Efficient photocatalytic oxygenation of alkenes by water soluble sensitizer in organic-water biphasic media

Article abstract of DOI:10.1142/S1088424616500577

A new green, environmentally and economically photooxygenation of olefins by molecular oxygen in the presence of 4-carboxyl tetra phenyl porphyrin (H₂TCPP), Rose Bengal (RB), Methylene Blue (MB) and some metallosensitizers (MS) such as cobalt phthalocyaninesulfonate (Coph(SO₃H)₄), MnTCPPCl, FeTCPPCl and SbTPP(OH)₂ as water-soluble sensitizers in organic-water biphasic media at room temperature under visible light was illustrated. The products were obtained with 100% conversion by H₂TCPP and 100% selectivity by Coph(SO₃H)₄. Also in this study, singlet oxygen production as the major route for oxidation of olefins was proved.

Full text of DOI:10.1142/S1088424616500577

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2016; 20: 1–7
DOI: 10.1142/S1088424616500577
Published at http://www.worldscinet.com/jpp/
Efficient photocatalytic oxygenation of alkenes by water
soluble sensitizer in organic–water biphasic media
Mahdi Hajimohammadi* and Hoda Ghasemi
Faculty of Chemistry, Kharazmi University, G. C, Mofateh, Tehran 14911-15719, Iran
Received 1 February 2016
Accepted 18 February 2016
ABSTRACT: A new green, environmentally and economically photooxygenation of olefins by molecular
oxygen in the presence of 4-carboxyl tetra phenyl porphyrin (H2TCPP), Rose Bengal (RB), Methylene
Blue (MB) and some metallosensitizers (MS) such as cobalt phthalocyaninesulfonate (Coph(SO3H)4),
MnTCPPCl, FeTCPPCl and SbTPP(OH)2 as water–soluble sensitizers in organic–water biphasic media at
room temperature under visible light was illustrated. The products were obtained with 100% conversion
by H2TCPP and 100% selectivity by Coph(SO3H)4. Also in this study, singlet oxygen production as the
major route for oxidation of olefins was proved.
KEYWORDS: olefine photooxygenation, singlet oxygen, water-soluble porphyrins, biphasic media,
green chemistry.
its by-product is H2O which is green and sustainable)
INTRODUCTION
is also interesting [11]. However spin rule forbids
Oxygenated compounds are useful synthetic
reaction of air/O2 with hydrocarbon. For this purpose,
intermediate in the laboratory and in industries [1–6].
photochemical reactions applied use porphyrins and
Many reactions have been studied for conversion of
MSs as regent require efficient energy to convert air/3O2
alkanes to corresponding oxygenated products [7]. The
to singlet oxygen/1O2, as an active regent [12]. The
popular conventional method to achieve carboxylic
key issues for using air/O2 as an oxidizing regent are
acids is Jones reagent [8] and epoxidation of alkenes
applying porphyrins and light that cause oxygen to
is carried out by peracids and alkyl peroxides [9].
change to active species for oxidation [13].
Although, all these methods have one or some of
Porphyrins and MSs complexes have received great
disadvantages such as the requirement of strong
attention, due in part to their direct relevance to many
acidic or basic conditions, stoichiometric or super
biological systems. The photosensitized production
stoichiometric amounts of costly or hazardous oxidizing
of singlet oxygen has significance in the areas of the
agents, heavy-metal toxicity and high-temperature [10].
photooxidation of organic compounds, DNA damage,
At the century of industrialization, global warming
and photodynamic therapy [13, 14]. Therefore a variety
and environmental pollution, using renewable energy,
of photosensitizers have been developed and their
in the chemical industry to environmentally friendly
photochemical and photo-physical properties have been
approach is important. For achieving this magnificent
extensively studied [15]. There are two main factors
goal, solar energy which is abundant, clean and safe can
which dictate the photo-activity of porphyrin sensitizers:
be used. However, molecular oxygen using as cheap
(i) quantum yields of the excited triplet states and its
and economical regent for oxidation or epoxidation in
photooxygenation reaction without no by-product (or
3
singlet oxygen generation from ground state O2 and
(ii) stability toward oxidative degradation (photo-
bleaching) [16]. In our previous studies, we introduced
*Correspondence to: Mahdi Hajimohammadi, email: hajimoh-
ammadi@khu.ac.ir, tel: +98 21-888-329-220-3, fax: +98 21-888-
308-57
efficient systems for the aerobic oxidation of alcohols,
aldehydes and alkenes under visible light or sunlight
[11, 14c, 17].
