Oxathiaborolium-Catalyzed Enantioselective [4 + 2] Cycloaddition and Its Application in Lewis Acid Coordinated and Chiral Lewis Acid Catalyzed [4 + 2] Cycloaddition
作者:Ramalingam Boobalan、Rong-Jie Chein
DOI:10.1021/acs.orglett.1c02345
日期:2021.9.3
catalysts for [4 + 2] cycloaddition. Oxathiaborolium pentachlorostannate (5–10 mol %) successfully catalyzed cycloaddition of various dienes and dienophiles to afford cycloadducts with excellent enantioselectivity (20 examples, up to 99% ee). This super Lewis acid also exhibited good enantioselectivity for the first Lewis acid coordinated and chiral Lewis acid catalyzed [4 + 2] cycloaddition to α,β-unsaturated
由嗜盐路易斯酸 SnCl 4产生的第二代硫稳定化硼阳离子的新生产生了高活性的手性路易斯酸,它是 [4 + 2] 环加成的非常有效的催化剂。Oxathiaborolium 五氯锡酸盐(5-10 mol%)成功地催化了各种二烯和亲二烯体的环加成反应,得到了具有优异对映选择性的环加合物(20 个例子,高达 99% ee)。这种超级路易斯酸对第一个路易斯酸配位和手性路易斯酸催化[4 + 2]环加成到α,β-不饱和混合酯酰胺也表现出良好的对映选择性。