Regioselective synthesis and side-chain metallation and elaboration of 3-aryl-5-alkylisoxazoles
摘要:
A number of 3-aryl-5-alkylisoxazoles have been synthesized in high yields by reacting arylnitrile oxides with free enolate ions regioselectively obtained by metallation of various alkyl methyl ketones with LDA in THF at -78degreesC followed by dehydration. Investigations concerning regioselective side-chain metallation and elaboration of one of them (3-phenyl-5-ethylisoxazole) have also been carried out. (C) 2002 Elsevier Science Ltd. All rights reserved.
5-羟基-3-苯基-5-乙烯基-2-异恶唑啉是通过使苄腈氧化物与甲基乙烯基酮的烯醇酸根离子反应而合成的。然后从5-羟基-5-乙烯基-2-异恶唑啉中,在酸性条件下通过脱水-芳构化定量获得5-乙烯基异恶唑。通过在碱性条件下(i -PrOH / H 2 O,Na 2 CO 3,回流)。与2-丙醇相反,在甲醇中进行的反应(以及部分在乙醇中进行的反应)显示出更复杂的行为,主要观察到ROH在乙烯基上的亲核加成。还发现与烷基锂的亲核加成。亲核加成的机理进行了讨论。还描述了3-羟基-5-苯基-5-乙烯基-2-异恶唑啉和3-苯基-5-乙烯基异恶唑的环氧化和与苄腈氧化物的进一步反应。