Synthesis of oxazines and thiazines by cyclodehydration of hydroxy amides and thioamides
作者:Peter Wipf、Gregory B. Hayes
DOI:10.1016/s0040-4020(98)00341-x
日期:1998.6
3-oxazines and -thiazines were obtained by cyclodehydration of hydroxy amides and thioamides with PEG-linked Burgess reagent or under Mitsunobu conditions. Yields were generally higher with polymer-Burgess reagent, but both conditions failed to cyclize δ- and ε-hydroxy amide precursors. In contrast, Burgess reagent was successful for the cyclodehydration of δ-hydroxy thioamide to give the expected
通过用PEG连接的Burgess试剂或在Mitsunobu条件下将羟基酰胺和硫酰胺进行环脱水反应,可获得二氢-1,3-恶嗪和噻嗪。用聚合物-Burgess试剂的产率通常较高,但两种条件均无法使δ-和ε-羟基酰胺前体环化。相反,Burgess试剂成功地将δ-羟基硫代酰胺进行环脱水,得到了预期的硫氮杂杂环,而Mitsunobu反应仅提供了硫代酰基吡咯烷。两组反应条件均导致ε-羟基硫酰胺的环脱水中的硫酰基哌啶。恶嗪的硫解以中等至良好的产率提供了羟基硫酰胺中间体,因此建立了将恶嗪转化为噻嗪的新方案。