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Direct Synthesis of Multi‐functional Pyrimidine, Pyrazine, and Pyridine Scaffolds via Inter‐ and Intramolecular Annulations of 3‐Amino‐thieno[2,3‐ b ]pyridine‐2‐carboxylate
Author(s) -
ElSayed Hassan A.,
Said Said A.
Publication year - 2019
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.3488
Subject(s) - chemistry , triethyl orthoformate , pyrazine , formamide , pyrimidine , diethyl malonate , hydrazine (antidepressant) , pyridine , hydrate , medicinal chemistry , curtius rearrangement , derivative (finance) , salicylaldehyde , annulation , malonate , organic chemistry , schiff base , stereochemistry , catalysis , chromatography , financial economics , economics
The synthesis of a new series of annulated thieno[2,3‐ b ]pyridines was performed. Ester compound 1 underwent heterocyclization upon reaction with phenylisothiocyanate and formamide to afford pyrimidines 2 and 3 , respectively. Thienopyrimidine 5 was resulted via reaction of amino derivative 1 with triethyl orthoformate to afford the non‐isolable intermediate 4 , which allowed hydrazinolysis with hydrazine hydrate to afford the target compound. Pyrimidine type 5 was condensed with p ‐nitrobenzaldehyde to afford Schiff base 6 . Refluxing of ester 1 with ethyl cyanoacetate and diethyl malonate followed by base‐mediated heterocyclization afforded condensed pyridines 8 and 9 , respectively. The tetracyclic pyrazine derivative 14 was obtained from the reaction of amino compound 1 with 2,5‐dimethoxytetrahydrofuran followed by hydrazinolysis to give carbohydrazide 11 , which undergo diazotization followed by Curtius rearrangement. The antibacterial results illustrated no significant results for the investigated compounds except compound 5 , which has moderate activity against Gram‐positive bacteria.