有机化学中的周环反应是指通过环状过渡态进行的一些协同反应,主要包括电环化反应、环加成反应,和a键迁移反应等几种类型。这些反应无论在基态(热反应)或激发态(光反应)下进行,都需服从R.B.woodward和R.Hoffmann提出的著名的轨道对称守恒原理。根据这一原理,可以推导出一系列选择规划,一般称为Woodward—Ho Pericyclic reactions in organic chemistry refer to some synergistic reactions via cyclic transition states, including electrocyclization reaction, cycloaddition reaction, and a-bond migration reaction. These reactions, both in the ground state (thermal reaction) or excited state (photoreaction), are subject to the well-known principle of conservation of orbital symmetry proposed by R.B.woodward and R. Hoffmann. Based on this principle, a series of selection plans can be derived, commonly referred to as Woodward-Ho