Polylithiation of Hydrocarbons - American Chemical Society

11 Polylithiation of Hydrocarbons ROBERT

WEST

University of Wisconsin, Madison, W i s . 53706

Certain

hydrocarbons

undergo

polymetalation

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lithium compounds, often with TMEDA

by alkyl

as a catalyst, to

give polylithiated organic compounds. For acetylenes, pro tons both α and β to the triple bond are replaced; thus is obtained from propyne, CH C Li 3

and C L i 5

4

substances

3

3

C Li 3

4

from 1- or 2-butyne,

from 1,3-pentadiyne. Further

reaction of these

with alkyl sulfates or organometallic

halides

yields highly unsaturated organic or organometallic deriva tives. Polylithiation of aromatic compounds also takes place; toluene, naphthalene, anthracene, fluorene, indene, ferrocene and

1- and 3-phenylpropyne have been converted

to mix

tures of polylithium compounds that have been studied by derivatization

with

DO

or trimethylchlorosilane.

2

Small

amounts of perlithiated aromatic compounds appear to be formed from some compounds.

T n recent years preparations of several polylithiated organic compounds ·*• have been reported. In a few cases it is even possible to make perlithio compounds, or "lithiocarbons," in which each hydrogen in a hydro carbon molecule has been replaced by a lithium atom. Some polylithio and perlithio compounds can be made simply by the interaction of hydro carbons or halocarbons with alkyllithium reagents, without catalysis by amines. In other cases, however, use of chelating diamines

(usually

T M E D A ) is either clearly beneficial or absolutely essential. This paper reviews the synthesis of poly- and perlithiated compounds, with emphasis on the use of chelating diamines as aids in the metalation reactions.

Aliphatic

Polylithio

Compounds

Excluding the well-known lithium acetylide, C L i , the first perlithio 2

2

compound to be reported was C L i , synthesized by West, Carney, and 3

Mineo in 1965

4

( I ) by the reaction of propyne with n-butyllithium in

hexane. When the propyne (chilled) is added slowly to the hexane 211 In Polyamine-Chelated Alkali Metal Compounds; Langer, A.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

212

POLYAMINE-CHELATED

ALKALI

M E T A L

COMPOUNDS

s o l u t i o n of the l i t h i u m reagent, the a l k y n e is p o l y l i t h i a t e d so r a p i d l y t h a t the hexane-insoluble

salt 1 - h t h i o p r o p y n e

never precipitates.

Refluxing

the m i x t u r e completes the m e t a l a t i o n ; r e c o v e r y of η-butane shows t h a t y i e l d s of C3L14 h i g h e r t h a n 8 0 % c a n b e o b t a i n e d . T h e s t r u c t u r e of C L i 3

4

is not k n o w n , b u t the i n f r a r e d s p e c t r u m , w h i c h shows a n e x t r e m e l y strong a b s o r p t i o n at 1670 c m " a n d n o b a n d at h i g h e r frequencies, suggests that 1

the structure is a l l e n i c , L i C = C = C L i 2

2

(2).

C3L14 often

precipitates

f r o m hexane as a r e d p o w d e r b u t sometimes r e m a i n s i n s o l u t i o n , p e r h a p s c o m p l e x e d w i t h excess n - b u t y l l i t h i u m . Recently, Shimp and L a g o w produced C L i 3

as t h e m a j o r p r o d u c t i n

4


t h e h i g h - t e m p e r a t u r e r e a c t i o n of l i t h i u m atoms w i t h c a r b o n v a p o r , a l o n g w i t h s m a l l e r a m o u n t s of C L i 2

and C L i

2

4

T h e same g r o u p has also

(4).

s h o w n that a m i x t u r e of p o l y l i t h i o c o m p o u n d s ,

including CLL*,

C Li , 2

4

a n d C L i , is o b t a i n e d i n the r e a c t i o n of l i t h i u m atoms w i t h C C L ; ; i n the 2

2

same r e a c t i o n u s i n g C C 1 , C L i 2

6

2

6

is t h e m a j o r p r o d u c t ( 5 ) .