Copyright © 2016 World Scientific Publishing Company

2
M. HAJIMOHAMMADI AND H. GHASEMI
OH
+
O
EXPERIMENTAL
Sen, hv
O
+
O2
Cyclohexene, cyclooctene, a-methyl styrene, cis-
stilbene, manganese(II) chloride (MnCl2 ·4H2O), iron(II)
chloride and solvents were purchased from Fluka and
Merck and used without further purification. RB and MB
purchased from Fluka. 4-carboxyl tetra phenyl porphyrin
(H2TCPP), FeTCPPCl and MnTCPPCl, Coph(SO3H)4
and SbTPP(OH)2 were synthesized according to the
literature [18]. For photooxygenation of olefins, 2 cc
water-soluble photosensitizer (1 × 10-3 M) H2TCPP,
MnTCPPCl, FeTCPPCl, Coph(SO3H)4, RB, MB,
SbTPP(OH)2 and 4.9 × 10-3 mol cyclohexene, 3.83 × 10-3
mol cyclooctene, 2.8 × 10-3 mol cis-stilbene, 3.8 × 10-3
mol a-methylstyrene) were added to 10 cc acetonitrile
and 5 cc water (2 acetonitrile:1 water) in a test tube.
Reactions were irradiated with the sun simulator light
(288 power LED lamps, 1 W, 2.3 V (59660 LUX)) for
64 h at room temperature under 1 atm of bubbling of air
in the solution. The stability of sensitizers was monitored
by UV-vis (Shimadzu 2100 spectrophotometer) during
the reaction by following soret intensity of porphyrin and
MS. At the end of the reaction, products were analyzed by
OH
+
O
Sen, hv
O2
O
+
+
CHO
Sen, hv
O2
Sen, hv
O2
+
OOH
O
O
Scheme 1. Photooxidation of different olefins in the presence of
H2TCPP in organic–water media
The current study develops the photocatalytic
oxygenation of alkenes by using air under visible
light irradiation with water soluble photosensitizers
in organic–water biphasic media at room temperature
(Schemes 1 and 2).
a
I
I
O
I
O
b
O
I
N
+
CH3
COO-
Cl
H3C
N
S
N
CH3
CH3
Cl
Cl
Cl
R1
R2
R2
R4
R4
R3
R4
R3
R3
R4
R3
R1
R5
R5
R2
d
R2
N
M
N
N
H
R5
R5
R1
R1
c
N
N
N
N
R1
R1
H
N
R5
R5
R2
R2
R4
R4
R5
R5
R1
R1
R3
R1
R3
R2
R2
R3
R2
R3
R4
R4
2
HO
M
N
N
N
N
N
N
N
3
f
1
M
N
e
N
N
N
OH
4
N
R4
R3
a: Rose Bengal
b: Methylene Blue
c: H2TCPP:
e: SbTPP(OH)2 : 1=2=3=4= ph
f: Coph(SO3H)4 : R1=R2=R3=R4=SO3H
R3 =COOH , R1=R2=R4=R5=H
M=Sb
M=Co
d: MnTCPPCl: R3=COOH, R1=R2=R4=R5=H
FeTCPPCl: R3= COOH, R1=R2=R4=R5=H
M=Mn
M=Fe
Scheme 2. Structure of different water soluble photosensitizers in photooxygenation of alkenes in acetonitrile–water media
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 2–7

EFFICIENT PHOTOCATALYTIC OXYGENATION OF ALKENES BY WATER SOLUBLE SENSITIZER
3
Thermo Quest Finnigan AQA GC-MS. For investigation
interrupted (Table 1 entry 6). Therefore, the presence of
a porphyrin, light and O2 are essential for the conversion
alkenes to corresponding products (Table 1 entry 1).
