Catalysed asymmetric reaction of aldehydes with dialkylzinc in the presence of chiral pyridyl alcohols as ligands
摘要:
The synthesis of homochiral pyridyl alcohols (1,2,3a-c) and a catalytic asymmetric addition of dialkylzinc to various aldehydes using 1-3 as ligands are described. Although the reaction of benzaldehyde with Et2Zn in the presence of (S)-1 and (R,R)-2 gave (S)- and (R)-1-phenyl-1-propanol, respectively, in moderate enantiomeric excess (e.e.), tridentate ligands (3a-c) accelerated the reaction to produce the corresponding alcohols in high e.e. Particularly, (S)-3b was found to be the most efficient catalyst, for which asymmetric reactions of various aldehydes with dialkylzinc gave the corresponding alcohols in good to high e.es. (up to 95% e.e.).
A Highly Active Manganese Catalyst for Enantioselective Ketone and Ester Hydrogenation
作者:Magnus B. Widegren、Gavin J. Harkness、Alexandra M. Z. Slawin、David B. Cordes、Matthew L. Clarke
DOI:10.1002/anie.201702406
日期:2017.5.15
A newhydrogenationcatalyst based on a manganese complex of a chiral P,N,N ligand has been found to be especially active for the hydrogenation of esters down to 0.1 mol % catalyst loading, and gives up to 97 % ee in the hydrogenation of pro‐chiral deactivated ketones at 30–50 °C.