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Resolution Circular Dichroism and Absolute Configuration of 1 1-Bis-azulenes.

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Accordingly rac. La i s considered t o be resolved completely by
fraction.
This manuscript is
to be cited as
Angew. Chem. Suppl.
Dieses Manuskript ist
zu zitieren als
Angew. Chem. Suppl.
1983, 1283 - 1290
I
the (+)-PTrMA column.
1983, 1283-1290
I0
Q Verlag Chernie GrnbH, D-6940 Weinhelm. 1983
0721 4227/8311111-1283102
5010
c5
Resolution, C i r c u l a r Dichroism and Absolute Configuration of
1*
- 0.5
1 ,l'-Bis-arulenes
I
Akio T a j i r i
, Masahiko Fukuda , Masahiro Hatano
- 1.0
Tadayoshi Moritat and Kahei Takaset
8
The o p t i c a l a c t i v i t i e s o f s t e r i c a l l y - h i n d e r e d b i a r y l s have been
.
,
0
.
-
extensively investigated, b o t h from experimental and t h e o r e t i c a l p o i n t s of
w
view, t o e s t a b l i s h the absolute c o n f i g u r a t i o n o f dissymetric b i p h e n y l s l l l ,
l,l'-binaphthyls/Zl
As f a r as we know, however,
and 1.1 ' - b i a n t h r y l s / 3 / .
no example and, i n turn, no CD measurement have been known t o date f o r
4
dissymetric molecules w i t h non-benzenoid aromatic hydrocarbon chromophores
Herein we r e p o r t the d i r e c t r e s o l u t i o n o f 1.1'-bis-azulenes
as constituents.
2
and t h e i r o p t i c a l a c t i v i t i e s associated w i t h t h e i r p a r t i c u l a r absorption
band system.
L : X = H
0
l a : X = CH..J
10
.a
20
30
50
LO
Lb: X = OCH3
~ I I O ~ ~ ~ ?
Experimental and t h e o r e t i c a l absorption (bottom) and
Fig. Z
*
Chemical Research I n s t i t u t e of Non-aqueous Solutions,
CD ( t o p ) spectra of La -(
Tohoku U n i v e r s i t y , Sendai 980, Japan
_._....2nd f r a c t i o n )
1st fraction,
t Department of Chemistry, Faculty o f Science, Tohoku University,
A given e x c i t e d e l e c t r o n i c s t a t e of the azulene chromophore ( F i g . 3a)
Sendai 980, Japan
**
This work was p a r t i a l l y supported by a Grant-in-Aid f o r S c i e n t i f i c Research
from the M i n i s t r y o f Education, Science and C u l t u r e of Japan, and by a
Grant from the Nissan Science Foundation (M.H. ).
-
1283
Both t h e 6
+
(L),
A and A
-
+
t o two states,
B
and A i n the
A t r a n s i t i o n s of 1,l'-bis-azulene
1285
-
coming from an azulene e x c i t a t i o n w i t h long a x i s p o l a r i z a t i o n have a f i n i t e
d i p o l e strength161 and a non-zero r o t a t i o n a l s t r e n g t h f o r a l l values of the
t i o n w i t h the a i d of the HPLC technique using a comnercially a v a i l a b l e
dihedral angle a between the planes of the azulene n u c l e i except 0
methacrylate) (PTrMA) columnlSI.
acetone
p o i n t group C2.
-
Racemic 1,l '-bis-azulene derivatives141 have been subjected t o r e s o l u
(+)-poly(triphenylmethy1
gives r i s e , i n rac. 1.1'-bis-azulene
f.)
180'.
more s t a b l e than the A s t a t e i n
L (Fig.
and
the B s t a t e i s calculated t o be
According t o Simpson's method/7/,
3b).
