L-脯氨酸催化一锅法合成4H-吡喃并[2,3-c]吡唑衍生物

以L-脯氨酸为绿色催化剂,3-甲基-5-吡唑酮(或1-苯基取代物)和芳醛及丙二腈为原料,就微波辅助的一锅法成环缩合反应进行研究。实验结果表明,乙醇/水为溶剂,催化剂用量10mol%,微波功率300W和80℃下反应10~15min,即可得到4H-吡喃并2,3-c]吡唑类化合物(4a^4j),合成收率达85~94%。该方法具有产率高、反应时间短、操作简单等优点。

L-proline catalyzed one-pot synthesis of 4H-pyrano[2,3-c]pyrazoles

A convenient procedure via one-pot cyclocondensation of 3-methyl-pyrazolidin-5-one or 3-methyl-1-phenyl-5-pyrozolene,aromatic aldehydes and malononitrile in the presence of L-proline in mixed solvent of ethanol and water under microwave irradiation was discussed.The results indicated that the green catalyst was efficient with the amount of 10mol%under irradiation at 300W with a temperature of 80℃for 10~15 min to afford 4 H-pyrano2,3-c]pyrazole derivatives(4a^4j)with good yields of 85~94%respectively.The protocol proved to be efficient and clean in terms of high yields,low reaction times and ease of work-up.