问题：LDA上羟基
类型：交流
提问：harriet
等级：▲
版块：有机化学问题(jimuwei,fpcwin1211,netpanda,yjgzfl,Ftian,)
信誉：100%
回复：1
阅读：564
时间：2010-11-13 14:50:14 编辑加入/取消收藏订制/取消短消息举报该贴

To a solution of chromone 26 (1.557 g, 4.0 mmol) in THF (40 mL) was added LDA (2M, 2.0 mL, 4.0 mmol) dropwise at -78°C. After 5 min, a solution of freshly distilled trimethylborate (0.45 mL, 4.0 mmol) in THF (5.0 mL) was added and the mixture was stirred for 40 mins at -78°C. Glacial acetic acid (350L, 6.0 mmol) was added followed by 30% hydrogen peroxide (450 L). The reaction was allowed to warm to rt for 1 h and quenched with sat. NaHCO3. The usual workup with EtOAc and purification by recrystallization and flash chromatography gave 27 (980 mg, 60%) as an orange crystalline solid.
这是一篇利用LDA上羟基的文献，在上述文献中，硼酸三甲酯（trimethylborate）的作用、机理是什么？加入LDA、硼酸三甲酯后搅拌的时间又是如何确定的？

回复人：ky3000t,▲▲ () 时间：2010-12-13 08:33:07 编辑	1楼
LDA活化chromone 26的alpha氢形成负碳离子，该负碳离子进攻硼酸三甲酯形成烷基硼酸二甲酯，过氧化氢氧化重排最后水解就是alpha氢转变成羟基的衍生物了

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