Chiral Aminal Templates: Diastereoselective Addition to Hydrazones; An Asymmetric Synthesis of α-Amino Aldehydes
作者:Alex Alexakis、Nathalie Lensen、Jean-Philippe Tranchier、Pierre Mangeney、J. Feneau-Dupont、J. P. Declercq
DOI:10.1055/s-1995-4042
日期:1995.8
The monohydrazone of glyoxal may be derivatized into a chiral aminal with diamine 7. The resulting chiral reagent 13 reacts with complete diastereocontrol with organolithium reagents in THF. This sterically controlled reaction may be altered to chelation control by using Grignard reagents in toluene, affording the opposite diastereomer in excellent de. The N-N bond of the hydrazine functionality is then cleaved with Raney nickel, assisted by ultrasound. After protection of the resulting primary amino functionality, the aminal is hydrolyzed to afford the desired α-amino aldehydes without epimerization. The same reaction sequence, without cleavage of the N-N bond, affords an α-hydrazino aldehyde.
乙二醛的单氢肼可与二胺7衍生化为一个手性氨胺。所得的手性试剂13在四氢呋喃中与有机锂试剂反应,具有完全的非对映体选择性。通过在甲苯中使用格氏试剂,这一立体控制反应可被改变为螯合控制,从而生成相反的非对映体,并获得优异的对映选择性。接着,利用超声波的辅助下,水合肼的N-N键被拉尼镍裂解。在保护产物中的初级氨基功能基后,氨胺被水解,生成所需的α-氨基醛而不发生表异构化。相同的反应序列,如果不裂解N-N键,则会生成α-肼醛。