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Photochemistry of the anthracene chromophore: Triplet-sensitized isomerizations of dianthrylethanes
Tetrahedron Letters,Vol.26,No.49,pp 6129-6132,1985 Printed in Great Britain
PHOTOCHEMISTRY TRIPLET-SENSITIZED
THE ANTHRACENE ISOMERIZATIONS
Of
Of
0040-4039185 $3.00 + .oo 01985 Pergamon Press Ltd.
CHROHOPHORE: DIANTHRYLETHANES
Hans-Dieter Becker* and Kjell Andersson Department of Organic Chemistry, Chalmers University of Technology and University of Gothenburg, S-412 96 Gothenburg, Sweden isomerization of 1,2-di(9-anthryllethane can be Abstract: The photochemical sensitized by biacetyl to proceed by intramolecular Diels-Alder reaction. The molecular geometry of dianthrylethanes affects their triplet state reactivity. The photochemical addition
established excited
isomerization
of dianthrylethane
to give 1 has been studied to involve
triplet
the excited
extensively, singlet
state may be partly
2, but its contribution
photoexcited
la
to be negligible. dianthrylethane
Previous
reactions, singlet
state
reactions.
in a solution apparatus; filter
sensitization
consisting
atmosphere;
[4+4] cycle adduct
to give
3 with a quantum
isomerization isosbestic
3 is remarkable
mercury
1 but results
lamp; Aexc
of
of dianthrylethanes
from those of the of biacetyl
(2.4 g)
(140 mL; immersion
> 420 nm through chromate
in an intramolecular
well
0.5 cm of
in 200 mL of water;
time 5 h) does not produce
the previously
Oiels-Alder
reaction
yield of 0.1 (cf. Table lj.3 The biacetyl-sensitized cleanly,
as is evident
in the set of reaction i nsofar
has been found
of triplet-sensitized
photoexcitation
of 380 mg of potassium
of 2 proceeds
point
isomerization
(0.1 g) in benzene
irradiation
to the
decay of
have not been successful.
characteristically
Thus, selective
125 W high-pressure
crossing
for the radiationless
and that the products
may differ
of dianthrylethane
solution
15 oc; argon known
by biacetyl,
significantly,
Intersystem
has been
to bring about the photoisomeriza;ion
We have now found that the photochemical can be sensitized
[4+4] cyclo-
to the [4+4] cycloaddition
attempts
by acetophenone
state-l
responsible
2 by
and the reaction
spectra
as the isomerization
6129
from the exhibition
of an
(see fig. la). The formation
of linked anthracenes
by intra-
of
6130
---
300
4DO
Ml
500
450
550
600
650
rrn
Fig. 1. a: Reaction spectra of biacetyl-sensitized isomerization of 2 after 15 and 45 eec. b: Biacetyl phosphorescence quenching by 2. Insert: Stem-Volmer plot of quenching data. The calculated quenching constant is based on the quenching constant found for anthracene (cf. Bkkstriim, H.L.J.; Samins. K. Acta Chem. Stand. 1958, l2, 823).
molecular
Diels-Alder
sensitized
reaction
isomerizations
diffusion
isomerization
ethanes
by intramolecular
transfer.
triplet
fluorescence triplet
process
by Diels-Alder
energy
the excited
of biacetyl
controlled
triplet
quantum
state
yield suggests
due to benzoyl
excitation,
and by biacetyl
conceivable
Diels-Alder
dianthrylethanone [4+4]cyclomer solution isomers
so 7
as
and
in
by
products
6,
of
4, whose
crossing
in benzene
low
to the solution
to give 5 both upon direct
7
and
8
biaceLy1
(ratio 75:22).
sensiiized
(xexc
> 400
Irradiation
triplet
9 (q 0.036)
Only 3X of the iso-
to give 9. Direct
excitation
of
nm) gives 7, 8, and the of 6 in air-saturated
state species
does not give any of
as only cycloaddition
Note: hv
in terms of of dianthryl-
a 6 in benzene gives mainly (97%) the two
benzene
excited
yields
2 in a
photochemical
to be characteristic
intersystem
reaction
[4+4] cycloaddition
degassed
quench but
appear
setlsitization. Likewise,
9 in a ratio of 6:2:2. to
is explicable isomerizations
isomerizes
Diels-Alder
of dianthrylethanone
proceeds
enhanced
substitution,
and
to be unprecedented. by dianthrylethane
benzoyl-dianthrylethane
For example,
by intramolecular
merization
most likely
photochemical
[4+2] cycloaddition
state.
appear
is quenched
previously,4-7
(cf. Fig. lb), the sensitized
reaction
Moreover,
exclusively
isomerization
been observed
of dianthrylethanes
As the phosphorescence nearly
has rarely
product.