These impor

tant studies p r o v i d e a n e n t i r e l y n e w m e t h o d for t h e synthesis of l i t h i o c a r bons, i n c l u d i n g t h e p r e v i o u s l y u n k n o w n p e r l i t h i o a l k a n e s . T h e l i t h i o c a r b o n C L L i reacts w i t h o r g a n i c a n d o r g a n o m e t a l l i c s u b 3

strates to g i v e a v a r i e t y of h i g h l y u n s a t u r a t e d d e r i v a t i v e s ( S c h e m e

1).

W i t h o r g a n o m e t a l l i c h a l i d e s s u c h as t r i a l k y l c h l o r o s i l a n e s , the u s u a l p r o d ucts are t e t r a s u b s t i t u t e d aliènes ( 2 ) .

A l k y l halides often give explosions,

b u t the a l k y l sulfates p r o d u c e m i x t u r e s of t e t r a a l k y l d e r i v a t i v e s of p r o p y n e and propadiene

(3). CH C=CH 3

4 n-BuLi hexane

mostly C D C = C D 3

(R Si) C=C=C(SiR3)2 3

Et

Et

I

I

ρΐΐί * -

^C Li 3

2

R = Me , Me Et, M e tert- Bu 3

3

2

2

4

C

EtC=C—C=C—C^C—Et, (cis or trans)

(Me Ge) C=C==C(GeMe ) 3

10%

2

3

2

R C = C = C R and R C — C = C R 2

2

R =

Scheme 1.

3

Et

Reactions of C Li s

u

P o l y m e t a l a t i o n is a p p a r e n t l y a g e n e r a l r e a c t i o n of 1-alkynes. t i o n of 1-butyne has b e e n s t u d i e d i n d e t a i l ( 2 ) .

Lithia

W h e n this c o m p o u n d is

t r e a t e d w i t h three equivalents of n - b u t y l l i t h i u m or

tert-butyllithium

in

h y d r o c a r b o n solvents, t r i l i t h i o d e r i v a t i v e , C H C L i , is f o r m e d .

Noncon-

jugated

reagents

3

i n t e r n a l acetylenes

3

resist m e t a l a t i o n b y

3

alkyllithium

In Polyamine-Chelated Alkali Metal Compounds; Langer, A.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

11.

213

Polylithiation of Hydrocarbons

WEST

CH3CH2C=CH

CH3C=CCH3

RLi n-BuLi i TMEDA CH3C3L13

tert- B u M e S i C l

(C H 0)2S04 2

6

2

Me SiCl 3

S

(C 2H 5) 2 C C = C C H 5

tert- B u M e S i


2

CH

3

/

2

\C=C=C(SiMe

^ (Me Si) CC=CSiMe3 w

3

,

2

I

45%

C H

Crl

3

4

0

3

2

t*rt-B\i)

2

70%

/

%

+ Me SiC=C==C(SiMe ) 3

3

2

I

CH

Scheme 2.

3

40%

Formation and reactions of

CH C Li s

s

s

u n d e r u s u a l c o n d i t i o n s . W h e n T M E D A is a d d e d , h o w e v e r , p o l y l i t h i a t i o n takes p l a c e . W i t h T M E D A , 2 - b u t y n e forms a t r i l i t h i o d e r i v a t i v e i d e n t i c a l to t h a t o b t a i n e d f r o m 1-butyne ( 6 ) ; see S c h e m e 2. R e a c t i o n of C H C L i 3

3

3

5-ethyl-5-methyl-3-heptyne, s u b s t i t u t e d acetylenes.

w i t h d i e t h y l sulfate gives a m o d e r a t e y i e l d of a l o n g w i t h s m a l l e r amounts

D e r i v a t i z a t i o n of C H C L i 3

3

3

of less h i g h l y

w i t h trimethylchloro-

silane y i e l d s a b o u t e q u a l amounts of the t r i s ( s i l y l ) b u t y n e a n d m e t h y l allene ( S c h e m e 2 ) .