Throughout the photolysis, this was also studied
in modified solvent mixtures with variable water to
acetonitrile ratios, and high conversion was observed in 2
acetonitrile:1 water media (Table 2).
High turnover number (TON) of the photooxygenation
of alkenes to corresponding products was observed with
H2TCPP in the presence of visible light (Table 3 entry 1).
It is clear that this reaction proceed under solar radiation
because the spectral distribution curve of a fluorescent lamp
is similar to that of sunlight (Table 3 entry 2).
of mechanism of photooxygenation of alkenes, 4.9 ×
10-3 mol cyclohexene was added to 2.5 × 10-3 mol 30%
H2O2 by using UV light from a high pressure 500 W
mercury lamp (l = 200–280 nm) in 2 acetonitrile: 1 water
for generation of OH· [19]. Also 0.44 gr of KO2 dissolved
in dried DMSO and added to 4.9 × 10-3 mol cyclohexene
for generation of O2- [20].
RESULTS AND DISCUSSION
Photooxygenation of cyclohexene was investigated as
a typical standard sample to evaluate the different factors
involved in the reactions (Table 1). It is important to note
that the oxidation of substrate stopped in the absence of
porphyrin (Table 1 entry 5) or when the irradiation was
Figure 1 shows the reaction of cyclohexene vs. time in
an oxygenated solution of CH3CN: H2O under visible light
irradiation in the presence of H2TCPP. The Soret band of
Table 1. Photooxygenation of cyclohexene in different reaction conditions
Entry
Condition
Conversion, %
1a
2
Cyclohexene + light + air + H2TCPP
Cyclohexene + light + air + DMSO + H2TCPP
Cyclohexene + light + air + NaN3- + H2TCPP
Cyclohexene + light + H2TCPP
Cyclohexene + light + air
100
22.89
22.59
8.32
Trace
Trace
0
3
4
5
6
Cyclohexene + air + H2TCPP
Cyclohexene+ OH·
Cyclohexene + O2·-
7b
8c
9d
0
Cyclohexene + H2O2
0
a 2 × 10-6 mol H2TCPP, 4.9 × 10-3 mol cyclohexene, air (1 atm) and 288 power LED
lamps, 1 W, 2.3 V (59660 LUX) in 2 acetonitrile: 1 water biphasic media. b OH•
produced from photolysis of 2.5 × 10-3 mol 30% H2O2 with using light from a high
pressure 500 W mercury lamp in 2 acetonitrile: 1 water biphasic media (l = 200–
280 nm) [19]. c O2·- was prepared by dissolving K2O in dried DMSO [20]. d 4 mmol
30% H2O2 dissolved in the reaction solution for generation of hydrogen peroxide.
Table 2. Solvent mixtures with variable water to acetonitrile for cyclohexene photooxygenationa
Entry
Solvent ratio Selectivity, %
Selectivity, % Selectivity, % Conversion, %
(H2O:CH3CN)
OH
O
O
1b
1:2
44.83
41.75
13.40
100
2c
3d
2:1
1:1
100
—
—
—
17.18
7.87
90.59
9.41
a 2 × 10-6 mol H2TCPP, 4.9 × 10-3 mol cyclohexene, air (1 atm) and 288 power LED lamps,
1 W, 2.3 V (59660 LUX). b 10 mL CH3CN and 5 mL H2O. c 5 mL CH3CN and 10 H2O. d 7.5 mL
CH3CN and 7.5 mL H2O.
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 3–7

4
M. HAJIMOHAMMADI AND H. GHASEMI
Table 3. Effect of photosensitizer on the cyclohexene photooxygenationa
Entry
Photosensitizers
Selectivity, %
Selectivity, %
Selectivity, %
Conversion, %
TONb
TOFc
OH
O
O
1
2d
3
H2TCPP
H2TCPP
44.83
Trace
100
41.75
77.09
—
13.40
10.80
—
100
2450
2250
2050
1800
1500
1250
140
38.28
35.15
32.03
28.12
23.43
19.53
2.18
88.72
85.46
73.5
Coph)((( (So3H()
)
4
4
Rose Bengal
Methylene Blue
SbTPP(OH)2
MnTCPPCL
74.61
100
25.38
—
—
5
—
63.83
48.32
5.79
6
100
—
—
7
100
—
—
8
FeTCPPCL
Trace
—
—
Trace
Trace
Trace
a 2 cc sensitizer 1 × 10-3 M, 4.9 × 10-3 mol cyclohexene, air (1 atm) and 288 power LED lamps, 1 W, 2.3 V (59660 LUX) in 2
acetonitrile:1 water media). b Turn over number of the catalyst. c Turn over frequency of catalyst (h-1). d sunlight (91000LUX).
