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Study on Cycloaddition Reaction of Nitrones with Alkenes Catalyzed by Metal Complexes of Bis(oxazolinyl) carbazole Ligand

Author: LiuLiXue
Tutor: LiuBo
School: Harbin University of Science and Technology
Course: Applied Chemistry
Keywords: Bisoxazoline carbazole Chiral catalytic 1,3 - dipolar cycloaddition reaction
CLC: O621.25
Type: Master's thesis
Year: 2010
Downloads: 23
Quote: 0
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Abstract


1,3 - dipolar cycloaddition reaction provides a step synthesis of a variety of five yuan heterocyclic compounds, therefore, 1,3 - dipolar cycloaddition reaction is widely used in the organic synthesis reactions. Many reported in the literature electron-deficient olefins with nitrone 1,3 - Dipolar cycloaddition reaction region, non diastereoisomers and enantiomers of selectivity, as well as the use of such various metal complexes like Lewis The acid catalyst to control this selectivity. Especially using a chiral ligand of the metal complex as a catalyst can be greatly improved to such selective catalytic achiral olefins with dipole reagent may direct the synthesis of an optically active product, which provide for the synthesis of optically active compounds a great convenience. This article is designed and synthesized tridentate structure bisoxazoline carbazole ligand structures were identified by means of infrared spectroscopy, nuclear magnetic resonance spectroscopy, high performance liquid chromatography detection of the synthesis of the final product and all intermediates. We choose an optically active tridentate the bisoxazoline carbazole ligand and Cu (II), Ni (II) and Zn (II) three metals consisting of four metal complexes (four metal complex no reported in the literature) for the catalyst, catalytic diphenyl nitrone (1a) with 3 - (2 - acryloyl) -1,3 - oxazolidin-2 - one (12a) of the cycloaddition reaction, and ultimately the catalytic effect using Daicel Chiracel-AD chiral column detection. The paper examines the structure of the ligand, cocatalyst 4? Molecular sieve (MS), the metal ions and the amount of catalyst and other factors on the regioselectivity of the reaction, the diastereomeric isomers and enantiomer selective. The results show that 12a and 1a of the cycloaddition reaction is carried out in the absence of the presence of a catalyst, a variety of poor selectivity, product 4 - the substituted isoxazoline piperidine derivative (13) and 5 - substituted isoxazoline piperidine derivatives (13a) is almost 50% each, and various isomers are racemic product. Add this study four post-catalyst, the reaction rate and selectivity has improved to some extent. Wherein the regioselectivity was significantly improved, with the increase in the amount of the catalyst, the regioselectivity of the reaction can be up to 100%. The structure of the ligand on the selectivity of the reaction, especially enantioselectivity has a very important impact. Two ligands, bis oxazoline ring four is a benzene ring, i.e. S-69A, when the amount of 30% S-69a, endo / exo selectivity to 85:15, Endo-13, the ee value of 94%, and the bisoxazoline ring four is benzyl, i.e. the S-69b, and when the addition of 30% S-69b, endo / exo was only 20:80, Endo-13, the ee value is only 10 %. Plays an important role in the coordination of metal ions on the enantioselectivity. Metal ligand for copper ions and nickel ions in the general performance of the catalytic system is a good enantioselectivity; the ligand metal is zinc ions generally poor performance of the catalytic system enantioselectivity was only 19% ee value . 4? MS on the rate of the reaction and enantioselectivity has a very large impact. When the catalyst is added the amount of S-69a 30% mol%, was not added the 4? MS, endo / eXo from 85:15 down to 26:74, the ee value of the of endo-13 from 94% to 3%. The results show that the bisoxazoline carbazole-Cu (OTf) 2 (S-69a) have the best chiral induction role, especially enantioselectivity, the amount of the catalyst is 30, when the presence of 4? MS %, the conversion rate of the product is greater than the percent, endo-13/exo-13 the proportion of 85:15, Endo-13, the ee value of 94%.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Properties of organic compounds > Chemical properties of organic reactions
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