Theoretical Studies On Nitrones And Alkenes Catalyzed By Chiral Binol-Al Complexes

1, 3-dipolar cycloaddition reaction is the most useful reaction in fundamental theory of organic chemistry and organic synthesis. The 1, 3-dipolar cycloaddition of nitrones with alkenes is one of the most studied reactions, among all the cycloadditions. It provides the efficient method to prepare isoxazolidines that are widely used as starting compounds in organic synthesis, especially for building natural products.The rapid developments of the application of chiral metal complexes in the field of catalytic stereoselective 1, 3-dipolar cycloaddition reactions are reported during the recent years. A series of catalysis has been used in the 1, 3-dipolar cycloaddition reactions of nitrones with electron-deficient and electron-rich alkenes, respectively. In several cases, a high degree of control of both the diastereoselectivity and enantioselectivity has been achieved in both Diels-Alder reactions and 1, 3-dipolar cycloaddition reactions.In this thesis, theoretical study approach has been used to study with Materials Studio and Gaussian03 on the workstation origin3800 of SGI Corporation.The 1, 3-dipolar cycloaddition reaction of 3, 4-dihydroisoquinoline N-oxides with vinyl ethyl ether has been caculated at B3LYP/6-31G* level using DFT theory. Because the regioselective of 1, 3-dipolar cycloaddition reaction is highly, four 5-substituted produces are available. The endo and exo reactants are approaching to each other from different faces (re-face or si-face), and four transition states are available.The optimized geometry and energy of various pro-formed complexes formed by the combination of chiral BINOL-AlMe complexes with 3, 4-dihydroisoquinoline N-oxides, (6, 7-dimethoxy-)-3, 4-dihydroisoquinoline N-oxides and vinyl ethyl ether was studied with theoretical modeling. The effect of optimized geometry of dominant per-formed complexes on the stereoselectivity of 1, 3-dipolar cycloaddition reaction of 3, 4-dihydroisoquinoline N-oxides or (6, 7-dimethoxy-)-3, 4- dihydro isoquinoline N-oxides with vinyl ethyl ether in the presence of chiral BINOL-AlMe complexes was discussed. The study results showed that the re-face of dipoles was sheltered by BINOL skeleton of chiral BINOL -AlMe complexes, and the (3S, 5S)-oxazole derivatives were obtained by the reaction of dipolarophile with dipoles from si-face of dipoles.