Photooxygenation in polystyrene beads with covalently and non-covalently bound tetraarylporphyrin sensitizers

Article abstract of DOI:10.1002/adsc.200303181

Two reaction protocols are described which involve the use of polymer supports as reaction media for photooxygenation processes: 1) The use of polystyrene beads (PS) loaded with tetraphenyl- (TPP) or tetratolylporphyrin (TTP), swollen with the substrate in an appropriate organic solvent and subsequent irradiation under air. Products were isolated simply by dissolution in alcoholic solvents and filtration. 2) Covalently linked tetrastyrylporphyrin in polystyrene-divinylbenzene beads were synthesized by emulsifier-free emulsion polymerization and directly used for the photooxygenation protocol described above. The latter alternative allows also the use of less polar solvents for the extraction of the oxygenation products from the polymer beads. From the sensitizer loading degree, an optimal substrate/sensitizer molar ratio of 1,000-2,000 was determined and recyclization is possible for at least five times resulting in a minimum turnover number (with respect to the sensitizer TTP) of 5 × 10⁴ (after five cycles). Both approaches were applied to the ene reaction of singlet oxygen with citronellol (1), the regioisomeric pinenes 3 and 5, and the allylic alcohols 9a - c, respectively, as well as to the [4 + 2]-cycloadditions of singlet oxygen to sorbinol (7) and the chiral diene 11.

Full text of DOI:10.1002/adsc.200303181

FULL PAPERS
Photooxygenation in Polystyrene Beads with Covalently and
Non-Covalently Bound Tetraarylporphyrin Sensitizers
Axel G. Griesbeck,* Tamer T. El-Idreesy, Anna Bartoschek
Institute of Organic Chemistry, University of Cologne, Greinstr. 4, 50939 Kˆln, Germany
Fax: ( ‡ 49)-221-470-5057, e-mail: griesbeck@uni-koeln.de
Received: October 18, 2003; Accepted: January 28, 2004
Abstract: Two reaction protocols are described which ucts from the polymer beads. From the sensitizer
involve the use of polymer supports as reaction media loading degree, an optimal substrate/sensitizer molar
for photooxygenation processes: 1) The use of poly- ratio of 1,000 ± 2,000 was determined and recycliza-
styrene beads (PS) loaded with tetraphenyl- (TPP) or tion is possible for at least five times resulting in a
tetratolylporphyrin (TTP), swollen with the substrate minimum turnover number (with respect to the
4
in an appropriate organic solvent and subsequent sensitizer TTP) of 5 Â 10 (after five cycles). Both
irradiation under air. Products were isolated simply approaches were applied to the ene reaction of singlet
by dissolution in alcoholic solvents and filtration. 2) oxygen with citronellol (1), the regioisomeric pinenes
Covalently linked tetrastyrylporphyrin in polystyr- 3 and 5, and the allylic alcohols 9a ± c, respectively, as
ene-divinylbenzene beads were synthesized by emul- well as to the [4 ‡ 2]-cycloadditions of singlet oxygen
sifier-free emulsion polymerization and directly used to sorbinol (7) and the chiral diene 11.
for the photooxygenation protocol described above.
The latter alternative allows also the use of less polar Keywords: allylic alcohols; cycloaddition; ene reac-
solvents for the extraction of the oxygenation prod- tion; photooxygenation; singlet oxygen
Introduction
complete atom economy can be reached and both
oxygen atoms incorporated in the final products.[ The
10]
Type II photooxygenation reactions involve the first energy source for activating molecular oxygen is simply
1
1
electronically excited singlet state of oxygen ( D - O ), visible light and, thus, photooxygenation is one of the
g
2
which is formed by energy transfer either from a singlet archetype reactions feasible also for solar chemistry
[
11]
or a triplet excited sensitizer molecule or by chemical applications.
In order to use photonic energy for
methods.[ In contrast to type I photooxygenation converting ground-state into reactive oxygen species,
radical type) or type III photooxygenation (electron long-wavelength light absorbing dyestuffs can be used
1]
(
transfer induced, either involving the reaction between which are widely distributed in nature.
