Environmentally friendly methods for syntheses of new aromatic bisesters

Article abstract of DOI:10.1080/00397910903219609

Two environmentally friendly methods, one in liquid and the other in solid phase, for preparation of phenyl bisesters (bearing alkylating groups) under microwave (MW) irradiation are presented. The MW remarkably enhanced the rate of acceleration for ester

Full text of DOI:10.1080/00397910903219609

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Environmentally Friendly Methods for
Syntheses of New Aromatic Bisesters
Gheorghita N. Zbancioc a , Ana Maria V. Zbancioc b & Ionel I.
Mangalagiu a
a Al. I. Cuza University of Iasi, Organic Chemistry Department , Iasi,
Romania
b Gr. T. Popa University of Iasi, Faculty of Pharmacy , Iasi, Romania
Published online: 07 Jul 2010.
To cite this article: Gheorghita N. Zbancioc , Ana Maria V. Zbancioc & Ionel I. Mangalagiu
(2010) Environmentally Friendly Methods for Syntheses of New Aromatic Bisesters, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
40:15, 2201-2208, DOI: 10.1080/00397910903219609
To link to this article: http://dx.doi.org/10.1080/00397910903219609
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Synthetic Communications1, 40: 2201–2208, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903219609
ENVIRONMENTALLY FRIENDLY METHODS FOR
SYNTHESES OF NEW AROMATIC BISESTERS
Gheorghita N. Zbancioc,1 Ana Maria V. Zbancioc,2
and Ionel I. Mangalagiu1
1Al. I. Cuza University of Iasi, Organic Chemistry Department,
Iasi, Romania
2Gr. T. Popa University of Iasi, Faculty of Pharmacy, Iasi, Romania
Two environmentally friendly methods, one in liquid and the other in solid phase, for
preparation of phenyl bisesters (bearing alkylating groups) under microwave (MW)
irradiation are presented. The MW remarkably enhanced the rate of acceleration for esteri-
fication: the reaction time decreased dramatically, the reaction conditions are milder, and the
consumed energy decreased considerably. In the most cases, in the liquid phase under MW
irradiation, the yields are better, in some cases substantially (almost 75%). In the solid phase
under MW irradiation, the yields are moderate to good compared to the liquid phase but
excellent compared to conventional heating. Both methods are fast, general, and facile,
but because the solid-phase reactions are solvent-free, we consider this one to be the most suit-
able for synthetic chemistry. A comparative study of MW and conventional heating was done.
Keywords: Bisesters; ecofriendly; microwave; solid and liquid phase
INTRODUCTION
During past decades, microwave (MW) irradiation has became an increasingly
valuable tool in organic chemistry, because it offers a versatile and facile pathway for
a large variety of syntheses.[1–7] Solid-phase reactions have the great advantage of
using no organic solvents (‘‘solvent-free’’); such reactions being more environmen-
tally friendly and generate less side products. The application of MW irradiation
under solvent-free conditions enables organic reactions to occur expeditiously at
ambient pressure, providing unique chemical processes with special attributes such
as better yields, shorter reaction times, milder conditions, and the associated ease
of manipulation. Among the MW-assisted reactions, esterification[1–3,4c,5,6] has
received attention, especially in the case of fatty acids. However, under conventional
heating, esterification of aromatic diols with chloroacyl chloride was extremely
poorly studied: only the case of benzene 1,2-diol with 2-chloroethanoyl chloride
was examined.[8] Moreover, under MW irradiation, these reactions have not been
studied at all.
Received May 28, 2009.
Address correspondence to Ionel I. Mangalagiu, Al. I. Cuza University of Iasi, Organic Chemistry
Department, Bd. Carol 11, 700506 Iasi, Romania. E-mail: ionelm@uaic.ro
2201

2202
G. N. ZBANCIOC, A. M. V. ZBANCIOC, AND I. I. MANGALAGIU
In view of new alkylating agents, and as a part of our work in this field,[7,9] we
report here synthesis in liquid and solid phase (in the absence of solvents) of such
compounds using MW technologies.
RESULTS AND DISCUSSION
To obtain the phenyl bisesters bearing alkylating groups, we perform the
esterification reaction of benzene diols (1,2-, 1,3-, and 1,4-) with chloroacyl chloride
(2-chloroethanoyl chloride, 3-chloropropanoyl chloride, 4-chlorobutanoyl chloride).
The reactions was carried out in liquid and solid phases, under both conventional
heating and MW irradiation (see Scheme 1).
Under conventional heating, in a liquid phase, the reactions have some major
disadvantages, including long reaction time (15–56 h), high energy consumption,
variable yields (from 18 to 85%), and great amounts of solvents (often toxic). Unfor-
tunately, in the solid phase, the situation was even worse: no matter the conditions
we employed, under conventional heating we got only a trace of the desired
compounds. This is why we decided to use MW technology.
The MW-assisted reactions were carried out using a monomode reactor at
800 W. Two methods were used: the so-called power control method (PCM), apply-
ing a constant irradiation power and varying the temperature, and the so-called
temperature control method (TCM), when temperature is maintained constant
and the irradiation power of magnetron is varied. Initially, we used the PCM
method. Although in the liquid phase the results are very good (Table 1), in the solid
phase the results were disappointing, with poor reaction yields (less than 10%). While
analyzing the temperature variation during the reaction time (Fig. 1), we noticed
than in the liquid phase the temperature rose up fast and then remained constant
(at approximately 60 ꢀC after approximately 60 s; Fig. 1, upper left). In the solid
phase, the temperature rose up again fast (but with greater speed) and remained
constant at a much greater value (approximately 145 ꢀC after approximately 60 s;
Fig. 1, upper right). This makes us conclude that the poor yield we obtained in
the solid phase could be explained by this very high temperature (145 ꢀC) that was
reached in a very short time (high reaction speed), which makes the final products
decompose. This is why we decided to change the method, limiting the temperature,
which is allowed by the TCM method. Indeed, when we used a constant temperature,
the yields improved significantly; the best results were obtained at 90 ꢀC (Fig. 1,
lower left).
Scheme 1. Reaction pathway of benzenediols with chloroacyl chloride.

ENVIRONMENTALLY FRIENDLY METHODS
2203
Table 1. Syntheses of phenyl bisesters under MW and conventional heating in liquid (toluene) and solid
phase (solid support KF–Al2O3)
Liquid phase
Conventional
Solid phase
Conventional
Reaction Yield
MW
MW
Reaction
Reaction
time (h)
Yield
(%)
Reaction
time (min)
Yield
(%)
Yield
(%)
Compound
time (h)
(%)
time (min)
4 (1,2-OH)
5 (1,2-OH)
6 (1,2-OH)
7 (1,3-OH)
8 (1,3-OH)
9 (1,3-OH)
10 (1,4-OH)
11 (1,4-OH)
12 (1,4-OH)
17
56
28
30
53
15
55
58
45
72
74
85
50
78
83
18
75
55
5
5
5
5
5
5
5
5
5
91
64
91
91
58
92
90
46
81
10–60
Trace
5
5
5
5
5
5
5
5
5
43
37
44
44
35
58
51
41
53
Table 1 lists the optimized conditions we employed, under MW irradiation as
well as under conventional heating. In the liquid phase, we used toluene as solvent,
whereas in the solid phase, we used a solid mineral support of KF–Al2O3.
The data from Table 1 showed us that MW-assisted reactions of phenyl
bisesters are environmentally friendly both in solid (solvent free) and in liquid (the
amount of used solvents is five times less, see Experimental section) phases. MWs
induced a remarkable acceleration for reactions, and the reaction time decreased
dramatically from hours to minutes (5 min). Consequently, the consumed energy
decreased considerably. In the liquid phase, in most cases under MW irradiation
the yields are better, in some cases substantially (almost 75%). In the solid phase,
under MW irradiation the yields are around 50%, whereas under conventional
heating only traces are obtained. However, under MW irradiation the yields in the
liquid phase are better than in the solid phase.
The structure of compounds was proven by elemental (C, H, N) and spectral
analysis [infrared (IR), 1H NMR, 13C NMR, two-dimensional correlation
spectroscopy (2D-COSY), 2D heteronuclear multiple bond correlation (HETCOR
or HMQC), and long-range 2D-HETCOR]. All the elemental and spectral data are
in accordance with the proposed structure and are presented in the next section.
EXPERIMENTAL
MW-assisted reactions were carried out using a monomod reactor [STAR-2,
CEM Corporation, USA (800 W)]. All the reagents and solvents employed were of
the best grade available and were used without further purification. Melting points
1
were determined using an electrothermal apparatus and were uncorrected. The H
and 13C NMR spectra and two-dimensional experiments (2D-COSY, 2D-HETCOR,
long-range 2D-HETCOR) were recorded on a Bruker Avance 400 DRX
spectrometer operating at 400 MHz. Chemical shifts are given in parts per million

