Microwave Assisted Catalytic Asymmetric Henry Reaction

The Henry reaction (or nitroaldol reaction), which essentially is a coupling reaction between a carbonyl compound and a nitroalkane having a-hydrogen atoms, constitutes a fundamental synthetic tool for the construction of carbon-carbon bonds in organic chemistry. The importance of the Henry reaction is typically further transformations involving the newly formed β-nitroalkanol functionality such as reduction to amines, the Nef reaction to carbonyl compounds, dehydration to nitroalkenes, etc.In this thesis, three parts are included. Firstly, we briefly review the application of Henry reactions in the preparation of some natural products and pharmaceuticals. Then microwave-assisted Henry reaction and asymmetric Henry reaction were studied.1. Microwave-assisted Henry reactionIn the traditional methods, long reaction time was often required for the Henry reactions. So we decided to use microwave irradiation to promote this reaction. And solvent-free conditions were chosen to meet the need of green chemistry. After careful investigation of reaction conditions, most Henry reactions can react very quickly to afford the corresponding nitroalkanol at moderate to excellent yields under the microwave irradiation. The reaction time was greatly shortened, for most carbonyl compounds only several minutes, even less than one minute. At the same time, the yields were largely improved.(1) By adding appropriate Lewis acid, high yields were achieved not only for aldehydes with electron-withdrawing group, but also for those with electron-donating group. The latter often needed much longer time with low yields in most former reports.(2) By changing the reaction conditions, we broadened the scope of the reaction substrates. Most reports on Henry reactions were about aldehydes, and ketones were...