substrate cation radicals and triplet oxygen or the
reaction of superoxide radical anion), singlet oxygen
reactions are highly selective and show all kinetic Approaches to the Problem
properties of pericyclic reactions.[ The most important
2]
[
3]
[4]
reaction modes are the ene reaction, the [4 ‡ 2]- and It has been recognized in recent years that in spite of the
[
5]
1
the [2 ‡ 2]-cycloaddition, as well as heteroatom oxi- favorable reactivity pattern of O , condensed phase
2
[
6]
dation (e.g., sulfide to sulfoxide). The first three photooxygenation conditions suffer from at least five
reaction modes represent efficient synthetic routes to major drawbacks: a) the sensitizer dye must be soluble in
a broad variety of oxyfunctionalized products. For the respective solvent, thus limiting the dye-solvent
practical purposes, singlet oxygen is generated in combinations which can be used, b) removal of the dye
solution phase by photochemical triplet-triplet sensiti- from the product after the reaction either by chroma-
zation from appropriate dyestuffs. For all relevant tography or distillation is often an elaborate process, c)
solvents, a variety of sensitizers is known and well singlet oxygen has its longest lifetimes in environ-
characterized concerning their chemical stability and mentally problematic solvents such as halogenated
[
7]
[12]
singlet oxygen quantum yields. From the standpoint of hydrocarbons (tetrachloromethane, freons, etc.), d)
green chemistry,[ photooxygenation appears to be the photobleaching of the dye is often observed in halo-
8]
most promising oxidation route: the sole oxygen source genated solvents due to the formation of acid or is
1
is natural triplet oxygen and, in contrast to hydrogen induced by O itself or other oxygenated reactive
2
[
9]
peroxide with a maximum atom efficiency of 47%,
intermediates, especially when long reaction times are
Adv. Synth. Catal. 2004, 346, 245 ± 251
DOI: 10.1002/adsc.200303181
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245

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Axel G. Griesbeck et al.
necessary,[13] e) solution purging with pure oxygen is [4 ‡ 2]-cycloadditions is described now in detail in this
highly problematic for industrial applications and some- contribution and, additionally, the synthesis and appli-
times also for small-scale laboratory syntheses. A global cation of insoluble polymer-bound, sensitizer-loaded,
solution to all these problems is desirable in order to nanosized particles as containers for solvent-free type II
make photooxygenation a real green chemical process. photooxygenation are described and compared with the
Another challenge for the singlet oxygen community is results of solution photochemistry. A highly important
to make ™chiral singlet oxygen∫, i.e., to modify the industrial application of singlet oxygen ene reactions is
reaction environment in such a way that matrix effects the photooxygenation of citronellol as a route to the
[
29]
might imprint stereochemical information in type II fragrant chemical specialty rose oxide, and thus this
reactions.
reaction is used as one of the model process.
In order to meet these requirements, several solutions
have been considered. Direct activation of triplet oxy-
gen has been described for zeolite irradiation in the Results and Discussion
[
14]
presence of adsorbed alkenes, presumably through
[
15]
low-energy oxygen-alkene CT complexes. The regio- The solubilty of the excellent singlet oxygen sensitizers
selectivity of singlet oxygen ene-reactions can be of the meso-tetraarylporphyrin-type (e.g., f ˆ 0.89 for
D
[
16]
[30]
modified in the supercages of NaY zeolites,
a
TPP in benzene) is low in aprotic polar solvents and
phenomena which has been widely explored in the last even lower in protic solvents. Therefore, the best way for
years.[ Photooxygenation of an alkene in the presence product isolation from the crude reaction mixture is
ofephedrine as chiral inductor was performed in an NaY extraction with a protic solvent such as ethanol or
zeolite yielding hydroperoxides with low enantioselec- methanol. On the other hand, tetrarylporphyrins and
tivities.[ In these cases, the singlet oxygen sensitizers hematoporphyrins are known to quench singlet oxy-
17]
18]
[
31]
are simply co-adsorbed in the zeolite supercages. Like- gen, and thus must not be applied in high concen-
wise, sensitizer molecules can be incorporated into trations in solution where they tend to dimer formation
[
19]
nafion membranes, an approach which enables the and increased singlet oxygen quenching. Two solutions
spatial separation of dye and substrate. The use of were developed in our group to circumvent these
microcontainers (micelles, vesicles) for photochemical problems in reaction processing: 1) the microcontainer
transformations has also been recently explored for approach where substrate and sensitizer are dissolved in
[
20]
photooxygenations. In contrast to these approaches, the polystyrene matrix and irradiated in the presence of
polymer-bound sensitizers have been developed quite air, and 2) the use of polymer-bound tetrarylporphyrin-
[
21]
early, initially with polystyrene-bound rose bengal.
sensitizers with the substrate likewise dissolved in the
Recently, numerous variations have been reported, e.g., matrix and irradiated. These processes are described
ionic porphyrins immobilized on cationically function- below in detail.
