The regioselectivity of the thermal cyclisations of enyneâallenes 1 can be toggled as a function of the ring size of the cycloalkene. With a cyclopentene as the ene moiety the MyersâSaito (C2âC7) cycloaromatisation product is formed, whereas with six- and seven-membered cycloalkenes the novel C2âC6 cyclisation is observed. DFT calculations are used to rationalise these changes. The implications of these findings for alternative thermal biradical cyclisations of neocarzinostatin are discussed.
                                    烯炔醛 1 热环化反应的区域选择性可随环烯的环径大小而变化。以
环戊烯作为烯分子时,会形成迈尔萨托(C2âC7)环芳香化产物,而以六元和七元环烯为烯分子时,则会出现新颖的 C2âC6 环化现象。DFT 计算用于合理解释这些变化。讨论了这些发现对新卡西诺司他汀的替代热双向环化反应的影响。