Fig. 1. (a) Time vs. conversion percent of cyclohexene, degradation percent and absorption of H2TCPP in cyclohexene
photooxygenation. (b) UV-vis spectra of H2TCPP degradation
hv
3Sen*
the H2TCPP was followed at 414 nm with UV-vis method.
This method showed that sensitizer bleaching for H2TCPP
was complete after 64 h in our reaction conditions.
After the disappearance of the porphyrin Soret band, the
formation of the oxidation products stopped.
Sen
1O2
Type II
According to the literature, there are two major
pathways for photooxygenation reaction in the presence of
non-metal sensitizers, Type I and Type II (Scheme 3) [21].
For investigation of the type I mechanism, we performed
our reactions in the presence H2O2, OH· and O2·-. In the
presence of these reactive oxygen species, the rates of
reaction significantly decreased (Table 1 entry 7–9).
Singlet oxygen generation (Type II) and its reaction
with the substrates is the foremost mechanism that occurs
in our circumstances, since conversions of cyclohexene
obey the order of H2TCPP > MnTCPPCl>FeTCPPCl.
Sen
A
+
3O2
Type I
Sen +O2
OH + H2O2
Scheme 3. The mechanisms for producing reactive oxygen
species in the presence of non-metallosensitizers
Paramagnetic metals are claimed to quench singlet
oxygen by energy transfer mechanism from oxygen
to the low-lying d electron levels and have very short
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 4–7

EFFICIENT PHOTOCATALYTIC OXYGENATION OF ALKENES BY WATER SOLUBLE SENSITIZER
5
Table 4. Photooxygenation of alkenes in organic–aqua mediaa
Entry
Substrate
Selectivity, %
Conversion, %
Time, h
TON
TOF
8.28
O
44.84
OH
4.9 × 10-3 mol
1
2
100
64
450
41.75
O
13.40
3.83 × 10-3 mol
O
0.8
98.33
192
626.66
3.26
OH
9
O
90.10
2.8 × 10-3 mol
3.8 × 10-3 mol
CHO
3
4
44.32
73.58
304
304
310
675
11.02
22.22
100
O
9.92
O
64.14
OOH
25.91
a 2 × 10-6 mol H2TCPP and 0.5 cc substrate, air (1 atm) and 288 power LED lamps, 1 W, 2.3 V (59660 LUX).
triplet lifetimes (Table 3, entry 7, 8) [22]. In addition,
in the presence of N3 , which is a well-known singlet
To check the generality of this method, the oxidation
of photocatalytic oxidation of cyclooctene, cis-stilbene
and a-methyl styrene with H2TCPP were accomplished
(Table 4).
-
oxygen scavenger [23] (Table 1, entry 3) conversion was
-
inhibited. In the presence of NaN3 degradation of the
porphyrin sensitizers was also inhibited. Table 1 entry
2 indicates that in the presence of DMSO conversion of
cyclohexene considerably diminished. According to the
literature for the m-THPC (5,10,15,20-tetra (m-hydroxy-
phenyl)chlorin) sensitizer, the singlet oxygen lifetime in
DMSO is 19 ms compared to 65 ms in acetonitrile [24].
It is interesting Coph(SO3H)4 was the best sensitizer for
selectivity in organic–aqua media (Table 3, entry 3).
Olefins bearing aromatic substituents are also not as
much reactive because their allylic forms are to smaller
extent stable [25]. Based on the variation in the oxidation
products, production of singlet oxygen in our reaction
condition and the literature the proposed mechanism
of O2 reactions with substrates are shown in Scheme 4
[26]. Also the proposed mechanism for the Coph(SO3H)4
sensitizer is presented in Scheme 5 [16c].
