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Chapter 10
Organometallic compounds
10.1 Introduction
10.2 Preparation of organolithium and
organomagnesium compounds
10.3 Carbanions as Brøsted bases
10.4 Applications of organometallic
comp. in organic synthesis
10.4.1 Synthesis of alcohols using
Grignard reagents
10.4.2 Retrosynthetic analysis
10.4.3 Alkane synthesis by using
organocopper reagents
10.4.4 Ziegle-Natta Catalysis of alkene
polymerization
What' s Organometallic Compounds?
C M
A carbon-metal bond Carbanions
Na OEt
H C C Na
(负碳离子)
Sodium acetylide Sodium ethoxide
The natures of C－M bonds
The electronegativity of
the metal
Depend on
C M
¦Ä ¦Ä
C M
C M
M= Na+or K+ M=Mg, Li M=Pb, Sn, Hg, Tl
Covalent bond
Ionic bond
10.2 Preparation of Organolithium and
Organomagnesium compounds
ether
R X+ M
R M + M X
Alkyl halide
CH
CH
H
CH
C
2
3
3
2
Solvents:
O
O
Ether
Diethyl ether Tetrahydrofuran
Hydrocarbon:
THF
Et2O
(四氢呋喃)
Pentane, Hexane
Anhydrous!
CH3CH2CH2CH2Br + 2Li
Butyl bromide
Et2O
-10¡æ
CH3CH2CH2CH2Li + LiBr
Butyllithium
(80% -90%)
Grignard reagents: Alkylmagnesium Halides
V. Grignard and
MgBr
Br + Mg
P. Sabatier
1912 Nobel Prize
Phenylmagnesium
Phenyl bromide
Bromide (95%)
Et2O
35¡æ
Characteristics of the reactions:
1. Alkyl groups: 1°, 2 °, 3 ° alkyl,
cycloalkyl alkenyl, aryl
2. Reactivity:
P223,7.4
Alkyl > Alkenyl or Aryl
Ch.P185(3)
RI > RBr > RCl > RF
O
3. Without substitutes: OH, C , C N Etc.
4. Exothermic
Grignard found that, in the presence
of ether, magnesium reacts with
alkyl and aryl halides at room
temperature to form organomagnesium compounds. These
solutions,called "Grignard reagents"
react with most functional groups
in a synthetically useful way.
For this discovery, tremendously useful
in laboratory and industrial synthesis,
François Auguste he was awarded the 1912 Nobel Prize
Victor Grignard in Chemistry(shared with
Paul Sabatier,discoverer of catalytic
1871-1935
hydrogenation).
http://www.nobel.se/chemistry/laureates/1912/grignard-bio.html
10.3 Carbanions as Brøsted bases:
Acidity of hydrocarbon:
C H
H + C
Conjugate acid
Conjugate base
The stronger the acid is, the weaker
the conjugate base is.
(CH3)3C H > CH3CH2 H > CH3 H > CH2 CH H >
Pka
71
62
60
45
H > H2N H > HC
Pka
43
36
C H > CH3CH2O H > HO H
26
16
15.7
Basicity of anions:
(CH3)3C > (CH3)2HC > CH3CH2 > H3C
CH3CH2 > CH2 CH >
>> HC
C
To different kinds of carbanions:
1) 3 ° > 2° > 1° > CH3
2) sp3 > sp2 > sp
To different element
basicity of anions
The basicity decreases in order decrease from left
to right in the
same period
C > N > O > X Carey(4th):
547
Organolithium compounds and
Grignard reagents as base:
¦Ä
¦Ä
R M + R'O H
Ch. P186
Li + H2O
tert-Butyllithium
MgBr + EtOH
Phenylmagnesiun
bromide
¦Ä
¦Ä
RC C H + R' MgX
R H + R'O M
H + LiOH
tert-Butane
H + EtOMgBr
Ethoxymagnesium
bromide
¦Ä
¦Ä
RC C MgX + R' H
R－M reacts with much weaker acid
than H2O
10.4.1 Synthesis of alcohols using P296,
9.10
Grignard reagents
Reactions with carbonyl compounds:
A.Grignard reagents react with
Formaldehyde(甲醛 ) — Primary alcohols:
¦Ä
¦Ä
R:MgX +
H
H
H
H
C O
R C O MgX
H
H3O
R C OH
H
B. Grignard reagents react with
higher aldehydes— secondary alcohols:
¦Ä
¦Ä
R:MgX +
R'
