Chapter 10 Organometallic compounds

10.1 Introduction10.2 Preparation of organolithium and organomagnesium compounds10.3 Carbanions as Brøsted bases10.4 Applications of organometallic comp. in organic synthesis10.4.1 Synthesis of alcohols using Grignard reagents10.4.2 Retrosynthetic analysis10.4.3 Alkane synthesis by using organocopper reagents10.4.4 Ziegle-Natta Catalysis of alkene polymerization

What' s Organometallic Compounds?C M A carbon-metal bond

Na OEt

Sodium acetylide Sodium ethoxide

The natures of C－M bondsThe natures of C－M bondsThe electronegativity of

the metalThe electronegativity of

the metalDepend on

C MM C M ¦Ä ¦Ä

C M

M= Na+or K+ M=Mg, Li M=Pb, Sn, Hg, Tl

Ionic bond Covalent bond

Carbanions(负碳离子 )

Carbanions(负碳离子 )

H C C Na

10.2 Preparation of Organolithium and Organomagnesium compounds

R X + Mether

R M + M XAlkyl halide

TetrahydrofuranTHF

(四氢呋喃 )

Solvents:EtherHydrocarbon:Pentane, Hexane Anhydrous!

CH3CH2CH2CH2Br + 2LiEt2O

-10¡æCH3CH2CH2CH2Li + LiBr

Butyl bromideButyllithium(80% -90%)

OH3CH2C CH2CH3

Diethyl etherEt2O

O

Br + Mg Et2O35¡æ

MgBr

Grignard reagents: Alkylmagnesium Halides

Phenyl bromide

Characteristics of the reactions:1. Alkyl groups: 1°, 2 °, 3 ° alkyl, cycloalkyl alkenyl, aryl2. Reactivity:

4. Exothermic3. Without substitutes: OH, C

O

, C N Etc.

V. Grignard andP. Sabatier1912 Nobel Prize

V. Grignard andP. Sabatier1912 Nobel Prize

Alkyl > Alkenyl or ArylRI > RBr > RCl > RF

PhenylmagnesiumBromide (95%)

P223,7.4Ch.P185(3)

P223,7.4Ch.P185(3)

Grignard found that, in the presenceof ether, magnesium reacts with alkyl and aryl halides at room temperature to form organo-magnesium 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, he was awarded the 1912 Nobel Prize in Chemistry(shared with Paul Sabatier,discoverer of catalytichydrogenation).

François Auguste Victor Grignard

1871-1935

http://www.nobel.se/chemistry/laureates/1912/grignard-bio.html

Acidity of hydrocarbon:

C H H + C

(CH3)3C HPka 71 62 60 45

>CH3CH2 H > CH3 H > CH2 CH H >

H > H2N H > HC C H> CH3CH2O H> HO H

Pka 43 36 26 16 15.7

(CH3)3C HPka 71 62 60 45

>CH3CH2 H > CH3 H > CH2 CH H >

H > H2N H > HC C H> CH3CH2O H> HO H

Pka 43 36 26 16 15.7

Conjugate acid Conjugate base

The stronger the acid is, the weaker the conjugate base is.The stronger the acid is, the weaker the conjugate base is.

10.3 Carbanions as Brøsted bases:

To different kinds of carbanions:3 ° >2° 1°>> > CH3

1)2) sp3 > sp2 > sp

The basicity decreases in order

(CH3)3C > (CH3)2HC > CH3CH2 > H3C

CH2 CH > > HC C>>CH3CH2

C > N > O > X

Basicity of anions:

To different element:basicity of anions decrease from left to right in the same period

Carey(4th):547

Carey(4th):547

R M + R'O H ¦Ä ¦Ä

R H + R'O M

Organolithium compounds and Grignard reagents as base:

Li + H2OLi H + LiOH

MgBr + EtOH H + EtOMgBr

tert-Butyllithium 　 tert-Butane

Phenylmagnesiun bromide

Ethoxymagnesiumbromide

RC C H + R' MgX ¦Ä ¦Ä

RC C MgX + R' H ¦Ä ¦Ä

R－M reacts with much weaker acid than H2O

Ch. P186Ch. P186

10.4.1 Synthesis of alcohols using Grignard reagents

Reactions with carbonyl compounds:A.Grignard reagents react with Formaldehyde( 甲醛 ) — Primary alcohols:

R:MgX¦Ä ¦Ä

+ C OH

HC

H

H

R O MgXH3O

C

H

H

R OHR:MgX¦Ä ¦Ä

+ C OH

HC

H

H

R O MgXH3O

C

H

H

R OH

R:MgX¦Ä ¦Ä

+ C OR'

HC

R'

H

R O MgXH3O

C

R'

H

R OHR:MgX¦Ä ¦Ä

+ C OR'

HC

R'

H

R O MgXH3O

C

R'

H

R OH

B. Grignard reagents react with higher aldehydes— secondary alcohols:

P296,9.10

P296,9.10

Example: PhMgBr + C OH

HEt2O PhCH2OMgBr

H3+O PhCH2OH

Synthesis of Acetylenic alcohols (炔基醇 ):RC CH + CH3CH2 MgBr

Et2ORC C MgBr + CH3CH3

Et2O

RC C MgBr + H C HO

1. Et2O

2. H3ORC CCH2OH

R:MgX¦Ä ¦Ä

+ C OR'

R"C

R'

R O MgXH3O

C

R'

R OH

R" R"

R:MgX¦Ä ¦Ä

+ C OR'

R"C

R'

R O MgXH3O

C

R'

R OH

R" R"

CH2 CHLi + C

O

H1. Et2O2. H3O

+ CHCH

OH

CH2

C. Grignard reagents react with ketones — Tertiary alcohols:

10.4.2 Retrosynthetic analysis ( 逆合成分析 )E. J. Corey

(1990 Nobel Prize)Target Molecule

Precursors

目标分子 前体

CH3CH2CH2CH2 C

CH3

CH3

OH n-BuMgX + CH3COCH3

+CH3CH2CH2CH2MgBr C OCH3

CH3

Et2O

CH3CH2CH2CH2COMgBr

CH3

CH3

H3O C OHCH3CH2CH2CH2

CH3

CH3

n-BuBr + Mg

Problem: suggest two waysTo prepare C6H5C(CH3)2

OH

Elias James Corey1928-

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. Hisresearch associates (graduate students and postdoctoral fellows) number over 500 and populate the academic and industrial laboratories of Europe, Asia and the Americas.

Professor Corey (to collea-Gues and friends, E.J.) is known for his many spectacular contributions to synthetic organic chemistry. The concept of "retrosynthetic analysis",

Preparation of lithium dialkylcuprate reagents:

2 R Li + CuXEt2O

or THFR2CuLi + LiX

Alkyllithium Cu (I) halides

Lithiumdialkylcuprate

Lithiumhalide

RLi CuX RCu RLi R2Cu- Li +

Coupling reactions of Organocoppers with Alkylhalides

(CH3)2CuLi + CH3(CH2)8CH2IEt2O

0¡æCH3(CH2)8CH2CH3

Undecane (90%)

Ch.P185(3)

Ch.P185(3)

10.4.3 Alkanes synthesis by using organocopper reagents

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 + IEt2O n-Bu

Lithium dibutylcuprate

Iodobenzene Butylbenzene(75%)

12.44 Ziegle-Natta Catalysis of Alkene Polymerization

Ziegle catalyst: TiCl4-Et2AlClnH2C CH2

TiCl4-Et2AlClCH3CH2(CH2CH2)n-2CH CH2

Ethylene Ethylene oligomersCharacteristics of the products:1. Ethylene oligomers with 6-18 carbons2. High-density

G. Natta’s contributions:

H HH3CH3C HH3C HH3C H H3C H H3C

Isotactic polypropylene 等规 ( 立构 ) 的聚丙烯

Carey:P56714.15

Carey:P56714.15

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)14.2314.2514.26* （选作）14.27

14.28 (b)14.29