定义Definition
硼氢化-氧化是先使硼烷(BH₃·THF、9-BBN 等)对烯烃进行顺式加成生成烷基硼烷,再用碱性过氧化氢氧化为醇的两步反应,总结果是对双键进行反马氏、顺式加水。
Hydroboration–oxidation adds a borane (BH₃·THF, 9-BBN, etc.) syn across an alkene to form an alkylborane, then oxidises it with basic hydrogen peroxide to the alcohol — overall anti-Markovnikov, syn addition of water.
区域与立体化学Regio- and stereochemistry
B–H 经四中心过渡态协同加成:硼加到位阻小、取代少的碳上(同时该碳在过渡态中带部分负电荷),H 加到取代多的碳上;H 与 B 从同一面加成。氧化时 B 被 OH 取代且构型保持,所以 H 与 OH 为顺式。不发生碳正离子重排。
B–H adds through a concerted four-centre TS: boron to the less hindered, less substituted carbon and H to the more substituted one, from the same face. Oxidation replaces B by OH with retention, so H and OH end up syn. No carbocation rearrangements occur.
由来Origin
赫伯特·C·布朗于 1956 年起系统发展,因有机硼化学获 1979 年诺贝尔化学奖(与维蒂希共享)。
Developed from 1956 by Herbert C. Brown, who shared the 1979 Nobel Prize in Chemistry with Wittig for organoboron chemistry.
扩展Extensions
大位阻硼烷(9-BBN、二仲异戊基硼烷)选择性更高;手性硼烷(Ipc₂BH,由 α-蒎烯制备)实现不对称硼氢化;炔烃硼氢化–氧化得醛;有机硼化合物还是铃木偶联的原料。
Bulky boranes (9-BBN, disiamylborane) sharpen selectivity; chiral Ipc₂BH from α-pinene enables asymmetric hydroboration; alkynes give aldehydes; organoboranes also feed Suzuki couplings.
反应Reactions
BH₃·THF,0 °C 至室温;然后 3 mol/L NaOH 与 30% H₂O₂
BH₃·THF at 0 °C to room temperature, then 3 M NaOH and 30 % H₂O₂
B–H 对双键顺式加成(反马氏)。
Syn, anti-Markovnikov B–H addition.
HOO⁻ 进攻硼形成硼酸根。
HOO⁻ adds to boron.
烷基从硼迁移到氧(构型保持),水解得醇。
Alkyl migrates from B to O with retention; hydrolysis gives the alcohol.
H 与 OH 顺式加成。
Syn addition of H and OH.
反应机理图Mechanism
红色弯箭头表示一对电子的移动方向:从电子来源(孤对电子或化学键)指向电子去向。Red curly arrows show where an electron pair moves: from its source (lone pair or bond) to its destination.
四中心协同加成:B 加到末端碳,H 加到另一碳(顺式)
Four-centre concerted addition: B to the terminal carbon, H to the other (syn)
烷基硼烷
Alkylborane
1-丙醇:反马氏取向,构型保持
Propan-1-ol: anti-Markovnikov, retention of configuration
年表Timeline
- 1956
布朗报道烯烃硼氢化
Brown reports alkene hydroboration
- 1961
首例不对称硼氢化(Ipc₂BH)
First asymmetric hydroboration with Ipc₂BH
- 1979
布朗获诺贝尔化学奖
Brown receives the Nobel Prize