Dihydrobenzoxazines and tetrahydroquinoxalines by a tandem reduction-reductive amination reaction
作者:Richard A. Bunce、Derrick M. Herron、Lu Y. Hale
DOI:10.1002/jhet.5570400611
日期:2003.11
A tandem reduction-reductive amination reaction has been applied to the synthesis of 3,4-dihydro-2H-1,4-benzoxazines and 1-acetyl-1,2,3,4-tetrahydroquinoxalines. The nitroketones required for the benzoxazine ring closures were prepared by (A) alkylation of the anion derived from 2-nitrophenol with an allylic halide or (B) nucleophilic aromatic substitution of an allylic alkoxide on 2-fluoro-1-nitrobenzene
串联还原-还原胺化反应已用于合成3,4-二氢-2 H -1,4-苯并恶嗪和1-乙酰基-1,2,3,4-四氢喹喔啉。苯并恶嗪环闭合所需要的硝基酮是通过(A)用烯丙基卤化物将2-硝基苯酚衍生的阴离子烷基化,或(B)在2-氟-1-硝基苯上进行烯丙基醇盐的亲核芳族取代,然后进行臭氧分解来制备的。喹喔啉的前体是通过将2-硝基乙酰苯胺的阴离子与烯丙基卤化物烷基化,然后进行臭氧分解来制备的。然后在甲醇中使用5%钯碳催化硝基酮的加氢反应,然后通过还原-还原胺化顺序得到目标杂环。该ñ通过在还原之前添加5-10当量的甲醛水溶液,可以轻松制备两个环系统的α-甲基衍生物。通过色谱法纯化后,高产率地分离出二氢苯并恶嗪。以相似的方式分离四氢喹喔啉,并在两个氮原子上具有不同的官能度。