A mild efficient iodine-catalyzed synthesis of novel anticoagulants with 2,8-dioxabicyclo[3.3.1]nonane core
摘要:
An efficient coupling of 2-hydroxychalcones/alpha,beta-enones with 4-hydroxycoumarin/5,5-dimethylcyclohexyl-1,3-dione (dimedone) has been accomplished to provide access to a novel class of potential anticoagulants with 2,8-dioxabicyclo[3.3.1]nonane core. The reaction proceeds by Michael-bicycloketalization sequence under iodine catalysis (10 mol %) in aqueous ethanol under reflux. Good to excellent yields, impressive selectivity, absence of byproduct formation, avoidance of toxic organic solvents, and utilization of metal-free water-compatible mild Lewis acid catalyst are the key attractive features of this protocol. (C) 2013 Elsevier Ltd. All rights reserved.
deliver structurally diverse hybrid flavonoids in good to excellent yields in the presence of a catalytic Brønsted acid. Moreover, moderate enantioselectivities could be obtained using a catalytic chiral phosphoric acid via counter anion directed addition. Based on mechanistic studies, the reaction is proposed to proceed via tandem double-bond isomerization/dehydratedcyclization of 2-hydroxychalcone
描述了一种由 2-羟基查耳酮合成的杂合类黄酮的仿生合成。在 24 W CFL 的照射下,2-羟基查耳酮与各种亲核试剂反应,在催化布朗斯台德酸存在下以良好至优异的产率提供结构多样的杂化黄酮类化合物。此外,使用催化手性磷酸通过反阴离子定向加成可以获得中等的对映选择性。基于机理研究,该反应被提议通过2-羟基查耳酮的串联双键异构化/脱水环化形成瞬时黄鎓阳离子,该阳离子被亲核试剂原位捕获以提供杂化黄酮类化合物。