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Photochemistry of the anthracene chromophore: novel isomerization of 1-(9-anthryl)-2-benzoylethylenes
Tetrahedron Letters,Vol.26,No.l2,pp Printed in Great Britain
PHOTOCHEMISTRY NOVEL
Hans-Dieter
Photoexcited
of Gothenburg,
alkenes
Neither
and Kjell
University
but quantum
by photochemical
rearrangement
Andersson
of Technology
S-412 96 Gothenburg,
chromophore
ring represents
rings
reacts
may undergo yields
cis-9-(B-styryl)anthracene
accessible
Chalmers
by skeletal
of the anthracene
upon photoexcitation moiety,
Kjell Sandros,
Sweden
undergo
a novel
to give
SH-dibenzo[a,dlcycloheptenes.
the central
one of the lateral
rarely,
alkene
in which
CHROMOPHORE:
cis-1-(9-anthryl)2_benzoylethylenes
furano-annelated
The photochemistry
Becker,
Chemistry,
type of isomerization
additions
0040-4039/85 $3.00 + .oo 01985 Peraamon Press Ltd.
OF I-(9-ANTHRYLJ-2-BENZOYLETHYLENES
Hans-Christian
of Organic
and University
Abstract:
OF THE ANTHRACENE
ISOMERIZATION
Becker*,
Department
1589-1592,1985
i s characterized
a 4s e 1 ectron
system
as a diene or dienophile.' geometrical
9-Anthryl-
i somerization
of the cis-trans-isomerization
by cycloor, more
of the vary greatly.
nor cis-1,2-di(9-anthryljethylene
isomerization
of their trans-isomers,
are but trans-l-
(9-anthryl)-2-benzoy,lethylene (la) isomerizes upon irradiation to give the cis2 2a. We have now found that photoexcited cis-I-(9-anthryl)-2-benzoyl-
isomer
ethylenes skeletal
2, in a reaction transformation
competing
with cis-trans
into furano-annelated
2
1589
isomerization,
undergo
5H-dibenzo[a,dlcycloheptenes
a 3.
l-3
R
R'
a
H
H
b
CH30
H
c
CH3C0
H
d
C6H5
H
e
H
'gH5
1590
Irradiation
of la (50 mg) in ethyl
(125 W high-pressure cut-off
filter,
of 2a. Work-up solvent, gives
Hg lamp,
by column
benzoylethylenes
are easily
solution
chromatography
as colorless
upon
by virtue
1. Photochemical R'
cut-off filter
mg
50 50 100 100 " C6H5 100
400nmC) Pyrex Pyrex
of structure
of
chloride
I-(9-anthryl)-2in the same way
photoproducts
3b - 3e which
(see Table
product (yield)
Il.
3 h 3h 7h 6h 7h
3a 3b 3c 3d 3e
FlUOreSCMlCe quantum yield d) ____-----0.47 0.47 0.0025 0.56 0.45
mp OC
(80%) (67%) (60%) (76%) (92%)
136-139 124-128 139-144 190-194 175-178
a) in 175 mL of ethyl acetate. b) 1 H aqueous solution of potassiUm c) potassium nitrite (150 g) in water (200 mL). d) in cyclohexane.
The assignment
a 330 nm
of 1 into 3 a) irr. time
;;; ;= ;;
H H CH30 H CH CO H CgS5 H
Conversion
with
evaporation
in solution
fluorescence
for 3 h
disappearance
gel/methylene
Substituted
irradiation
of their blue
equipped
by vacuum
on silica
crystals.
argon
and subsequent
for la, and they give the substituted
R
la, lb, le. ld, le,
well apparatus
colorless
lb-le isomerize
detected
Table
(175 mL) under
in the formation
of the virtually
followed
as described
immersion
18 'C) results
3a in 80% yield
acetate
3 rests
on the spectroscopic
nitrate.
properties
of the
photoproducts. Their high-resolution mass spectra confirm them to be isomers of 13 1. In their C-NMR spectra, two singlets at 6 150 and 153 ppm are typical of C-2 and C-5 in furans (cf. Table 2). 1 H-NMR data are summarized in Table 3. The sharp
singlet
transformed
at 6 3.8 ppm due to the methylene
at -65 'C into an AR spectrum
the conformational the phenyl benzo
group
moieties,
mobility
of 7-membered
at the sp3 carbon as is deduced
protons
in 3a - 3d is
(JAIl=14Hz), as is in agreement carbocycles;3
in 3e is associated
from the upfield
Table 2. Selected 'k-NHR Data of 3a-3c ----------______________________________ c-o-c 3 =CH CH2 R ----__-------___________________________ 153.3. 149.7 105.7 41.7 : 153.7; 149.0 104.3 41.9 55.4 c 152.1; 151.0 108.1 41.8 197.0;26.5
axial
The
with
position
with shielding
of
by the
shift of two multiplets
(3H:2H).