2204
G. N. ZBANCIOC, A. M. V. ZBANCIOC, AND I. I. MANGALAGIU
Figure 1. Graphic of temperature variation by PCM method (25% from the full power of the magnetron:
upper left in liquid phase; upper right in solid phase) and TCM method (90 ꢀC constant temperature:
bottom) for compound 12.
(ppm, d scale), with coupling constants (J) in hertz (Hz). The IR spectra were
recorded on a Fourier transform (FT)–IR Shimadzu Prestige 8400s spectrophot-
ometer in KBr.
General Procedure for Syntheses of Aromatic Bisesters Under
Conventional Heating in Liquid Phase
Chloroacyl chloride (22 mmol) was added dropwise to 10 mmol of benzene
diols and 10 mmol (2.43 g) of magnesium curlings in 50 mL anhydrous toluene in
1 h while stirring and refluxing the mixture. This continued to be refluxed for a
period of 15 to 58 h (according to the reagents’ nature, Table 1). The excess of
magnesium was filtered off, the resulted oil was poured into water, and the pre-
cipitate was filtered. The product was crystallized from an appropriate solvent.
When the oil did not precipitate in water, it was first separated by flash and then
crystallized.

ENVIRONMENTALLY FRIENDLY METHODS
2205
General Procedure for Syntheses of Aromatic Bisesters Under MW
Irradiation in Liquid Phase
In MW irradiation, the best results were obtained using a constant irradiation
power (25% from the full power of the magnetron, 800 W) and varying the tempera-
ture (the so-called power control).
Ten mmol of benzene diols and 24 mmol (24.24 g) triethylamine in 10 mL anhy-
drous toluene were placed in the reaction vessel (Pyrex glass or quartz). Chloroacyl
chloride (22 mmol) was added dropwise over 3–5 min. The tubes were then placed in
the microwave cell and heated for the appropriate time. Once the heating cycle was
complete and tube was cooled to ambient temperature, the tube was removed, and
the triethylamine chlorohydrate was filtered off. The resulting oil was poured into
water, and the precipitate was filtered. The product was crystallized from an appro-
priate solvent. When the oil did not precipitate in water, first it was separated by
flash and then crystallized.
General Procedure for Syntheses of Aromatic Bisesters Under MW
Irradiation in Solid Phase
Ten mmol of benzene diols and 20 mmol of KF were ground in an agate mortar
until a fine homogenous mixture was obtained. Three g of mineral support
KF-Al2O3 (prepared according with the literarure[15]) was added, and the mixture
was ground again in the agate mortar until a fine homogenous greenish solid was
obtained. Chloroacyl chloride (22 mmol) was added to the obtained solid, and the
mixture was heated in classical conditions (oil bath) or exposed to microwaves.
The activated solid was cooled and washed three times with 10 mL of acetonitrile.
The acetonitrile was then evaporated, the obtained slurry was cooled in a freezer
for 30 min, and then 100 mL distilled water were added and stirred vigorously until
a white precipitate was obtained (ꢁ1 min). The precipitate was filtered off and did
not require other purification.
Chloro-acetic Acid 2-(2-Chloro-acetoxy)-phenyl Ester, 4
This compound was obtained from pyrocatechol as white crystals: mp
54–56 ꢀC (anal. calc. for C10H8Cl2O4 (263): C, 45.66; H, 3.07; found: C, 45.58; H,
3.00). IR (KBr, cmꢂ1): 3016 (CꢂH arom.), 2975 (CꢂH aliph.), 1782, 1751 (C O
=
1
=
est.), 1601, 1515, 1491, 1416 (C C), 1248, 1128 (CꢂOꢂC), 814, 761 (CꢂCl). H
0
00
NMR (CDCl3, d, ppm, J, Hz): 4.33 (s, 4H: 2H2 , 2H2 ), 7.27–7.24 [m, 2H (overlaped
peaks): 1H4, 1H5], 7.33–7.30 [m, 2H (overlaped peaks): 1H3, 1H6]. 13C NMR (TMS,
0
00
CDCl3, d, ppm): 43.77 (C2 , C2 ), 123.45 (C3, C6), 126.83 (C4, C5), 141.88 (C1, C2),
=
169.01 (C1 , C1 : C O).
0
00
3-Chloro-propionic Acid 2-(3-Chloro-propionyloxy)-phenyl Ester, 5
This compound was obtained from pyrocatechol as white-yellow crystals: mp
45–47 ꢀC (anal. calc. for C12H12Cl2O4 (291): C, 49.51; H, 4.15; found: C, 49.57; H,
4.12). IR (KBr, cmꢂ1): 3080 (CꢂH arom.), 2976 (CꢂH aliph, 1763 (C O est.),
=

