Reactions of 1 ,Zdihydropyridines (la-c) and 1,4-dihydropyridines (2a-c) in the
presence of benzyne (3) under thermal conditions, and in the case of (2c) under
photochemical conditions, have been investigated. Benzyne acts as an oxidizing
agent to convert dihydropyridine (la) and (2a) to the corresponding pyridine (4) or
adds as a dienophile to (lb-c).