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Electron-transfer photooxygenation. 8. dicyanoanthracene-sensitized photooxidation of ortho-dimethoxybenzene
Tetrahedron Letters,Vo1.23,No.30,pp Printed in Great Britain
0040-4039/82/303039-04$03.00/O 01982 Pergamon Press Ltd.
3039-3042,1982
ELECTRON-TRANSFER
PHOTOOXYGENATION.
8.
DICYANOANTHRACENE-SENSITIZED PHOTOOXIDATION
OF ORTHO-DIMETHOXYBENZENE'
Jang-JengLiang and Christopher Department
of Chemistry, Los Angeles,
Two cleavage
Summary: muconate
products,
(2), are inefficiently
oxidation
dioxetane
in which superoxide
(3), which cleaves
to 2 and other
products
mimics
Although
to form (1).
cleavage
more
of ring-oxygenated
highly substituted
been reported3
that dimethoxylated
benzenes
to photosensitized
oxygenation
ly substituted
phenols are comparatively
the photooxidation essentially although
unreactive
esters
Photolysis' (-10m4M)
is rapidly
compounds
converted
are of interest to muconic
react with singlet oxygen,
as
acid
it has
3,5-di-t-butyl-1,2_dimethoxybenzene)
under the usual conditions.
In contrast,
Our recent
of organic
compounds
(g-DMB).
These compounds
sensitized
oxygenation.3*4c
is extremely
acetonitrile
inefficient,
of their spectra of irradiation
poorly characterized
and methanol
slowly destroys
A complex mixture
as a function
aromatic
compounds
mechanism
to form a
similar-
interest4
in the
led us to study
were reported
to be
We now report that,
some cleavage
of the ring
is observed. of oxygenated
and trans,trans-dimethylmuconate comparison
is 1, which
easy to photooxygenate.
in the cyanoaromatic
transfer
of phenols and catechols
photooxygenation
of dimethoxybenzenes
at room temperature
in benzene.
An electron
photo-
isomer is formed.
(in particular,
of ortho-dimethoxybenzene
the reaction
to muconic
(DCA) sensitized
product
-no cis-trans
cleavages
(DCA) sensitized
with ortho-dimethoxybenzene
The initial
are unreactive
9,10-dicyanoanthracene
(1) and trans,trans-dimethyl-
(c-DMB) in polar solvents.
ion (0;) combines
for dioxygenase-mediated
derivatives.'
of California, 90024
in the 9,10-dicyanoanthracene
under the conditions;
Studies of oxidative possible
University California
cis,cis-dimethylmuconate produced
of ortho-dimethoxybenzene
is proposed
S. Foote*
of products
solutions
is formed,
(2) were isolated
3039
was observed
from which cis,cis-dimethylmuconate
time are shown in Table I. is also present.
(-O.lM) and DCA
No reaction
by gas chromatography6
with those of known compounds.9
polar products
of o-DMB
the starting material.
and identified
(1) by
The yields of products l_ and 2
In addition,
a large amount of
The time course of the reaction
shows
3040
that the product
1 does not build up, but is destroyed
Product 2 is destroyed sensitizer,8 analogous (Scheme
more slowly.
to photooxygenate
to that proposed
I).
Radical
The inability
g-DMB
for cyanoaromatic
products.
the failure of ion pairs to separate effects observed
(which also makes methoxybenzenes
The factors which control
oxygenation
of reaction
in nonpolar
solvents,
The inefficiency
excellent
implies
quenchers
that back electron
reaction -* vs
leads us to propose a mechanism
the dioxetane
The absence
with aryl 01efins.~~
tion of other compounds4b)
sensitized
to yield
than it is created.
of Rose Bengal, a known singlet oxygen
under the same conditions
ion recombination
age leads to the observed
more rapidly
back electron
of aromatic
olefins
(2) and subsequent
ring cleav-
in benzene can be attributed
and is comparable
of the reaction,
even in acetonitrile
for the cyanoaromatic-sensitized transfer
predominates
transfer
to
to the solvent
oxida-
over reaction.
from the ions have not yet
been elucidated. Scheme
I DCA .L,
DCA*
o-DMB bb
electron
DCA' t g-DMB+ -+
transfer
DCA + g-DMB
C02CH3 2 As the formation dimethylmuconate oxygenation starting Table
After two hours irradiation
conditions.
had disappeared
is subsequently photooxidation
is, therefore,
isomerized
assumed
to the trans,trans
of dimethoxybenzene.
The isomerization
isomer
although
of DCA.
quantum
is well known in triplet-sensitized
isomerization
of two double
photooxygenation
destroyed
by DCA is interesting
have been detected.
absence
(34%) was observed
product and
is fast compared
to
in side reactions,
and was examined
carefully
was found at any stage of the No isomerization
bonds following
reactions,"'
(see isomer.
may be quite high.
