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The Darzens reaction (also known as the Darzens condensation or glycidic ester condensation) is the chemical reaction of a ketone or aldehyde with an α-haloester in the presence of base to form an α,β-epoxy ester, also called a "glycidic ester". This reaction was discovered by the organic chemist Auguste George Darzens in 1904. :400px ==Reaction mechanism== The reaction process begins when a strong base is used to form a carbanion at the halogenated position. Because of the ester, this carbanion is a resonance-stabilized enolate, which makes it relatively easy to form. This nucleophilic structure attacks another carbonyl component, forming a new carbon–carbon bond. These first two steps are similar to a base-catalyzed aldol reaction. The oxygen anion in this aldol-like product then does an intramolecular SN2 attack on the formerly-nucleophilic halide-bearing position, displacing the halide to form an epoxide.〔 This reaction sequence is thus a condensation reaction, since there is a net loss of HCl when the two reactant molecules join. : The primary role of the ester is to enable the initial deprotonation to occur, and other carbonyl functional groups can be used instead. If the starting material is an α-halo amide, the product is an α,β-epoxy amide. If an α-halo ketone is used, the product is an α,β-epoxy ketone.〔 Any sufficiently strong base can be used for the initial deprotonation. However, if the starting material is an ester, the alkoxide corresponding to the ester side-chain is commonly in order to prevent complications due to potential acyl exchange side reactions. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Darzens reaction」の詳細全文を読む スポンサード リンク
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