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Efficient regioselective five-component synthesis of novel thiazolo[3,2-a]pyridine carbohydrazides and oxazolo[3,2-a]pyridine carbohydrazides

Efficient regioselective five-component synthesis of novel thiazolo[3,2-a]pyridine... Two new categories of fused pyridines include 2H-thiazolo[3,2-a]pyridine-6-carbohydrazides and 2H-oxazolo[3,2-a]pyridine-6-carbohydrazides have been successfully synthesized via five-component cascade reactions using 9-fluorenone, cyanoacetohydrazide, 1,1-bis(methylthio)-2-nitroethene, aromatic aldehydes and cysteamine hydrochloride or ethanol amine as starting materials. This new approach involves a subsequence of key steps: N,S-acetal or N,O-acetal formation, Knoevenagel condensation, Michael addition, tautomerization and N-cyclization. It also has some advantages, such as convenience of operation, tolerance of a wide diversity of functional groups, use of green solvent and ease of purification by washing the crude products with ethanol.Graphical abstract[graphic not available: see fulltext] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Molecular Diversity Springer Journals

Efficient regioselective five-component synthesis of novel thiazolo[3,2-a]pyridine carbohydrazides and oxazolo[3,2-a]pyridine carbohydrazides

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References (40)

Publisher
Springer Journals
Copyright
Copyright © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2022
ISSN
1381-1991
eISSN
1573-501X
DOI
10.1007/s11030-022-10446-0
Publisher site
See Article on Publisher Site

Abstract

Two new categories of fused pyridines include 2H-thiazolo[3,2-a]pyridine-6-carbohydrazides and 2H-oxazolo[3,2-a]pyridine-6-carbohydrazides have been successfully synthesized via five-component cascade reactions using 9-fluorenone, cyanoacetohydrazide, 1,1-bis(methylthio)-2-nitroethene, aromatic aldehydes and cysteamine hydrochloride or ethanol amine as starting materials. This new approach involves a subsequence of key steps: N,S-acetal or N,O-acetal formation, Knoevenagel condensation, Michael addition, tautomerization and N-cyclization. It also has some advantages, such as convenience of operation, tolerance of a wide diversity of functional groups, use of green solvent and ease of purification by washing the crude products with ethanol.Graphical abstract[graphic not available: see fulltext]

Journal

Molecular DiversitySpringer Journals

Published: Apr 1, 2023

Keywords: Thiazolopyridine; Oxazolopyridine; Cyanoacetohydrazide; Nitroketene acetal; One-pot reaction

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