Table 3. 'H-NHR Data of 3a-3e =CH CH2 R 3 arom H ---------_____---____________----7.88-7.29 7.15 3.84 : 7.82-6.97 7.02 3.83 3.87
---------------_____..____________________
:
8.06-7.25 7.94-7.29
7.29 7.18
3.84 3.85
2.64
aron
all spectra in deuteratedchloroform; 7.94-6.62 6.94 (CHR': 5.45) E~~~~~~_s_hlft~~~~_~~~~~~~~~~~_~____________~_______________________________
The electronic
absorption
closely
resemble
reflect
the extended
spectrum
3c probably
the absorption appearance
by resonance
low fluorescence reflects
Mechanism
of photoproducts
studies
enhanced
yield
spectral
changes
contributions
(0.0025;
intersystem
were carried
of 3a by emission
3a, 3b, and 3e (Fig.
The enhanced
absorption
and the large bathochromic
conjugation,
of 3c is explicable
exceptionally
spectra
that of tetraphenylfuran.
out with
during
cf.Table
crossing
shift
3~'.
The
I) of "acetophenone"
la in degassed
to reveal
of the
of structure
to the triplet
the irradiation,
spectroscopy,
1)
of 3d may
state.
benzene
by measuring
and by monitoring
the following.
the
1531
~~~~~~
yy
’
\
o250
300
350
:: I”
reaction
0.28.
when virtually
exhibits
The
yield
quantum
Photoexcited
formation
is absorbed
2a increases, state
point
to reform
by the trans-isomer.
of the cis-trans
Therefore,
by photoexcitation
la with a quattum of TJxIO-~.
isomerizations
Fig.2.
2a are noticeably proceed
yield
Neither
we conof the la is
of 0.10,
and
the rate of
la, nor the rate of formation of 3a from 5 Apparently, both affected by molecular oxygen.
from the excited
Absorption and
has
and the set of
of 2a from its trans-isomer
yield
As
of 3a
isomerization
constant,
(see Fig.2).
or exclusively,
a quantum
low at the beginning
of 2a from photoexcited
photoexcited
3c’
the rate of formation
of 3a becomes
of formation
2a isomerizes
to give 3a with
3c
to be negligibly
all light
an isosbestic
predominantly,
400 cm
3e
the rate of formation
spectra
it isomerizes
-
350
of 3a is found
3a is formed
cis-isomer.
3a
the photostationary
established,
clude,
of
300
of the cis-isomer
After
increases. been
250
Spectra
The rate of formation
the concentration
‘....
400
Fig.l.Electron
of the irradiation
Crclohexane
‘.....
Emission
singlet
Spectroscopic
state.
Detection
of
3s.
1592
The
conversion
of cis-I-(9-anthryll-2-benzoylethylenes
ed 5H-dibenzo[a,d]cycloheptenes both anthracene a reaction photoexcited
and enone
sequence
which
conjugated
The
plane
begins
There
geometry
conversion
of
2 probably
the cis-enone This means
9-position
3 A, and the conversion
References _---------~---------
(I)
and
in ground
plays
state
an important models
undergoing
of the anthracene
of photoexcited
carbene
between
presumably
leading chemistry
7
role in the photosuggests
of about
the photoreaction
that the distance
of 3 by the
steps
from anthracene.
of molecular
in
involving
I).6 The subsequent
and that of the ene form an angle
s-cis
and the reacting
2 (Scheme
are examples
and, significantly, conformation.
precedence
the formation
with a 4 + 2 cycloaddition
into 3. Inspection
of the anthracene
into furano-annelat-
without
We rationalize
of SH-dibenzo[a,dlcycloheptenes
molecular
chemical
photochemistry.
"dienone"
to 3 are straightforward. for the formation
is a transformation
that the 80 degrees'
exists
in the
the carbdnyl
oxygen
is not larger
2 into 3 is geometrically
than
facilitated.
