A facile synthesis of deuteroporphyrins derivatives under ultrasound irradiation

Article abstract of DOI:10.1016/j.ultsonch.2009.09.008

A facile, efficient and general method for preparing deuteroporphyrin derivatives by using concentrated H₂SO₄ and alcohol under ultrasound irradiation has been developed. A series of new deuteroporphyrin derivatives bearing different propionic ester groups have been synthesized in good yields starting from readily accessible deuterohemin. The characterization of these compounds confirms the synthetic methodology. Compared with conventional methods, the main advantages of the present procedure are shorter reaction time and higher yields.

Full text of DOI:10.1016/j.ultsonch.2009.09.008

Ultrasonics Sonochemistry 17 (2010) 288–291
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Ultrasonics Sonochemistry
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Short Communication
A facile synthesis of deuteroporphyrins derivatives under ultrasound irradiation
*
Bingcheng Hu , Weiyou Zhou, Ying Tang, Chengmei Huang, Zuliang Liu
School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu Province 210094, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A facile, efficient and general method for preparing deuteroporphyrin derivatives by using concentrated
H2SO4 and alcohol under ultrasound irradiation has been developed. A series of new deuteroporphyrin
derivatives bearing different propionic ester groups have been synthesized in good yields starting from
readily accessible deuterohemin. The characterization of these compounds confirms the synthetic meth-
odology. Compared with conventional methods, the main advantages of the present procedure are
shorter reaction time and higher yields.
Received 29 June 2009
Received in revised form 20 September
2009
Accepted 21 September 2009
Available online 26 September 2009
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Deuteroporphyrin derivatives
Ultrasound
Demetalation
Esterification
1. Introduction
Recently, ultrasound has been successfully applied in various
organic reactions [17]. Many papers have indicated that some or-
Porphyrins and phthalocyanines peripherally bearing with dif-
ferent substituents are of great interest in areas [1–6] as diverse
as biomimetic reactions, biological and photobiological processes,
photodynamic therapy, energy migration, analytical chemistry
and so on. The nature and location of the substituents in porphyrin
rings have a great influence on their properties. For this reason
considerable efforts have been devoted to the synthesis of porphy-
rin derivatives bearing various substituents to improve their per-
formance [7–11]. However, to the best of our knowledge, the
reported methods are all inconvenient and time-consuming. As de-
scribed in the literature, deuteroporphyrin IX dimethyl ester
(DPDME) is generally synthesized from deuterohemin by the pro-
cedure of Chu and Dolphin [12,13]. The procedure involves two
steps: demetalation of deuterohemin by the mixture of glacial
CH3COOH and concentrated HCl and esterification of deuteropor-
phyrin with CH3OH–H2SO4 (20:1) overnight, with the total yield
of 46.5–80% (Scheme 1). And other deuteroporphyrins bearing
two propionic ester groups are always prepared from DPDME
[14,15]. Another method for the synthesis of these deuteroporphy-
rin derivatives was reported by Caughey and coworkers [16], these
compounds could be prepared from deuterohemin using anhy-
drous FeSO4, dry HCl and methanol in one-pot, with a yield of only
66%. Thus, the development of a simple, highly efficient methodol-
ogy for the synthesis of deuteroporphyrin derivatives remains
desired.
ganic reactions can be carried out in high yields, short reaction
times and mild conditions under ultrasound irradiation [18–20].
Therefore, ‘‘sonochemistry” has been a new trend in organic chem-
istry, offering a versatile and facile pathway for a large variety of
synthesis [21,22]. We have now developed a convenient method
for the synthesis of deuteroporphyrin derivatives directly from
deuterohemin under ultrasound irradiation in one-pot based on
alcohols and concentrated H2SO4 (Scheme 1). We describe here
the successful use of this reaction procedure to prepare a series
of deuteroporphyrins bearing different propionic ester groups in
high yields.
