Cascade Michael Addition/Cycloketalization of Cyclic 1,3-Dicarbonyl Compounds: Important Role of the Tethered Alcohol of α,β-Unsaturated Carbonyl Compounds on Reaction Rate and Regioselectivity
作者:Hongliang Yao、Liyan Song、Yuan Liu、Rongbiao Tong
DOI:10.1021/jo501604e
日期:2014.9.19
Reactions of α,β-unsaturated aldehydes and cyclic 1,3-dicarbonyl compounds proceed primarily by cascade Knoevenagel condensation/six-π-electron electrocyclization (K6EC, formal [3 + 3] cycloaddition), while α,β-unsaturated ketones usually react with cyclic 1,3-dicarbonyl compounds in a 1,4-addition manner. This paper discloses our findings that under acidic conditions, α,β-unsaturated carbonyl compounds
α,β-不饱和醛与环状1,3-二羰基化合物的反应主要通过Knoevenagel缩合/六-π-电子电环化(K6EC,正式的[3 + 3]环加成反应)进行,而α,β-不饱和酮通常会发生反应以1,4-加成方式与环状1,3-二羰基化合物反应。本文揭示了我们的发现,即在酸性条件下,α,β-不饱和羰基化合物(酮和醛)与束缚醇通过原位生成环己烯酮,以高度区域选择性的1,4-加成方式与环状1,3-二羰基化合物反应。假设的α-亚甲基环状氧鎓离子作为反应性迈克尔受体。我们的研究发现了束缚醇对反应速率和/或效率的重要影响,以及级联迈克尔加成/环缩酮化的一些新机理。最后,