Silva López Carlos, Nieto Faza Olalla, de Lera Angel R
Departamento de Química Orgánica, Facultade de Química, Universidade de Vigo, Lagoas Marcosende, 36310, Vigo, Galicia, Spain.
J Org Chem. 2009 Mar 20;74(6):2396-402. doi: 10.1021/jo802678d.
The ring opening reactions of fused cyclobutenes have been the subject of mechanistic debate for decades. Some reports have been published recently suggesting that, in some heterocyclic derivatives, the disrotatory anti-Woodward-Hoffmann mechanism might be responsible for the ring opening. We hereby show that the conrotatory pathway is still the lowest energy alternative for all cases examined, including push-pull substituted 2-thia-4-azabicyclo[3.2.0]hepta-3,6-dienes. Actually, we found that the disrotatory transition state exchanges roles with a double-bond isomerization depending on the substituents around the bicyclic structure.
几十年来，稠合环丁烯的开环反应一直是机理争论的主题。最近有一些报道表明，在某些杂环衍生物中，顺旋反伍德沃德-霍夫曼机理可能是开环的原因。我们在此表明，对于所有研究的情况，包括推挽取代的2-硫杂-4-氮杂双环[3.2.0]庚-3,6-二烯，顺旋途径仍然是能量最低的选择。实际上，我们发现，根据双环结构周围的取代基，顺旋过渡态与双键异构化交换了角色。
