Rapid and Efficient Uncatalyzed Knoevenagel Condensations from Binary Mixture of Ethanol and Water

This paper presents a new green protocol for Knoevenagel condensations of aldehydes and compounds with an active methylene group in a binary mixture of ethanol/water (3:7, v/v). This medium favored the uncatalyzed Knoevenagel reactions and easy workup products can be obtained by precipitation in this medium and showed good isolated yields (55-100%) in short reaction times (1-60 min).本论文报道了一种全新的绿色合成工艺，用于在体积比为3:7的乙醇/水二元混合溶剂中，实现醛与含活泼亚甲基基团（active methylene group）化合物的克诺文格尔缩合（Knoevenagel condensation）反应。该溶剂体系可促进无催化的克诺文格尔缩合反应，产物可通过在该体系中直接沉淀完成简便后处理，且在1~60分钟的短反应时间内即可获得55%~100%的优良分离收率。