2206
G. N. ZBANCIOC, A. M. V. ZBANCIOC, AND I. I. MANGALAGIU
1
=
1496, 1438, 1419, 1404 (C C), 1244, 1232, 1139, 1124 (CꢂOꢂC), 760 (CꢂCl). H
0
00
NMR (CDCl3, d, ppm, J, Hz): 3.05–3.02 (t, J ¼ 6.0, 4H: 2H2 , 2H2 ), 3.85–3.82 (t,
0
00
J ¼ 6.0, 4H: 2H3 , 2H3 ), 7.22–7.19 [m, 2H (overlaped peaks): 1H4, 1H5], 7.28–7.26
[m, 2H (overlaped peaks): 1H3, 1H6]. 13C NMR (TMS, CDCl3, d, ppm): 37.41
0
00
0
00
(C2 , C2 ), 38.82 (C3 , C3 ), 123.47 (C3, C6), 126.95 (C4, C5), 141.77 (C1, C2),
=
167.82 (C1 , C1 : C O).
0
00
4-Chloro-butyric Acid 2-(4-Chloro-butyryloxy)-phenyl Ester, 6
This compound was obtained from pyrocatechol, as white-grey crystals, mp
41–42 ꢀC (anal. calc. for C14H16Cl2O4 (319): C, 52.68; H, 5.05; found: C, 52.74; H,
5.01). IR (KBr, cmꢂ1): 3071 (CꢂH arom.), 2964 (CꢂH aliph.), 1757 (C O est.),
=
1
=
1592, 1547, 1491, 1409 (C C), 1240, 1207, 1128, 1113 (CꢂOꢂC), 763 (CꢂCl). H
0
00
NMR (CDCl3, d, ppm, J, Hz): 2.23–2.16 (m, 4H: 2H3 , 2H3 ), 2.79–2.76 (t,
0
00
0
00
J ¼ 7.2, 4H: 2H2 , 2H2 ), 3.69–3.66 (t, J ¼ 6.4, 4H: 2H4 , 2H4 ), 7.20–7.18 [m, 2H
(overlaped peaks): 1H4, 1H5], 7.27–7.25 [m, 2H (overlaped peaks): 1H3, 1H6]. 13C
0
00
0
00
0
00
NMR (TMS, CDCl3, d, ppm): 27.42 (C3 , C3 ), 30.81 (C2 , C2 ), 43.79 (C4 , C4 ),
=
123.44 (C3, C6), 126.69 (C4, C5), 141.94 (C1, C2), 170.11 (C1 , C1 : C O).
0
00
Chloro-acetic Acid 3-(2-Chloro-acetoxy)-phenyl Ester, 7
This compound was obtained from resorcine, as reddish crystals, mp 66–68 ꢀC
(anal. calc. for C10H8Cl2O4 (263): C, 45.66; H, 3.07; found: C, 45.57; H, 3.02). IR
(KBr, cmꢂ1): 3090 (CꢂH arom.), 2954 (CꢂH aliph.), 1766, (C O est.), 1593, 1544,