alized polystyrene as photosensitizers,[22] pyrylium salts
immobilized on Merrifield resins as electron-transfer
sensitizers,[ polystyrene-bound benzophenones as im- Polystyrene Matrix with Adsorbed Singlet Oxygen
23]
[
24]
mobilized triplet photosensitizers,
photosensitizers Sensitizer
[
25]
ionically bound at polymeric ion exchanging resins,
polymer-bound ruthenium(II) complexes, and poly- The singlet oxygen photooxygenation is performed with
[
26]
ethylene glycol supported tetra(hydroxyphenyl)-substi- the organic substrate embedded in commercially avail-
tuted porphyrins.[
27]
able polystyrene-divinylbenzene beads (60 Æ 15 mm di-
The combination of a microreactor system as the ameter unswelled). The non-polar sensitizer (para-
reaction medium and visible light as reagent offers a new substituted meso-tetraarylporphyrins or the parent
and convenient approach towards green photochemis- meso-tetraphenylporphyrin TPP) for the generation of
try, where not only the production of side products is singlet oxygen was transferred in catalytic amounts into
retarded as a result of the enhanced selectivity but also the polystyrene network by swelling the resin with a
the use of microcontainers reduces the amounts of solution of the sensitizer in dichloromethane (or in
environmentally problematic and expensive solvents. secondary cycles also with ethyl acetate) and subsequent
The term microcontainer refers to organized and con- evaporation of the solvent. As investigated in detail, the
strained media which provide microcavities and/or polystyrene beads change their space structures while
surfaces to accommodate the substrates and allows the swelling with a non-polar solvent. After swelling with
reaction to take place. In a recent communication, we ethyl acetate, an average bead diameter of 120 Æ 25 mm
have described the use of tetraarylporphyrin sensitizers was determined by optical microscopy (Figure 1).[ In
embedded in a commercially available polystyrene- the polystyrene-matrix, the sensitizer to substrate molar
divinylbenzene (PS-DVB) copolymer as reaction me- ratio was typically 1:1000, but also ratios as low as
[
32]
33]
[
28]
dium for photooxygenation reactions.
The experi- 1:5000 were still effective. The substrate was transferred
mental protocol for singlet oxygen ene reactions and to the polymer beads by the same procedure. Depending
246
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Adv. Synth. Catal. 2004, 346, 245 ± 251

Photooxygenation in Polystyrene Beads with Tetraarylporphyrin Sensitizers
FULL PAPERS
on the polarity and the volatility of the substrate, the Polystyrene Matrix with Covalently Linked Singlet
polystyrene beads can be loaded with 80 ± 120 wt %. Oxygen Sensitizer
After evaporation of the excess solvent, a layer of sandy
solid was obtained which was irradiated in a loosely For the second approach, tetrakis(4-ethenylphenyl)por-
covered petri dish by means of a sodium street lamp or a phyrin (tetrastyrylporphyrin, TSP) was synthesized[
halogen lamp without external cooling or purging with and copolymerized with styrene and divinylbenzene
oxygen. After irradiation, the product was extracted (DVB). The technique used therefore is emulsifier-free
from the polymer beads by repeated washing with emulsion polymerization, allowing the synthesis of the
ethanol. Due to the extreme low solubility of meso- resin particles readily and with high reproducibility. The
tetraarylporphyrins in more polar solvents the sensitizer TSP-PS-DVB resin beads are translucent nanoparticles
37]
[
38]
stayed nearly completely in the solid support and the (size range 150 ± 300 nm). The polymer beads shows
substrate loading process could be repeated. The load- high mechanical stability and behave as inexpensive,
ing, photolysis and the unloading process were repeated highly efficient and resistant sensitizers. They show (like
five times with citronellol (1) without noticeable sensi- other commercial polystyrene resins) high loading
tizer bleaching or decreasing of the efficiency. Citronel- capacity due to the large surface area. They are also
lol gave the hydroperoxide mixture 2a:2b in 95 ± 98% easily and efficiently recycled with photooxygenation
yields without need for purification in the same regio- turnover numbers up to 3000 without any sensitizer
and stereoisomeric composition as in non-polar solvents bleaching or bleeding. It is especially worthy of mention
(
Scheme 1). Under solvent-free conditions the degree of that the polymer matrix was stable even against the
conversion was comparable to the solution photoox- potential oxidants produced during the photooxygena-
ygenation in tetrachloromethane. We investigated sev- tion (hydroperoxides or endoperoxides). The solvent-
eral additional examples for the ene-reaction and [4 ‡ free photooxygenation procedure using the polymer-
2
]-cycloaddition and found that in many cases the bound sensitizer follows the same protocol as with the
reactivity and selectivity behavior are identical to those non-covalently bound sensitizer.
