products 6 and/or 7 are observed if the nitronates, generated from the substrate 1a, are added to 85% aqueous H2SO4 but only the hydrolyzed carboxylic acids 9 are generated when the β-nitrostyrenes 2 are reacted with Grignard reagents and worked up under the same condition. The nitrile oxides 7 can undergo 1,3-dipolar cycloaddition with alkenes or alkynes to generate 2-isoxazolines or isoxazoles. A one-pot
β型硝基苯乙烯1或2与格氏或有机锂试剂反应在乙醚或THF溶液由1,4-加成中间nitronates以产生甲。当用稀盐酸处理A时,获得高产率的硝基烷3(和肟4)或5。当将中间体A缓慢加入到冰冷的浓氢卤酸中时,可以分离出羟甲酰卤6、8或一氧化氮7。如果从基材1a产生的硝酸盐观察到相同的产物6和/或7。将β-硝基苯乙烯2加入到85%的H 2 SO 4水溶液中,但是当β-硝基苯乙烯2与格氏试剂反应并在相同条件下进行后处理时,仅产生水解的羧酸9。腈氧化物7可与烯烃或炔烃进行1,3-偶极环加成反应以生成2-异恶唑啉或异恶唑。据报道,通过分子内一氧化氮-烯烃环加成反应可以一锅合成[n,3,0]双环(n = 3或4)化合物23-27。
One-pot synthesis of five- or six-membered carbocycles through intramolecular cycloadditions by the use of ethyl chloroformate
作者:Ju-Tsung Liu、Wen-Wei Lin、Jeong-Jiunn Jang、Jing-Yuan Liu、Ming-Chung Yan、Chihua Hung、Kuo-Hsi Kao、Yeh Wang、Ching-Fa Yao
DOI:10.1016/s0040-4020(99)00351-8
日期:1999.6
compounds 9 is proposed to proceed through intramolecular nitrile oxide-olefin cycloadditions (INOC) because compounds 14a-d, obtained from the trapping of the nitrile oxides by ethyl chloroformate, could be isolated. The mechanism of the generation of compounds 10 is proposed to proceed through intramolecular alkoxycarbonyl nitronate-olefin cycloadditions (IAOC) to form intermediates N-(ethoxycarbonyl)isoxazolidines