H
R'
R'
C O
R C O MgX
H
H3O
R C OH
H
C. Grignard reagents react with ketones
— Tertiary alcohols:
¦Ä
¦Ä
R'
R'
R'
H3O
R C OH
R C O MgX
R"
R"
R"
H
Example: PhMgBr + C O Et2O PhCH2OMgBr
H
H3+O
PhCH2OH
R:MgX +
C O
Synthesis of Acetylenic alcohols (炔基醇):
Et2O
RC
CH + CH3CH2 MgBr
O
RC C MgBr + H C H
O
CH2 CHLi +
C
RC
1. Et2O
C MgBr + CH3CH3
RC
2. H3O
1. Et2O
H 2. H O +
3
CCH2OH
CHCH
OH
CH2
10.4.2 Retrosynthetic analysis (逆合成分析)
Target
Molecule
目标分子
Precursors
前体
E. J. Corey
(1990 Nobel Prize)
Problem: suggest two ways
To prepare C6H5C(CH3)2
OH
CH3CH2CH2CH2
CH3
C OH
CH3
n-BuMgX + CH3COCH3
n-BuBr + Mg
CH3
Et2O
CH3CH2CH2CH2MgBr +
C O
CH3
CH3
CH3
CH3CH2CH2CH2COMgBr H3O CH3CH2CH2CH2C OH
CH3
CH3
Elias James Corey
1928Professor Corey (to colleaGues and friends, E.J.) is
known for his many spectacular
contributions to synthetic
organic chemistry. The concept
of "retrosynthetic analysis",
which changed the way organic
chemists undertake the synthesis
of complex natural products,
the synthesis of longifolene,
maytansine, the ginkolides,
prostaglandins and leukotrienes,
the development of new synthetic
methods, particularly using chiral
catalysts, and the application of
computers to synthesis design are
among his most notable achievements.
Corey has received many honors,
including the Wolf Prize (1986), the National
Medal of Science (1988), the Japan Prize
in Medicinal Science (1989) and the Nobel
Prize in Chemistry (1990).
Born in Massachusetts, Corey obtained
the Ph.D. at M.I.T. (1951), was on the
faculty at the University of Illinois
(1951-59) where he became full professor
at the early age of 27, and since 1959 he
has been professor at Harvard. His
research associates (graduate students and
postdoctoral fellows) number over 500
and populate the academic and industrial
laboratories of Europe, Asia and the
Americas.
10.4.3 Alkanes synthesis by using Ch.P185
organocopper reagents
(3)
Preparation of lithium dialkylcuprate reagents:
2 R Li + CuX
Et2O
or THF
R2CuLi + LiX
Alkyllithium Cu (I)
Lithium
Lithium
halides
dialkylcuprate halide
CuX
RLi
RCu RLi R2Cu- Li +
Coupling reactions of Organocoppers with
Alkylhalides
(CH3)2CuLi + CH3(CH2)8CH2I
Et2O
0¡æ
CH3(CH2)8CH2CH3
Undecane (90%)
Characteristics of the reaction:
1. SN2 reaction
The order of the reactivity :
CH3 > 1°> 2°> 3°
I > Br > Cl > F
2. To alkyl halides, R: primary,vinyl and
aryl groups.
To Lithium dialkylcuprate,
R’: primary group or -CH3.
(n-Bu)2CuLi +
I
Et2O
n-Bu
Lithium
Iodobenzene Butylbenzene
dibutylcuprate
(75%)
12.44 Ziegle-Natta Catalysis of Alkene
Carey:P567
Polymerization
Ziegle catalyst: TiCl4-Et2AlCl
nH2C CH2
Ethylene
TiCl4-Et2AlCl
14.15
CH3CH2(CH2CH2)n-2CH CH2
Ethylene oligomers
Characteristics of the products:
1. Ethylene oligomers with 6-18 carbons
2. High-density
Isotactic polypropylene
G. Natta’s contributions:
等规 (立构) 的聚丙烯
H3C H H3C HH3C H H3C H H3C H H3C H
Coordination polymerization
配位络合聚合
Polypropylene industry was started
K. Ziegle and G. Natta shared
the 1963 Nobel Prize in Chemistry
Problems: Carey(4th)P573
14.15 (b), (d)
14.17 (h), (m), (n)
14.18 (d), (e)
14.19 ((b), (f)
14.20 (d), (e)
14.21 (a)-(c)
14.22 (b), (f), (g)
14.23
14.25
14.26*（选作）
14.27
14.28 (b)
14.29