The hetero-Diels-Alder reaction of 2-methyl-1-(1-phenylalkoxy)-butadienes 5a-d with cyclic triketones proceeds smoothly at room temperature in excellent yield and high diastereoselectivity. The configuration of the cycloadducts 6a and 6b was determined by X-ray single crystal analysis. Mild acidic hydrolysis of the cycloadduct 6a using SiO2 as a promoter yielded an α,β-unsaturated aldehyde trans-9. The trans-epoxides 10a-d can be obtained from 6a-d using a freshly prepared solution of dimethyldioxirane in acetone.
2- 甲基-1-(1-苯基烷氧基)-
丁二烯 5a-d 与环状三酮的异狄尔斯-阿尔德反应在室温下顺利进行,产率极好,非对映选择性极高。通过 X 射线单晶分析确定了环加成物 6a 和 6b 的构型。以
二氧化硅为
促进剂,对环加合物 6a 进行弱酸性
水解,得到了δ,δ-不饱和醛反式-9。使用新制备的
二甲基二环氧乙烷在
丙酮中的溶液,可以从 6a-d 得到反式
环氧化物 10a-d。