2. Method
2.1. Apparatus and analysis
All reagents were analytical purity obtained from commercial
sources and used without further purification unless otherwise
stated. Deuterohemin chloride was synthesized from hemin chlo-
ride following the reference procedures [12,16]. Ultrasonication
was performed in a KQ-250B ultrasound cleaner with a frequency
of 40 kHz and an output power of 250 W. High speed stirring was
carried out with the Biaoma JB50-D series aggregating heat
constant temperature blender. Melting points were determined
on a XT4 micro hot-stage apparatus and was uncorrected; 1H
NMR was recorded on a Bruker 500 MHz spectrometers in CDCl3
with tetramethylsilane (TMS) as an internal standard. Elemental
analysis was conducted on an PE-2004 (Perkin–Elmer) elemental
* Corresponding author. Fax: +86 25 84315030.
E-mail address: hubingcheng@yahoo.com (B. Hu).
1350-4177/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ultsonch.2009.09.008

B. Hu et al. / Ultrasonics Sonochemistry 17 (2010) 288–291
289
C@O), 1435 (m), 1361 (m), 1300 (w), 1235 (w), 1196 (m), 1165
(s, C–O), 1125 (m), 1055 (w), 1016 (m), 970 (m), 894 (w), 845
(s); ESI+-MS (42 eV, m/z): 539.1 [M+H]+, 524.1 [M+HÀCH3]+,
451.1 [M+HÀCH2CH2COOCH3]+. Anal. Calcd. for C32H34N4O4: C,
71.36; H, 6.36; N, 10.40. Found: C, 71.28; H, 6.40; N, 10.29.
Deuteroporphyrins IX diethyl ester (2) mp 199–200 °C; 1H NMR
(500 MHz, CDCl3) d/ppm = À3.92 (s, 2H), 1.12, 1.14, 1.15 (t,
J = 7.25 Hz 6H), 3.26, 3.27, 3.29 (t, J = 7.75, 4H), 3.63, 3.65, 3.73,
3.74 (4s, 12H), 4.12, 4.13, 4.15, 4.16 (m, J = 7.25, 4 H), 4.43, 4.42,
4.4 (t, J = 7.75, 4H), 9.08 (s, 2H), 10.02, 10.06, 10.11, 10.12 (s,
4H). IR (KBr, cmÀ1): 3452 (w, N–H), 3309 (m, C–H(C3,8)); 2911
(w, –CH3), 1730 (s, C@O), 1444 (m, –CH2–), 1172(s, C–O), 839(m,
C–H(C5,10,15,20)); ESI+-MS (40 eV, m/z): 567.1 [M+H]+, 552.1
[M+HÀCH3]+, 466.0 [M+HÀCH2CH2COOCH2CH3]+. Anal. Calcd for
C34H38N4O4: C, 72.06; H, 6.76; N, 9.89. Found: C, 71.98; H, 6.80;
N, 9.82.
CH3
CH3
H3C
H3C
H3C
H3C
N
N
NH
N
Cl
N
N
N
CH3COOH
HCl
Fe
HN
CH3
CH3
COOH
COOH
COOH
COOH
CH3OH : H2SO4
(20:1)
overnight
H2SO4 / ROH
CH3
ultrasound
(46.5-80%)
CH3
H3C
H3C
H3C
H3C
NH
N
NH
N
N
N
Deuteroporphyrins IX dipropyl ester (3) mp 194–195 °C; 1H
NMR (500 MHz, CDCl3) d/ppm = À3.93 (s, 2H), 0.76–0.79 (m,
J = 6.67 Hz, 6H), 1.50–1.57 (m, 4H), 1.12–1.15 (m, J = 8.75 Hz,
4H), 3.26, 3.27, 3.29 (t, J = 7.25, 2H), 3.62, 3.64, 3.72, 3.73 (4s,
12H), 4.03, 4.05, 4.06 (t, J = 6.75 Hz, 4H), 4.40, 4.41, 4.42 (t, J =
7.25 Hz, 4H), 9.07 (s, 2H), 10.00, 10.04, 10.08, 10.09 (4s, 4H). IR
(KBr, cmÀ1): 3566 (w, N–H), 3306 (m, C–H(C3,8)); 2964 (w, –CH3),
1735 (s, C@O), 1455 (m, –CH2–), 1170 (s, C–O), 839 (m, C–
H(C5,10,15,20)); ESI+-MS (40 eV, m/z): 595.1 [M+H]+, 553.1
[M+HÀCH2CH2CH3]+, 479.3 [M+HÀCH2CH2COOCH2CH2CH3]+. Anal.
Calcd for C36H42N4O4: C, 72.70; H, 7.12; N, 9.42. Found: C, 72.56; H,
7.26; N, 9.55.
HN
HN
CH3
CH3
COOR
COOCH3
COOR
COOCH3
Scheme 1. Synthesis of deuteroporphyrin derivatives bearing different propionic
ester groups.
analyzer. ESI-MS/MS mass spectra were recorded on a Finnigan
TSQ Quantum ultra AM mass spectrometer. Infrared spectra were
obtained on a Perkin–Elmer 681 instrument.
Deuteroporphyrins IX diisopropyl ester (4) mp 219–220 °C; 1H
NMR (500 MHz, CDCl3) d/ppm = À3.91 (s, 2H), 1.10–1.12 (d,
J = 6.0 Hz, 12H), 3.24, 3.25, 3.27 (t, J = 7.25 Hz, 4H), 3.64, 3.67,
3.73, 3.76 (4s, 12H), 4.40, 4.42, 4.43(t, J = 7.25 Hz, 4H), 5.03–5.10
(m, J = 6.0 Hz, 2H), 9.09 (d, 2H), 10.03, 10.08, 10.13 10.14(4s,
4H). IR (KBr, cmÀ1): 3567 (w, N–H), 3311 (m, C–H(C3,8)); 2973
(w, –CH3), 1771 (s, C@O), 1456 (m, –CH2–), 1174 (s, C–O), 840
(m, C–H(C5,10,15,20)); ESI+-MS (45 eV, m/z): 595.1 [M+H]+, 553.1
[M+HÀCH2CH2CH3]+, 479.3 [M+HÀCH2CH2COOCH2CH2CH3]+. Anal.
Calcd for C36H42N4O4: C, 72.70; H, 7.12; N, 9.42. Found: C, 72.60; H,
7.22; N, 9.53.
2.2. Conventional synthesis of deuteroporphyrin derivatives
To the mixture of deuterohemin chloride (1.0 g, 1.67 mmol) and
concentrated H2SO4 (15 ml, 0.28 mol) in a boiling florence 3-neck-
flask of 150 ml under the condition of mechanical stirring, excess
alcohol (0.6 mol) was added dropwise (15 min) at refluxing. The
reaction was monitored by TLC. After the reaction, the result mix-
ture was stored in refrigeratory for more than 2 h to cool down.
After neutralization by cooled ammonia, the mixture was then ex-
tracted with CH2Cl2 (100 ml, three times). The organic layer was
washed with brine, dried over anhydrous Na2SO4. After solvent re-
moval, the residue was further purified by column chromatogra-
phy on silica gel with dichloromethane: ethyl acetate = 10:1 to
afford product as a pure solid.
Deuteroporphyrins IX dibutyl ester (5) mp 189.5–190 °C; 1H
NMR (500 MHz, CDCl3) d/ppm = À3.90 (s, 2H), 0.70, 0.71, 0.73 (t,
J = 7.25 Hz, 6H), 1.15–1.22 (m, J = 7.75 Hz, 4H), 1.44–1.50 (m,
J = 7.25 Hz, 4H), 3.26, 3.27, 3.29 (t, J = 7.75 Hz, 4H), 3.62, 3.64,
3.72, 3.74 (4s, 12H), 4.06, 4.07, 4.08 (t, J = 7.25 Hz, 4H), 4.40,
4.41, 4.43(t, J = 7.25 Hz, 4H), 9.07, 9.08 (2s, 2H), 10.01, 10.05,
10.10 10.11 (s, 4H). IR (KBr, cmÀ1): 3447 (w, N–H), 2959 (w,
–CH3), 1730 (s, C@O), 1462 (m, –CH2–), 1169 (s, C–O), 804 (m,
C–H(C5,10,15,20)); ESI+-MS (45 eV, m/z): 623.1 [M+H]+, 567.1
[M+HÀ(CH2)3CH3]+, 492.8 [M+HÀCH2CH2COO(CH2)3CH3]+. Anal.