H o w e v e r the b u l k i e r d e r i v a t i z i n g agent

d i m e t h y l c h l o r o s i l a n e converts C H C L i 3

allenic

product,

3

3

tert-butyl-

e x c l u s i v e l y i n t o the less-strained

1,1,3-tris ( i e r f - b u t y l d i m e t h y l s i l y l ) -1,2-butadiene.

This

r e a c t i o n exemplifies t h e c o m m o n finding t h a t p r o d u c t s of s i l y l d e r i v a t i z a t i o n of h t h i u m c o m p o u n d s are s t e r i c a l l y d e t e r m i n e d . CH C Li 3

3

(1750

is u n c e r t a i n , b u t f r o m its l o w - f r e q u e n c y

3

c m ) , i t p r o b a b l y has a n a l l e n i c s t r u c t u r e , 3

(7, 8 ) .

3

2

(6).

I n 1971 the s e c o n d p e r l i t h i o c o m p o u n d , l i t h i a t i o n of 1,3-pentadiyne

absorption

CH CLi=C=CLi ,

- 1

s i m i l a r to that also p r o p o s e d for C L i 4

T h e s t r u c t u r e of

infrared

C L i , was 5

4

obtained

by

W h e n t h e latter is t r e a t e d w i t h a l k y l -

l i t h i u m c o m p o u n d s i n the absence of T M E D A , a d d i t i o n of a l k y l l i t h i u m reagents to one of t h e t r i p l e b o n d s is t h e m a i n r e a c t i o n , a n d n o h i g h l y metalated products

form.

H o w e v e r w i t h T M E D A , p o l y l i t h i a t i o n takes


214

POLYAMINE-CHELATED

p l a c e to g i v e m a i n l y C L i 5

ALKALI

METAL

COMPOUNDS

as a r e d - b r o w n s o l u t i o n i n η-butane.

4

s o l u t i o n shows strong i n f r a r e d a b s o r p t i o n at 1800 c m " ; the

The

cumulene

1

structure, L i C = C = C = C = C L i , thus seems most p r o b a b l e for C L i . 2

2

5

W h e n t r e a t e d w i t h w a t e r , the s o l u t i o n of C L i 5

4

4

gives a m i x t u r e of

three h y d r o c a r b o n s : the o r i g i n a l 1,3-pentadiyne; the n o n c o n j u g a t e d m e r 1,4-pentadiyne;

and the allenyne, l,2-pentadien-4-yne.

the c o r r e s p o n d i n g d e u t e r a t e d p r o d u c t s c o n t a i n a b o u t 7 0 % a t e d m o l e c u l e s , s h o w i n g that C L i 5

4

iso

With

D 0 2

tetradeuter-

is the p r i n c i p a l p o l y l i t h i o c o m p o u n d

i n the s o l u t i o n . D e r i v a t i z a t i o n s of C L i 5

w i t h a l k y l sulfates or o r g a n o m e t a l l i c c h l o

4


r i d e s p r o v i d e u s e f u l syntheses for some h i g h l y u n s a t u r a t e d substances. A

m i x t u r e of

(Scheme

three h y d r o c a r b o n s

3).

is o b t a i n e d

Trialkylchlorosilanes convert

with

C Li 5

d i m e t h y l sulfate

exclusively

4

to

a l l e n y n e p r o d u c t s , w h i c h are less h i n d e r e d t h a n t h e o t h e r isomers. ever w i t h t r i m e t h y l c h l o r o g e r m a n e , C L i 5

the How

gives, a l o n g w i t h the a l l e n y n e

4

isomer 1 , 5 , 5 , 5 - t e t r a k i s ( t r i m e t h y l g e r m y l - l , 3 - p e n t a d i y n e ) ( S c h e m e 3 ) . latter is the first k n o w n c o m p o u n d w i t h t h r e e g e r m a n i u m atoms to a single c a r b o n

The

bonded

(8). CH —C^C—C = CH 3

n-BuLi TMEDA n-butane

CH C = C—C = CH 3

+ HC = C—CH C = C H

C Li

2

2

(CH 0)2S0 , 3

2

CH C = CC(CH ) C = C C H 3

2

3

10%

3

32%

+ (CH ) C==C=C(CH )C^CCH 3

C—CH=CH

2

3

2

(Me Ge) C = C = C — C = I GeMe

2

3

2

C—GeMe

2

3

Scheme 3. of Aromatic

3

3

Reactions of C Li 5

h

Compounds

L i t h i a t i o n of a r o m a t i c a n d a l k y l a r o m a t i c c o m p o u n d s

markedly catalyzed by organosodium

3

3

M e G e C = C — C s C — C (GeMe )

Toluene.

23%

+

R = M e , E t , iert-Bu

'Polylithiation

3

2

(RMe Si) C = C = C — C = C — S i M e R I SiMe R 2

3

3

5

+ HC =

C H C = C — C = C — C (CH ) + 3

H 0

chelating diamines.

Toluene

is m e t a l a t e d

is by

reagents b u t is r a t h e r u n r e a c t i v e t o w a r d o r g a n o l i t h i u m

c o m p o u n d s i n t h e absence of d i a m i n e catalysts. H o w e v e r i n the presence


11.

WEST

215

Polylithiation of Hydrocarbons CH; + CH SiMe 2

2

C H

3

CH SiMe Downloaded by UNIV OF ARIZONA on August 6, 2012 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0130.ch011

Me SiCl 3

ra-BuLi—TMEDA

3

CH

3

CH SiMe 2

SiMe

3

3

CH(SiMe ) 3

SiMe

3

11%

2

3

46% Journal of the American Chemical Society

Scheme 4.

Polylithiation of toluene and derivatization with trimeihylchlorosilane (10)

of T M E D A or d i a z a b i c y c l o [2.2.2] octane, t o l u e n e undergoes q u a n t i t a t i v e m e t a l a t i o n b y n - b u t y l l i t h i u m to f o r m b e n z y l h t h i u m ( 9 ) . P o l y l i t h i a t i o n of toluene u s i n g excess n - B u L i - T M E D A p r o d u c e s

a

b r i g h t o r a n g e s o l u t i o n f r o m w h i c h a r e d s o l i d g r a d u a l l y separates. D e r i v a tization

of

the

reaction mixture w i t h

trimethylchlorosilane

produces

m o n o - , b i s - , a n d tris ( t r i m e t h y l s i l y l ) isomers, as s h o w n i n S c h e m e 4 ( J O ) . U n d e r a v a r i e t y of m e t a l a t i o n c o n d i t i o n s of the m a n y p o s s i b l e isomers o n l y those s h o w n i n S c h e m e 4 w e r e isolated. P o l y l i t h i a t i o n of b e n z y l lithium

(prepared from dibenzylmercury and lithium) with

TMEDA

present gave the same m i x t u r e of c o m p o u n d s after d e r i v a t i z a t i o n w h e r e a s attempts t o p o l y l i t h i a t e o-, m - , a n d p - l i t h i o t o l u e n e s g a v e o n l y v e r y s l o w reactions a n d l o w y i e l d s of p o l y l i t h i o c o m p o u n d s .

T h i s a n d other s u p -

p o r t i n g e v i d e n c e i n d i c a t e s t h a t d i l i t h i a t i o n of toluene takes p l a c e m o s t l y at the a l p h a - c a r b o n r e p l a c i n g t w o h y d r o g e n s to f o r m P h C H L i . 2

T h e t h i r d l i t h i a t i o n takes p l a c e e x c l u s i v e l y p a r a . W h e n r i n g m e t a l a t i o n occurs at a n y p o i n t , the r e s u l t i n g a r y l l i t h i u m c o m p o u n d is u n r e a c t i v e t o w a r d f u r t h e r m e t a l a t i o n (see S c h e m e

5).

T h e p r i n c i p a l m o n o t r i m e t h y l s i l y l t o l u e n e is the m e t a isomer.

