Synthesis, characterization and catalytic performance in enantioselective reactions by mesoporous silica materials functionalized with chiral thiourea-amine ligand

• Published in: Research on chemical intermediates 2021-02, Vol.47 (2), p.853-874
• Main Authors: Gök, Yaşar, Gök, Halil Zeki
• Format: Article
• Language: English
• Subjects: Acetylacetone; Catalysis; Catalysts; Catalytic converters; Chemical synthesis; Chemistry; Chemistry and Materials Science; Derivatives; Diamines; Emission analysis; Enantiomers; Field emission microscopy; Fourier transforms; Hydrogenation; Infrared analysis; Inorganic Chemistry; Ketones; Michael reaction; Physical Chemistry; Silicon dioxide; Thermogravimetric analysis
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-020-04301-w

Chiral heterogeneous catalysts have been synthesized by grafting of silyl derivatives of (1 R , 2 R )- or (1 S , 2 S )-1,2-diphenylethane-1,2-diamine on SBA-15 mesoporous support. The mesoporous material SBA-15 and so-prepared chiral heterogeneous catalysts were characterized by a combination of different techniques such as X-ray diffractometry (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) surface area. Results showed that (1 R , 2 R )- and (1 S , 2 S )-1,2-diphenylethane-1,2-diamine were successively immobilized on SBA-15 mesoporous support. Chiral heterogeneous catalysts and their homogenous counterparts were tested in enantioselective transfer hydrogenation of aromatic ketones and enantioselective Michael addition of acetylacetone to β-nitroolefin derivatives. The catalysts demonstrated notably high catalytic conversions (up to 99%) with moderate enantiomeric excess (up to 30% ee ) for the heterogeneous enantioselective transfer hydrogenation. The catalytic performances for enantioselective Michael reaction showed excellent activities (up to 99%) with poor enantioselectivities. Particularly, the chiral heterogeneous catalysts could be readily recycled for Michael reaction and reused in three consecutive catalytic experiments with no loss of catalytic efficacies.