Asymmetric Mannich Reactions with α-Silylated Trimethylsilyl Enol Ethers and N-Alkoxycarbonyl Imines
作者:Dieter Enders、Stefan Oberbörsch
DOI:10.1055/s-2002-20468
日期:——
The Mannich reaction of enantiomerically pure α-dimethylthexylsilylated trimethylsilyl enol ether (Z,S)-2 with titanium complexes of N-alkoxycarbonyl imines afforded αŽ-silylated α,β-disubstituted β-amino ketones (S,R,S)-4a-e in good to excellent yields (70-92%) and diastereomeric excesses (de ≥ 96%). Removal of the directing silyl group gave N-protected and anti-configured β-amino ketones (R,S)-5a-e in excellent yields (90-95%) and stereoselectivities (de, ee ≥ 96%- > 98%).
艾尼酮纯的α-二甲基硅基化三甲基硅醇醚(Z,S)-2与N-烷氧基羧基亚胺的钛配合物反应,生成α-硅基化α,β-二取代的β-氨基酮(S,R,S)-4a-e,收率良好到优秀(70-92%)且具有很高的反式异构体过量(de ≥ 96%)。去除指导性硅基后,得到N保护的和反式构型的β-氨基酮(R,S)-5a-e,收率优秀(90-95%),立体选择性也很高(de, ee ≥ 96%- > 98%)。