Guanidine-Catalyzed Asymmetric Synthesis of 2,2-Disubstituted Chromane Skeletons by Intramolecular Oxa-Michael Addition
作者:Noriko Saito、Akemi Ryoda、Waka Nakanishi、Takuya Kumamoto、Tsutomu Ishikawa
DOI:10.1002/ejoc.200800089
日期:2008.6
The guanidine-catalyzed 6-exo-trig-type intramolecular asymmetric oxa-Michael addition of α,β-unsaturated esters with a 2-hydroxyaryl moiety at the C-5 carbon has been examined for the construction of chromane skeletons with a quaternary carbon chiral center. The bulkiness of the alkyl group and the E/Z geometry of the α,β-unsaturated ester function played important roles in the asymmetric induction
已经研究了胍催化的 6-exo-trig 型分子内不对称氧杂-迈克尔加成,在 C-5 碳上具有 2-羟基芳基部分的 α,β-不饱和酯,以构建具有季碳手性的色满骨架中央。烷基的体积和α,β-不饱和酯官能团的E/Z几何结构在不对称诱导和(4S,5S)-2-[(R)-1-羟甲基-2-苯基乙基亚氨基]发现在 4 位和 5 位带有芳基侧基的 -1,3-二甲基咪唑烷(或其对映体)是所检测的 18 种手性胍中最有效的催化剂。这样,体积较小的甲酯的 Z 异构体进行环化反应,以高达 83% 的收率和 76% ee 得到手性色满。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany,