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Chap 15 Organometallic Compounds
15.1 Organomganesium and organolithium compounds
15.2 Lithium diorganocopper (Gilman) reagents
15.3 Carbenes and carbenoids
Organometallic compound(유기금속 화합물) : 탄소-금속 결합을 포함하는 화합물
R-M, M=Li, Mg, Cu, Zn, Hg
Polar, Nucleophilic and basic property
15.1 Organomagnesium and Organolithium Compounds
electrophilic
nucleophilic
M
X
R-MgX (X=Br, Cl) : organomagnesium compound (Grignard reagent)
alkylmagnesium bromide or chloride
R = 1o, 2o, 3o alkyl ; aromatic
R-Li : organolithium compound, alkyllithium
R = 1o, 2o, 3o alkyl ; aromatic
A. Formation and Structure
1) Grignard reagent
R
X
+
Et2O
Mg
R
MgX
X = I, Br, Cl, F
Reactivity of halide : I > Br > Cl >> F
R = alkyl, aryl, allylic, vinyl
+
Br
Br
+
Mg
Mg
Et2O
MgBr
THF
MgBr
Exothermic reaction
Anhydrous 및 oxygen free 조건에서 반응
Butylmagnesium bromide
Phenylmagnesium bromide
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Solvent : 무수 Et2O, 무수 tetrahydrofuran (THF)
Solvation에 의한 RMgBr의 용해 및 안정화
CH3CH2
CH3CH2
CH2CH3
O
Mg
Br
O
CH3CH2
CH2CH3
Property : highly nucleophilic and highly basic
2) Organolithium reagent
Cl
+
hexane
2 Li
+
Li
LiCl
Butyllithium
Solvent : CH3Li in Et2O
CH3CH2CH2CH2Li in hexane
불활성 기체(N2 or Ar) 하에서 사용
Property : highly nucleophilic and highly basic
Table 15.1 : Percent ionic character of some C-M bonds
B. Reaction with Proton Acids
RMgX와 RLi 시약은 염기성이 매우 강하므로 proton donor(양성자 주개)와 매우
빠르게 반응하여 분해된다.
CH3CH2
MgBr
+
H
CH3CH2
OH
H
+
Mg(OH)Br
C6H5OH
RSH
RMgX 및 RLi 시약과 반응하는 proton donor :
R2NH
R-C≡C-H
ROH
HOH
RCOOH
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C. Reaction with Oxiranes
Oxirane : Reactive toward RMgX and RLi
MgBr
MgBr
O
+
THF
OMgBr
O
H3O+
THF
+
OH
O
문제 15.2 :
X
O
+
H
15.2 Lithium Diorganocopper (Gilman) Reagents
RCu : alkyl copper
R2CuLi : lithium dialkylcuprate
more reactive than RCu
A. Formation and Structure
1) Preparation of lithium diorganocuprates
CH3Li + CuI
n-BuLi + CuI
Et2O
- 20
oC
Et2O
0
oC
CH3Cu LiI
CH3Li
yellow
n-BuCu LiI
colorless
n-BuLi
black suspension
R2CuLi : highly nucleophilic
less basic than RLi and RMgBr
thermally unstable
(CH3)2CuLi LiI
(n-Bu)2CuLi LiI
black suspension
OH
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2) Coupling with Organohalogen Compounds
Organocuprate 시약은 vinyl bromide or iodide, alkyl bromide와 SN2 반응으로
coupling하여 새로운 C-C σ bond를 형성한다.
2
I
4 Li, pentane
2
Li
CuI, THF
Br
2 CuLi
2-Methyl-1-dodecene
Coupling with vinyl halide of organocuprate - stereospecific reaction
I
Et2O
+
2 CuLi
trans-5-Tridecene
◆ Synthesis of Muscalure
Mg
Br
CH3(CH2)7
H
MgBr
THF
CuI
THF
Cu MgBrI
(CH2)7CH2-Br
H
(Z)-9-Tricosene (Muscalure)
C. Reaction with Oxiranes
R2CuLi 시약은 epoxide의 less hindered 탄소에 공격(SN2)하여 alcohol을 생성한
다.
O Cu(CH2=CH)Li
O
+ (CH2=CH)2CuLi
THF
OH
H3O+
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15.3 Carbenes and Carbenoids
Carbene(카벤, R2C:) - 탄소 원자가 6개의 원자가전자로 둘러싸인 중성 분자
Very reactive, Strong electrophile
Formation of cyclopropane
A. Methylene
Methylene(메틸렌) : diazomethane(CH2N2)의 photolysis(광분해) or thermolysis
(열분해)에 의하여 생성됨
H
H
hv
H
C
N
N
H
C
N
H
C
H
Methylene
N
+
N
N
B. Dichlorocarbene
Dichlorocarbene(다이클로로카벤, :CCl2) - C과 Cl의 비공유
전자쌍 사이의
resonance에 의하여 methylene보다 안정
1) Formation of dichlorocarbene
Cl
Cl
O K+
+
H
C
OH
Cl
+
C
Cl
Cl
Cl
Cl
2) Reaction of dichlorocarbene
Cl
+
Cl
Cl
C
C
Cl
Cl
Cl
+
CHCl3
Cl
(CH3)3CO K+
H
H
Cl
Syn stereoselectivity
문제 15.5 :
+ CHBr3 +
OK
C
Cl
+
Cl
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C. Simmons-Smith Reaction
Carbenoid(카베노이드) : 자유 carbene을 생성하지 않으면서 carbene의 요소를 가
진 화합물
I
CH2
I
+
Diiodomethane
Zn(Cu)
Et2O
Zinc-copper
couple
I
CH2
ZnI
Iodomethylzinc iodide
(Carbenoid, Simmons-Smith reagent)
Reaction of carbenoid - Formation of cyclopropane
I
H
CH2
+
+
I Zn
O
O
+
CH2I2
ZnI2
H
O
H
H
Zn(Cu)
Et2O
CH2
+
CH2
H
H
Bicyclo[4.1.0]heptan-2-one
(racemic)
+
ZnI2
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Problems
15.7 : Reaction of alkyl halide and lithium diorganocopper reagent
Br
(b)
CuLi
+
Et2O
2
H
+
(d)
Cl
Et2O
2
CuLi
15.11 : Synthesis of trans-2-allylcyclohexanol from cyclohexane
OH
Br
O
CH2CH=CH2
15.12 : Reaction product
(a)
(c)
H
+ EtMgBr
+ CHBr3 + K O
(e) I CH2 I + Zn(Cu)