1
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 5–7

6
M. HAJIMOHAMMADI AND H. GHASEMI
(n=6, 8)
(m=10, 14)
CnHm
O
n
OH
+
sen
+
3O2
1O2
OH
hv
O
n
H
O
OH
o
+
n
n
n
n
H
o
n
n
CHO
O2
O
2
hv
O
Scheme 4. Photooxygenation mechanism of alkenes by molecular oxygen in the presence of none-metallated photosensitizers under
visible light in acetonitrile: water biphasic media
Acknowledgements
Co +3
O
O
We gratefully acknowledge support from the Kharazmi
university.
Co +2
O
O2
1/2
+
hv
Co +3
O
Co +3
REFERENCES
1. Nishiyama Y, Nakagawa Y and Mizuno N. Angew.
Chem., Int. Ed. 2001; 40: 364.
2. Jiang W, Gordenand JD and Goldsmith CR. Inorg.
Chem. 2012; 51: 2725.
Scheme 5. Proposed mechanism for photooxygenation of
cyclohexene with Coph(SO3H)4 in organic–aqua biphasic
media
3. Wong OA and Shi Y. Chem. Rev. 2008; 108: 3958.
4. Song WJ, Seo MS, George SD, Ohta T, Song R,
Kang MJ, Tosha T, Kitagawa T, Solomon EI and
Nam W. J. Am. Chem. Soc. 2007; 129: 1268.
5. Bawaked S, Dummer NF, Bethell D, Knight DW
and Hutchings G. J. Green. Chem. 2011; 13: 127.
6. Sienel G, Rieth R and Rowbottom KT. Ullmann’s
encyclopedia of organic chemicals, Wiley VCH:
Weinheim, 1999.
7. (a) Hollingworth GJ. In Comprehensive Organic
Functional Group Transformations, Vol. 5, Katritzky
AR, Meth-Cohn O, Rees CW and Pattenden G.
(Eds.) Elsevier Science: Oxford, 1995; pp. 23.
CONCLUSION
In the present study, we applied an organic–aqua
media for photooxygenation of alkenes with reasonable
and good conversion, in the presence of water soluble
sensitizer by type II mechanism for generation of singlet
oxygen. H2TCPP as none metal photosensitizer was the
finest photo catalyst for conversion of cyclohexene to
oxygenated products. Also Coph(SO3H)4 was the optimal
catalyst for conversion of cyclohexene to cyclohexene
oxide in organic–aqua media.
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 6–7

EFFICIENT PHOTOCATALYTIC OXYGENATION OF ALKENES BY WATER SOLUBLE SENSITIZER
7
(b) Hudlicky M. In Oxidations in Organic Chemistry,
15. Redmond RW and Gamlin JN. Photochem. Photo-
biol. 1999; 70: 391.
ACS Monograph Series 186, American Chemical
Society: Washington, DC, 1990; p. 174. (c) Larock
RC. In Comprehensive Organic Transformations, A
Guide to Functional Group Preparations, 2nd ed.,
Wiley-VCH: New York, 1999; pp. 1653. (d) Smith
MB and March J. Advanced Organic Chemistry:
Reactions, Mechanisms, and Structure, 5th ed.,
Wiley-Interscience: New York, 2001; pp. 917–919.
(e) Sheldon RA and Van Bekkum H. In Fine Chemi-
cals through Heterogeneous Catalysis, Wiley-VCH
Verlag GmbH & Co.: Weinheim, 2001.
16. Bonchio M, Carofiglio T, Carraro M, Fornasier R
and Tonellato U. Org. Lett. 2002; 4: 4635.
17. (a) Hajimohammadi M, Mofakham H, Safari N and
Manesh AM. J. Porphyrins Phthalocyanines 2012;
16: 93. (b) MehrabiKalajahi SS, Hajimohammadi
M and Safari N. Reac. Kinet. Mech. Cat. 2014; 113:
629. (c) Hajimohammadi M, Safari N, Mofakham
H and Shaabani A. Tetrahedron Lett. 2010; 51:
4061. (d) Hajimohammadi M, Safari N, Mofakham
H and Deyhimi F. Green Chem. 2011; 13: 991.