Notes
Appl. Chem. 1980, H.; Castellan, A.; Desvergne, J.-P . Pure Wang, T.; Shou, H.; Yang. N. C.: Masnovi, J.; Chianq, W.; 2633. b) Pure Appl. Chem. Becker, H.-D. Eng, D. H. Tetrahedron, i981, E,‘3285. C) P .: Mak, K. T. 1982, 54, 1589. d) Yang, N. C.; Chen, M.-J. ; Chen, J. W. K .;‘Saltiel, Smothe rs, J. Am.Them. Sot. 1983, 104, 853. e) Andersson, K. , H.-D.; J’. Am. Chem. Sot. 1983, 105, 2794. f) Becker Tetrahedron Letters, 1983, 2, 3273. 4542. 48, Becker, H.-D.; Andersson, K. J. Org. Chem. 1 983, ation enerqy associated From the coalescence temoerature of 238 K. t he ac=v with the folding process’was calculated to be 11 kcal/mol, (cf:.Kost, D.; Carlson, E. H.; Raban, M. Chem. Comm. 1971, 656 ). For the parent an activation energy of 9.2 kcal/mol has been 5H-dibenzo[a,d]cycloheptene, a)
Bouas-Laurent,
52.
(2) (3)
(7) (8)
found: Hales, N .J.; Smith, D. J. H.; Swindles, M. E. Chem. Comm. 1976, 981. Cf. also Tochtermann, W. Fortschr. Chem. Forsch. 1970, 15, 378. based on the K-ferrioxalate actinometer. Quantum yield measurements are Molecular oxygen does react with photoexcited 3. The formation of the 4 + 2 cycloaddition product may be described to the photochemical isomerizations of involve biradical intermediates. Cf. 2,4-dienones and a,8,6,E_unsaturated carbonyl compounds which give Biichi, G.; Yang, N. C. a-pyrans and dihydropyrans, respectively: a) J. Am. Chem. Sot. 1957, 2, 2318. b) Schneider, R. A.; Meinwald, J. J. Am. Chem. Sot. 1967, 2, 2023. a) Miiller, E.; Kessler, H. Liebigs Ann. Chem. 1966, 692, 58. Letters, 1960, 27. b) Murray, R. W. Tetrahedron The corresponding angle in cis-9-(B-styryl)anthracene is 78.4 degrees: Becker, H.-D.; Patrick, V. A.; White, A. H. Aust. J. Chem. 1984, 11, 2215.
(Received
in
UK
18
January
1985)
PHOTOCHEMISTRY NOVEL
Hans-Dieter
Photoexcited
of Gothenburg,
alkenes
Neither
and Kjell
University
but quantum
by photochemical
rearrangement
Andersson
of Technology
S-412 96 Gothenburg,
chromophore
ring represents
rings
reacts
may undergo yields
cis-9-(B-styryl)anthracene
accessible
Chalmers
by skeletal
of the anthracene
upon photoexcitation moiety,
Kjell Sandros,
Sweden
undergo
a novel
to give
SH-dibenzo[a,dlcycloheptenes.
the central
one of the lateral
rarely,
alkene
in which
CHROMOPHORE:
cis-1-(9-anthryl)2_benzoylethylenes
furano-annelated
The photochemistry
Becker,
Chemistry,
type of isomerization
additions
0040-4039/85 $3.00 + .oo 01985 Peraamon Press Ltd.
OF I-(9-ANTHRYLJ-2-BENZOYLETHYLENES
Hans-Christian
of Organic
and University
Abstract:
OF THE ANTHRACENE
ISOMERIZATION
Becker*,
Department
1589-1592,1985
i s characterized
a 4s e 1 ectron
system
as a diene or dienophile.' geometrical
9-Anthryl-
i somerization
of the cis-trans-isomerization
by cycloor, more
of the vary greatly.
nor cis-1,2-di(9-anthryljethylene
isomerization
of their trans-isomers,
are but trans-l-
(9-anthryl)-2-benzoy,lethylene (la) isomerizes upon irradiation to give the cis2 2a. We have now found that photoexcited cis-I-(9-anthryl)-2-benzoyl-
isomer
ethylenes skeletal
2, in a reaction transformation
competing
with cis-trans
into furano-annelated
2
1589
isomerization,
undergo
5H-dibenzo[a,dlcycloheptenes
a 3.
l-3
R
R'
a
H
H
b
CH30
H
c
CH3C0
H
d
C6H5
H
e
H
'gH5
1590
Irradiation
of la (50 mg) in ethyl
(125 W high-pressure cut-off
filter,
of 2a. Work-up solvent, gives
Hg lamp,
by column
benzoylethylenes
are easily
solution
chromatography
as colorless
upon
by virtue
1. Photochemical R'
cut-off filter
mg
50 50 100 100 " C6H5 100
400nmC) Pyrex Pyrex
of structure
of
chloride
I-(9-anthryl)-2in the same way
photoproducts
3b - 3e which
(see Table
product (yield)
Il.
