Photochemistry of 4-Hydroxypyrylium Cations in Aqueous Sulfuric Acid
4-Hydroxypyrylium cations that are known to undergo phototransposition to 2-hydroxypyrylium cations in concentrated sulfuric acid were observed to undergo photo-ring contraction in 50percent sulfuric acid.The initial products observed when the irradiations are carried out at 0 deg C are 4,5-dihydroxycyclopent-2-enones that can be isolated.At higher temperatures these initial products undergo secondary acid catalyzed thermal reactions to yield substituted acetylfurans.
Pavlik, James W.,Spada, Alfred P.,Snead, Thomas E.