The problem about the Woodward-Hoffmann 's orbital symmetry conservation of such reactions in the literatures has been solved and then the reasons why these reactions may be thermally allowed are pointed out .

很好地解决了文献中用Woodward-Hoffmann轨道 对称守恒原理对此反应进行分析时所遇到的问题，指出了此反应是热 允许的原因。