No cis,trans-dimethylmuconateg
a few percent would
Although
reaction
90% of
of the trans,trans
(2) at a rate which
Both isomers are rapidly
of 1 and 2 sensitized
stages by NMR.
to be the primary
of cis,cis-
under the same photo-
of cis,cis-dimethylmuconate,
and trans,trans-dimethylmuconate
that the yield of the inital cleavage
at intermediate reaction,
(2) was examined
No cis,cis isomer was found after 4 hours irradiation
Cis,cis-dimethylmuconate
suggesting
3 photoisomerization
isomer was unexpected,
(1) and trans,trans-dimethylmuconate
material
II).
1 of the trans,trans
occurred
absorption
it is always accompanied
in the
of a single by isomeri-
3041
zation of one double tentative
working
Scheme
To explain
hypothesis
via two consecutive be required
bond.
the puzzling
that the isomerization
thermal
conrotatory
to substantiate
reactions
stereospecificity, proceeds
we suggest as a
on the radical
as shown in Scheme
cation
surface
Further work will
II.
this hypothesis.
II
Addition crease
Table
of trans-stilbene
in the rate of g-DMB
I.
DCA Sensitized
TiiazG
Conversia
Time(hrs
CH3CN
to the photooxygenation
disappearance;
Photooxygenation
of o-DMB (%) CH30H
results
in a slight
Yielc
Yiel CH3CN
CH3CN
0
0
0.37
-a--
0
5
4.25
----
0 ____
0
of
CH30H 0
0
0
2
0
_____
2.72
_____
_____
____
5.13
0
-_---
3.84
mm---
0
4.97
6.80
15.04
4.01
0.88
7.28
7.38
28.46
5.84
6.45
0.75
5.28
7.14
22.99
2.89
10.71
0.74
4.00
7.52
20.31
----
0.64
_____
7.12
_____
Isomerization
of Cis,Cis-'
7
____
0.77
8
9.21
____
10
5.24
4.51
12
9.84
14
17
5.07
in-
this phenomenon.
of g-DMB
T
0
20
mixture
work is being done to examine
16.60
*Based on reacted c-DMB.
Table
II.
DCA Sensitized
rradlatlon Time(hrs)
Conversion of l(X)
and Trans,Trans-' Yield of of 2. (%)
0
0
0
2
90
34
4
97
34.8
dimethylmuconate
3042
References: 1.
2.
Paper no 7:
L.E. Manring,
M.K. Kramer and C.S. Foote, J. Phys. Chem.,
J.J-Liang
thanks
Supported
by NSF Grants CHE77-21560
the government
a) 0. Hayaishi,
"Oxygenases",
b)
H. Matsushima,
T. Matsuura,
of the Republic
of China for fellowship
New York:
Academic
Press, 1962;
S. Kato and I. Saito, Tetrahedron,
I. Saito and T. Matsuura,
4.
a)
J. Eriksen, C.S. Foote and T.L. Parker, J. Am. Chem. Sot., 2,
b)
J. Eriksen
c)
J. Eriksen and C.S. Foote, J. Am. Chem. Sot.,
d)
D.S. Steichen
All of these
Tetrahedron
Lett.,
2,
5119
( 1972).
4987 (1970); see also ref. 2b. 6455
(1977 1;
and C.S. Foote, J. Phys. Chem., 82, 2659 (1978);
102, 6083 (1980);
and C.S. Foote, J. Am. Chem. Sot.,
photolyses
103, 1855 (1981).
were carried out at room temperature
with a CuS04 filter solution reaction
support.
and CHE80-20141.
3.
5.
in press.
and oxygen
of 1,1-diphenylethylene
bubbling
with a 1200 W mercury
at various times
under comparable
conditions
(see Table
is complete
I).
lamp The
in 30 minutes
(see ref. 4~). 6. 7.
UCW-98 column. Cis,cis-dimethylmuconate oxidation in ether.
was obtained
of phenol with peracetic Trans,trans-muconic
by treating
acid
cis,cis-muconic
[C.A. 26, 2970
acid is commercially
acid,
(prepared
by
(1932)], with diazomethane
available
and was also methylated
with diazomethane. 8.
R.W. Denny and A. Nickon, Molecular
9.
Compared
Photochemistry",
Reactions,
Menlo Park, CA:
20, 133 (1973); N.J. Turro, Benjamin/Cummings,
with the NMR spectra of cis,trans-dimethylmuconate.
acid was prepared 10.
Organic
as described
Y.C. Butt, A.K. Singh, and references
by J.A. Elvidge,
B.H. Barett,
cited therein.
(Received in USA 3 May 1982)
"Modern
1978; p.587. Cis,trans-muconic
et. al., J. Chem Sot., 2235 (1950).
