The mechanism of the Stevens and Sommelet−Hauser Rearrangements. A Theoretical Study

详细信息    查看全文

• 作者：Giovanni Ghigo ; Stefania Cagnina ; Andrea Maranzana ; Glauco Tonachini
• 刊名：Journal of Organic Chemistry
• 出版年：2010
• 出版时间：June 4, 2010
• 年：2010
• 卷：75
• 期：11
• 页码：3608-3617
• 全文大小：885K
• 年卷期：v.75,no.11(June 4, 2010)
• ISSN：1520-6904

文摘

The [1,2] and [2,3] migration steps in the Stevens and Sommelet−Hauser rearrangements which occur in the ylides of quaternary ammonium salts have been studied at M05-2x levels. The Stevens migration has been found to take place through a diradical pathway in several cases (tetramethylammonium, benzyltrimethylammonium, benzylphenacyldimethylammonium ylides). By contrast, in the phenyltrimethylammonium ylide this reaction takes place through a concerted process. The Sommelet−Hauser rearrangement takes place through a concerted transition structure. The most important factor determining the extent of competition with the Stevens rearrangement is the difference in the reaction energies as the formation of the Sommelet−Hauser intermediate is significantly less endoergic.