of solution photochemistry: the highly reactive a-pinene In order to explore the potential of the new TSP-PS-
gave the allylic hydroperoxide 4 in excellent yields and DVB solvent-free photooxygenation procedure and
3
the singlet oxygen [4 ‡ 2]-cycloaddition with sorbinol identify its influence on the chemo-, regio- and stereo-
(
5)[ proceeded with high yields and negligible sub- selectivity pattern in the type II photooxygenation
34]
strate loss in the polystyrene matrix. The regiochemistry reaction, the same substrates for both ene and [4 ‡ 2]-
of the singlet oxygen addition to mesitylol (9a) was cycloaddition reactions with singlet oxygen have been
unaffected by the polymer support, however, the investigated as described above for the polystyrene
diastereoselectivity of this hydroxy-directed ene reac- resin with non-covalently bound sensitizer. The dia-
tion[ showed to be strongly dependent on the environ- stereoselectivity of both the ene and [4 ‡ 2]-cyclo-
35]
1
ment: the syn:anti-ratio changed from 1.5:1 in ethanol, addition reactions of O was investigated using the
2
3
:1 in polystyrene to 10:1 in tetrachloromethane, chiral allylic alcohols 9a ± c and the chiral dienol 11,[36]
indicating strong intermolecular hydrogen-bonding be- respectively. The photooxygenation of 9a ± c (Table 1)
tween substrate (9a) molecules in the unpolar matrix. yielded the syn-hydroxy allylic hydroperoxide as the
The chiral diene alcohol 11 gave the endoperoxides syn- major diastereoisomers referring to the hydroxy-di-
and anti-11[ in acceptable yields but low diastereose- recting effect of O in the conformationally fixed (by
36]
1
2
1
,3
[35]
lectivity. Even less reactive substrates like b-pinene (3)
A-strain) substrates. Both the polymer-bound as
and ethyl tiglate[ were transformed into the corre- well the free sensitizer systems gave similar diaster-
28]
sponding allylic hydroperoxides with complete conver- eoselectivity (with the polymer-bound sensitizer some-
sion.
what higher), however considerably lower than in non-
polar solvents (photooxygenation of 9a in CCl pro-
4
ceeds with a diastereoselectivity of 93%). Intermolec-
ular hydrogen-bonding between the highly concen-
trated substrates molecules in both microcontainer
systems accounts for the decrease in diastereoselectiv-
ity; this assumption was further supported by the fact
that photooxygenation of 9a in a rose bengal/cellulose
acetate film (showing additional intermolecular hydro-
gen-bonding between the matrix and the substrates)
results in even lower diastereoselectivity (dr: syn:anti
7
0:30) in comparison with the photooxygenation
Figure 1. Left: TTP-loaded polystyrene beads (swollen with
EtOAc and treated with 1) in a petri dish, irradiated with a
carried out either in the sensitizer-bound or free
halogen lamp; right: polymer beads with substrate (1) and sensitizer PS-DVB matrices.[ In order to estimate
39]
TPP (PS-DVP-TPP), average bead diameter 120 mm.
the percentage of TSP covalently bound in the TSP-PS-
Adv. Synth. Catal. 2004, 346, 245 ± 251
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Axel G. Griesbeck et al.
Scheme 1. Photooxygenation of substrates in polystyrene (PS) matrices.
DVB resin, two parallel photooxygenation reactions lently linked dyestuff) an average loading degree of
À1
were run using identical amounts of the synthesized 1 ±2 mmol g is adjusted.
TSP-PS-DVB resin and the commercially available PS-
DVB copolymer (loaded with a given amount of the
sensitizer). Both reactions were carried out under Conclusion
identical reaction conditions using identical amounts
of 9b. From the comparison of the degrees of con- In summary, two effective, environmentally friendly
version in both experiments, a loading degree of 0.1% protocols for type II (singlet oxygen) photooxygenation
TSP in the polystyrene resin was determined. For both reactions were developed. The new solvent-free method
reaction setups (adsorbed porphyrins as well as cova- utilizes only atmospheric oxygen as oxidant and a
248
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Photooxygenation in Polystyrene Beads with Tetraarylporphyrin Sensitizers
FULL PAPERS
Table 1. Singlet oxygen ene reaction with the chiral allylic
alcohols 9a ± c.
135.0 (d, 1C, COOHCHˆCH); characteristic signals for 2b: d ˆ
16.9/17.0 (q, 1C, C CH ) 19.4/19.5 (q, 1C, CHCH ), 24.2/24.3 (t,
q
3
3
1
C, COOHCH ) 28.3/29.2 (d, 1C, CHCH ), 32.5/32.7 (t, 1C,
2
3
Entry
R
TSP-PS-DVB
Commercial
COOHCH CH ), 39.3/39.5 (t, 1C, CH CH OH), 60.8 (t, 1C,
CH OH), 89.4/89.8 (d, 1C, CHOOH), 113.8/114.2 (t, 1C,
C ˆCH ), 143.7/143.9 (s, 1C, C ).
2
2
2
2
dr (syn:anti)[
a]
PS-DVB-TPP
2
dr (syn:anti)[
a]
q
2
q
(
3,6-Dihydro-6-methyl-1,2-dioxin-3-yl)methanol
(8):[34]
a
b
c
CH3
Et
i-Pr
81: 19
78: 22
82: 18
75: 25
77: 23
81: 19
1
H NMR (300 MHz, CDCl ): d ˆ 1.13 (dd, J ˆ 6.7 Hz, J ˆ
3
1
.32 Hz, 3H, CH ), 3.78 (m, 1H, CH OH), 3.60 (m, 1H,
3 2
CH OH), 4.37 (m, 1H, CH OHCH), 4.72 (m, 1H, CHCH ),
2
2
3
[
a]
dr values were calculated by 1H NMR from the crude
reaction mixture.
