1,2,4‐Triazines and Calcium Carbide in the Catalyst‐Free Synthesis of 2,3,6‐Trisubstituted Pyridines and Their D‐, 13C‐, and Doubly D2‐13C2‐Labeled Analogues

Abstract A novel synthetic approach to 2,3,6‐trisubstituted pyridines, their 4,5‐dideuterated derivatives, 4,5‐13C2‐ and doubly‐labeled D2‐13C2‐pyridines has been developed using catalyst‐free [4+2] cycloaddition of 1,2,4‐triazines and in situ generated acetylene or labeled acetylene. Calcium carbide and water or deuterium oxide were used for the in situ generation of acetylene and dideuteroacetylene. Calcium carbide‐13C2 in the mixture with water or deuterium oxide was applied as 13C2‐acetylene and D2‐13C2‐acetylene source.