(e) Hajimohammadi M, Schwarzinger C and Knorr
G. RSC. Advances 2012; 2: 3257.
18. (a) Adler AD and Longo FR. J. Am. Chem. Soc.
1964; 843: 145. (b)Yan GP, Bischa D and Bottle SE.
Free Rad. Boil. Med. 2007; 43: 111. (c) Kulinich
VP, Shaposhnikov GP and Badaukaite RA. Macro-
heterocycles 2010; 3: 23. (d) Kno¨r G. Chem. Bio.
Chem. 2001; 2: 593.
8. (a) Bowden K, Heilbron IM, Jones ERH and
Weedon BCL. J. Chem. Soc. 1946; 39. (b) Heil-
bron I, Jones ERH and Sondheimer F. J. Chem. Soc.
1949; 604. (c) Bladon P, Fabian JM, Henbest HB,
Koch HP and Wood GW. J. Chem. Soc. 1951; 2402.
(d) Curtis RG, Heilbron I, Jones ERH and Woods
GF. J. Chem. Soc. 1953; 457. (e) Bowers A, Hal-
sall TG, Jones ERH and Lemin AJ. J. Chem. Soc.
1953; 2548. (f) Djerassi C, Engle RR and Bowers
A. J. Org. Chem. 1956; 21: 1547.
19. Aschengrau D, Diamant Y and Rabani J. Environ.
Sci. Technol. 2007; 41: 7486.
9. (a) Swern D. Organic peroxides, Wiley: New York
1972. (b) Hiatt R (1971) In Oxidation, Augustine RL
and Trecker DJ. (Eds.) Marcel Dekker: New York.
(c) Othmer K. Encyclopedia of chemical technology,
Wiley, New York, 1993; p. 140.
20. Sawyer DT. Oxygen Chemistry, Oxford University
Press: USA, 1991.
21. Laing M. J. Chem. Ed. 1989; 66: 453.
22. Bonnett R and Martinez G. Tetrahedron Lett. 2001;
57: 9513.
10. (a) Sheldon RA, Arends IWCE, Brink GJT and
Dijksman A. Acc. Chem. Res. 2002; 35: 774.
(b) Muzart J. Tetrahedron Lett. 2003; 59: 5789.
(c) Zhan BZ and Thompson A. Tetrahedron Lett.
2004; 60: 2917.
23. Harbour JR and Issler SL. J. Am. Chem. Soc. 1982;
104: 903.
24. Chen Y, Xu S, Li L, Zhang M, Shen J and Shen T.
Dyes Pigm. 2001; 51: 63.
25. Bressan M and Morvillo A. Inorg. Chem. 1989; 28:
950.
26. (a) Hasty NM and Kearns DR. J. Am. Chem. Soc.
1973; 16: 3380. (b) Esser PE, Drießen-Hölscher B
and Keim W. J. Mol. Catalysis A 1999; 140: 13–24.
(c) Lykakis IN and Orfanopoulos M. Synlett. 2004;
2131–2134. (d) Kanno T, Hisaoka M, Sakuragi H
and Tokumaru K. Bull. Chem. Soc. Jpm. 1981; 54:
2330–2336. (f) Ameta SC, Punjabi PB, Chobisa CS,
Mangal N and Bhardwaj R. Asian J. Chem. Rev.
1990; 1: 106–124.
11. Hajimohammadi M and Safari N. J. Porphyrins
Phthalocyanines 2010; 14: 639.
12. (a) Nam W. Acc. Chem. Res. 2007; 40: 522.
(b) Hendrickson DN, Kinnaird MG and Suslick
KS. J. Am. Chem. Soc. 1987; 109: 1243. (c) Peter-
son MW and Richman RM. Inorg. Chem. 1985;
24: 722.
13. Derosa MC and Crutchley R. J. Coord. Chem. Rev.
2002; 233: 351–371.
14. (a) Greer A. Acc. Chem. Res. 2006; 39: 797.
(b) Hajimohammadi M, Bahadoran F, Davarani
SSH and Safari N. Reac. Kinet. Mech. Catal. 2010;
99: 243–250.
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 7–7