5.79 (m, 1H, CH CHCHˆCH), 5.89 (m, 1H, CHˆCHCHCH );
2
3
1
3
C NMR (75.5 MHz, CDCl ): d ˆ 17.5 (q, 1C, CH ), 63.0 (d,
3
3
1
C, COH), 74.3 (d, 1C, CH CH), 79.7 (d, 1C, CH OHCH),
3 2
1
22.9 (d, 1C, CH CHCH), 131.2 (d, 1C, CHCHCH ).
1
2
3
-(6-Methyl-3,4-dihydro-[1,2]dioxin-3-yl)-ethanol (12):[36]
synthetic porphyrin-linked resin as reaction medium.
Sensitizer characterization and application on different
substrates were discussed and compared with solution
photooxygenation and other commercial polystyrene
resin systems.
Diastereoisomeric ratio ˆ 1.1:1; signal assignments by peak
1
13
1
intensities and H- C-COSY. Major diastereomer: H NMR
(
300 MHz, CDCl ): d ˆ 1.21 (d, J ˆ 5.1 Hz, 3H, CH CHOO),
3
3
1
4
.22 (d, J ˆ 6.4 Hz, 3H, CHOHCH ), 4.07 (m, 1H, CHOH),
3
.20 (m, 1H, CHOHCH), 4.69 (dq, J ˆ 6.8 Hz, 1.8 Hz, 1H,
1
3
CHˆCHCHCH ), 5.99 (m, 2H, CHˆCH);
CNMR
3
(
75.5 MHz, CDCl ): d ˆ 17.8 (q, CH CHOO), 19.0 (q,
3
3
CH CHOH), 68.2 (d, COH), 74.3 (d, CH CHOO), 81.6 (d,
Experimental Section
TPP (meso-tetraphenylporphyrin) and TTP (meso-tetrakis-4-
methylphenylporphyrin) were purchased from Porphyrin
Systems. Polystyrene beads (1% divinylbenzene copolymer,
3
3
CHOHCH), 122.7 (d, CHˆCHCHCH ), 130.9 (d,
3
1
CHˆCHCHCH ). Minor diastereomer: H NMR (300 MHz,
3
CDCl ): d ˆ 1.14 (d, J ˆ 6.7 Hz, 3H, CH CHOO), 1.19 (d, J ˆ
3
3
4
.9 Hz, 3H, CHOHCH ), 3.96 (m, 2H, CHOHCH), 4.78 (dq,
3
100 ± 200 mesh) were purchased by Acros Organics.
J ˆ 6.7 Hz, 1.3 Hz, 1H, CHˆCHCHCH ), 5.86 (m, 1H,
3
1
3
CHˆCHCHCH ), 5.90 (m, 1H, CHˆCHCHCH ); CNMR
3
3
(
75.5 MHz, CDCl ): d ˆ 17.3 (q, CH CHOO), 18.0 (q,
3
3
General Procedure for Route 1: Photooxygenation of
Citronellol (1)
CH CHOH), 69.9 (d, CHOH), 74.2 (d, CH CHOO), 83.2 (d,
CHOHCH), 123.2 (d,
CHˆCHCHCH ).
3
3
CHˆCHCHCH ), 130.9 (d,
3
3
A slurry of 3 g of polystyrene beads with a solution of 2 mg (3 Â
À3
10
mmol) of tetraphenylporphyrin and 780 mg of citronellol
(
1, 5 mmol) in 30 mL of dichloromethane was dispensed on a
petri dish (Æ19 cm). The excess solvent was evaporated by 5,10,15,20-Tetrakis(4-ethenylphenyl)-21H,23H-
leaving the petri dish for a few minutes in a well ventilated porphine (tetrastyrylporphyrin, TSP)
hood. The sandy solid which was obtained was irradiated for
TSP could be synthesized either by Wittig reaction of
5
h inthe looselycovered petri dish by asodium street lamp or a
5
,10,15,20-tetrakis(4-formylphenyl)porphyrin (prepared from
halogen lamp without external cooling and without external
oxygen purging. The polymer beads were subsequently rinsed
with 3 Â 20 mL of ethanol and filtered. After evaporation of
the solvent, the product was obtained as a 1:1.1 mixture of the
two regioisomers 2a,b; yield: 900 mg (96%). The residual
polystyrene beads could be used for five additional photo-
oxygenations; advantageously, ethyl acetate was used instead
of dichloromethane for all further photooxygenation reactions.
[37]
terephthalaldehyde and pyrrole) with methyltriphenylphos-
phonium bromide or by dehydrohalogenation of 5,10,15,20-
tetrakis-[4-(2-haloethyl)-phenyl]porphyrin (prepared from 4-
2-haloethyl)benzaldehyde and pyrrole).[ The latter process
41]
(
appeared advantageous because of higher yields and better
reproducibility.
