Immobolization Of The Chiral Imidazolidin On Polymer Of Amino Acids And Its Application In The Enantioselective Diels-Alder Reaction

This dissertation consists of two parts: (1) Immobolization of the chiral imidazolidin on polymer of amino acids and its application in the enantioselective Diels-Alder reaction. (2) Lanthanide-catalyzed Cross- Cannizzaro reduction of aromatic aldehydes with formaldehyde.Three new compounds: 3-(4-amino-butyl)-5-benzyl-2,2-dimethyl- imidazolidin -4-one, 3-(6-amino-hexyl)-5-benzyl-2,2-dimethyl-imidazolidin-4-one, 3-(4-amino-benzyl)-5-benzyl-2,2-dimethyl-imidazolidin-4-one were prepared and grafted on polymer of amino acid. The chiral imidazolidin supported on polymer of amino acid has been successfully applied to catalyze the enantioselective Diels-Alder reaction of cyclopenta-l,3-diene and 3-phenyl- propenal. The degree of polymerization (n) was important to the performance of the supported catalysts. When n increased (n>10), the catalytic yield declined while the difficulties of the catalyst recycling increased when n <10. As for the amino acid, L-leucine was identified to be the choice.Under the optimized condition: 5%eq. with silica, in CH₃OH:H₂O=19:19 (v/v) or CH₃OH:H₂O=2:l(v/v) , at RT, the Diels-Alder reaction of cyclopenta- 1,3-diene and 3-phenyl- propenal showed that a good yield upto 99% and the enantiomeric excess for the product was 77% in all 5 repeated runs, indicating that the catalytic system could be reused for at least 5 times without loss of the catalytic activity and enantioselectivity.A modified Cross-Cannizzaro reaction catayzed by lanthanides for reduction of aromatic aldehydes with formaldehyde was disclosed under a weekly basic aqueous condition with organic or ingorganic bases e.g. 4%NaOH, Et₃N and DBU.Under the optimized condition: 10%eq.CeCl₃, 3.5eq.HCHO(aq.), base (3eq.Et₃N,or 2eq.DBU,or 6eq.5%NaOH(aq.), in water at 25-30 °C, a variety of aromatic aldehydes were examined, showing that electron-withdrawing groups remarkably accelerated the reaction while electron-donating ones slowed the reduction down significantly. Organic bases such as Et₃N and DBU displayed advantages over dilute aqueous NaOH with respect to functional group tolerance. Forexample, in the reduction of p-cyanobenzaldehyde, Et₃N and DBU provided alcohol in 50% and 70% yields, respectively, while use of 5%NaOH(aq.) led to the complete hydrolysis of the cyano group. A plausible mechanism for the lanthanide-catalyzed Cross-Cannizzaro reduction of aromatic aldehydes with formaldehyde was proposed in which the true catalytic speciescould probably be the active Ln(OH)₃ generated in situ.