R.S.H. Liu, J. Phys. Chem., g,
2091-2097
(1981)
0040-4039/82/303039-04$03.00/O 01982 Pergamon Press Ltd.
3039-3042,1982
ELECTRON-TRANSFER
PHOTOOXYGENATION.
8.
DICYANOANTHRACENE-SENSITIZED PHOTOOXIDATION
OF ORTHO-DIMETHOXYBENZENE'
Jang-JengLiang and Christopher Department
of Chemistry, Los Angeles,
Two cleavage
Summary: muconate
products,
(2), are inefficiently
oxidation
dioxetane
in which superoxide
(3), which cleaves
to 2 and other
products
mimics
Although
to form (1).
cleavage
more
of ring-oxygenated
highly substituted
been reported3
that dimethoxylated
benzenes
to photosensitized
oxygenation
ly substituted
phenols are comparatively
the photooxidation essentially although
unreactive
esters
Photolysis' (-10m4M)
is rapidly
compounds
converted
are of interest to muconic
react with singlet oxygen,
as
acid
it has
3,5-di-t-butyl-1,2_dimethoxybenzene)
under the usual conditions.
In contrast,
Our recent
of organic
compounds
(g-DMB).
These compounds
sensitized
oxygenation.3*4c
is extremely
acetonitrile
inefficient,
of their spectra of irradiation
poorly characterized
and methanol
slowly destroys
A complex mixture
as a function
aromatic
compounds
mechanism
to form a
similar-
interest4
in the
led us to study
were reported
to be
We now report that,
some cleavage
of the ring
is observed. of oxygenated
and trans,trans-dimethylmuconate comparison
is 1, which
easy to photooxygenate.
in the cyanoaromatic
transfer
of phenols and catechols
photooxygenation
of dimethoxybenzenes
at room temperature
in benzene.
An electron
photo-
isomer is formed.
(in particular,
of ortho-dimethoxybenzene
the reaction
to muconic
(DCA) sensitized
product
-no cis-trans
cleavages
(DCA) sensitized
with ortho-dimethoxybenzene
The initial
are unreactive
9,10-dicyanoanthracene
(1) and trans,trans-dimethyl-
(c-DMB) in polar solvents.
ion (0;) combines
for dioxygenase-mediated
derivatives.'
of California, 90024
in the 9,10-dicyanoanthracene
under the conditions;
Studies of oxidative possible
University California
cis,cis-dimethylmuconate produced
of ortho-dimethoxybenzene
is proposed
S. Foote*
of products
solutions
is formed,
(2) were isolated
3039
was observed
from which cis,cis-dimethylmuconate
time are shown in Table I. is also present.
(-O.lM) and DCA
No reaction
by gas chromatography6
with those of known compounds.9
polar products
of o-DMB
the starting material.
and identified
(1) by
The yields of products l_ and 2
In addition,
a large amount of
The time course of the reaction
shows
3040
that the product
1 does not build up, but is destroyed
Product 2 is destroyed sensitizer,8 analogous (Scheme
more slowly.
to photooxygenate
to that proposed
I).
Radical
The inability
g-DMB
for cyanoaromatic
products.
the failure of ion pairs to separate effects observed
(which also makes methoxybenzenes
The factors which control
oxygenation
of reaction
in nonpolar
solvents,
The inefficiency
excellent
implies
quenchers
that back electron
reaction -* vs
leads us to propose a mechanism
the dioxetane
The absence
with aryl 01efins.~~
tion of other compounds4b)
sensitized
to yield
than it is created.
of Rose Bengal, a known singlet oxygen
under the same conditions
ion recombination
age leads to the observed
more rapidly
back electron
of aromatic
olefins
(2) and subsequent
ring cleav-
in benzene can be attributed
and is comparable
of the reaction,
even in acetonitrile
for the cyanoaromatic-sensitized transfer
predominates
transfer
to
to the solvent
oxida-
over reaction.
from the ions have not yet
been elucidated. Scheme
I DCA .L,
DCA*
o-DMB bb
electron
DCA' t g-DMB+ -+
transfer
DCA + g-DMB
C02CH3 2 As the formation dimethylmuconate oxygenation starting Table
After two hours irradiation
conditions.
had disappeared
is subsequently photooxidation
is, therefore,
isomerized
assumed
to the trans,trans
of dimethoxybenzene.
The isomerization
isomer
although
of DCA.
quantum
is well known in triplet-sensitized
isomerization
of two double
photooxygenation
destroyed
by DCA is interesting
have been detected.
absence
(34%) was observed
product and
is fast compared
to
in side reactions,
and was examined
carefully
was found at any stage of the No isomerization
bonds following
reactions,"'
(see isomer.
may be quite high.
