- Unusual aluminum chloride-assisted conversion of isopropenyl acetate into 3-acetyl- and 3,5-diacetyl-2,6-dimethyl-4H-pyran-4-ones
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Reflux of isopropenyl acetate with an excess of AlCl3 in 1,2-dichloroethane affords 3,5-diacetyl-2,6-dimethyl-4H-pyran-4-one in 17% yield. The mild acidic cleavage of the latter (2% HCl, 20°C, 16 h) gives 3-acetyl-2,6-dimethyl-4H-pyran-4-one in 87% yield, whereas this reaction under more drastic conditions (17% HCl, reflux, 3 h) gives 2,6-dimethyl-4H-pyran-4-one in 61% yield.
- Novikov,Shestak,Denisenko
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experimental part
p. 1600 - 1604
(2011/05/04)
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- Kinetic and Spectroscopic Studies on the Thermal Decomposition of 2,2,6-Trimethyl-4H-1,3-dioxin-4-one: Generation of Acetylketene
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Acetylketene is shown to be a reactive intermediate in thermolytic reactions of 2,2,6-trimethyl-4H-1,3-dioxin-4-one (the diketene-acetone adduct) via a series of kinetic studies.The uncatalyzed acetoacetylations of phenol, 1-butanol, and di-n-butylamine with the title dioxinone at 82-107 deg C are first-order reactions in which the rate-limiting step is the formation of acetylketene and acetone, presumably via a retro-Diels-Alder reaction.Isopropenyl acetoacetate is not an intermediate in the aforementioned reactions but also provides acetylketene when heated.Acetylketene was observed by FT-IR spectroscopy in an argon matrix.
- Clemens, Robert J.,Witzeman, Stewart J.
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p. 2186 - 2193
(2007/10/02)
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