Reactivity and diastereoselectivity of Grignard reagents toward the hydrazone functionality in toluene solvent
作者:Alex Alexakis、Nathalie Lensen、Jean Philippe Tranchier、Pierre Mangeney
DOI:10.1021/jo00043a001
日期:1992.8
Grignard reagents, in toluene solvent, display a strongly increased reactivity toward the hydrazone functionality. With the chiral synthon 1, a highly diastereoselective addition occurs, through chelation control, whereas with pyrazolines 4 and 9 only the d,l diastereomer is formed, leading to a very short synthesis of 1,3-diphenyl-1,3-diaminopropane (11).
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.