Chemistry of thienopyridines. XIII. Selective formation of sulfones in Bi‐ and tricyclic Systems. Thieno[2,3‐b]pyridine 1,1‐dioxide as a dienophile

Abstract

Bicyclic and tricyclic thienopyridines are converted into sulfones in 13‐73% yield by means of acid‐hypochlorite. The sulfone thieno[2,3‐b]pyridine 1,1‐oxide (Ib) undergoes Diels‐Alder condensation with furan (both exo and endo products formed), anthracene, and naphthacene. Self‐condensation of Ib occurs with elimination of sulfur dioxide to give 8‐(3‐pyridyl)quinoline (XV). The structure of XV was established by means of pmr and a europium shift reagent. Ultraviolet, pmr, and mass spectral data for various compounds are presented and discussed.

Synthesis and Reactivity of Dithienopyrazines**

“…Thus, oxidation with H 2 O 2 in acetic acid or m-chloroperbenzoic acid in chloroform led to the corresponding pyridine N-oxide, [59,60] oxidation with sodium hypochlorite in diluted hydrochloric acid to the 1,1-dioxide. [61] Structural proofs came from 1 H NMR and IR data. In this respect, thiophene 1,1-dioxide units show much larger coupling constants (7-7.5 Hz) for the thiophene α,βprotons [62] than thiophene units itself (5.6-5.9 Hz).…”

Unusual Oxidative Dimerization in the 3-Aminothieno[2,3-b]pyridine-2-carboxamide Series

“…In general, selective oxidation of thienopyridines with a variety of reagents can be considered as an effective route to functionalization of the bicyclic core and has been used for preparation of the corresponding N-oxides 16 and 17 , − halo derivatives 18 and 19 , , S-oxides 20 – 22 , ,,, sulfones 23 and 24 , ,− and functionalized molecules 25 – 29 (Scheme ).…”