Rouzban Hadiseh, Bayat Mohammad, Hosseini Hajar
Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran.
Mol Divers. 2023 Apr;27(2):667-678. doi: 10.1007/s11030-022-10446-0. Epub 2022 May 19.
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.
通过使用9-芴酮、氰基乙酰肼、1,1-双(甲硫基)-2-硝基乙烯、芳香醛以及盐酸半胱胺或乙醇胺作为起始原料，经五组分串联反应成功合成了两类新型稠合吡啶，即2H-噻唑并[3,2-a]吡啶-6-碳酰肼和2H-恶唑并[3,2-a]吡啶-6-碳酰肼。这种新方法涉及一系列关键步骤：N，S-缩醛或N，O-缩醛的形成、克诺文纳格尔缩合、迈克尔加成、互变异构和N-环化。它还具有一些优点，如操作方便、对多种官能团具有耐受性、使用绿色溶剂以及通过用乙醇洗涤粗产物易于纯化。
