Cl
Cl
H
OH
Ph Ph
CH3 O
Ph H
CH3 AgBF4 O H Et2O
Ph
CH3
O Ph
Ph O
H
OH +
Ph > CH3 > Cl
Cl
Cl
H
OH
CH3
Ph
CH3 H
Ph AgBF4
CH3 Ph
Ph O
O H Et2O
Ph O
Ph O
H
OH +
R. Bach, J. Am. Chem. Soc. 1979, 101, 3118.
OH
OH 1,2-shift
1,3-shift OH
H O
H+
H O
OH
O
H H+
H
CHO
12
1,2-迁移的立体化学及能量需求 C-Z键及C-C键和空P轨道要共平面
Z β
R
R
+ α
The ideal relationship of the empty p orbital to the migrating group (Z) for a 1,2-shift
14
1，2-shift: stereochemistry
If X departs before Z begins to move, either retention or inversion can
occur at the migration terminus. If the lifetime of the carbocation is very short, retention will result if Z was gauche to the leaving group in the unreacted starting material and inversion will result if Z was anti
13
1,2-shift: stereochemistry
If Z begins to migrate before X has completely departed, the migration terminus C will be inverted. This is the situation most commonly encountered in solvolysis reactions that involve neighboring-group participation.
10
1,2-迁移: Tiffeneau-Demjanov rearrangement
i) HCN
O
or CH3NO2/NaOH HO
NH2
+ HO N N
ii) LAH
NaNO2 + HCl
HO + - N2
H O+
O - H+
11
Meinwald重排: 双环环氧化物经酸处理重排为醛
O H+
OH
第 8 章 分子重排
重排反应: 在反应中原子或基团迁移使分子的碳骨架发生变化
缺电子重排
缺电子碳（正碳离子）
(nucleophilic or anionotropic)
分
缺电子氮（氮烯）
类
富电子重排 (electrophilic or cationotropic)
芳香环上的重排
研究方法
化学动力学 示踪原子 交叉实验 中间体分离鉴定 立体化学等
Wagner-Meerwein Rearrangement, Pinacol Rearrangement, Friedel-Crafts Acylation and Alkylation, Bischler-Napieralski Reaction, Pictet-Spengler Reaction, Beckmann Rearrangement, Tiffaneau-Demjanov Rearrangement, Ferrier Rearrangement, Nazarov Cyclization, Pechmann Reaction, Prins Reaction, Ritter Reaction, Leuckhart-Wallach Reaction, Meyer-Schuster Rearrangement, Rupe Reaction
1
8.1 碳正离子的重排
形成碳正离子的主要途径 卤代烃与Lewis acid 作用
X + AlX3
醇的酸介质脱水
H+ OH
+ OH2
SN1反应
L
+ + AlX4-
+ + H2O
+
+ L-
双键的亲电加成
+ X+
X
2
Some named reactions which involve carbocation intermediates
3
DO YOU HAVE A CARBOCATION?
ALWAYS
STOP - LOOK - THINK
STOP
EVALUATE FOR A REARRANGEMENT
E
R
X
E
RG
ANE M
D
E
CAN YOU FORM A BETTER CARBOCATION ?
8.1.1 1,2-迁移（Wagner-Meerwein 重排）
Synthesis 2005, (15), 2562.
9
1,2-迁移: 示例
Br Br
MeLi, -70 。C
Cl
O NEt3, 120 。C
窗格烃合成
H2NNH2/KOH 160-190 。C
ห้องสมุดไป่ตู้
O
Li
PhS HO
SPh
p-TsOH.H2O
O
0 。C
C6H6, 80 。C
see JACS 1998, 120, 317-328.
基团迁移大致顺序：芳基 > 烷基 (３ > 2 >1 ) > H 5
6
1,2-迁移: 示例
Cascade of ring expansion (see Chem Ber. 1984, 117, 203; 1988, 121, 525.)
CH3 OH
Me OH
TsOH Me2C=O/H2O
R OH
8
1,2-迁移: 示例
HO R
R
O
O
O
Synthesis and Wagner–Meerwein Rearrangement of 9-(aHydroxyalkyl) xanthenes to 10-Substituted Dibenz[b,f]oxepins: Scope, Limitations and ab initio Calculations
R
SOCl2
+
Py.
RH N +
R Elimination involving five Wagner-Meerwein rearrangements
7
1,2-迁移: 示例
Total synthesis of (+)quadrone by A. B. Smith
Smith, A. B., III, Konopelski, J. P. J. Org. Chem. 1984, 49, 40944095.