The Assignment of Long-Range13C-1H Coupling Constants in Pyrazoles13C NMR, Selective Decoupling

Abstract

Although quite a few papers have been devoted to the ¹³C NMR study of pyrazoles, there is one problem that has not yet been satisfactorily solved, namely the assignment of the ²JCH and ³JCH coupling constants. In general, the ³C chemical shifts and ¹JCH coupling constants can be easily attributed, but the assigment of the long-range ²JCH and ³JCH coupling constants is not straight forward. In N- substituted pyrazoles, where annular tautomerism is prevented, each carbon atom can have two long-range coupling constants with the ring protons.