A convenient synthesis of 4-substituted 3-ethoxy-5-methylisoxazoles by palladium-catalyzed coupling reactions
作者:Hasse Kromann、Frank A Sløk、Tommy N Johansen、Povl Krogsgaard-Larsen
DOI:10.1016/s0040-4020(01)00052-7
日期:2001.3
The coupling reactions were performed using 3-ethoxy-4-iodo-5-methylisoxazole (4) as the key intermediate. Coupling of 4 under Suzuki–Miyaura or Stille conditions using Pd(PPh3)2Cl2 and arylboronic acids or aryltin analogues, respectively, gave 4-aryl substituted isoxazoles in yields ranging from 49% for the 3-pyridyl analogue 14, to 96% for the 4-pyridyl analogue 12. Under Heck reaction conditions
使用3-乙氧基-4-碘-5-甲基异恶唑(4)作为关键中间体进行偶联反应。的耦合4铃木-宫浦或Stille条件下使用的Pd(PPh下3)2氯2和芳基硼酸或aryltin类似物,分别得到4-芳基取代的异恶唑在产率为49%,为3-吡啶基类似物14,至96 %的4-吡啶类似物12。在Heck反应条件下使用Pd(PPh 3)2 Cl 2和4合成了在4-位含有乙烯基或炔基的3-乙氧基-5-甲基异恶唑的类似物,产率为58-98%。由4和异丙基溴化镁制得的3-乙氧基-5-甲基异恶唑-4-基溴化镁(19)与苯甲醛或苯甲酰氯平稳反应,得到所需的4- [羟基(苯基)甲基]类似物21和4-苯甲酰基- 3-乙氧基-5-甲基异恶唑(22)。的金属转移19与的ZnCl 2,并用的Pd(PPh后续处理3)2氯2和4-碘甲苯,得到3-乙氧基-5-甲基-4-(4-甲基苯基)异恶唑(23),产率为80%。