A one-pot synthesis of substituted 3-oxo-2-azabicyclo [2.2. 0] hex-5-enes (Dewar pyridones) from alkynes, aluminum halides, and isocyanates is deacribed. The mechanism of the reaction of isocyanates with the intermediate aluminum halide u complexes of cyclobutadienes is discussed on the basis of the substitution pattern of the obtained bicyclic products. The thermal and acid-promoted reactions of some of the compounds are ...