Preparation Of Immobilized Organocatalyst And Their Applications In Asymmetric Organic Reactions

In the first part of this work, two kinds of Proline-derived immobilized nanocatalysts L1A and L1B were prepared using multi-wall nanotubes (MWNTs) as the solid supports, which were acidified by 2.6 mol?L-1 HNO3 and HNO3/H2SO4 (1/3), respectively. The structures of the catalysts were characterized by infrared spectroscopy, and the loading ratios of the ligand 4-hydroxy proline were determined through TGA. These two immobilized catalysts were applied in the asymmetric Aldol reaction of aromatic aldehydes with cyclohexanone, and L1A could catalyze the reaction of 4-nitrobenzaldehyde and cyclohexanone in high diastereoselectivity but with very low yield and enantioselectivity. L1A could be recycled by simple filtration and reused for two more times, affording the similar results.In the second part of this work, two kinds of chiral phosphoric acid catalysts, (S)-3-(1-naphthalenyl)-1,1'-Binaphthyl phosphoric acid (S1) and (S)-3-[2,4,6-tri(isopropyl)phenyl]-1,1'-Binaphthyl phosphoric acid (S2) were synthesized using (S)-1,1′-bi-2-naphthol (BINOL) as the starting material. The structures of these two new compounds were characterized by IR, 1HNMR and 31PNMR. S1 was effective for the reaction of N-tosyl aldimine and indole to give the desired product in high yield and moderate enantioselectivity, while S2 could catalyze the Friedel-Crafts reaction of 2,2,2-trifluoroacetophenone and indole as well as the three component reaction of 3,4,5-trimethoxylaniline, trifluoroacetaldehyde methyl hemiacetal and indole in high yield and moderate enantioselectivity.S1 was further immobilized on MWNTs acidified by 2.6 mol?L-1 HNO3 or polyethylene glycol monomethyl ether (Mw = 1900) to give two kinds of solid chiral phosphoric acid catalysts L2 or L3. Their structures were characterized by IR spectrum and the loading ratio of the ligand S1 in L2 was determined through TGA. For the asymmetric Friedel-Crafts reaction of N-tosyl aldimine and indole, both L2 and L3 only gave racemic products.