐formyl‐4‐iodopyridine, 2‐formyl‐3‐iodopyridine, 3‐bromo‐4‐formylpyridine and 2‐bromo‐3‐formylpyridine with t‐butyl N‐(2‐trimethylstannyl‐3‐thienyl)car‐bamate and t‐butyl N‐(3‐trimethylstanny‐2‐thienyl)carbamate.

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Through the use of Pd(0)‐catalyzed couplings between 2‐(2‐trimethylstannyl‐3‐pyridyl)‐1,3‐dioxolane, 3‐trimethylstannyl‐2‐pyridine carboxaldehyde, 3‐trimethylstannyl‐4‐pyridine carboxaldehyde and 4‐trimethyl‐stannyl‐3‐pyridine carboxaldehyde with t‐butyl‐N‐(3‐bromo‐2‐thienyl)carbamate, t‐butyl‐N‐(2‐bromo‐3‐thienyl)carbamate and t‐butyl‐N‐(4‐bromo‐3‐thienyl)carbamate in N,N‐dimethylformamide at 100°, using cupric oxide as a coreagent, all twelve isomeric thieno[b]naphthyridines have been synthesized in an one‐pot procedure. A detailed study of the 1H and 13C nmr spectra of these isomers has been undertaken.