By comparing the stability of the sulfur nitrogenring system it is proved that not all the plannar S-N heterocycles belong to a class of"electro-rich" aromaticitys.
通过各硫氮环分子稳定性的比较，确定只有一部分硫氮环分子具有“多电子芳香性”。
2
Cytosine organic compound of the pyrimidine family often called a base consisting of a single ring containing both nitrogen and carbon atoms and an amino group.
胞嘧啶：嘧啶族的有机化合物。常被称为基，包含一个单环，内有氮原子和碳原子，还有氨群。
3
This paper reviews the catalyst system in RCM reaction and RCM application in the synthesis of natural products including carbon ring, oxygen heterocycles and nitrogen heterocycles, etc.