Synthesis Of Chiral β-Amino Alcohol Derivatives And The Research In As Ymmetric Epoxidation Of Chalcones

The development of efficient methods for the asymmetric epoxidation ofα,β-unsaturated carbonyl compounds is significant in organic synthesis since optically active epoxy ketones are among the most versatile building blocks for access to several natural products and pharmaceuticals. Until now, a variety of valuable systems have been proposed for this reaction. Asymmetric reactions promoted by small organic molecules are an emerging investigated area. A great application potential of organocatalysts has been displayed in asymmetric epoxidation, such as polyamino acid, cinchona alkaloid combinations and chiralβ-amino alcohols.A series of novel chiralβ-amino alcohols were prepared from the hydrogen chloride salt of L-phenylalanine methylester. The structures of these compounds were confirmed by IR, 1H NMR, 13C NMR and MS. All of theβ-amino alcohols were examined as chiral catalysts in the asymmetric epoxidation of chalcones with tertbutyl hydroperoxide as the oxidant. The results obtained showed that the catalyst 20 possessed the best catalytic activity, the yield and optical purity were 91.0%, 77.6%. The effect of different solvents and organic base (DBU) loading were studied with the chiralβ-amino alcohol 20 as the catalyst. The best reaction conditions were: n-hexane as solvent, 5 eq TBHP loading, 3 eq DBU loading. The substrate scope of this reaction was studied in the end.We have also designed and synthesized non-symmetric/single chiral thiourea catalysts and C2 symmetry/double chiral (thio)urea catalysts based on chiralβ-amino alcohols. Chiral (thio)urea derivatives are rapidly emerging as versatile, high catalytic active, low catalyst loading, excellent enantioselective, high functional group tolerant, ease of prepared/modified organocatalyst for the promotion of a wide range of synthetically useful asymmetric processes. Chiral (thio)urea derivatives are very effective organocatalysts for the nuclephilic addition reactions of imines, aldehydes and electron-deficient olefins. They have been successfully applied in varieties of enantioselective organic reactions, such as asymmetric Strecker, Michael addition, Mannich, Henry reactions , etc. The application and catalytic activity of these chiral (thio)urea derivatives are in studing.