=
1
=
1481, 1406 (C C), 1234, 1182, 1141 (CꢂOꢂC), 785 (CꢂCl). H NMR (CDCl3, d,
13
0
00
ppm, J, Hz): 4.28 (s, 4H: 2H2 , 2H2 ), 7.02 (s, 1H: H2), 7.08–7.06 (d, J ¼ 8.4, 2H: 1H4,
0
1H6), 7.43–7.39 (t, J ¼ 8.4, 1H: H5). C NMR (TMS, CDCl3, d, ppm): 40.78 (C2 ,
=
C2 ), 114.77 (C2), 119.18 (C4, C6), 130.13 (C5), 150.71 (C1, C3), 165.47 (C1 , C1 : C O).
00
0
00
3-Chloro-propionic Acid 3-(3-Chloro-propionyloxy)-phenyl Ester, 8
This compound was obtained from resorcine as yellow oil (anal. calc. for
1
C12H12Cl2O4 (291): C, 49.51; H, 4.15; found: C, 49.51; H, 4.11). H NMR (CDCl3,
0
00
0
d, ppm, J, Hz): 2.98–2.95 (t, J ¼ 6.8, 4H: 2H2 , 2H2 ), 3.78–3.75 (t, J ¼ 6.8, 4H: 2H3 ,
13
00
2H3 ), 6.99 (s, 1H: H2), 7.04–7.02 (d, J ¼ 8.4, 2H: 1H4, 1H6), 7.40–7.36 (t, J ¼ 8.4,
0
00
0
00
1H: H5). C NMR (TMS, CDCl3, d, ppm): 36.68 (C2 , C2 ), 38.23 (C3 , C3 ),
=
113.74 (C2), 119.05 (C4, C6), 129.38 (C5) 150.74 (C1, C3), 169.33 (C1 , C1 : C O).
0
00
4-Chloro-butyric Acid 3-(4-Chloro-butyryloxy)-phenyl Ester, 9
This compound was obtained from resorcine as a yellow oil (anal. calc. for
1
C14H16Cl2O4 (319): C, 52.68; H, 5.05; found: C, 52.72; H, 5.02). H NMR (CDCl3,
0
00
0
00
d, ppm, J, Hz): 2.22–2.15 (m, 4H: 2H3 , 2H3 ), 2.76–2.73 (t, J ¼ 6.4, 4H: 2H2 , 2H2 ),
0
00
3.69–3.65 (t, J ¼ 7.6, 4H: 2H4 , 2H4 ), 6.92 (s, 1H: H2), 7,00–6.97 (dd, J ¼ 8.0, 2H:
1H4, 1H6), 7.39–7.34 (t, J ¼ 8.0, 1H: H5). 13C NMR (TMS, CDCl3, d, ppm): 27.22
0
(C3 , C3 ), 31.18 (C2 , C2 ), 43.81 (C4 , C4 ), 115.27 (C2), 118.89 (C4, C6), 129.68
00
0
00
0
00
=
(C5), 150.91 (C1, C3), 170.73 (C1 , C1 : C O).
0
00