This

agrees w i t h the results of earlier experiments w h i c h find m a i n l y m - l i t h i o t o l u e n e i n the r i n g - l i t h i a t e d b y p r o d u c t s i n the synthesis of b e n z y l h t h i u m b y l i t h i a t i o n of t o l u e n e w i t h n - b u t y l l i t h i u m - T M E D A ( I I , 12).

O n the

basis of t h e c u r r e n t v i e w that m e t a l a t i o n of a r o m a t i c c o m p o u n d s p r o c e e d s



216

POLYAMINE-CHELATED

ALKALI

M E T A L

COMPOUNDS

ι I n-BuLi—TMEDA

CHL12

Li Journal of the American Chemical

Scheme 5.

Probable course of lithiation of toluene with n-BuLi-TMEDA

Society

(10)

via n u c l e o p h i l i c attack o n h y d r o g e n b y t h e a l k y l a n i o n (13,14), t h e m e t a isomer should predominate. Further lithiation, however,

seems t o take p l a c e

by a

different

mechanism. A m o n g the disilyl compounds, only ortho a n d para trimethyl s i l y l isomers a r e o b t a i n e d ( S c h e m e 4 ) . T o a c c o u n t f o r this shift i n i s o m e r preference, W e s t a n d Jones suggest that t h e h i g h n e g a t i v e c h a r g e present i n t h e b e n z y l l i t h i u m causes a change

i n mechanism to one i n w h i c h

e l e c t r o p h i l i c attack o n t h e c a r b o n b y t h e p o s i t i v e l i t h i u m p r e d o m i n a t e s (JO):

Li+CH

2

A c t u a l l y , t h e t r a n s i t i o n state m i g h t l o o k v e r y s i m i l a r to t h a t f o r n u c l e o p h i l i c attack o n r i n g h y d r o g e n ; t h e difference lies i n t h e degree of p a r t i c i pation by lithium. Finally,

t h e only tris ( t r i m e t h y l s i l y l )

a,«,para c o m p o u n d

compounds

f o r m e d is t h e

( S c h e m e 4 ) . L i t h i a t i o n of α,α-dilithiotoluene at the

ortho p o s i t i o n , w h i c h w o u l d b e e l e c t r o n i c a l l y as f a v o r a b l e as p a r a s u b s t i -


11.

217


WEST

t u t i o n , m a y b e p r e c l u d e d b y t h e h i n d e r i n g effect of

the t w o

bulky


T M E D A m o l e c u l e s c o o r d i n a t e d to t h e l i t h i u m a t o m s :

P o l y c y c l i c A r o m a t i c s . E x t e n s i v e r e p l a c e m e n t of h y d r o g e n b y l i t h i u m i n p o l y c y c l i c a r o m a t i c h y d r o c a r b o n s has b e e n d e m o n s t r a t e d b y (15).

Anthracene, biphenyl,

fluorene,

indene,

and

Halasa

ferrocene

(16)

u n d e r g o p o l y m e t a l a t i o n b y n - b u t y l l i t h i u m - T M E D A i n h e x a n e at 7 0 ° C for 24 hours.

T h e p r o d u c t s are i n s o l u b l e m i x t u r e s of p o l y l i t h i o c o m -

p o u n d s c o n t a i n i n g u p to 10 l i t h i u m atoms p e r m o l e c u l e . D e r i v a t i z a t i o n was accomplished using both D 0 2

and trimethylchlorosilane and

by

a n a l y z i n g the m i x t u r e of d e u t e r a t e d o r s i l y l a t e d p r o d u c t s b y mass spect r o m e t r y . T h e results for anthracene, w h i c h are t y p i c a l , a p p e a r i n T a b l e I. T h e p r o d u c t d i s t r i b u t i o n s for the d e u t e r a t e d anthracenes are the m o s t significant n u m b e r s ; these d a t a are c o r r e c t e d for on the (untested) during

1 3

C content b u t d e p e n d

a s s u m p t i o n of e q u a l p r o b a b i l i t y of loss of H a n d D

fragmentation.