3 h 3h 7h 6h 7h
3a 3b 3c 3d 3e
FlUOreSCMlCe quantum yield d) ____-----0.47 0.47 0.0025 0.56 0.45
mp OC
(80%) (67%) (60%) (76%) (92%)
136-139 124-128 139-144 190-194 175-178
a) in 175 mL of ethyl acetate. b) 1 H aqueous solution of potassiUm c) potassium nitrite (150 g) in water (200 mL). d) in cyclohexane.
The assignment
a 330 nm
of 1 into 3 a) irr. time
;;; ;= ;;
H H CH30 H CH CO H CgS5 H
Conversion
with
evaporation
in solution
fluorescence
for 3 h
disappearance
gel/methylene
Substituted
irradiation
of their blue
equipped
by vacuum
on silica
crystals.
argon
and subsequent
for la, and they give the substituted
R
la, lb, le. ld, le,
well apparatus
colorless
lb-le isomerize
detected
Table
(175 mL) under
in the formation
of the virtually
followed
as described
immersion
18 'C) results
3a in 80% yield
acetate
3 rests
on the spectroscopic
nitrate.
properties
of the
photoproducts. Their high-resolution mass spectra confirm them to be isomers of 13 1. In their C-NMR spectra, two singlets at 6 150 and 153 ppm are typical of C-2 and C-5 in furans (cf. Table 2). 1 H-NMR data are summarized in Table 3. The sharp
singlet
transformed
at 6 3.8 ppm due to the methylene
at -65 'C into an AR spectrum
the conformational the phenyl benzo
group
moieties,
mobility
of 7-membered
at the sp3 carbon as is deduced
protons
in 3a - 3d is
(JAIl=14Hz), as is in agreement carbocycles;3
in 3e is associated
from the upfield
Table 2. Selected 'k-NHR Data of 3a-3c ----------______________________________ c-o-c 3 =CH CH2 R ----__-------___________________________ 153.3. 149.7 105.7 41.7 : 153.7; 149.0 104.3 41.9 55.4 c 152.1; 151.0 108.1 41.8 197.0;26.5
axial
The
with
position
with shielding
of
by the
shift of two multiplets
(3H:2H).
Table 3. 'H-NHR Data of 3a-3e =CH CH2 R 3 arom H ---------_____---____________----7.88-7.29 7.15 3.84 : 7.82-6.97 7.02 3.83 3.87
---------------_____..____________________
:
8.06-7.25 7.94-7.29
7.29 7.18
3.84 3.85
2.64
aron
all spectra in deuteratedchloroform; 7.94-6.62 6.94 (CHR': 5.45) E~~~~~~_s_hlft~~~~_~~~~~~~~~~~_~____________~_______________________________
The electronic
absorption
closely
resemble
reflect
the extended
spectrum
3c probably
the absorption appearance
by resonance
low fluorescence reflects
Mechanism
of photoproducts
studies
enhanced
yield
spectral
changes
contributions
(0.0025;
intersystem
were carried
of 3a by emission
3a, 3b, and 3e (Fig.
The enhanced
absorption
and the large bathochromic
conjugation,
of 3c is explicable
exceptionally
spectra
that of tetraphenylfuran.
out with
during
cf.Table
crossing
shift
3~'.
The
I) of "acetophenone"
la in degassed
to reveal
of the
of structure
to the triplet
the irradiation,
spectroscopy,
1)
of 3d may
state.
benzene
by measuring
and by monitoring
the following.
the
1531
~~~~~~
yy
’
\
o250
300
350
:: I”
reaction
0.28.
when virtually
exhibits
The
yield
quantum
Photoexcited
formation
is absorbed
2a increases, state
point
to reform
by the trans-isomer.
of the cis-trans
Therefore,
by photoexcitation
la with a quattum of TJxIO-~.
isomerizations
Fig.2.