Depending
on
rate of heating, photoproducts
cycloreversion 200-220
Oc.
the
the
undergo
around
6131
2.
Fig.
Electron
spectra
of
10.
13.
and
J!L
7.
8,
+
6 Table
cyclomers
11,
7
8
in Benzene
‘PF : 0.20 0.002 <0.0001 Addition: 4+4 4+2 4+2 (80%); 4+4 (20%) (Pa : 0.26 0.005 o.ll(*) --------------------~---~_~--~___________-------_----_----__---____-___________ Sensitized: 4+2 4+2 4+2 (97%); 4+4 (3X) 0.1 0.007 (‘1 PR : ____~____~__~-~___~______-____---__----_________-___--_________________________ (*I Concentration-dependent quantum yield
appears borne
to govern out
molecular
ground terized
the course
in the excited geometry
state
is
high quantum
molecular
of their
triplet
state
by
overlapping spectrum
sensitization,9
yield
properties their
geometry
10
13 0.07 4+4 0.16
4+4 0.43
4+2 0.02
of dianthrylethanes
state reaction.
This feature
of chloro-dianthrylethanes substitution
(cf. Table
aromatic
moieties,
pattern.
from its
photoexcitation,
[4+4]cycloaddition the
Product +
hv
with fairly
molecular
sensitized:
ilb
geo-
Ratio lla : llb
_--_--__--__--_--------
direct exe: 68 : 32
lla
the
(10) is charac-
as is evident
1) to give 11. By contrast,
is
whose
For example,
(see Fig. Za). Upon direct 10 undergoes
by
0.013 4+4 0.39
of l,l', 5,5'-tetrachlorodianthrylethane
UV-absorption
and by biacetyl
state
affected
geometry
by partially
broadened
ground
14.
9
Deactivation of Electronically Excited Dianthrylethanes Fluorescence (‘Pf) and Cycloaddition (‘PS) _________________________-____----_----_-____________~_____-____-____----__---_ Compound: 2 4 6
the
and
+
1.
Interestingly,
12.
86 : 14
6132
metry
of the isomeric
4,4' ,5,5'-tetrachlorodianthrylethane that of the parent dianthrylethane 2, and should
resembles
anti-conformation, excited
state
as we conclude
properties
tion of 13 in benzene biacetyl
gives
sensitization
Diels-Alder products
adduct
from their similar
of 13 indeed
parallel
14 (cp 0.02).
most likely
those of 2. Direct
the [4+4] cycloaddition
of 13 leads
(13)"
be characterized by absorption spectra. The
to exclusive
'H-NMR spectral
product
formation
photoexcita-
12 (cp 0.161,
but of the intramolecular
data of the cycloaddition
are summarized
distinguishable
in Table 2. The Diels-Alder adducts also are easily from their isomeric [4+4] cycloadducts by their characteristic
1,2-dihydroanthracene
UV spectra
(see Fig. Zb; cf. ref. 5, 6,
and
7a).
Cl
h”
Slac.tyl
Table 2. 270 MHz ‘H-NHR Spectral Data of Isomeric in Oeuterated Chloroform (6, ppm downfield ____________________-_----_----___--_-----______~___--~~_---~~-----~---~~-----
Cycloadducts from TMS)
lla: llb: 12: 14:
7.17-6.70, m, 12 H; 5.06, s, 2 H; 3.76, m, 2 H; 7.10-6.75. m, 12 H; 5.15, 8, 2 H; 4.19, m. 2 H; 7.03-6.84, III, 12 H; 5.98, s. 2 H; 2.99, s, 4 H 8.18, 8, 1 Ii; 7.92-6.69, m, 9 H; 6.31, d, J=4.4 3~1.7 Hz, 1 H; 3.84, in, 1 H; 3.42, n, 1 H; 3.38, 3.27, ddd, 11.5, 4.4, 1.7 Hz, 1 H; 3.09, RI, 2 H ____________________--__----__---_-----_----_____---~__-----~----------------
In conclusion, proceed
triplet-sensitized
by [4+2] cycloaddition,
is such as to be characterized yields
of triplet-sensitized
unless
References and ---_______----__----
(1) (2) (3) (4)
(5) I;; (8) (9)
(11)
overlapping favored
2 2
12,
and
14
H H
5.45, Hz,
d 1’H;
of dianthrylethanes ground
conformation
s-systems.
