Stereocontrolled Synthesis of 1,3,5-Triols by an Iteration of Asymmetric Dihydroxylation and Deoxygenation
作者:Patrick Walleser、Reinhard Brückner
DOI:10.1002/ejoc.201000280
日期:2010.9
Asymmetric dihydroxylation of the C γ =C δ bonds in trans-configured α,β,γ,δ-unsaturated esters, carbonate formation, and Pd°-catalyzed deoxygenation of C γ provided α,β-unsaturated δ-hydroxy esters. Protection and chain-extension provided the corresponding α,β-unsaturated ketones. Their asymmetric dihydroxylation in the presence of phenylboronic acid delivered dioxaborolanes. SmBr 2 -mediated deoxygenation
在反式构型的 α,β,γ,δ-不饱和酯中,C γ =C δ 键的不对称二羟基化、碳酸酯形成和 Pd° 催化的 C γ 脱氧提供了 α,β-不饱和 δ-羟基酯。保护和扩链提供了相应的 α,β-不饱和酮。它们在苯基硼酸存在下的不对称二羟基化产生二氧杂硼烷。SmBr 2 介导的 C α 脱氧,随后分别是 Narasaka-Prasad 和 Claisen-Tishchenko 还原,分别选择性地提供单保护的 1,3 syn、3,5 syn-、1,3 syn、3,5 anti-、1,3 anti, 3,5 syn-, and 1,3 anti, 3,5 anti-configured 1,3,5-triols。在 C δ 处具有庞大 OSiR 3 基团的烯酮被二羟基化,具有显着较差的顺式(相对于反式)选择性。通过反对(“不匹配的情况”)或增强(“