2,5-二甲氧基苯基烷基酮与t-BuMgCl反应的机理研究

2,5-二甲氧基苯基烷基酮1_(a-d)(烷基分别为甲基、乙基、异丙基和叔丁基)与t-BuMgCl反应后,主要生成了1,2-加成产物、1.6-共轭加成产物及还原产物,产物及其分布在不同程度上受酮的结构、反应介质以及金属镁中过渡金属杂质的含量等因素的影响。据此,提出了反应的可能机理。

A Mechanistic Study on Reactions of Alkyl 2,5-Dimethoxyphenyl Ketones with t-Butylmagnesium Chloride

Reactions of alkyl 2, 5-dimethoxyphenyl ketones with t-butylmagnesium chloride were shown to yield the 1, 2-adducts, 1, 6-adducts, and the corresponding alcohols as the major products.The product distributions were found largely dependent on the alkyl group of the ketone and the solvent used. The bulkier the alkyl group . the more favoured the formation of the 1.6-adduct or the alcohol. On the other hand, the formation of the 1, 6adducts became a more important pathway when the reactions were carried out in tetrahydrofuran than in ether.In addition. the trace amount of transition metals in magnesium alsoshowed a little effect on the product distribution. Based on the experimental observations, we suggested that the above reactions, initiated by a single electron transfer, would possiblyundergo via the intermediates, radical ion pairs and radical pair, and the final product distributions greatly depended on the nature of the generated intermediates in each of the reactions.