The quantum
[4+4] cycloadditions
those of the corresponding
excited
;
of 10 to invoive
mainly
(>90%)
the excited
Compound 13, mp 343-344 C, was prepared by corresponding lepidopterene (Becker, H.-D.; J. Org. Chem. 1980, 2, 4549. see also ref. a) Eiouas-Laurent, H.; Castellan, A.; Desvergne, 1980, 52, 2633. b) Becker, H.-D.; Elebring, 1982, 47, 1064. c) Becker, H.-D.; Andersson,
(Received
in UK 1 October
1985)
singlet
are
singlet
Notes
a) Livingston, R.; Wei, K.S. .I. Am. Chem. Sot. 1967, 89, 3098. b) Manring, L.E.; Peters, K.S.; Jones, G., II; Bergmark, W.R. J. Am. Chem. Sot. 1985, 107, 1485; and references cited therein. Bergmark, W.R.; Jones, G., II Reinhardt, T.E.; Halpern, A.M. J. Am. Chem. Sac. 1976, m, 6665. Cf. Becker, H.-D.; Andersson, K. Tetrahedron Symposium, 1985, in press. Photochemical isomerization by intramolecular Diels-Alder reaction has been observed in the case of cis-dianthrylethylene (ref. 5), dimethyldianthrylethane (ref. 6), and dianthryldimethylsilane (-germane) (ref. Becker, H.-D.; Sandros, K.; Andersson, K. Anqew. Chem. 1983, 95, 507. Becker, H.-D.; Andersson, K. Tetrahedron Lett. 1983, 24, 3273. a) Daney, M.; Vanucci, C.; Desvergne, J.-P.; Bouas-Laurent, H. Tetrahedron c. 1985, 26, 1505. b) Sakurai, H.; et al. Chem. Lett. 1985, 497. The synthesis and photochemistry of 6 will be published in detail. Oxygen quenching experiments suggest the formation of 11 by direct
excitation (10)
1 H; 3~11.5
their low-energy
geometrically
high, and they exceed state reactions."
“, IA,
Hz, d,
isomerizations
by partially
remarkably
3.45, 2.94,
11,
7).
state.
thermolysis of the Andersson, K.; Sandros, K. 6). J.-P. Pure App 1. Chem. 1.; Sandros, K. J. Org. Chem. K. ibid. 1983, 48, 4552.
PHOTOCHEMISTRY TRIPLET-SENSITIZED
THE ANTHRACENE ISOMERIZATIONS
Of
Of
0040-4039185 $3.00 + .oo 01985 Pergamon Press Ltd.
CHROHOPHORE: DIANTHRYLETHANES
Hans-Dieter Becker* and Kjell Andersson Department of Organic Chemistry, Chalmers University of Technology and University of Gothenburg, S-412 96 Gothenburg, Sweden isomerization of 1,2-di(9-anthryllethane can be Abstract: The photochemical sensitized by biacetyl to proceed by intramolecular Diels-Alder reaction. The molecular geometry of dianthrylethanes affects their triplet state reactivity. The photochemical addition
established excited
isomerization
of dianthrylethane
to give 1 has been studied to involve
triplet
the excited
extensively, singlet
state may be partly
2, but its contribution
photoexcited
la
to be negligible. dianthrylethane
Previous
reactions, singlet
state
reactions.
in a solution apparatus; filter
sensitization
consisting
atmosphere;
[4+4] cycle adduct
to give
3 with a quantum
isomerization isosbestic
3 is remarkable
mercury
1 but results
lamp; Aexc
of
of dianthrylethanes
from those of the of biacetyl
(2.4 g)
(140 mL; immersion
> 420 nm through chromate
in an intramolecular
well
0.5 cm of
in 200 mL of water;
time 5 h) does not produce
the previously
Oiels-Alder
reaction
yield of 0.1 (cf. Table lj.3 The biacetyl-sensitized cleanly,
as is evident
in the set of reaction i nsofar
has been found
of triplet-sensitized
photoexcitation
of 380 mg of potassium
of 2 proceeds
point
isomerization
(0.1 g) in benzene
irradiation
to the
decay of
have not been successful.
characteristically
Thus, selective
125 W high-pressure
crossing
for the radiationless
and that the products
may differ
of dianthrylethane
solution
15 oc; argon known
by biacetyl,
significantly,
Intersystem
has been
to bring about the photoisomeriza;ion
We have now found that the photochemical can be sensitized
[4+4] cyclo-
to the [4+4] cycloaddition
attempts
by acetophenone
state-l
responsible
2 by
and the reaction
spectra
as the isomerization
6129
from the exhibition
of an
(see fig. la). The formation
of linked anthracenes
by intra-
of
6130
---
300
4DO
Ml
500
450
550
600
650
rrn
Fig. 1. a: Reaction spectra of biacetyl-sensitized isomerization of 2 after 15 and 45 eec. b: Biacetyl phosphorescence quenching by 2. Insert: Stem-Volmer plot of quenching data. The calculated quenching constant is based on the quenching constant found for anthracene (cf. Bkkstriim, H.L.J.; Samins. K. Acta Chem. Stand. 1958, l2, 823).
molecular
Diels-Alder
sensitized
reaction
isomerizations
diffusion
isomerization
ethanes
by intramolecular
transfer.
triplet
fluorescence triplet
process
by Diels-Alder
energy
the excited
of biacetyl
controlled
triplet
quantum
state
yield suggests
due to benzoyl
excitation,
and by biacetyl
conceivable
Diels-Alder
dianthrylethanone [4+4]cyclomer solution isomers
so 7
as
and
in
by
products
6,
of
4, whose
crossing
in benzene
low
to the solution
to give 5 both upon direct
7
and
8
biaceLy1
(ratio 75:22).
sensiiized
(xexc
> 400
Irradiation
triplet
9 (q 0.036)
Only 3X of the iso-
to give 9. Direct
excitation
of
nm) gives 7, 8, and the of 6 in air-saturated
state species
does not give any of
as only cycloaddition
Note: hv
in terms of of dianthryl-
a 6 in benzene gives mainly (97%) the two
benzene
excited
yields
2 in a
photochemical
to be characteristic
intersystem
reaction
[4+4] cycloaddition
degassed
quench but
appear
setlsitization. Likewise,
9 in a ratio of 6:2:2. to
is explicable isomerizations
isomerizes
Diels-Alder
of dianthrylethanone
proceeds
enhanced
substitution,
and
to be unprecedented. by dianthrylethane
benzoyl-dianthrylethane
For example,
by intramolecular
merization
most likely
photochemical
[4+2] cycloaddition
state.
appear
is quenched
previously,4-7
(cf. Fig. lb), the sensitized
reaction
Moreover,
exclusively
isomerization
been observed
of dianthrylethanes
As the phosphorescence nearly
has rarely
product.
Depending
on
rate of heating, photoproducts
cycloreversion 200-220
Oc.
the
the
undergo
around
6131
2.
Fig.
Electron
spectra
of
10.
13.
and
J!L
7.
8,
+
6 Table
cyclomers
11,
7
8
in Benzene
‘PF : 0.20 0.002 <0.0001 Addition: 4+4 4+2 4+2 (80%); 4+4 (20%) (Pa : 0.26 0.005 o.ll(*) --------------------~---~_~--~___________-------_----_----__---____-___________ Sensitized: 4+2 4+2 4+2 (97%); 4+4 (3X) 0.1 0.007 (‘1 PR : ____~____~__~-~___~______-____---__----_________-___--_________________________ (*I Concentration-dependent quantum yield
appears borne
to govern out
molecular
ground terized
the course
in the excited geometry
state
is
high quantum
molecular
of their
triplet
state
by
overlapping spectrum
sensitization,9
yield
properties their
geometry
10
13 0.07 4+4 0.16
4+4 0.43
4+2 0.02
of dianthrylethanes
state reaction.
This feature
of chloro-dianthrylethanes substitution
(cf. Table
aromatic
moieties,
pattern.
from its
photoexcitation,
[4+4]cycloaddition the
Product +
hv
with fairly
molecular
sensitized:
ilb
geo-
Ratio lla : llb
_--_--__--__--_--------
direct exe: 68 : 32
lla
the
(10) is charac-
as is evident
1) to give 11. By contrast,
is
whose
For example,
(see Fig. Za). Upon direct 10 undergoes
by
0.013 4+4 0.39
of l,l', 5,5'-tetrachlorodianthrylethane
UV-absorption
and by biacetyl
state
affected
geometry
by partially
broadened
ground
14.
9
Deactivation of Electronically Excited Dianthrylethanes Fluorescence (‘Pf) and Cycloaddition (‘PS) _________________________-____----_----_-____________~_____-____-____----__---_ Compound: 2 4 6
the
and
+
1.
Interestingly,
12.