No cis,trans-dimethylmuconateg
a few percent would
Although
reaction
90% of
of the trans,trans
(2) at a rate which
Both isomers are rapidly
of 1 and 2 sensitized
stages by NMR.
to be the primary
of cis,cis-
under the same photo-
of cis,cis-dimethylmuconate,
and trans,trans-dimethylmuconate
that the yield of the inital cleavage
at intermediate reaction,
(2) was examined
No cis,cis isomer was found after 4 hours irradiation
Cis,cis-dimethylmuconate
suggesting
3 photoisomerization
isomer was unexpected,
(1) and trans,trans-dimethylmuconate
material
II).
1 of the trans,trans
occurred
absorption
it is always accompanied
in the
of a single by isomeri-
3041
zation of one double tentative
working
Scheme
To explain
hypothesis
via two consecutive be required
bond.
the puzzling
that the isomerization
thermal
conrotatory
to substantiate
reactions
stereospecificity, proceeds
we suggest as a
on the radical
as shown in Scheme
cation
surface
Further work will
II.
this hypothesis.
II
Addition crease
Table
of trans-stilbene
in the rate of g-DMB
I.
DCA Sensitized
TiiazG
Conversia
Time(hrs
CH3CN
to the photooxygenation
disappearance;
Photooxygenation
of o-DMB (%) CH30H
results
in a slight
Yielc
Yiel CH3CN
CH3CN
0
0
0.37
-a--
0
5
4.25
----
0 ____
0
of
CH30H 0
0
0
2
0
_____
2.72
_____
_____
____
5.13
0
-_---
3.84
mm---
0
4.97
6.80
15.04
4.01
0.88
7.28
7.38
28.46
5.84
6.45
0.75
5.28
7.14
22.99
2.89
10.71
0.74
4.00
7.52
20.31
----
0.64
_____
7.12
_____
Isomerization
of Cis,Cis-'
7
____
0.77
8
9.21
____
10
5.24
4.51
12
9.84
14
17
5.07
in-
this phenomenon.
of g-DMB
T
0
20
mixture
work is being done to examine
16.60
*Based on reacted c-DMB.
Table
II.
DCA Sensitized
rradlatlon Time(hrs)
Conversion of l(X)
and Trans,Trans-' Yield of of 2. (%)
0
0
0
2
90
34
4
97
34.8
dimethylmuconate
3042
References: 1.
2.
Paper no 7:
L.E. Manring,
M.K. Kramer and C.S. Foote, J. Phys. Chem.,
J.J-Liang
thanks
Supported
by NSF Grants CHE77-21560
the government
a) 0. Hayaishi,
"Oxygenases",
b)
H. Matsushima,
T. Matsuura,
of the Republic
of China for fellowship
New York:
Academic
Press, 1962;
S. Kato and I. Saito, Tetrahedron,
I. Saito and T. Matsuura,
4.
a)
J. Eriksen, C.S. Foote and T.L. Parker, J. Am. Chem. Sot., 2,
b)
J. Eriksen
c)
J. Eriksen and C.S. Foote, J. Am. Chem. Sot.,
d)
D.S. Steichen
All of these
Tetrahedron
Lett.,
2,
5119
( 1972).
4987 (1970); see also ref. 2b. 6455
(1977 1;
and C.S. Foote, J. Phys. Chem., 82, 2659 (1978);
102, 6083 (1980);
and C.S. Foote, J. Am. Chem. Sot.,
photolyses
103, 1855 (1981).
were carried out at room temperature
with a CuS04 filter solution reaction
support.
and CHE80-20141.
3.
5.
in press.
and oxygen
of 1,1-diphenylethylene
bubbling
with a 1200 W mercury
at various times
under comparable
conditions
(see Table
is complete
I).
lamp The
in 30 minutes
(see ref. 4~). 6. 7.
UCW-98 column. Cis,cis-dimethylmuconate oxidation in ether.
was obtained
of phenol with peracetic Trans,trans-muconic
by treating
acid
cis,cis-muconic
[C.A. 26, 2970
acid is commercially
acid,
(prepared
by
(1932)], with diazomethane
available
and was also methylated
with diazomethane. 8.
R.W. Denny and A. Nickon, Molecular
9.
Compared
Photochemistry",
Reactions,
Menlo Park, CA:
20, 133 (1973); N.J. Turro, Benjamin/Cummings,
with the NMR spectra of cis,trans-dimethylmuconate.
acid was prepared 10.
Organic
as described
Y.C. Butt, A.K. Singh, and references
by J.A. Elvidge,
B.H. Barett,
cited therein.
(Received in USA 3 May 1982)
"Modern
1978; p.587. Cis,trans-muconic
et. al., J. Chem Sot., 2235 (1950).
R.S.H. Liu, J. Phys. Chem., g,
2091-2097
(1981)