Calcium Carbide: From Elemental Carbon to Isotope‐Economic Synthesis of 13C2‐Labeled Heterocycles†

Abstract

Comprehensive Summary13C‐Carbon is the most available source of carbon‐13. It is a relatively inexpensive solid material, which can be easily converted to calcium carbide‐13C2. In current work, Ca13C2 was used for in situ generation of 13C2‐acetylene in 1,3‐dipolar cycloaddition and [4+2] cycloaddition reaction. For the first time, 1H‐1,2,3‐triazoles‐4,5‐13C2 and isoxazoles‐4,5‐13C2 were synthesized using calcium carbide‐13C2. A Diels‐Alder type cycloaddition of 3,6‐di(pyridin‐2‐yl)‐1,2,4,5‐tetrazine and Ca13C2 was investigated, and the best way for the synthesis of 3,6‐di(pyridin‐2‐yl)pyridazine‐4,5‐13C2 was proposed for the first time. Here we perform a detailled description of NMR spectra of 13C2‐labeled triazoles, isoxazoles and 3,6‐di(pyridin‐2‐yl)pyridazine.