23-3. Synthesis of Enone

　今回は 23-3. アルドール生成物の脱水：エノンの合成 を要約します。

 This theme is 23-3. Dehydration of Aldol Products: Synthesis of Enone.

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23-3. Dehydration of Aldol Products: Synthesis of Enone

 The β-hydroxy aldehydes or ketones yielded from aldol reactions can give α,β-unsaturated products or conjugated enones by dehydration: condensation.  Aldol products easily cause it for their carbonyl group.  The dehydrations under each condition are shown as below.

 The aldol dehydration proceeds by a bit more vigorous condition (slightly higher temperature) than the condition which cause the aldol formation itself.  So, conjugated enones are usually formed by aldol reactions without isolating the intermediate β-hydroxy carbonyl compounds.
 Also, conjugated dienes are more stable than nonconjugated enones, because π electrons are delocalized on the diene.
 The aldol dehydration can lead the aldol equilibrium toward the product side.  Even though we use unfavorable starting materials for the aldol reactions, most aldol condensations can be carried out in good yield.

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 So, the aldol reaction can give either a β-hydroxy aldehyde/ketone or an α,β-unsaturated aldehyde/ketone by the experimental conditions.

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　以上、23-3. アルドール生成物の脱水：エノンの合成 でした。
　次回は 23-5.混合アルドール反応を要約します。

 23-3. Dehydration of Aldol Products: Synthesis of Enone has finished.
 I'm going to summarize 23-5. Mixed Aldol Reaction for next entry.