Salts between (R,R)- or meso-N,N'-oxalylbis(phenylglycine) 1 and (R)-, (S)-, or (+/-)-1-phenylethylamine 2 construct three different layer structures depending on their stereochemistry. By X-ray crystallography, it is elucidated that the formation of a hydrogen bonding network between the amino and carboxyl groups and the planarity of the oxalyl functionality are important to construct the sheet structure. The salt of (R,R)-1 and 2 forms a bilayer or puckered structure, whereas the salt of meso-1 and 2 constructs a monolayer structure. (C) 2000 Elsevier Science Ltd. All rights reserved.
Chiral bis(amino alcohol)oxalamides as ligands for asymmetric catalysis. Ti(IV) catalyzed enantioselective addition of diethylzinc to aldehydes
作者:Gonzalo Blay、Isabel Fernández、Alícia Marco-Aleixandre、José R. Pedro
DOI:10.1016/j.tetasy.2005.01.039
日期:2005.3
Several chiral bis(aminoalcohol)oxalamides with C2-symmetry have been prepared and used as ligands for the enantioselectiveaddition of diethylzinc to aromatic and aliphatic aldehydes. The reaction proceeds in the presence of titanium isopropoxide to give the corresponding (S)-alcohols with ee up to 78%. In the absence of Ti(IV), the alcohols with the opposite configuration are obtained.