amide (4), which is difficult to isolate, although isolation of some divinylamines similar to 4 has been rep~ rted.~ Compounds 2 and 3 are interconvertible to each other, reaching the equilibrium from 2 and 3 in 20 and 60 min, respectively, at 110" C in dimethyl sulfoxide= 4.88). Prolonged heating of the equilibrium mixture of 2 and 3 at 110" C yields 6. Both 2 and 3 yield the pyrimidone 6 in quantitative yields by heating at 180" C. The reaction pathway ...