86 : 14
6132
metry
of the isomeric
4,4' ,5,5'-tetrachlorodianthrylethane that of the parent dianthrylethane 2, and should
resembles
anti-conformation, excited
state
as we conclude
properties
tion of 13 in benzene biacetyl
gives
sensitization
Diels-Alder products
adduct
from their similar
of 13 indeed
parallel
14 (cp 0.02).
most likely
those of 2. Direct
the [4+4] cycloaddition
of 13 leads
(13)"
be characterized by absorption spectra. The
to exclusive
'H-NMR spectral
product
formation
photoexcita-
12 (cp 0.161,
but of the intramolecular
data of the cycloaddition
are summarized
distinguishable
in Table 2. The Diels-Alder adducts also are easily from their isomeric [4+4] cycloadducts by their characteristic
1,2-dihydroanthracene
UV spectra
(see Fig. Zb; cf. ref. 5, 6,
and
7a).
Cl
h”
Slac.tyl
Table 2. 270 MHz ‘H-NHR Spectral Data of Isomeric in Oeuterated Chloroform (6, ppm downfield ____________________-_----_----___--_-----______~___--~~_---~~-----~---~~-----
Cycloadducts from TMS)
lla: llb: 12: 14:
7.17-6.70, m, 12 H; 5.06, s, 2 H; 3.76, m, 2 H; 7.10-6.75. m, 12 H; 5.15, 8, 2 H; 4.19, m. 2 H; 7.03-6.84, III, 12 H; 5.98, s. 2 H; 2.99, s, 4 H 8.18, 8, 1 Ii; 7.92-6.69, m, 9 H; 6.31, d, J=4.4 3~1.7 Hz, 1 H; 3.84, in, 1 H; 3.42, n, 1 H; 3.38, 3.27, ddd, 11.5, 4.4, 1.7 Hz, 1 H; 3.09, RI, 2 H ____________________--__----__---_-----_----_____---~__-----~----------------
In conclusion, proceed
triplet-sensitized
by [4+2] cycloaddition,
is such as to be characterized yields
of triplet-sensitized
unless
References and ---_______----__----
(1) (2) (3) (4)
(5) I;; (8) (9)
(11)
overlapping favored
2 2
12,
and
14
H H
5.45, Hz,
d 1’H;
of dianthrylethanes ground
conformation
s-systems.
The quantum
[4+4] cycloadditions
those of the corresponding
excited
;
of 10 to invoive
mainly
(>90%)
the excited
Compound 13, mp 343-344 C, was prepared by corresponding lepidopterene (Becker, H.-D.; J. Org. Chem. 1980, 2, 4549. see also ref. a) Eiouas-Laurent, H.; Castellan, A.; Desvergne, 1980, 52, 2633. b) Becker, H.-D.; Elebring, 1982, 47, 1064. c) Becker, H.-D.; Andersson,
(Received
in UK 1 October
1985)
singlet
are
singlet
Notes
a) Livingston, R.; Wei, K.S. .I. Am. Chem. Sot. 1967, 89, 3098. b) Manring, L.E.; Peters, K.S.; Jones, G., II; Bergmark, W.R. J. Am. Chem. Sot. 1985, 107, 1485; and references cited therein. Bergmark, W.R.; Jones, G., II Reinhardt, T.E.; Halpern, A.M. J. Am. Chem. Sac. 1976, m, 6665. Cf. Becker, H.-D.; Andersson, K. Tetrahedron Symposium, 1985, in press. Photochemical isomerization by intramolecular Diels-Alder reaction has been observed in the case of cis-dianthrylethylene (ref. 5), dimethyldianthrylethane (ref. 6), and dianthryldimethylsilane (-germane) (ref. Becker, H.-D.; Sandros, K.; Andersson, K. Anqew. Chem. 1983, 95, 507. Becker, H.-D.; Andersson, K. Tetrahedron Lett. 1983, 24, 3273. a) Daney, M.; Vanucci, C.; Desvergne, J.-P.; Bouas-Laurent, H. Tetrahedron c. 1985, 26, 1505. b) Sakurai, H.; et al. Chem. Lett. 1985, 497. The synthesis and photochemistry of 6 will be published in detail. Oxygen quenching experiments suggest the formation of 11 by direct
excitation (10)
1 H; 3~11.5
their low-energy
geometrically
high, and they exceed state reactions."
“, IA,
Hz, d,
isomerizations
by partially
remarkably
3.45, 2.94,
11,
7).
state.
thermolysis of the Andersson, K.; Sandros, K. 6). J.-P. Pure App 1. Chem. 1.; Sandros, K. J. Org. Chem. K. ibid. 1983, 48, 4552.