The synthesis and chemical reactivity of thieno[2,3‐c]‐ and thieno[3,2‐c] pyridines

Abstract

The syntheses and reactions of various thieno[2,3‐c]‐ and thieno[3,2‐c] pyridines are described. Molecular orbital calculations were performed on thieno[2,3‐c]pyridine (1) in order to determine the most susceptible sites to electrophilic and nucleophilic attack. Superdelocalizability values, Sr‐ are reported for each position in this molecule to give relative orders of reactivity towards the two types of reactions. Electrophilic attack was found to occur experimentally at C‐3 in all the thienopyridines studied. Peracid oxidation of thieno[2,3‐c]‐ and thieno[3,2‐c]pyridines produced only the N‐oxide. The lack of reactivity of certain thienopyridines under Vilsmeier formylation and Friedel‐Crafts acetylation conditions was related to their basicities. The dissociation constants of various thienopyridinium salts are reported.

A Rapid Synthesis of Thieno[2,3-c]pyridine and 2-Substituted Thieno[2,3-c]pyridines

“…In addition, thieno [2,3-c]pyridine undergoes electrophilic attack only at C-3 as reported for benzo[b]thiophene, thieno [2,3-b]-and thieno [3,2-b]pyridines. 6 So a synthesis would be of great synthetic interest which allows for obtaining of the C-2 isomers.…”

1,3‐Dipolare Additionen an 7‐Methylthieno[2,3‐c]pyridin‐1,1‐dioxid

“…Aus Doppelresonanz-Experimenten geht hervor, dass das Proton an C(8b) nur das Proton an C(3a) als direkten Nachbarn besitzt, wahrend sich letzteres mit 2 weiteren Protonen koppelt. [2,3-c]pyridin [3] in 340 ml 30proz. Wasserstoffperoxid wurde unter Kiihlen innert 3 Std.…”

“…,, 48,45 ,, 3,99 ,, 18,68 6 liess sich durch Kochen in methanolischer Natriummethylatlosung nicht in das entsprechende Natriumsulfinat iiberfiihren. 3,4': 4,5]thieno [Z, 3-clpyridin -4,4-dioxid (8). Eine Losung von 12 g (66,4 mmol) 1 in 180 ml THFIMethanol 11:7 wurde bei -15" mit einem Uberschuss atherischer Diazoathanlosung versetzt.…”