An efficient one-pot synthesis of 3-aryl-5-methylisoxazoles from aryl aldehydes
摘要:
An efficient protocol for the one-pot preparation of alkyl 3-aryl-5-methylisoxazole-4-carboxylates from aryl aldehydes is described. This method is readily amenable to the large scale preparation of isoxazoles as well as the parallel synthesis of isoxazole libraries. (C) 2011 Elsevier Ltd. All rights reserved.
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。
An improved synthesis of 1,2-benzisoxazoles: TBAF mediated 1,3-dipolar cycloaddition of nitrile oxides and benzyne
作者:Christian Spiteri、Pallavi Sharma、Fengzhi Zhang、Simon J. F. Macdonald、Steve Keeling、John E. Moses
DOI:10.1039/b922489k
日期:——
An efficient synthesis of a range of 1,2-benzisoxazoles using an improved1,3-dipolarcycloaddition of nitrileoxides and benzyne is described. Key to the procedure is the in situgeneration of the reactive nitrileoxide and benzyne reaction partners mediated by TBAF. Reactions are complete within 30 s, giving the target products in good to excellent yield.
An efficient entry to 1,2-benzisoxazoles via 1,3-dipolar cycloaddition of in situ generated nitrile oxides and benzyne
作者:Christian Spiteri、Christopher Mason、Fengzhi Zhang、Dougal J. Ritson、Pallavi Sharma、Steve Keeling、John E. Moses
DOI:10.1039/b927235f
日期:——
An efficient protocol for the synthesis of a range of 1,2-benzisoxazoles using an improved1,3-dipolarcycloaddition of nitrileoxides and benzyne is described. Key to the procedure is the in situgeneration of the reactive nitrileoxide and benzyne reactants simultaneously.
A facile one-pot preparation of isothiocyanates from aldoximes
作者:Jae Nyoung Kim、Keum Shin Jung、Hong Jung Lee、Ji Suk Son
DOI:10.1016/s0040-4039(97)00121-4
日期:1997.3
Isothiocyanates 2a-1 were prepared in excellent yields in a one-pot reaction from aldoxime derivatives 1a-1 by successive treatment of aldoxime with N-chlorosuccinimide (NCS), thiourea, and triethylamine. The use of HCl/DMF/Oxone system in the reaction instead of NCS was equally effective. (C) 1997 Elsevier Science Ltd.
A convenient synthesis for α,β-acetylenic ketoximes