Calcd. for C38H46N4O4: C, 73.28; H, 7.44; N, 9.00. Found: C,
73.14; H, 7.56; N, 9.12.
2.3. Ultrasound-promoted synthesis of deuteroporphyrin derivatives
To the mixture of deuterohemin chloride (1.0 g, 1.67 mmol) and
concentrated H2SO4 (15 ml, 0.28 mol) in a boiling florence 3-neck-
flask of 150 ml, excess alcohol (0.6 mol) was added dropwise
(15 min) at room temperature in an ultrasound bath having a fre-
quency of 40 kHz. After the addition, the mixture was irradiated by
ultrasound for another 1 h. Then the result mixture was stored in
refrigeratory for more than 2 h to cool down. After neutralization
by cooled ammonia, the mixture was then extracted with CH2Cl2
(100 ml, three times). The organic layer was washed with brine,
dried over anhydrous Na2SO4. After solvent removal, the residue
was further purified by column chromatography on silica gel with
dichloromethane: ethyl acetate = 10:1 to afford product as a pure
solid.
Deuteroporphyrins IX diisobutyl ester (6) mp 188–188.5 °C; 1H
NMR (500 MHz, CDCl3) d/ppm = À3.89 (s, 2H), 0.78–0.80 (m, 12H),
1.79–1.87 (m, 2H), 3.28, 3.39, 3.41 (t, J = 8.0 Hz, 4 H), 3.64, 3.66,
3.73, 3.76 (m, 12H), 3.88–3.89 (d, J = 8.0 Hz, 4H), 4.42, 4.43, 4.44
(t, 4H), 9.09, 9.10 (d, 2H), 10.03, 10.07, 10.11, 10.14 (4s, 4H). IR
(KBr, cmÀ1): 3452 (w, N–H), 3312 (m, C–H(C3,8)); 2959 (w, –CH3),
1736(s, C@O), 1379 (m, –CH2–), 1169 (s, C–O), 845 (m,
C–H(C5,10,15,20)); ESI+-MS (45 eV, m/z): 623.1 [M+H]+, 567.2
[M+HÀCH(CH3)2]+, 433.0 [M+HÀCH2CH2COO CH(CH3)2À4CH3]+.
Anal. Calcd. for C38H46N4O4: C, 73.28; H, 7.44; N, 9.00. Found: C,
73.16; H, 7.55; N, 9.08.
Deuteroporphyrins IX dimethyl ester (1) mp 224–225 °C; 1H
NMR (500 MHz, CDCl3): d/ppm = À3.87 (s, 2H), 3.30, 3.29,3.27(t,
J = 7.25, 4H), 3.73, 3.75 (2s, 6H), 3.63–3.66 (4s, 12H), 4.41, 4.42,
4.44 (t, J = 7.25, 4H), 9.08, 9.09 (2s, 2H), 10.03, 10.07, 10.10,
10.13 (4s, 4H); IR (KBr, cmÀ1): 3400 (m, N–H), 2900 (w), 1733 (s,
Deuteroporphyrins IX diisooctyl ester (7) mp 110–111 °C; 1H
NMR (500 MHz, CDCl3) d/ppm = À3.90 (s, 2H), 0.84–0.88 (m,
12H), 1.02–1.06 (m, 12H), 1.12–1.15 (m, 4H), 1.25 (s, 2H),
1.38–1.40 (m, 4H), 3.26, 3.28, 3.29 (t, J = 7.25 Hz, 4H), 3.62–3.74

290
B. Hu et al. / Ultrasonics Sonochemistry 17 (2010) 288–291
(m, 12H), 3.95–4.01 (m, 4H), 4.40, 4.41, 4.43 (t, J = 7.25 Hz, 4H),
9.07, 9.08 (d, 2H), 10.01, 10.05, 10.09, 10.11 (s, 4H). IR (KBr,
cmÀ1): 3524 (w, N–H), 3316 (m, C–H(C3,8)); 2928 (w, –CH3),
1736 (s, C@O), 1460 (m, –CH2–), 1167 (s, C–O), 860 (m, C–
H(C5,10,15,20)); ESI+-MS (50 eV, m/z): 735.5 [M+H]+, 623.1
[M+HÀCH(CH3)(CH2)5CH3]+, 511.1 [M+HÀ2CH(CH3)(CH2)5CH3]+.
