Formation of the Pyridine Ring in the Synthesis of Dipyrido[3′,2′:4,5]thieno[3,2‐b:3,2‐d]pyridines.

Abstract

Fused pyridine derivatives R 0450 Formation of the Pyridine Ring in the Synthesis of Dipyrido[3',2':4,5]thieno[3,2-b:3,2-d]pyridines. -Attempts to reduce the carbonyl group in ketones (I) with NaBH4 results in formation of the pentacyclic title heterocycle (II) instead of the expected alcohols. -(VASILIN, V. K.; LIPUNOV, M. M.; KONYUSHKIN, L. D.; KAIGORODOVA, E. A.; KRAPIVIN, G. D.; Chem. Heterocycl. Compd. (N. Y.) 42 (2006) 10, 1368-1369; Kuban State Technol. Univ., Krasnodar 350072, Russia; Eng.) -R. Langenstrassen 26-132

Furan ring recyclization in 2‐furfurylthieno[2,3‐b]pyridines: An intramolecular N‐alkylation of pyrrole ring under acid conditions

“…We suppose that the formation of 5a and 6 proceeds as follows: the furan ring opening leads to a diketone, which in turn reacts with amino group to afford A (Scheme ). The aromatization of A leads to pyrrole ring formation as observed earlier for benzylfurans [11–13] to give compound 5a (Path a ). Another route—pyrrolizine 6 formation—is a concurrent process.…”

“…Thieno[2,3‐ b ]pyridine derivatives are well known to possess varied biological and pharmacological activities, and hence, their synthesis has been of interest to chemists [1–7]. We have successively used different thieno[2,3‐ b ]pyridine derivatives as intermediates for synthesis of some interesting conjugated and annulated heterocyclic systems [8–11].…”