自然轨道福井函数和成键活性描述符应用于解释苯硫醌和1,3-二烯的2+4和4+2环加成反应中的成键机理

摘要

o-Thioquinones can undergo either [2 + 4] or [4 + 2] cycloaddition reactions with acyclic dienes.To illustrate the bonding processes in these cycloadditions,the natural orbital Fukui function (NOFF) and bonding reactivity descriptor have been employed.The electrophilicity of a bond or an orbital in the o-thioquinone as well as in the acyclic diene has been found using the NOFF,which suggests that electron transfer takes place from an electron-donating bonding orbital to an electron-accepting antibonding/bonding orbital,leading to the cyclic product via the formation of a circular loop and two covalent bonds.The bonding reactivity descriptor shows that covalent bonds readily form between atom k1 of one molecule with a large f+k1 value and atom k2 of another molecule with a large f-k2 value.Both the NOFF and the bonding reactivity descriptor are efficient tools for interpreting the mechanism underlying the [2 + 4] and [4 + 2] cycloaddition between o-thioquinones and acyclic dienes.%苯硫醌与脂肪族烯烃可以发生[2+4]和[4+2]环加成反应.为了解释这些环加成反应中的成键过程,本文使用了自然轨道福井函数(NOFF)与成键活性描述符.自然轨道福井函数揭示了苯硫醌和脂肪族烯烃的键或轨道的亲电性,表明电子供体的成键轨道和电子受体的反键/成键轨道之间发生了电子转移,然后成环,在这一过程中有两个共价键形成,得到了环状产物.成键活性描述符表明共价键比较容易在一个分子中具有较大f+k1值的k1原子与另一个分子中具有较大f-k2值的k2原子之间形成.自然轨道福井函数与成键活性描述符都可以有效解释苯硫醌与1,3-二烯之间的[2+4]与[4+2]环加成反应的机理.