Truly Catalytic and Enantioselective Pinacol Coupling of Aryl Aldehydes Mediated by Chiral Ti(III) Complexes<sup>†</sup>
作者:A. Chatterjee、T. H. Bennur、N. N. Joshi
DOI:10.1021/jo0342875
日期:2003.7.1
A variety of chiral Ti(IV) complexes were reduced in situ with zinc in acetonitrile. The resulting chiral Ti(III) complexes were found to catalyze the pinacol coupling reaction stereoselectively. The best results were obtained from the Ti-SALEN complex, which was found to be an efficient catalyst at 10 mol % concentration. Various aromatic aldehydes were coupled to obtain chiral hydrobenzoin derivatives
reactivity of achiral and enantiomerically pure acylketene acetals are described. The key reactions of these substrates involve facile conjugate hydroboration and organolithium addition. Enantiomerically pure acylketene acetals were employed to generate a homochiral β-keto ketal through a highly diastereoselective lithium enolate quench. This β-keto ketal, which was also prepared through a desymmetrization
Manganese-Promoted, Titanocene-Catalyzed Stereoselective Pinacol Coupling of Aldehydes
作者:Melinda S. Dunlap、Kenneth M. Nicholas
DOI:10.1080/00397919908086078
日期:1999.4
Abstract Aromatic and aliphatic aldehydes undergo pinacolcoupling when treated with Mn/Me3SiCl in the presence of Cp2TiCl2 as catalyst. Good yields of bis-silyl pinacol ethers are obtained with varying degrees of diastereoselectivity. Enantioselective pinacolization has been achieved using an enantiomerically enriched catalyst
A variety of novel hydroxyl-containing tetradentate bisoxazolines were successfully synthesized from natural l-serine and β-DDB. The applications of these ligands in the asymmetricpinacolcoupling of aromatic aldehydes revealed that the absoluteconfigurations of the resulting pinacols were entirely dominated by the axial chirality of the biphenyl component and that the bulky substituent adjacent