Preparing (2S)- or (2R)- flavones comprises reducing a racemic mixture of the flavones with formic acid and a base in the presence of a chiral imidazolidine catalyst and a chiral diamine ligand, and removing the unreacted enantiomers

摘要

Preparation of (2S)- or (2R)- flavones comprises reducing a racemic mixture of the flavones (I) with a mixture of formic acid and a base in the presence of a chiral imidazolidine catalyst (II) and a chiral diamine ligand (Q); and removing the unreacted enantiomers of (I), where if a (R,R)-diamine-ligand is used, only (2R)-enantiomer of (I) are hydrogenated, and if a (S,S)-diamine-ligand is used, only the (2S)-enantiomer of (I) are hydrogenated. Preparation of (2S)- or (2R)- flavones comprises reducing a racemic mixture of the flavones of formula (I) with a mixture of formic acid and a base in the presence of a chiral imidazolidine catalyst of formula (II); and a chiral diamine ligand (Q) of formula (R4a-NH-CH(R1a)-(R2a)-N-S(=O) 2(R3a)); and removing the unreacted enantiomers of (I), where if a (R,R)-diamine-ligand is used, only (2R)-enantiomer of (I) are hydrogenated, and if a (S,S)-diamine-ligand is used, only the (2S)-enantiomer of (I) are hydrogenated. R 1>, R 2>H, alkyl or halo (preferably I, Br, Cl or F); R 3>, R 5>alkyl or acyl (preferably C nH 2n+1-CO); R 4>H, alkyl or acyl (preferably C nH 2n+1-CO); M : rhodium(III), ruthenium(II) or iridium(III); A : a pi-ligand of pentane compound of formula (B1) or benzene compound of formula (B2), preferably pentamethylcyclopentadienyl, 1-methyl-4-isopropylbenzene or 1,3,5-trimethyl benzene; R 5>a, R 6>alkyl or aryl; R 7>, R 8>H or alkyl; R1a, R2a, R3a : aryl or alkyl; R4a : H or alkyl; B 1>H, Cl or an anion; and n : 0-4. [Image] [Image].