Nevertheless

it

is

apparent

that substantial

amounts of anthracenes b e a r i n g u p to seven l i t h i u m atoms w e r e p r o d u c e d , a n d that traces of p e r l i t h i o a n t h r a c e n e , C i L i i , m u s t h a v e b e e n o b t a i n e d . 4

0

T h e figures f o r r e l a t i v e a b u n d a n c e of the t r i m e t h y l s i l y l d e r i v a t i v e s a r e d i s c o r d a n t a n d less r e l i a b l e ; w h e n t r i m e t h y l c h l o r o s i l a n e is u s e d as a d e r i v a t i z i n g agent, f u r t h e r l i t h i a t i o n often occurs d u r i n g the d e r i v a t i z a t i o n , T a k e , f o r e x a m p l e , t h e h t h i a t i o n - s i l y l a t i o n of a c e t o n i t r i l e . T r e a t m e n t of C H C N w i t h three e q u i v a l e n t s of a l k y l l i t h i u m f o l l o w e d b y three e q u i v a 3

lents of

3

but

studies of the l i t h i a t i o n r e a c t i o n s h o w t h a t i t does not p r o c e e d

trimethylchlorosilane produces

(Me Si) C=C=NSiMe ,

past

3

d i l i t h i a t i o n (to C H N L i ) u n t i l M e S i C l is a d d e d 3

2

3

2

(17).

S i m i l a r experiments demonstrate the f o r m a t i o n of m i x t u r e s c o n t a i n i n g p o l y l i t h i o c o m p o u n d s u p to C i L i i 3

b i p h e n y l , a n d u p to C H L i 9

2

7

0

for

for indene.

fluorene,

u p to C i H L i 2

4

6

for

W i t h ferrocene the effect of

T M E D A w a s s t u d i e d b y c o m p a r a t i v e experiments, results of w h i c h are s u m m a r i z e d i n T a b l e I I (16).

T h e d r a m a t i c increase i n p o l y l i t h i a t i o n

u s i n g T M E D A is c l e a r l y s h o w n . W i t h T M E D A the most a b u n d a n t single p r o d u c t is the hexadeutero isomers, r e s u l t i n g f r o m C i H L i ; 0

4

6

T M E D A the most p r o b a b l e p r o d u c t is t h a t f r o m CioHeLL;.


without

218

POLYAMINE-CHELATED

Table I.

ALKALI

M E T A L

COMPOUNDS

Mass Spectra of Products

D2O Derivatization


Relative Abundance

Ions

m/e 179 180 181 182 183 184 185 186 187 188

Ci4H D 8

Product Distribution,

9.5 38.0 71.4 100.00 66.6 52.3 23.8 9.5 4.7 2.3

2

C14H7D3 C14H6D4 C14H5D5 C14H4D6 G14H3D7

%

11.33 20.14 27.75 17.02 14.73 6.55 1.92 0.10 0.02

P o l y l i t h i o f e r r o c e n e w a s also d e r i v a t i z e d w i t h t r i m e t h y l c h l o r o s i l a n e , yielding

a m i x t u r e of

polysilyl derivatives f r o m

tetrakis(trimethylsilyl)ferrocene

was

isolated

and

w h i c h a crystalline shown

to

be

the

1,3,Γ,3' d e r i v a t i v e . P o l y l i t h i o f e r r o c e n e a n d t h e p o l y l i t h i o a r o m a t i c s g e n e r a l l y c a t a l y z e the p o l y m e r i z a t i o n of c o n j u g a t e d dienes l e a d i n g to starshaped polymers. T h e p o l y l i t h i a t i o n of 1 - p h e n y l p r o p y n e has b e e n s t u d i e d i n s o m e w h a t greater d e t a i l .

T h e first e v i d e n c e

that this c o m p o u n d

might

undergo

l i t h i a t i o n at t h e a r o m a t i c n u c l e u s as w e l l as o n t h e s i d e c h a i n w a s p r e sented b y M u l v a n e y , F o l k , a n d N e w t o n w h o f o u n d that b o t h C H — C L i e

and C H L i — C L i e

4

3

3

were produced from C H C = C C H 6

b u t y l l i t h i u m i n refluxing hexane ( I S ) .