2a are noticeably proceed
yield
Neither
we conof the la is
of 0.10,
and
the rate of
la, nor the rate of formation of 3a from 5 Apparently, both affected by molecular oxygen.
from the excited
Absorption and
has
and the set of
of 2a from its trans-isomer
yield
As
of 3a
isomerization
constant,
(see Fig.2).
or exclusively,
a quantum
low at the beginning
of 2a from photoexcited
photoexcited
3c’
the rate of formation
of 3a becomes
of formation
2a isomerizes
to give 3a with
3c
to be negligibly
all light
an isosbestic
predominantly,
400 cm
3e
the rate of formation
spectra
it isomerizes
-
350
of 3a is found
3a is formed
cis-isomer.
3a
the photostationary
established,
clude,
of
300
of the cis-isomer
After
increases. been
250
Spectra
The rate of formation
the concentration
‘....
400
Fig.l.Electron
of the irradiation
Crclohexane
‘.....
Emission
singlet
Spectroscopic
state.
Detection
of
3s.
1592
The
conversion
of cis-I-(9-anthryll-2-benzoylethylenes
ed 5H-dibenzo[a,d]cycloheptenes both anthracene a reaction photoexcited
and enone
sequence
which
conjugated
The
plane
begins
There
geometry
conversion
of
2 probably
the cis-enone This means
9-position
3 A, and the conversion
References _---------~---------
(I)
and
in ground
plays
state
an important models
undergoing
of the anthracene
of photoexcited
carbene
between
presumably
leading chemistry
7
role in the photosuggests
of about
the photoreaction
that the distance
of 3 by the
steps
from anthracene.
of molecular
in
involving
I).6 The subsequent
and that of the ene form an angle
s-cis
and the reacting
2 (Scheme
are examples
and, significantly, conformation.
precedence
the formation
with a 4 + 2 cycloaddition
into 3. Inspection
of the anthracene
into furano-annelat-
without
We rationalize
of SH-dibenzo[a,dlcycloheptenes
molecular
chemical
photochemistry.
"dienone"
to 3 are straightforward. for the formation
is a transformation
that the 80 degrees'
exists
in the
the carbdnyl
oxygen
is not larger
2 into 3 is geometrically
than
facilitated.
Notes
Appl. Chem. 1980, H.; Castellan, A.; Desvergne, J.-P . Pure Wang, T.; Shou, H.; Yang. N. C.: Masnovi, J.; Chianq, W.; 2633. b) Pure Appl. Chem. Becker, H.-D. Eng, D. H. Tetrahedron, i981, E,‘3285. C) P .: Mak, K. T. 1982, 54, 1589. d) Yang, N. C.; Chen, M.-J. ; Chen, J. W. K .;‘Saltiel, Smothe rs, J. Am.Them. Sot. 1983, 104, 853. e) Andersson, K. , H.-D.; J’. Am. Chem. Sot. 1983, 105, 2794. f) Becker Tetrahedron Letters, 1983, 2, 3273. 4542. 48, Becker, H.-D.; Andersson, K. J. Org. Chem. 1 983, ation enerqy associated From the coalescence temoerature of 238 K. t he ac=v with the folding process’was calculated to be 11 kcal/mol, (cf:.Kost, D.; Carlson, E. H.; Raban, M. Chem. Comm. 1971, 656 ). For the parent an activation energy of 9.2 kcal/mol has been 5H-dibenzo[a,d]cycloheptene, a)
Bouas-Laurent,
52.
(2) (3)
(7) (8)
found: Hales, N .J.; Smith, D. J. H.; Swindles, M. E. Chem. Comm. 1976, 981. Cf. also Tochtermann, W. Fortschr. Chem. Forsch. 1970, 15, 378. based on the K-ferrioxalate actinometer. Quantum yield measurements are Molecular oxygen does react with photoexcited 3. The formation of the 4 + 2 cycloaddition product may be described to the photochemical isomerizations of involve biradical intermediates. Cf. 2,4-dienones and a,8,6,E_unsaturated carbonyl compounds which give Biichi, G.; Yang, N. C. a-pyrans and dihydropyrans, respectively: a) J. Am. Chem. Sot. 1957, 2, 2318. b) Schneider, R. A.; Meinwald, J. J. Am. Chem. Sot. 1967, 2, 2023. a) Miiller, E.; Kessler, H. Liebigs Ann. Chem. 1966, 692, 58. Letters, 1960, 27. b) Murray, R. W. Tetrahedron The corresponding angle in cis-9-(B-styryl)anthracene is 78.4 degrees: Becker, H.-D.; Patrick, V. A.; White, A. H. Aust. J. Chem. 1984, 11, 2215.
(Received
in
UK
18
January
1985)