A d i s t i n c t CD couplet observed i n the energy region o f 30000
?r
40000 cm-'
c l a r i f i e s two e l e c t r o n i c t r a n s i t i o n s associated w i t h t h e strongest absorption
of La, which a r i s e s from the i n t e r a c t i o n between t h e 'Ba states w i t h long
Provided the absolute
a x i s p o l a r i z a t i o n w i t h i n the azulene chromophore/8/.
configuration i s R ( F i g . 3c), a c h i r a l i t y c o n s i d e r a t i o n l 9 l leads t o the
negative s i g n f o r CD associated w i t h the 8
s i g n f o r t h a t associated w i t h the A
+
+
A t r a n s i t i o n and the p o s i t i v e
A t r a n s i t i o n (Fig. 3d).
A similar
consideration reverses the s i g n o f CD f o r S-configuration, w h i l e keeping
the 8-state below the A-state.
This was f u r t h e r c c n f i m d on the basis of the CNOOIS method assuming
R-COnfigUratiOn w i t h t h e dihedral angle of 130
/lo/
for
i.
Calculated
o s c i l l a t o r strengths and r o t a t i o n a l strengths a r e represented i n Fig. 2
5
0
10
15
w i t h bars.
The B
+
A t r a n s i t i o n p r e d i c t e d a t 37300 cm-' i s c a l c u l a t e d
Elution Volurne/rnl
t o e x h i b i t negative
Fig.1
Resolution o f r a c . La a t room temperature,
a t 34400 cm-',
solvent; hexaneI2-propanol (80 : 20).
CD which i s assigned t o the observed negative CD band
w h i l e the A
+
A t r a n s i t i o n a t 37900 cm-' i s p r e d i c t e d t o
show p o s i t i v e CD which i s assigned t o the observed p o s i t i v e CD band a t
flow r a t e ; 0.5 mllmin.
ern-'.
Figure 1 i l l u s t r a t e s a chromatogram o f r a c . 2,2'-dimethyl-l.l'-bis-azulene
37200
(La) obtained by HPLC w i t h a hexanel2-propanol (80 : 20 i n volume) mixture
corresponds t o 1,i '-bis-azulene w i t h t h e absolute configuration o f R ( - )
as solvent.
and t h a t t h e 2nd f r a c t i o n t o t h a t w i t h
The f r a c t i o n o f
2
t h a t was e l u t e d f i r s t and gave negative r o t a t i o n
e x h i b i t s a d i s t i n c t negative CD couplet i n the energy r e g i o n of 30000
40000 cm-'
as shown i n F i g . 2, w h i l e t h e 2nd f r a c t i o n which e x h i b i t s
I.
Therefore we conclude t h a t the 1 s t f r a c t i o n o f rac. .la
s(+).
I n c o n t r a s t t o the remarkable s t a b i l i t y o f R- and S-la i n s o l u t i o n l l l l ,
R- and S-2,2'-dimethoxy-l
.la-bis-azulene (Lb) i s found t o be c o n f i g u r a t i o n a l l y
unstable by CD spectroscopy, i n d i c a t i n g a r a t h e r r a p i d racemization a t room
p o s i t i v e r o t a t i o n gives a m i r r o r image o f t h e CD spectrum of t h e 1 s t
-
1284
-
- 1286
-
References and l o t e s
E. Bunnenberg, C. D j e r a s s i , K . Mislow and A. Moscowitz, J . Am. Chem.
_Soc. 84(1962)2823,
5003 ; K. Mislow, E. Bunnenberg, R . Records, K .
ibid.g ( 1 9 6 3 ) 1 3 4 2
Wellman and C . D j e r a s s i ,
; K . Mislow, S. Hyden
and H . Schaefer, i b i d . 84(1961)1449 ; K. Mislow, M. A. Glass, R . E.
O'Brien, P . Rutkin,
D.
ibid.
H. Steinberg, J . Weiss and C . O j e r a s s i ,
84(1961)1455.
0. 0. F i t t s , M. Siege1 and K . Mislow, i b i d . 80(1958)480 ; I .
