Orgnical Base Catalyzed Annulation Reactions Based On Electron- Deficient Alkyne

Organic base-catalyzed reaction is one of fundamental synthesis methodology. This research areas have attracted much attention due to their high catalytic selectivity and their high efficiency in the synthesis of organic building blocks from easily available starting materials. The zwitterions formed from the addition of organic base to electron-defecient alkyne is a class of important dipolar speciesm, which could be reacted with various substrates to afford various novel products.This dessertation focus on the reacion of theβ-carbonyl compounds with the zwitterion intermediates to prepare multi-substituted benzene and 2-pyrone derivatives and it includes the following sections:1. Highly substituted benzenes are important synthetic intermediates in organic chemistry. As a continuation of this annulation research, a benzannulation reaction ofβ-diketones with dimethyl acetylenedicarboxylate catalyzed by pyridine and potassium tert-butoxide is described. During the course of our investigation on the reaction of dimethyl acetylenedicarboxylate withβ-diketones, it is found that potassium tert-butoxide (KOBut) is crucial for this benzannulation reaction. This methodology supplies a facile way to synthesize fully substituted benzenes with high yields from simple and commercially available starting materials.2. 2-pyrone molecules have attracted much attention from organic chemists due to their potential biological activity and pharmaceutical significance. Moreover, they have also been used as important intermediates in organic synthesis. Cycloaddition of alkynyl ketones withβ-ketoesters mediated by PPh3 and KOBut to synthesize 2-pyrone derivatives was systematically described. A variety ofβ-ketoesters reacted with alkynyl ketones to give functionalized 2-pyrones in moderate to good yields under mild conditions. the obvious advantage of this work is that it is more diverse and easier to synthesize the starting materials.Through those rsearches, we extened the appliacation of the zwitterions formed from the addition of organic base to electron-defecient alkyne and developed new approach to synthesis of highly substituted benzenes and 2-pyrone derivatives.