(E)-7-Hydroperoxy-3,7-dimethyloct-5-en-1-ol (2a) and 6-
hydroperoxy-3,7-dimethyloct-7-en-1-ol (2b): 1.2:1 mixture of
regioisomers, 2b as a 1:1 mixture of diastereoisomers (esti-
Polymerization of Tetrastyrylporphyrin with Styrene
and Divinylbenzene
13
[40] 1
mated from the CNMR signal intensities):
H NMR
(
(
300 MHz, CDCl ): d ˆ 0.85 (d, J ˆ 6.5 Hz, 3H, CHCH ), 0.87
Deionized water (200 mL), acidified to pH ˆ 2.3 with sulfuric
acid, was purgedwith nitrogen and heated to 708Cfor 20 min in
a 500-mL three-necked flask equipped with stopper, reflux
condenser and gas inlet. Subsequently, 10 g of styrene, 100 mg
of divinylbenzene and 10 mg of TSP were added rapidly and
the system was sealed in order to prevent contamination with
air. While the mixture was being vigorously stirred, 120 mg of
potassium peroxodisulfate in 10 mL of water were added at
once. After a polymerization period of 7 h, the reaction
mixture was quenched with 200 mL of methanol and then
cooled to room temperature. The polymer particles were
3
3
d, J ˆ 6.4 Hz, 3H, CHCH ), 1.2 ± 1.7 (m, 10H,CH CHCH ),
3
2
2
3
6
5
1
.64 (m, 4H, CH OH); characteristic signals for 2a: d ˆ 1.29 [s,
2
H, COOH(CH ) ], 5.51 (d, J ˆ 15.8 Hz, 1H, COOHCHˆCH),
3
2
.63 (m, 1H, COOHCHˆCH); characteristic signals for 2b: d ˆ
.65 (s, 3H, C CH ). 1.95 (m, 2H, COOHCH ), 4.24 (m, 1H,
q
3
2
1
3
CHOOH), 4.95 (s, 2 H, C ˆCH ); CNMR (75.5 MHz,
q
2
CDCl ): characteristic signals for 2a: d ˆ 19.7 (q, 1C,
3
CHCH ), 28.0 (d, 1C, CH CH), 29.5 [q, 2C, CH(CH ) ], 38.9
3
3
3 2
(
t, 1C, CHˆCHCH ), 39.7 (t, 1C, CH CH OH), 60.8 (t, 1C,
2
2
2
CH OH), 81.9 (s, 1C, COOH), 129.8 (d, 1C, COOHCHˆCH),
2
Adv. Synth. Catal. 2004, 346, 245 ± 251
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¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
249

FULL PAPERS
Axel G. Griesbeck et al.
separated by centrifugation at 3500 rpm, washed with meth-
ylene chloride several times to remove any free (non-poly-
merized) TSP, and dried at 408Cunder vacuum to afford the
polymer-bound sensitizer; yield: 4.2 g (42%).
[5] a) W. Adam, M. Heil, T. Mosandl, C. R. Saha-Mˆller, in:
Organic Peroxides, (Ed.: W. Ando), Wiley, New York,
1992, pp. 221 ± 254; b) A. L. Baumstark, A. Rodriguez,
Handbook of Organic Photochemistry and Photobiology,
(
Eds.: W. M. Horspool, P.-S. Song), CRC Press: Boca
Raton, 1995, pp. 335 ± 345.
General Procedure for Route 2: Photooxygenation of
5
[6] E. L. Clennan, Acc. Chem. Res. 2001, 34, 875 ± 884.
[7] F. Wilkinson, W. P. Helman, A. B. Ross, J. Phys. Chem.
Ref. Data 1995, 24, 663 ± 1021.
8] P. T. Anastas, J. C. Warner, Green Chemistry, Theory and
Practice, Oxford University Press, Oxford, 1998.
-Methylhex-4-en-3-ol (9b)[
42]
The dye-cross-linked polymer beads (0.60 g) were added into a
petri dish (14 cm diameter) and treated with 20 mL methylene
chloride, subsequently with 0.50 g of 5-methylhex-4-en-3-ol
[
[
9] See the excellent discussion by Noyori: R. Noyori, M.
Aoki, K. Sato, Chem. Commun. 2003, 1977 ± 1986.
(
4.5 mmol) dissolved in 20 mL ethyl acetate and the excess
solvent was evaporated. The petri dish was covered with a glass
plate and irradiated with a 150 W halogen lamp for 42 h. The
product was extracted with 2 Â 30 mL of methanol and filtered.
After evaporation of the solvent and purification by column
chromatography, the hydroperoxide 10b was isolated; yield:
[10] W. Adam, M. Braun, A. G. Griesbeck, V. Lucchini, E.
