Chemistry of thienopyridines. XXXVIII. Diels‐Alder reactions of thienopyridine sulfones. Part 2

Abstract

AbstractThieno[3,2‐b]pyridine 1,1‐dioxide (2) undergoes Diels‐Alder condensation with the dienophiles cyclopentadiene, anthracene, and naphthacene in a manner analogous to its isomer thieno[2,3‐b]pyridine 1,1‐dioxide (1). Compound 2 dimerizes in refluxing xylene with the loss of sulfur dioxide plus either the loss or transfer of hydrogen to give a small yield (ca. 2%) of pyrido[2′,3′:4,5]thieno[3,2‐f]quinoline 7,7‐dioxide (7) and its 5,6‐dihydro derivative 12. Formation of 7 and 12 are compared and contrasted with products reported from dimerization of 1 and of benzo[b]thiophene 1,1‐dioxide and its derivatives.