Ring Expansion of Epoxides under Brønsted Base Catalysis: Formal [3+2] Cycloaddition of β,γ-Epoxy Esters with Imines Providing 2,4,5-Trisubstituted 1,3-Oxazolidines
作者:Azusa Kondoh、Kenta Odaira、Masahiro Terada
DOI:10.1002/anie.201505893
日期:2015.9.14
developed. The formal [3+2] cycloaddition reaction of β,γ‐epoxy esters with imines proceeds in the presence of triazabicyclodecene (TBD) as a superior Brønsted base catalyst to afford 2,4,5‐trisubstituted 1,3‐oxazolidines in a highly diastereoselective manner. This reaction involves the ring opening of the epoxides with the aid of the Brønsted base catalyst to generate α,β‐unsaturated esters having an alkoxide
开发了在布朗斯台德碱催化下环氧化物的新型扩环反应。β,γ-环氧酯与亚胺的正式[3 + 2]环加成反应是在三氮杂双环癸烯(TBD)作为优良的Brønsted碱催化剂存在下进行的,可在高浓度下提供2,4,5-三取代的1,3-恶唑烷非对映选择性方式。该反应涉及在布朗斯台德碱催化剂的帮助下环氧化物的开环,生成在烯丙基位置具有醇盐的α,β-不饱和酯,将其正式用作1,3-偶极的合成等价物,随后通过与亚胺的环加成反应逐步进行。这种方法可以从容易获得的对映体富集的环氧化物轻松合成对映体富集的1,3-氧恶唑烷。