[有機]The Diel-Alder Reaction
今天上課提到的 Diels-Alder reaction
這是我找傑克學長的課本找到的資料(傑克學長大感謝)
po上來和大家分享
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CH2 CH2 ↙newσbond
║ new π bond ／ ╲
CH CH2 ↘ CH CH2
│ + ║ ───→║ ｜
CH CH2 CH CH2
║ ＼ ╱
CH2 CH2 ↖ new σ bond
1,3-butadiene ethylene cyclohexene
(eq.3.35)
Conjugated dienes undergo another type of 1,4-addition when they react
with alkenes(or alkynes). The simplest example is the addition of ethylene
to 1,3-butadiene to give cyclohexene.
This reaction is an example of a cycloaddition reaction, an addition that
results in a cyclic product. This cycloaddition, which converts three πbonds
to two σ bonds and one new π bond, is called the Diel-Alder reaction, after
its discoverers, Otto Diels and Kurt Alder. It is so useful for making cyclic
compounds that it earned the 1950 Nobel Prize in chemistry for its discover-
ers. As with hydroboration, this reaction is concerted. All bond-breaking and
bond-making occurs at the same time.
The two reaction are a diene and a dienophile. The simple example in
eq.3.35 is not typical of most Diels-Alder reaction because it proceeds only
under pressure and not in good yield. However, this type of reaction gives
excellent yields at moderate temperatures if the dienophile has electron-
withdrawing groups* attached, as in the following examples:
O O
∥ ∥
CH CH
＼∥ ／ 30。C ＼／╲／
｜ + ∥ ──→ ∥ ∣
／∥ ╱╲／
NC NC
∥ ╲／ 0。C ╱╲↙接2個CN
︱ + ∥ ──→ ∥ │
∥ ╱╲ ╲／↖接2個CN(我畫不出來 蒐哩啦)
NC NC
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※ 編輯: pinkunicorn 來自: 140.112.238.173 (03/29 20:51)
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