Staab, B. Will, J. Am. Chem. Soc. 1989, 111, 203 ± 212.
[11] a) P. Esser, B. Pohlmann, H.-D. Scharf, Angew. Chem.
Int. Ed. Engl. 1994, 33, 2009 ± 2023; b) K.-H Funken, J.
Ortner, Z. Phys. Chem. 1999, 213, 99 ± 105.
[12] Lifetime data in halogenated solvents are described in an
extensive database: http://allen.rad.nd.edu/compilations/
SingOx/table1/t1.htm.
13] Higher photostability was observed with perfluoroalkyl-,
see: S. G. DiMagno, P. Dussault, J. A. Schultz, J. Am.
Chem. Soc. 1996, 118, 5312 ± 5313 and dichlorophenyl-,
see: H. Quast, T. Dietz, A. Witzel, Liebigs Ann. 1995,
0
.44 g (69%); dr (syn:anti) ˆ 78:22. Syn-diastereoisomer:
1
H NMR (300 MHz, CDCl ): d ˆ 0.89 (t, 3H, J ˆ 7.42 Hz,
3
CH CH ), 1.17 ± 1.52 (m, 2H, CH CH ), 1.65 (s, 3H, CH ),
2
3
2
3
3
3
8
.52 (ddd, 1H, J ˆ 8.53, 8.53, 3.24 Hz, CH-OH), 4.12 (d, 1H, J ˆ
1
3
.53 Hz, CH-OOH), 4.97 (m, 2H,ˆCH ); CNMR (75.5 MHz,
2
[
CDCl ): d ˆ 9.5 (q, CH CH ), 17.7 (q, CH Cˆ), 25.4 (t, CH ),
3
2
3
3
2
7
1.7 (d, CH-OH), 93.4 (d, CH-OOH), 116.3 (t,ˆCH ), 141.5 (s,
2
1
Cq). Anti-diastereoisomer: H NMR (300 MHz, CDCl ): d ˆ
3
0
.90 (t, 3H, J ˆ 7.42 Hz, CH CH ), 1.17 ± 1.52 (m, 2H,
2
3
1
495 ± 1501, substituted porphyrine photosensitizers.
[14] F. Blatter, H. Sun, S. Vasenkov, H. Frei, Catalysis Today
998, 41, 297 ± 309.
CH CH ), 1.73 (s, 3H, CH ), 3.65 (m, 1H, CH-OH), 4.27 (d,
2
3
3
1
3
1
(
H, J ˆ 4.55 Hz, CH-OOH), 5.00 (m, 2H, ˆCH ); CNMR
2
1
75.5 MHz, CDCl ): d ˆ 10.2 (q, CH CH ), 19.2 (q, CH Cˆ),
3
2
3
3
[
15] S. Vasenkov, H. Frei, J. Phys. Chem. B. 1997, 101, 4539 ±
4543.
16] J. Shailaja, J. Sivaguru, R. J. Robbins, V. Ramamurthy,
R. B. Sunoj, J. Chandrasekhar, Tetrahedron 2000, 56,
24.9 (t, CH ), 72.1 (d, CH-OH), 91.3 (CH-OOH), 115.1 (t,
2
ˆ
CH ), 141.2 (s, Cq).
2
[
6
927 ± 6943.
Acknowledgements
[
17] E. L. Clennan, Molecular and Supramolecular Photo-
chemistry, (Eds: V. Ramamurthy, K. S. Schanze), Marcel
Dekker, Inc., New York, Basel, 2003, Vol. 9, pp. 275 ±
308.
Financial support from the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie is greatly acknowl-
edged.
[
[
18] A. Joy, R. J. Robbins, K. Pitchumani, V. Ramamurthy,
Tetrahedron Lett. 1997, 38, 8825 ± 8828.
19] a) C.-H. Tung, J.-Q. Guan, J. Am. Chem. Soc. 1998, 120,
References and Notes
1
1874 ± 11879; b) D. Zhang, L.-Z. Wu, Q.-Z. Yang, X.-H.
Li, L.-P. Zhang, C.-H. Tung, Org. Lett. 2003, 3221 ± 3224.
20] C.-H. Tung, L.-Z. Wu, L-P. Zhang, H.-R. Li, X.-Y. Yi, K.
Song, M. Xu, Z.-Y. Yuan, J.-Q. Guan, H.-W. Wang, Y.-M.
Ying, X.-H. Xu, Pure Appl. Chem. 2000, 71, 2289 ± 2298.
21] A. P. Schaap, A. L. Thayer, E. C. Blossey, D. C. Neckers,
J. Am. Chem. Soc. 1975, 97, 3741 ± 3745.
22] J. J. Inbaraj, M. V. Vinodu, R. Gandhidsan, R. Muruge-
san, M. Padmanabhan, J. Appl. Polymer Sci. 2003, 89,
3925 ± 3930.
