Synthesis of New 1<i>H</i>-Indazoles through Diels-Alder Transformations of 4-Styrylpyrazoles under Microwave Irradiation Conditions
作者:Vera L. M. Silva、Artur M. S. Silva、Diana C. G. A. Pinto、José Elguero、José A. S. Cavaleiro
DOI:10.1002/ejoc.200900513
日期:2009.9
Microwave irradiation under solvent-free conditions induces 1-acetyl-4-styrylpyrazoles to undergo Diels–Alder cycloaddition reactions with N-methyl- or N-phenylmaleimide to give tetrahydroindazoles in good yields and with high selectivities. With conventional heating, these reactions either do not occur or afford only traces of the cycloadducts. These cycloadducts were then converted into the corresponding
在无溶剂条件下的微波辐射诱导 1-乙酰基-4-苯乙烯基吡唑与 N-甲基-或 N-苯基马来酰亚胺进行 Diels-Alder 环加成反应,以高产率和高选择性得到四氢吲唑。使用常规加热,这些反应要么不发生,要么仅提供痕量的环加合物。然后,在微波辐射或经典加热条件下,通过在干燥的 1,2,4-三氯苯中用 DDQ 脱氢,将这些环加合物转化为相应的 1H-吲唑。所有新衍生物的结构和环加合物的立体化学均通过 NMR 光谱确定。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)