Electrocyclic ring closure of alpha,beta-cis1,3-pentadienyl isocyanate affords 3-methyl-2(1H)-pyridone in fair yield. The isocyanate is formed in good yield by treatment of sorboyl chloride with trimethylsilyl azide in refluxing toluene. In refluxing heptane this reaction affords tetrazolinone 1 rather than isocyanate. The sensitive pentadienyl isocyanate is converted to polymer by either pyrolysis or acid treatment. Chem Abstr. Vol 79, 91930y.