Enhancement of enantioselectivity by alcohol additives in asymmetric hydrogenation with bis(oxazolinyl)phenyl ruthenium catalysts
作者:Jun-ichi Ito、Tomoki Teshima、Hisao Nishiyama
DOI:10.1039/c1cc16057e
日期:——
Bis(oxazolinyl)phenyl ruthenium(II) complexes were found to catalyze asymmetrichydrogenation of ketones, in which chiral bulky alcohol additives showed significant enhancement of enantioselectivity even in protic solvents.
Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes
作者:Shanshan Liu、Gao-Wei Li、Xiao-Chao Yang、De-Yang Zhang、Min-Can Wang
DOI:10.1039/c7ob01717k
日期:——
A general AzePhenol dinuclear zinc catalytic system has been successfully developed and introduced into the asymmetric addition of dimethylzinc and alkynylzinc to aromaticaldehydes. In this system, an azetidine derived chiral ligand has proven to be an effective enantioselective promoter. Under the optimal reaction conditions, a series of chiral 1-hydroxyethyl (up to 99% ee) and secondary propargylic
We describe here a manganese-catalyzed asymmetric transfer hydrogenation of hindered ketones containing 2,6-disubstituted phenyl group. This method is enabled by using a readily available chiral aminobenzimidazole manganese(I) complex as the catalyst in combination with ammonia borane compounds as the hydrogen source (especially, dimethylamine borane), producing the chiral alcohols with up to 99 %
derivative‐Ru(II) complexescatalyzedasymmetrichydrogenation of significantly sterically hindered 2’,3’,4’,5’,6’‐pentamethylacetophenone, which was not reduced with NaBH4 at 25 °C, with a substrate‐to‐catalyst molar ratio (S/C) of 2000 under 50 atm of H2 in a base‐containing 2‐propanol to afford the alcohol in 99 % ee quantitatively. A series of polysubstituted aromatic ketones was smoothly reacted