| P-Hydroxyl-a-vinyl carboxylic esters are considered as important ubiquitous building blocks in organic synthesis and their applications have been well documented in total synthesis as well as in medicinal chemistry.In contrast to their wide use in synthesis, only few methods have been developed to prepare these compounds:1) Metal-mediated Bartier-type reactions of aldehydes with y-halogenated or ?-halogenated ?, ?-unsaturated ester,2) Deconjugative Aldol condensation of crotyl derivatives with aldehydes or ketones. However, those processes suffer from some drawbacks, for instance: the harsh reaction conditions, the use of stoichiometric metal catalyst and highly toxic regent as well as the poor regioselesivity.In our group, we have developed an organocatalyzed reaction in which P-hydroxyl-a-vinyl carboxylic esters could be formed by treatment of ?, ?-unsaturated ester possessing a y-hydrogen with aldehydes in the presence of catalytic amount of DBU. In the previous work, the optimization of reaction conditions and mechanistic studies have been done.On the basis of our group previous research work, we did extensive studies on this new type of reaction, which include the following topics in this thesis:1. Further optimization of the reaction condition with aromatic aldehyde, including hetero(aryl)aldehyde and investigation of the electronic effect as well as sterohindrance effect on the reactivity.2. Rapid preparation of seven types of substrates of ?, ?-unsaturated esters via Wittig or Suzuki coupling strategies and exploration of the substrate scope.3. Conversion of ?-hydroxyl-a-vinyl carboxylic esters into dihydrofuran and furan derivatives in the presences of NBS, followed by elimination and oxidation.4. Efficient syntheses of a series of highly functionalized epoxides with high diastereoselectivity using a-bromide ?, ?-unsaturated ester as the substrate under the similar reaction conditions to those in the syntheses of ?-hydroxyl-a-vinyl carboxylic esters. |
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