5

3

5

3

3

a n d excess n -

T h i s r e a c t i o n is s t r o n g l y c a t a l y z e d

b y T M E D A ; i n t h e p r e s e n c e of t h e c h e l a t i n g d i a m i n e , p r e d o m i n a n t t r i a n d t e t r a l i t h i a t i o n o c c u r s , e v e n at 25 ° C L i t h i a t i o n of 3 - p h e n y l p r o p y n e pounds.

(19).

produced

W i t h t h r e e e q u i v a l e n t s of

similar polylithium com

n-butyllithium i n cyclohexane,

3-

Table II. Degree of Polylithiation of Ferrocene w i t h and without T M E D A from Mass Spectra of Deuterium Derivatives (16) Number of Li atoms 0 1 2 3 4 5 6 7 8

No TMEDA 1.3 4.2 25.6 28.3 30.8 7.4 1.5 0.3 0.1

mth

TMEDA 0.3 0.7 2.4 5.9 23.0 26.0 29.0 9.6 3.2


11.

from Polylithioanthracene

(15)

MesSiCl


219


WEST

Derivatization Relative Abundance

m/e

Ions

322 394 466 538 610 682 754 826 898

C H (SiMe )2 Ci H (SiMe )3 Ci H (SiMe ) Ci H (SiMe ) C H (SiMe ) Ci H (SiMe ) Ci H (SiMe ) Ci H(SiMe ) C (SiMe ) 8

1 4

4

3

4

6

3

4

4

5

3

5

1 4

80 100 60 50 20 20 10 10 10

3

7

4

4

3

4

2

6

3

7

3

8

3

4

1 4

3

3

9

1 0

p h e n y l p r o p y n e is c o n v e r t e d m a i n l y to a b r i g h t - r e d t r i l i t h i o d e r i v a t i v e , C H C Li3. 6

5

T h e i n f r a r e d s p e c t r u m of this substance shows o n l y a s i n g l e

3

strong C = C

b a n d at 1780 c m " , consistent w i t h the a l l e n i c s t r u c t u r e 1

PhCLi=C=CLi .

Derivatization w i t h trimethylchlorosilane produced

2

the tris ( t r i m e t h y l s i l y l ) p h e n y l a l l e n e , P h C ( S i M e ) = C = C ( S i M e ) 2 3

3

(19).

T r a p p i n g w i t h t r i m e t h y l c h l o r o s i l a n e s e r v e d to i d e n t i f y the p o s i t i o n s of n u c l e a r l i t h i a t i o n of 1 - p h e n y l p r o p y n e . C H Li—C Li 6

4

3

T h e tetrasilyl products

from

w e r e i d e n t i f i e d as the ortho a n d p a r a d e r i v a t i v e s , i n d i -

3

c a t i n g t h a t n u c l e a r l i t h i a t i o n takes p l a c e p r e f e r e n t i a l l y o r t h o or p a r a t o the side c h a i n : SiMe

3

and SiMe

S i M e! ;

3

3

U n d e r f o r c i n g c o n d i t i o n s , 1 - p h e n y l p r o p y n e c a n be m u c h m o r e h i g h l y lithiated.

T h e greatest s u b s t i t u t i o n w a s o b t a i n e d b y h e a t i n g 1 - p h e n y l -

p r o p y n e neat w i t h a 5 0 - f o l d excess of n - B u L i at 7 5 ° to 8 5 ° C for 48 hours. Q u e n c h i n g w i t h D 0 p r o d u c e d a m i x t u r e of d e u t e r a t e d 1- a n d 3 - p h e n y l 2

p r o p y n e s , w h i c h w a s s t u d i e d b y mass spectroscopy. T h e i s o m e r d i s t r i b u t i o n is s h o w n i n T a b l e I I I . T h e m a j o r p r o d u c t s arise f r o m the p e n t a - a n d h e x a l i t h i o c o m p o u n d s , b u t a significant a m o u n t of C H L i 9

C Li —C Li 6

5

3

3

apparently form.