Anal. Calcd. for C46H62N4O4: C, 75.17; H, 8.50; N, 7.62. Found: C,
75.08; H, 8.64; N, 7.79.
Deuteroporphyrins IX tert-butyl ester (8) mp 236.5–237.5 °C;
1H NMR (500 MHz, CDCl3) d/ppm = À3.94 (s, 2H), 0.64–0.68 (m,
12H), 1.24–1.29 (m, 9H), 3.70, 3.72, 3.73, 3.74 (m, J = 7.0 Hz,
4H), 4.50, 4.51, 4.52, 4.54 (m, J = 6.67 Hz, 4H), 9.06, 9.08 (d,
2H), 10.03, 10.05, 10.08, 10.12(s, 4H), 12.11(s, 1H). IR (KBr,
cmÀ1): 3526 (w, N–H), 3423 (w, O–H), 3317 (m, C–H(C3,8));
2925 (w, –CH3), 1734(s, C@O), 1462 (m, –CH2–), 1164 (s, C–O),
861 (m, C–H(C5,10,15,20)); ESI+-MS (38 eV, m/z): 567.0 [M+H]+,
511.0 [M+HÀC(CH3)3]+, 493.1 [M+HÀC(CH3)5CH3ÀH2O]+. Anal.
Calcd. for C46H62N4O4: C, 72.05; H, 6.76; N, 9.89. Found: C,
71.68; H, 6.64; N, 9.96.
3. Results and discussion
To optimize the reaction conditions, the ratio of reactants was
investigated in the synthesis of DPDME (1) as model compound.
The best result was obtained by the reaction of deuterohemin
(1.0 g), methanol (25 ml) and concentrated H2SO4 (15 ml) at
room temperature under silent condition by ultrasound irradia-
tion (40 kHz) to produce DPDME in 1 h with 97% yield. In the
reaction, the concentrated H2SO4 played an important role as
demetalation reagent and absorber of H2O produced in the reac-
tion. The effect of the content of concentrated H2SO4 is shown in
Table 1. The yields of deuteroporphyrin increased with the in-
crease of H2SO4 at the beginning, when the volume of H2SO4
was 15 ml, the yield reached the highest (97%). However, the
yields decreased when the content of H2SO4 unceasingly in-
creased, the phenomenon is due to the fact that the esterifica-
tion is reversible and the superfluous H2SO4 may help the
hydrolysis of the product.
In addition, the influence of the power of ultrasound irradiation
on the reaction has also been studied. Raising the ultrasound
power in our study by from 100, 150, 200 to 250 W, we could iden-
tify an increase of the yield of DPDME (Table 2). The sonication
power influences the level of cavitations produced by ultrasound
in the liquid. Higher power ultrasound generates the larger num-
ber of cavitation events due to more transient cavitations bubbles
being formed and causes the reaction rapidly.
Table 1
Synthesis of deuteroporphyrin IX dimethyl ester.a
Entry
Vb
rc(mol)
Yieldd (%)
1
2
3
4
5
10
15
20
25
30
110
165
220
275
330
88
97
96
92
91
a
Reaction conditions: deuterohemin chloride (1.0 g, 1.67 mmol), methanol
(25 ml, 0.6 mol), reaction time 60 min, rt.
b
The volume of concentrated H2SO4.
The mol ratio of H2SO4 to deuterohemin chloride.
Yields refer to the isolated products.
c
d
To investigate the scope and generality of the present meth-
od, various alcohols were tested for the reactions with deuter-
ohemin under the optimum conditions. The results showed
that these reactions proceeded smoothly to give the expected
compounds in good to excellent yields. In addition, the compar-
ative study of the one-pot reaction under conventional high
speed stirring conditions was also carried out to investigate
the specific effect of ultrasonic on these reactions and the repre-
Table 2
Effect of the power of ultrasound irradiation on the reaction.a
Ultrasonic power (W)
Yieldb(%)
100
41
150
56
200
75
250
97
a
Reaction conditions: deuterohemin chloride (1.0 g, 1.67 mmol), methanol
(25 ml, 0.6 mol), concentrated H2SO4 (15 ml, 0.28 mol), reaction time 60 min, rt.
b
Yields refer to the isolated products.
