PyrazoloneおよびPyrazole誘導体の合成研究(第7報)Ethyl 5-Allyloxy-1-phenylpyrazole-3-carboxylateのClaisen転位

抄録

The allylation of 5-position in ethyl 5-hydroxy-1-phenylpyrazole-3-carboxylate (I) was attempted and ethyl 5-allyloxy-1-phenylpyrazole-3-carboxylate (II) and ethyl 4, 4-diallyl-5-oxo-1-phenyl-2-pyrazoline-3-carboxylate (III) were obtained. The chemical structures of II and III were determined by infrared and nuclear magnetic resonance spectroscopies. To clarify the mechanism to form III, I was allylated under appropriate conditions and it was found that at room temperature II was obtained as a sole product and that heating was necessary for the formation of III. 4-Allyl-5-hydroxy-1-phenylpyrazole-3-carboxylate (IV) was obtained by heating II in benzene. The reaction of II or IV with allyl bromide gave III. These results suggest that Claisen rearrangement occurred in the above reaction.