Silyloxyazadienes: one intermediate and two competitive pericyclic reactions

文献情報

出版日 2010-03-29

DOI 10.1039/B925351C

インパクトファクター 3.676

著者

Alessandro Bongini, Mauro Panunzio, Alessandro Venturini

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要旨

The two competing mechanisms in the reaction of 3-trialkylsilyloxy-2-aza-1,3 dienes to form β-lactams through a [2+2] electrocyclic ring closure or tetrahydrooxazinan-4-ones via a [4+2] hetero-Diels–Alder reaction were studied using Density Functional computations. Although the [2+2] and [4+2] mechanisms are typical of dienes, their competition, starting from the same diene intermediate, has not yet been observed and analyzed. This competition is governed by a delicate interplay between temperature and substituents at the diene and dienophile, respectively. Clearly, entropy tends to favor the [4+2] hetero-Diels–Alder at low temperatures and the [2+2] electrocyclic ring closure at high temperatures, but simple substituent modifications at the diene and dienophile, can make the [4+2] competitive at high temperatures and sometimes even transform the [4+2] concerted mechanism into a two-step Mukaiyama-type process. Moreover, a study of the global electrophilicity values showed that charge transfer in the hetero-Diels–Alder transition states is driven by chemical hardness rather than by chemical potential.

掲載誌

Physical Chemistry Chemical Physics

CiteScore: 5.5

自己引用率: 10.3%

年間論文数: 3036

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