有机合成专业英语 5

PPh3 Cl Cl
R
PPh3 CHR + Cl Cl Cl Ru PPh3 PPh3 Cl Cl Ru PPh3
R
PPh3 Cl R R Cl Cl Ru PPh3 PPh3 Ru PPh3 CHR+ CH2 CH2 CH2 + CHR CHR
Ru PPh3 PPh3
R CH2 +
Cl Cl
Ru PPh3
OHC
McMurry Humulene
5.2 Radical Addition Reactions
tributylstannane as the provider of radical
Bu3SnH AIBN X
I Bu3SnH AIBN
H
H
OMe
I
H
OMe
Bu3SnH AIBN O O
O
O
O
O
Indentify the individual steps in the following radical cascade cyclization:
Synthetically useful radical reactions coupling, addition and substitution Kolbe electrolysis of carboxylic acids.
O
-e
CH3 CH3 +
C O
CH3
O C O
CH3 + CO2
CH3
The elimination of I2 from diiodomethane
Zn + I2CH2 I Zn CH2 I
ZnI2 + CH2
2 Losing nitrogen from diazomethane
H H
C
hν
N N
CH2 + N2
3 Losing CO from ketene
H H
CH3CH3
CH2
H2C
CO2Na CO2Na
-2e
CO2R CO2R
The Ullmann coupling of aryl iodides to give diphenyls
Cu 2 I Ullmann
the Pschorr synthesis of phenanthrenes菲
+ N2 CO2H
hν C
C O
CH2
+
CO
The Simmons-Smith methylenation reaction
CH2I2, Zn/Cu HO
Et Et
Simmons-Smith HO
Et Et
C
H
C H
+ CH2I2(Zn/Cu
H
H
Synthesis the following compound
O
Cl O
COOH
CO2Et
O COOH
P2O5
COOH
O O
EtOH H2SO4
COCHN2 COOEt
COOH COCl
SOCl2
CH2N2
COOEt
COOEt
Ag2O
EtOH H2SO4
T.M
5.4 Alkene Metathesis (易位) Outcome: coupling of two chains via an alkene.
+
+
endo main
exo
The Ene Reaction
The ene reaction is a sigmatropic(σ移 位的) rearrangement
O O
O H
O
O
O
(a) 200℃ + HC
H
CCO2Et
(b) OMe + O AlCl3
(b) OMe + O AlCl3
CN
propagation step
CN Me C Me CH2 CH2
H H
C
C
H H
Me C Me
CN CH2 CH2 CH2 CH2
termination step: Two radical combining with each other to form a covalent bond by losing a hydrogen atom.
Sigmatropic rearrangement involving the cleavage of a σ bond at an oxygen atom are called Claisen rearrangement .
O
Claisen
O
CH2 O
CH
14
CH2
OH
14
200 C
0
CH2
CH
Cu Pschorr CO2H
NH2
H2SO4
(CH3)2CHCH2CH2ONO
COOH
+ N2 CO2H
Cu CO2H
The Cadiot-Chodkiewicz oxidative coupling of terminal alkynes using ammoniacal氨的 copper (1) chloride
5.5 The Diels-Alder Reaction
[ 4+2 ] addition
HOMO LUMO Symmetry allowed
O
LUMO HOMO Symmetry allowed
H
O
H 1. LiAlH4 2. H3O+
+
O
O
O
O
O
H
H
No intermediate exist in this process Cis-formed ring junction Endo form is the main product
5 Free Radical and Pericyclic Reactions in the Formation of Carbon-carbon Bonds
5.1carbon radical reaction 5.2 radical addition reaction 5.3 carbene 5.4 alkene metathesis 5.5 the Diels-Alder reaction 5.6 the ene reaction 5.7 the cope and claisen rearrangements
empty P orbital
SP2 hybrid containing a pair of elctrons
A singlet carbene
Formation of carbene 1σ-elimination The elimination of HCl from chloroform
Cl HO- H C Cl Cl Cl C Cl Cl Cl C Cl + Cl-
O O
Na OMe Me3SiCl
H
MeO
O OH
O
O
Na toluene-ethanol OMe
O
MeO
CO2Me
The McMurry coupling of aldehydes and ketones using low oxidation titanium
O
TiCl3-LiAlH4
O
TiCl3, LiAlH4
CO2Et
(a) 200℃ +
H H CO2Et
CO2Et
5.7 The Cope and Claisen Rearrangements
The Cope rearrangement is a 3,3sigmatropic reaction
R 185 ℃ R
C-H σ-HOMO Diene л-LUMO
PhC CH CuCl, NH4Cl, O2 Cadiot-Chodkiewicz
Ph
Ph
Reductive free radical coupling processes The reducing of ketones by Magnesium
Me Me Mg C Me
O
Me C O
Me C
2
Me
O O O O C Ph
Ph
C
azobisisobutyronitrile (AIBN)偶氮二异丁腈
Me Me C H
Me Me N2 + 2 Me CN Me Me C C N
Me Me
Me C CN
C N N C
H C C H H
H2 C C CH2
O
Mg Me
pinacol
Me C Me O Mg O C
Me
The acyloin酮醇 condensation 酮醇 of esters with sodium
O
R
C
OR'
Na EtOH
R
CH2OH
O
Na R
C OR'
H2O
Toluene
O
OH CH R
R
C
Addition of TMSCl favor Acyloin condensation , Prevent Dieckmann reaction
O
O O Me Me Bu3SnH Me AIBN H O
Me
Br
Me
Me Me
O
O
O
O
Me Me Br Me O O Me H O Bu3SnH