The Design of Chial β-Amino Alcohols and their Application to the Asymmetric Henry Reaction and the Asymmetric Reduction of Prochiral Ketones
|School||Zhejiang University of Technology|
|Keywords||chiralβ-amino alcohol asymmetric catalysis Henry reaction asymmetric reduction prochiral ketones|
Catalytic asymmetric synthesis is a hot field in modem organicsynthesis．Henry reaction is an important C-C bond forming reaction, forthe productβ-nitroalcohol can be transformed to amine, nitroalkene, andnitro-containing carbonyl compound, which are all useful chemicalintermediate. Asymmetric borane reduction of prochiral ketones is a goodprocess to the synthesis of enantiomerically enriched secondaryalcohols．And, the asymmetric reduction of prochiral ketone is one of themost indispensable tools for approach chiral secondary alcohols, whichare obtained as versatile building blocks for biologically andpharmaceutically active compounds.For the low price, convenient prepare procedure and great catalystactivity, the chiralβ-amino alcohol can be an efficient ligand and catalyzevarious enantioselective reactions.So, it is significance and necessary to continue the study ofasymmetric Henry reaction and asymmetric borane reduction of prochiral ketones catalyzed by chiralβ-amino alcohol. In this paper we haveprepared 2 groups chiral amino alcohol ligands from L-Phenylglycinemethyl ester hydrochloride or L-Phenylalanine methyl ester hydrochloridein a simplified way and used them as chiral catalysts in the asymmetricHenry reaction and asymmetric borane reduction of prochiral ketones.This thesis mainly focuses on the following three aspects:1. Synthesis of chiralβ-amino alcohol①Treat the L-Phenylglycine methyl ester hydrochloride and LPhenylalaninemethyl ester hydrochloride with NaBH4 or Grignardreagent give 6 chiralβ-amino alcohols, which can be condensed with 2-hydroxyl- Naphthaldehyde to proceed 6 chiral Schiff Base.②The other 9 chiralβ-amino alcohols were prepared by reductionof the aldimine （can be obtained by condensed with chiral primary aminoalcohol and aromaticity aldehyde） with NaBH4.2. The catalysis of chiral Schiff Base was studied for the asymmetricaddition of nitroalkanes to aldehydes at ambient conditions. During thisperiod we also check the effect of the solvents, copper salts and theamount of the nitromethane. When 3-nitrobenzaldehyde was used assubstrate, the corresponding adduct catalyzed by 10mol% of ligand S2was obtained in 95% yield and 91% ee values.3. The chiralβ-amino alcohol were applied in asymmetric borane reduction of prochiral ketones, it proved that the catalyst developed fromsalicylaldehyde would be more efficient then others. The asymmetricreduction of 2’-nitro-acetophenone catalyzed by AL0AL01 （10mol %） canobtained the corresponding secondary alcohols with 87% ee values.