Hanazaki and H. Akimoto, i b i d . 94(1972)4102.
G. M. Badger, R .
J. Orewer and
G. E . Leiws, J . Chem. SOC. (1962)
1342 ; R . G r i n t e r and S. F. Mason, i r a n s . Faraday Soc. g ( l 9 6 4 )
274.
T. M o r i t a and K. Takase, B u l l . Chem. SOC. Japan 55(1982)1144.
H. Yuki, Y . Okamoto and I . Okamoto, J . Am. Chem. SOC. z ( 1 9 8 0 )
6355 ; M. Nakazaki, K . Yamamoto and M. Maeda, J . Org. Chem.
46
(1981)1985 ; Y . Yuki, I . Okamoto and H. Yuki. Chem. L e t t . (1981)
835 ; Y . Okamoto, 5 . Honda, I . Okamoto, H . Yuki, S. Murata, R .
c
s
.-
Noyori and H. Tanaka, J . Am. Chem. Soc. E ( 1 9 8 1 ) 6 9 7 1 ; A PTrMA
u
a
x,
column was a generous g i f t from Daicel Chemical I n d u s t r i e s Ltd..
H i m e j i 671.12,
Japan, t o whom the authors would l i k e t o d i r e c t
t h e i r sincere appreciation.
R . Hagen, E . Heilbronner and P. A . Straub, Helv. Chim. Rcta
(1968)45.
W. 7. Simpson i n : Theories o f Electrons i n Molecules, P r e n t i c e H a l l Inc. New Jersey (1962) p141.
0.
Abiaua
- 1287
temperature.
-
derivatives/lZ/.
-
E x c i t o n Coupling i n Orqanic Stereochemistry, U n i v e r s i t y Science
The observed energy of racemization f o r R- and
S-Lb i s comparable w i t h those f o r 1 , l ' - b i n a p h t h y l
1289 -
N. Harada and K . Nakanishi : C i r c u l a r Dichroism Spectroscofi
From an Arrhenius p l o t t h e energy o f a c t i v a t i o n i s
(39OC).
Mann, J . R . P l a t t and H. 6. Klevens, J. Chem. Phys. z ( 1 9 4 9 )
-
detetmined t o be ca. 71 kJ/mol and the r a t e o f racemization t o be
ca. 3 . 8 ~ 1 0 - s-'
~
E.
481.
ihe
s t e r i c hindrance caused by two s u b s t i t u e n t s i s considered t o be smaller i n
Books, Cal i f o r n i a ( l 9 8 3 ) .
The t o t a l energy of t h e parent l , l ' - b i s - a z u l e n e
was c a l c u l a t e d on
the b a s i s o f the CNDO/L method, w h i l e v a r y i n g the d i h e d r a l angle o
.
i b than i n La, because the two methyl groups a r e away from each o t h e r due
between 0
t o the oxygen atom i n s e r t e d between the azulene s k e l e t o n and methyl group
e x h i b i t s the minimum a t a = 130
i n t h e former
thus c a l c u l a t e d was used f o r c a l c u l a t i n g e l e c t r o n i c spectra,
and 180
The c a l c u l a t e d p o t e n t i a l energy curve
.
The s t a b l e c o n f i g u r a t i o n
o s c i l l a t o r strengths and r o t a t i o n a l strengths of 1.1'-bis-azulene.
NO CD s p e c t r a l change has been detected f o r R- and S-2,Z'-dimethyl1.1'-bis-azulene
i n s o l u t i o n even a f t e r standing f o r several days
a t room temperature.
A. S. Cooke and
M. M. H a r r i s , J . Org. Chem.(C) (1967)988.
Received July 5 ,
-
1288 -
-
revised August 3 0 , 1 9 8 3 / Z 4 5 2 S /
1290 -
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circular, dichroism, resolution, absolute, configuration, bis, azulene
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