Pyrilium oxide

Primary amines via pyrilium salts react with 2-pyrid ie N-oxides and on decomposition give aldehydes in fair yields (equation 36). ... 

Since many furans are not particularly sensitive to light they often form as products of photochemical reactions. A high pressure mercury arc can be used to eject nitrogen from pyridazine Ai-oxides and form cyclopropenyl ketones and their furan isomers.29 High yields of 2-acetylfuran can be achieved by irradiating the pyrilium ion in Scheme 5 (i.e., the requisite pyrone dissolved in sulfuric acid) although the conditions, mainly the acidity, have to be carefully controlled.30 Surprisingly, the intermediate cyclopen-tenone diol can be isolated with 50% sulfuric acid it is converted to the furan in a separate step. 

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