[23] J. Mattay, M. Vondenhof, R. Denig, Chem. Ber. 1989,
122, 951 ± 958.
[24] J. L. Bourdelande, J. Font, F. Sachez-Ferrando, Can. J.
Chem. 1983, 61, 1007 ± 1016.
[
1] a) A. A. Frimer, (Ed.), Singlet Oxygen, CRC Press, Boca
Raton, Fl, 1985; b) H. H. Wasserman, R. W. Murray,
Organic Chemistry, Vol. 40: Singlet Oxygen, Academic
Press, New York, 1979; c) B. Ranby, J. F. Rabeck, Singlet
Oxygen Reactions with Organic Compounds and Poly-
mers, Wiley, Chichester, New York, 1978.
2] a) J.-M. Aubry, B. Mandard-Cazin, M. Rougee, R. V.
Benasson, J. Am. Chem. Soc. 1995, 117, 9159 ± 9164;
b) A. G. Griesbeck, M. Fiege, M. S. Gudipati, R. Wagner,
Eur. J. Org. Chem. 1998, 2833 ± 2838.
3] A. G. Griesbeck, T. T. El-Idreesy, W. Adam, O. Krebs,
CRC Handbook of Organic Photochemistry and Photo-
biology, (Eds.: W, M. Horspool, F. Lenci), CRC Press:
Boca Raton, 2004, 8/1 ± 8/20.
4] W. Adam, S. Bosio, A. Bartoschek, A. G. Griesbeck,
CRC Handbook of Organic Photochemistry and Photo-
biology, (Eds.: W. M. Horspool, F. Lenci), CRC Press:
Boca Raton, 2004, 25/1 ± 25/19.
[
[
[
[
[
[
[25] R. Gerdes, O. Bartels, G. Schneider, D. Wˆhrle, G.
Schulz-Ekloff, Polym. Adv. Technol. 2001, 12, 152 ± 160.
[26] M. Suzuki, O. Bartels, R. Gerdes, G. Schneider, D.
Wˆhrle, G. Schulz-Ekloff, M. Kimura, K. Hanabusa, H.
Shirai, Phys. Chem. Chem. Phys. 2000, 2, 109 ± 114 .
250
¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2004, 346, 245 ± 251

Photooxygenation in Polystyrene Beads with Tetraarylporphyrin Sensitizers
FULL PAPERS
[
[
[
27] M. Benaglia, T. Danelli, F. Fabris, D. Sperandio, G. Pozzi,
Org. Lett. 2002, 4, 4229 ± 4232.
28] A. G. Griesbeck, A. Bartoschek, Chem. Commun. 2002,
[34] A. A. Trabanco, A. G. Montalban, G. Rumbles, A. G. M.
Barrett, B. M. Hoffman, Synlett 2000, 1010 ± 1012.
[
35] A. G. Griesbeck, W. Adam, A. Bartoschek, T. T. El-
Idreesy, Photochem. Photobiol. Sci. 2003, 2, 877 ± 881.
36] W. Adam, M. Prein, Acc. Chem. Res. 1996, 29, 275 ± 283.
37] A. Osuka, B.-L. Liu, K. Maruyama, Chem. Lett. 1993,
1
594 ± 1595.
29] a) G. Ohloff, E. Klein, G. O. Schenck, Angew. Chem.
961, 73, 578; b) W. Pickenhagen, D. Schatkowski
Dragoco Gerberding & Co AG), Ger. Offen. DE
9645922 A1, 1998.
30] C. Tanielian, L. Golder, C. Wolff, J. Photochem. 1984, 25,
17 ± 125.
31] a) R. Schmidt, H.-D. Brauer J. Am. Chem. Soc. 1987,
09, 6976 ± 6981; b) C. Tanielian, G. Heinrich, A. En-
[
[
1
(
1
9
49 ± 952.
[
38] A. G. Griesbeck, T. T. El-Idreesy, M. Antonietti, unpub-
lished results.
[
[
[
[
39] A. G. Griesbeck, A. Bartoschek, unpublished results.
40] H NMR data are published only for the corresponding
1
1
allylic alcohols: G. Ohloff, B. Lienhard, Helv. Chim. Acta
1
1
965, 48, 182 ± 189.
tezami, J. Chem. Soc. Chem. Commun. 1988, 1197 ± 1198.
32] D. C. Sherrington, Chem. Commun., 1998, 2275 ± 2286.
33] A. Griesbeck, A. Bartoschek, R. Strey, L. Belkoura,
unpublished results.
[
41] A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher,
[
[
J. Assour, L. Korsakoff, J. Org. Chem. 1967, 32, 476.
[42] Analogous procedure: A. G. Griesbeck, T. T. El-Idreesy,
M. Fiege, R. Brun, Org. Lett. 2002, 4, 4193 ± 4195.
Adv. Synth. Catal. 2004, 346, 245 ± 251
asc.wiley-vch.de
¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
251