微波与有机化学反应的选择性*

本文综述了微波辅助下有机化学反应的选择性，包括化学选择性、区域选择性、顺反选择性、非对映选择性、对映选择性,与传统加热条件下反应选择性的区别。讨论了微波对有机化学反应选择性的影响。从文献报道的结果来看，虽然观察到了一些反应在微波照射与加热条件下显示出不同的选择性，但绝大部分例子并不是在严格相同的条件下进行的对比，还有一些虽然做了对比研究，但却忽略了温度的影响。对于绝大多数例子，微波产生的选择性的差别似乎都可以用热效应来解释。可以认为微波辅助的反应中基本不存在特殊的"非热效应"。微波辅助技术可以通过改变反应温度来实现改变某些反应的选择性。希望本文对微波效应和微波对有机反应加速效应的本质的理解提供一些有用信息。

Microwave Irradiation and Selectivities in Organic Reactions

The different selectivities, including chemoselectivity, regioselectivity, syn/trans selectivity, diastereoselectvity, and enantioselectivity, of organic reactions under the microwave-assisted and conventional heating conditions are reviewed. The effect of microwave irradiation on these selectivities is discussed. According to a survey of literature, although some differences on the selectivities between the microwave-assisted and classical heating conditions are observed in some reactions, most of the reactions are not conducted under the strict same conditions except for heating mode, such as in different solvents, even under solvent-free conditions, under the catalysis of different catalysts or additives, at different temperatures. Some examples are conducted under the same reaction systems, but at different temperatures. For most of examples, the effects of the microwave irradiation on the selectivities are possibly caused by the actually different temperature and could be explained by the thermal effect. I am prone to consider that no specific athermal effect exists generally in the microwave-assisted organic reactions. The microwave-assisted technology can tune selectivities via changing reaction temperature for some organic reactions. I hope this review will provide some useful information to understand the microwave effect on the organic reactions and the origin of the microwave-induced organic reaction enhancement chemical techniques.