5-Chloropyrazole-4-carbaldehydes were efficiently prepared via Vilsmeier reaction of 1H-pyrazol-5(4H)-ones with bis(trichloromethyl) carbonate-DMF instead of the traditional POCl3–DMF system. The Baylis–Hillman reaction of these aldehydes with activated alkenes promoted by various catalysts were investigated. It was found DMAP accelerated the reaction of methyl acrylate or acrylonitrile with the aldehydes, while in the case of but-3-en-2-one, a catalyst mixture of imidazole and L-proline (1:1) was efficient. Overall, the reactivities of the aldehydes were low.
通过 1H-吡唑-5(4H)-酮与碳酸二(三氯甲基)酯-DMF 的 Vilsmeier 反应而非传统的 POCl3-DMF 体系,有效地制备了 5-氯吡唑-4-甲醛。研究了这些醛与活化烯在各种催化剂促进下发生的 Baylis-Hillman 反应。结果发现,DMAP 加快了丙烯酸甲酯或丙烯腈与醛的反应,而对于丁-3-烯-2-酮,咪唑和 L-脯氨酸(1:1)的催化剂混合物则很有效。总体而言,醛的反应活性较低。