The use of phosphonium anhydrides for the synthesis of 2-oxazolines, 2-thiazolines and 2-dihydrooxazine under mild conditions
作者:Maria J. Petersson、Ian D. Jenkins、Wendy A. Loughlin
DOI:10.1039/b818310d
日期:——
β-Hydroxy amides6 and 7 were treated with triphenylphosphonium anhydride trifluoromethane sulfonate (3), or the cyclic analogue 4, to generate 2-oxazolines 5 and 8 under mild conditions. The reaction was optimised by examining the number of equivalents of reagents 3 or 4, or diisopropylethyl amine required to best effect cyclisation. The effects of altering the reaction temperature, reaction time,
β-羟基酰胺6和7用三苯基anhydride酸酐三氟甲烷磺酸盐(3)或环状类似物4在温和条件下产生2-恶唑啉5和8。通过检查试剂3或4或二异丙基乙胺的当量数来优化反应,以达到最佳环化效果。还研究了改变反应温度,反应时间,浓度,溶剂和添加速率的影响。然而,发现使用三苯甲基来封闭起始酰胺的羟基或硫醇基团上的反应,以及随后在不存在碱的情况下进行原位去三苯甲基化反应,可以大大提高收率。试剂4 在提纯产品方面具有显着优势,可用于脱水一系列三苯甲基衍生物,以高产率(85-99%)生成四恶唑啉,噻唑啉和二氢-1,3-恶嗪,以及四氢呋喃。 -1,3-奥氮平(31%)。