- An easy and short preparation of pentachloroacetone by selective dechlorination of hexachloroacetone under Appel conditions
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We report a very convenient laboratory preparation of pentachloroacetone (PCA) by selective dechlorination of hexachloroacetone (HCA) via reaction with triphenylphosphine in the presence of methanol or aromatic alcohols.
- Rajendran, Kamalraj V.,Carr, Damien J.,Gilheany, Declan G.
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- Studies on the Mechanism of an Olefination of Aldehydes to 1,1-Bis(trifluoromethyl)alkenes
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1,1-Bis(trifluoromethyl)olefins 3 are obtained from aldehydes, 2,2-dichlorohexafluoropropane (1), and triphenylphosphine.The mechanism of this olefination reaction is studied, and it is shown that it takes place not by Wittig- but by a Knoevenagel-type of reaction.Ketones react with 1 and triphenylphosphine to form olefins 3 only when they are activated by a CF3 group.Chlorosubstituted ketones, e.g. 1,1,1-trichloroacetone or hexachloroacetone, cannot be converted to the corresponding 1,1-bis(trifluoromethyl)olefins.Hexachloroacetone reacts with triphenylphosphine predominantely with formation of perchloroallene (24), which quantitatively dimerizes to form perchloro-1,2-dimethylenecyclobutane (25). - Key Words: Aldehyde olefination / Alkenes, 1,1-bis(trifluoromethyl)- / Olefination reaction
- Korhummel, Claus,Hanack, Michael
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p. 2187 - 2192
(2007/10/02)
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