Synthesis of Enantiopureo-Hydroxybenzylamines by Stereoselective Reduction of 2-Imidoylphenols: Application in the Catalytic Enantioselective Addition of Diethylzinc to Aldehydes
o-hydroxybenzylamines 2a–i were synthesized by diastereoselective reduction of the 2-imidoylphenols (R)-1a–i. Conformational analysis enabled the assignment of the absolute configurations of compounds 2a–i. The accessible o-hydroxybenzylamine (R,R)-2h serves as an effective catalyst precursor for highly enantioselectiveaddition of diethylzinc to aliphatic and aromatic aldehydes. This pathway represents a practical
Asymmetric reduction of enantiopure imines with zinc borohydride: stereoselective synthesis of chiral amines
作者:Cristina Cimarelli、Gianni Palmieri
DOI:10.1016/s0957-4166(00)00209-3
日期:2000.6
The first application of zincborohydride in the reduction of enantiopure imines for the stereoselective preparation of both the enantiomers of secondary amines is described. A possible explanation of the stereoselectivity and of the reaction mechanism is suggested on the basis of theoretical calculations.
methods available till now. The sense of asymmetricinduction has been explained and confirmed in agreement with the results previously obtained by hydride reduction of the same substrates. In some cases this procedure is complementary to the reductive one, allowing the preparation of the diastereomers less abundant in the reduction. The reaction allows the synthesis of one or the other of the two diastereomers
alkylation of aminophenols to enantiopure tertiary aminophenols, which are useful chiral ligands for metal-catalysed asymmetric reactions, is reported. This very simple synthetic methodology, through reduction or alkylation of an intermediate benzoxazine, was performed in mild conditions, suitable for the conservation of the configuration of the stereogenic centres. Some crystalline aminophenols show the
作者:E. Peter Kündig、Candice Botuha、Gilles Lemercier、Patrick Romanens、Lionel Saudan、Sylvie Thibault
DOI:10.1002/hlca.200490054
日期:2004.3
Three different routes were probed for the synthesis of enantiomerically enriched 2-(1-aminoethyl)phenols and their methyl ethers. The first route centers on diastereoselective nucleophile addition to chiral imines. The second route has as key steps the enantioselective reduction of a ketone followed by nucleophilic substitution, and the third route involves a diastereoselective imine reduction. The