Tandem one-pot synthesis of flavans by recyclable silica–HClO4 catalyzed Knoevenagel condensation and [4 + 2]-Diels–Alder cycloaddition
作者:Sandip B. Bharate、Ramesh Mudududdla、Jaideep B. Bharate、Narsaiah Battini、Satyanarayana Battula、Rammohan R. Yadav、Baldev Singh、Ram A. Vishwakarma
DOI:10.1039/c2ob25376c
日期:——
An efficient one-pot multi-component synthesis of flavans using perchloric acid supported on silica as a recyclable heterogeneous catalyst has been described. This is the first report of direct one-step construction of a flavan skeleton from a phenolic precursor. The method involves a Knoevenagel-type condensation leading to in situ formation of transient O-quinone methide which further undergoes [4 + 2]-DielsâAlder cycloaddition with styrene to yield a flavan skeleton. The method provides easy access to a wide range of bio-active natural products viz. flavonoids, anthocyanins and catechins.
描述了一种高效的一锅多组分合成黄酮的方法,使用支持在硅胶上的高氯酸作为可回收的异相催化剂。这是首次通过一步法直接从酚类前体构建黄酮骨架。该方法涉及Knoevenagel类型的缩合反应,导致瞬态的O-醌亚甲基的原位生成,进一步与苯乙烯发生[4 + 2]的Diels–Alder环加成,产生黄酮骨架。该方法为广泛获取生物活性天然产物,如黄酮类、花青素和儿茶素等,提供了便捷途径。