ENVIRONMENTALLY FRIENDLY METHODS
2207
Chloro-acetic Acid 4-(2-Chloro-acetoxy)-phenyl Ester, 10
This compound was obtained from hydroquinone as white crystals: mp
122–123 ꢀC (anal. calc. for C10H8Cl2O4 (263): C, 45.66; H, 3.07; found: C, 45.71;
H, 3.01). IR (KBr, cmꢂ1): 3003 (CꢂH arom.), 2953 (CꢂH aliph.), 1770, 1761
1
=
=
(C O est.), 1506, 1409, 1311 (C C), 1188, 1232, 1146 (CꢂOꢂC), 736 (CꢂCl). H
13
0
00
NMR (CDCl3, d, ppm, J, Hz): 4.30 (s, 4H: 2H2 , 2H2 ), 7.17 (s, 4H: 1H2, 1H3,
1H5, 1H6). C NMR (TMS, CDCl3, d, ppm): 40.98 (C2 , C2 ), 122.45 (C2, C3, C5,
0
00
=
C6), 148.20 (C1, C4), 165.39 (C1 , C1 : C O).
0
00
3-Chloro-propionic Acid 4-(3-Chloro-propionyloxy)-phenyl Ester, 11
This compound was obtained from hydroquinone as white crystals: mp
88–90 ꢀC (anal. calc. for C12H12Cl2O4 (291): C, 49.51; H, 4.15; found: C, 49.59; H,
4.10). IR (KBr, cmꢂ1): 3080 (CꢂH arom.), 2976 (CꢂH aliph.), 1753 (C O est.),
=
1
=
1503, 1437, 1410, 1378 (C C), 1176, 1141 (CꢂOꢂC), 767 (CꢂCl). H NMR (CDCl3,
13
0
00
0
d, ppm, J, Hz): 3.05–3.02 (t, J ¼ 6.8, 4H: 2H2 , 2H2 ), 3.87–3.84 (t, J ¼ 6.8, 4H: 2H3 ,
00
0
2H3 ), 7.13 (s, 4H: 1H2, 1H3, 1H5, 1H6). C NMR (TMS, CDCl3, d, ppm): 37.77 (C2 ,
=
C2 ), 38.99 (C3 , C3 ), 122.60 (C2, C3, C5, C6), 148.12 (C1, C4), 168.93 (C1 , C1 : C O).
00
0
00
0
00
4-Chloro-butyric Acid 4-(4-Chloro-butyryloxy)-phenyl Ester, 12
This compound was obtained from hydroquinone as white crystals: mp
48–50 ꢀC (anal. calc. for C14H16Cl2O4 (319): C, 52.68; H, 5.05; found: C, 52.64; H,
5.00). IR (KBr, cmꢂ1): 3076 (CꢂH arom.), 2952 (CꢂH aliph.), 1755, 1745 (C O
=
=
est.), 1508, 1440, 1423, 1380 (C C), 1219, 1194, 1162, 1140 (CꢂOꢂC), 786 (CꢂCl).
1
0
00
H NMR (CDCl3, d, ppm, J, Hz): 2.23–2.17 (m, 4H: 2H3 , 2H3 ), 2.78–2.74
0
00
0
00
(t, J ¼ 7.2, 4H: 2H2 , 2H2 ), 3.68–3.65 (t, J ¼ 6.4, 4H: 2H4 , 2H4 ), 7.10 (s, 4H: 1H2,
13
0
00
0
1H3, 1H5, 1H6). C NMR (TMS, CDCl3, d, ppm): 27.44 (C3 , C3 ), 31.23 (C2 ,
=
C2 ), 43.88 (C4 , C4 ), 122.35 (C2, C3, C5, C6), 147.95 (C1, C4), 171.06 (C1 , C1 : C O).
00
0
00
0
00
CONCLUSIONS
In conclusion, two new fast, general, environmentally friendly, and facile meth-
ods for preparation of phenyl bisesters under microwave irradiation are presented.
The microwave enhances the esterification rate, the reaction time decreases dramati-
cally, the reaction conditions are milder, and the consumed energy decreases
considerably. In liquid phase under MW irradiation, the amount of used solvents
is reduced substantially, and solid phase assisted reactions are solvent-free. Conse-
quently, the microwave-assisted esterification reactions can be considered eco-
friendly. In most cases, in the liquid phase, under MW irradiation the yields are
greater, in some cases substantially (almost 75%). In the solid phase, under MW
irradiation the yields are moderate to good compared with the liquid phase but excel-
lent compared with conventional heating. Both methods are of interest for synthetic
chemistry, but because solid phase–assisted reactions are solvent-free, we consider
this one to be the most suitable. A comparative study of microwave and conven-
tional heating was done.

2208
G. N. ZBANCIOC, A. M. V. ZBANCIOC, AND I. I. MANGALAGIU
ACKNOWLEDGMENT
This work was financially supported by the Romanian Ministry of Education
and Research, grant C.N.C.S.I.S. cod 88 under the PN-II-ID-PCE-2008 Program.
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