Synthesis of 2,4,5-Trisubstituted Oxazoles with Complementary Regioselectivity from α-Oxoketene Dithioacetals and β-(Methylthio)-β-(het)aryl-2-propenones
作者:Siripuram Vijay Kumar、Anand Acharya、Hiriyakkanavar Ila
DOI:10.1021/acs.joc.8b00900
日期:2018.6.15
An efficient protocol for the synthesis of 2,5-substituted 4-acyloxazoles and the related 2,4-substituted 5-acyloxazoles with complementary regioselectivity from the corresponding α-oxoketene dithioacetals or β-(het)aryl/(methylthio)enone precursors has been reported. In the first protocol, the α-oxoketene dithioacetals or β-(methylthio)enones were converted to the corresponding α-bromo-β-(methylthio)enones
从相应的α-氧杂环丁烯二硫缩醛或β-(杂)芳基/(甲硫基)烯酮前体合成具有互补区域选择性的2,5-取代的4-酰基恶唑和相关的2,4-取代的5-酰基恶唑的有效方案是被报道。在第一个方案中,将α-氧杂环丁烯二硫缩醛或β-(甲硫基)烯酮转化为相应的α-溴-β-(甲硫基)烯酮,然后用各种伯酰胺将这些中间体进行铜催化的中间/分子内环化,得到2- (杂)芳基/烷基-4-(杂)芳酰基-5-(甲硫基)/(杂)芳基恶唑是通过酰胺中间体同时形成C4-N和C5-O键。在第二种方法中 首先,将起始的α-氧杂环丁烯二硫缩醛或β-(甲硫基)-β-(杂)芳基酮与各种伯酰胺进行碱诱导的共轭加成消除反应,以提供β-芳烯酰胺,随后碘将其催化的分子内氧化C–H官能化/ CO键的形成,以优异的收率提供了相应的区域异构体2-(杂)芳基/烷基-4-(甲硫基)/(杂)芳基-5-(杂)芳酰基恶唑。该方法也已扩展到合成区域异构的4-或5-