7

and 1%

of the p e r l i t h i o c o m p o u n d

D e r i v a t i z a t i o n of t h e p o l y l i t h i a t e d m i x -

t u r e u s i n g M e S i C l p r o d u c e s n u m e r o u s s i l y l - s u b s t i t u t e d isomers, w h i c h 3

c o u l d o n l y b e s e p a r a t e d w h e n the n u m b e r of silicons w a s less t h a n six.


220

POLY AMINE-CHELATED

ALKALI

M E T A L

COMPOUNDS

T h e most significant p r o d u c t is p r o b a b l y the p e n t a s i l y l c o m p o u n d , i d e n t i fied as ο-, p-bis(trimethylsilyl)phenyltris(trimethylsilyl)aliène: SiMet Me Si ~ ^ Q ^ - C = C = C ( S i M e ) 2 3

3

SiMe

3

Table III. Products from D 0 Derivatization of Polylithiated 1 -Phenylpropyne Downloaded by UNIV OF ARIZONA on August 6, 2012 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0130.ch011

2

Isomer

% Produced 0 0 0 5 12 36 37 8 1

do di d d d d* d d d 2 z

4

6

7

s

P o l y l i t h i a t i o n o f a r o m a t i c c o m p o u n d s offers m u c h p r o m i s e for f u t u r e research.

I t i s e v i d e n t t h a t p e r l i t h i o a r o m a t i c s c a n b e p r e p a r e d , albeit

o n l y m i x e d w i t h l e s s - h i g h l y l i t h i a t e d species.

Moreover t h e perlithio

aromatics seem t o b e stable species once f o r m e d . A major p r o b l e m l i m i t i n g f u r t h e r a d v a n c e i n this area is the l a c k o f a p o l a r solvent i n e r t to a l k y l lithium compounds at moderate

temperatures.

Activation of organo-

l i t h i u m c o m p o u n d s b y c h e l a t i n g d i a m i n e s seems l i k e l y t o p l a y a n i m p o r tant role i n t h e f u r t h e r d e v e l o p m e n t o f l i t h i o c a r b o n c h e m i s t r y , b o t h i n t h e a l i p h a t i c a n d a r o m a t i c series. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

West, R., Carney, P. Α., Mineo, I.C.,J.Amer. Chem. Soc. (1965) 87, 3788. West, R., Jones, P. C., J. Amer. Chem. Soc. (1969) 91, 6156. Priester, W., West, R., unpublished data. Shimp, L . Α., Lagow, R. J., J. Amer. Chem. Soc. (1973) 95, 1343. Chung, C., Lagow, R. J., Chem. Comm. (1972) 1078. Chwang, T. L., Ph.D. Thesis, University of Wisconsin (1971). Chwang, T. L . , West, R., Chem. Commun. (1971) 813. Chwang, T. L . , West, R., J. Amer. Chem. Soc. (1973) 95, 3224. Eberhardt, G. G., Butte, W. Α., J. Org. Chem. (1964) 29, 2928. West, R., Jones, P. C., J. Amer. Chem. Soc. (1968) 90, 2656. Chalk, A. J., Hoogeboom, T. J., J. Organometal. Chem. (1968) 11, 615. Broaddus, C. D., J. Org. Chem. (1970) 35, 10. Bryce-Smith, D., J. Chem. Soc. (1954) 1079.


11.

WEST


221

14. Hall, G. E . , Piccolini, R., Roberts, J. D., J. Amer. Chem. Soc. (1955) 77, 4540. 15. Halasa, Α., J. Organometal. Chem. (1971) 31, 369. 16. Halasa, Α., Tate, D., J. Organometal. Chem. (1970) 24, 769. 17. Gornowicz, G. Α., West, R., J. Amer. Chem. Soc. (1971) 93, 1720. 18. Mulvaney, J. C., Folk, T. L., Newton, D. J., J. Org. Chem. (1967) 32, 1674. 19. West, R., Gornowicz, G. Α., J. Amer. Chem. Soc. (1971) 93, 1720.


RECEIVED March 30, 1973.


Polylithiation of Hydrocarbons - American Chemical Society

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