Vapor phase phototransposition of pyrazine deuterium labeling studies

2,5-Dideuteriopyrazine (1-2,5-d₂) and 2,6-dideuteriopyrazine (1-2,6-d₂) phototranspose in the vapor phase to mixtures of 4,6-dideuteriopyrimidine (2-4,6-d₂) and 2,5-dideuteriopyrimidine (2-2,5-d₂) or 4,5-dideuteropyrimidine (2-4,5-d₂) and 2,4-dideuteriopyrimidine (2-2,4-d₂), respectively. In each case, a trace quantity of a dideuteriopyridazine (7-d₂) photoproduct was also observed. These products are consistent with a diazaprefulvene mechanism involving, 2,6-bonding, one or two nitrogen migrations, and rearomatization.