Table 3
Synthesis of deuteroporphyrin derivatives under ultrasound and conventional stirring.a
Entry
Alcohol
Ultrasound
Conventional
t/h
t/min
Yieldb(%)
Yieldb(%)
1
2
H3C–OH
60
60
97
95
7
7
90
89
3
4
60
96
89
7
88
69
100
14
5
6
100
120
94
88
12
16
76
56
7
8
120
120
84
16
16
52
68c
31c
a
b
c
Reaction conditions: deuterohemin chloride (1.0 g, 1.67 mmol), concentrated H2SO4 (15 ml, 0.28 mol), alcohol (0.6 mol), rt.
Yields refer to the isolated products.
Yields of monoester.

B. Hu et al. / Ultrasonics Sonochemistry 17 (2010) 288–291
291
sentative examples are summarized in Table 3. From Table 3, it
4. Conclusion
is found that under conventional conditions the yield of deutero-
porphyrins varied with the structures of alcohols. For example,
when the alcohol was isooctanol, the yields of deuteroporphyrins
IX diisooctyl ester (7) was only 52%, markedly lower than others.
That is to say, steric factors played a key role in affecting the
yield and rate of reaction under conventional conditions. How-
ever, the yields of products changed little under ultrasound irra-
diation conditions. These results indicate that ultrasound
irradiation could evidently reduce the steric influence of reactant
on the reaction compared with conventional conditions, in ac-
cord with the results of Zengs’ [23]. To gain further insight, we
performed the reactions with tert-butyl alcohol under the same
reaction conditions. The central iron has been absolutely taken
off after irradiation for 2 h, but the esterification was incomplet-
ed. The monoester was the dominant reaction product, suggest-
ing that the reduction of dimensional effect is limited for the
reaction with more hindered alcohols.
In conclusion, we have developed a new general and convenient
method for synthesis of a series of deuteroporphyrin derivatives in
high yields under ultrasound irradiation. The method leads to a
series of porphyrins bearing different propionic ester groups. Ultra-
sounds induce a remarkable acceleration for these reactions, the
reaction times decreasing dramatically and the yields increasing
considerably.
Acknowledgments
This research was supported by Science and Technology Devel-
opment Foundation of Nanjing University of Science and Technol-
ogy (No. XKF 09008) and Jiangsu Natural Science Foundation (No.
BK2009386).
References
Another influence of ultrasound on chemical reaction is that
it can markedly shorten the reaction time compared with con-
ventional conditions [24–26]. The similar effect was also ob-
served in our experiments. The results in Table 3 show that
ultrasound is much more efficient than magnetic stirring. Clearly,
sluggish reactions were observed under conventional conditions
and longer reaction time was required to achieve better yield.
However, to our delight, ultrasound irradiation efficiently accel-
erated the reaction and markedly shortened the reaction time.
In case of methanol reaction time was reduced from 7 h to
60 min to get the similar yield (Table 3, entry 1). Likewise with
other alcohols with more carbon atoms, a considerable shorten-
ing of reaction time is observed (Table 3, entries 2–7). These re-
sults indicated that there was remarkable ultrasonic effect on
the one-pot reaction. We presume that the efficiency using ultra-
sound irradiation is due to the cavitations phenomena. Cavita-
tion was the production of microbubble in liquid when a large
negative pressure was applied to it. In succeeding compression
cycles bubbles can collapse violently with the release of large
amounts of energy. The ‘‘hot-spot” theory suggested that tem-
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atmospheres were produced during this collapse [27,28]. The en-
ergy being more efficiently transmitted to the substrates com-
pared to the reactions performed at conventional conditions
and cause reaction rapidly. Also, the collapse of bubbles induces
the efficient mixing, increase in mass transfer and mechanical
stress that can be transmitted to a target single bond and accel-
erates the reaction.
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