Enantioselective diethylzinc addition to the exocyclic CN double bond of some 4-arylideneamino-3-mercapto-6-methyl-4H-1,2,4-triazin-5-one derivatives
作者:Ashraf A. El-Shehawy
DOI:10.1016/j.tetasy.2006.10.013
日期:2006.10
4-triazin-5-ones 2a–f have been evaluated as substrates in the enantioselective diethylzinc addition reaction in the presence of (1S,2R)-N-alkyl-N-benzylnorephedrines 3a–d as chiral ligands. The utility of using a dual catalytic system (amino alcohol/halosilane) for the diethylzinc addition reaction has been also examined. The addition products 4-(1-arylpropyl)amino-3-mercapto-6-methyl-4H-1,2,4-triazin-5-ones 4a–f
4- Arylideneamino -3-巯基-6-甲基-4- ħ -1,2,4-三嗪-5-酮2A - ˚F被评价为在(1的存在对映二乙基锌加成反应基板小号,2 - [R)-N-烷基-N-苄基去氧麻黄碱3a – d作为手性配体。还研究了使用双重催化体系(氨基醇/卤代硅烷)进行二乙基锌加成反应的效用。加成产物4-(1-芳丙基)氨基-3-巯基-6-甲基-4 H -1,2,4-三嗪-5-酮4a – f以高收率获得对映体,对映体过量高达92%。尽管侧链的CN双键确实发生了加成反应以生成C-乙基化产物4a - f,但是用二乙基锌试剂处理芳丙胺2a - f不会影响杂环的开环。来自加成产物4a - f的1,2,4-三嗪基杂环的还原裂解平稳地导致相应的游离伯胺5a - f,而对映体纯度没有明显损失。