Electrocatalytic multicomponent assembling of phthalhydrazide, aldehydes and malononitrile: An efficient approach to 1H-pyrazolo[1,2-b]phthalazine-5,10- diones

Article abstract of DOI:10.1016/j.crci.2013.09.017

Electrocatalytic multicomponent transformation of phthalhydrazide, aromatic aldehydes and malononitrile in n-propanol in an undivided cell in the presence of sodium bromide as an electrolyte leads to 1H-pyrazolo[1,2-b]phthalazine-5,10- diones in short reaction times (4-8 min) and high yields (85-98%) at room temperature. The developed efficient electrocatalytic approach to the corresponding 1H-pyrazolo[1,2-b]phthalazine-5,10-diones is beneficial from the viewpoint of diversity-oriented large-scale processes and represents a new example of the ecologically pure synthetic concept for electrocatalytic multicomponent reactions strategy.

Full text of DOI:10.1016/j.crci.2013.09.017

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CRAS2C-3832; No. of Pages 5
C. R. Chimie xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Comptes Rendus Chimie
www.sciencedirect.com
Preliminary communication/Communication
Electrocatalytic multicomponent assembling of
phthalhydrazide, aldehydes and malononitrile: An efficient
approach to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones
b
c
Hassan Kefayati a, , Shadi Homayoon Amlashi , Reyhaneh Kazemi-Rad , Adeleh
*
Delafrooz b
a Department of Chemistry, Guilan Science and Research Branch, Islamic Azad University, Rasht, Iran
b Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran
c Young Researchers and Elite Club, Guilan Science and Research Branch, Islamic Azad University, Rasht, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
Electrocatalytic multicomponent transformation of phthalhydrazide, aromatic aldehydes
and malononitrile in n-propanol in an undivided cell in the presence of sodium bromide as
an electrolyte leads to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones in short reaction times
(4–8 min) and high yields (85–98%) at room temperature. The developed efficient
electrocatalytic approach to the corresponding 1H-pyrazolo[1,2-b]phthalazine-5,10-
diones is beneficial from the viewpoint of diversity-oriented large-scale processes and
represents a new example of the ecologically pure synthetic concept for electrocatalytic
multicomponent reactions strategy.
Received 12 July 2013
Accepted after revision 30 September 2013
Available online xxx
Keywords:
Electrocatalytic transformation
Electrogenerated base
Pyrazolo[1,2-b]phthalazine-5,10-dione
Phthalhydrazide
ß 2013 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Multicomponent reaction
1. Introduction
To our knowledge, there are only a few multicompo-
nent reports for the synthesis of 1H-pyrazolo[1,2-b]phtha-
Pyrazoles are an important class of compounds for
new drugs’ development, as they are the core structure
of numerous biologically active compounds, including
blockbuster drugs such as celecoxib, Viagra, pyrazofurine,
and many others [1–4]. Furthermore, heterocycles
containing a phthalazine moiety are of current interest
due to their pharmacological and biological activities
[5–7]. For example, 1H-pyrazolo[1,2-b]phthalazine-dione
is described as an anti-inflammatory, analgesic, anti-
hypoxic, and anti-pyretic agent [6]. Phthalazine deriva-
tives are also found to possess anti-convulsant [8],
cardiotonic [9], and vasorelaxant [10] activities.
lazine-5,10-diones [11]. However, in spite of their
potential utility, some of the reported synthetic methods
suffer from limitations such as the use of an expensive
catalyst, long reaction times, difficult work-up and drastic
reaction conditions. Therefore, any new facile and highly
efficient synthetic approach to corresponding heterocycles
containing a phthalazine ring fragment is highly desirable.
Recently, it was found that chemical bases could be
replaced with an electrogenerated base (EGB) to promote
reactions in higher yields [12]. Electroorganic reactions
proceed generally smoothly and take place with good to
excellent yields with easy work-up and do not require the
use of harsh conditions such as high temperatures and
expensive reagents. Also, to date, no reports have been
published on the electrosynthesis of 1H-pyrazolo[1,2-
b]phthalazine-5,10-diones.
*
Corresponding author.
E-mail addresses: haskefayati@gmail.com, kefayati@iaurasht.ac.ir (H.
Kefayati).
1631-0748/$ – see front matter ß 2013 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.crci.2013.09.017
Please cite this article in press as: Kefayati H, et al. Electrocatalytic multicomponent assembling of phthalhydrazide,
aldehydes and malononitrile: An efficient approach to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. C. R. Chimie (2014),
http://dx.doi.org/10.1016/j.crci.2013.09.017

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H. Kefayati et al. / C. R. Chimie xxx (2014) xxx–xxx
O
O
O
O
Ar
CN
N
N
NH
NH
Electrolysis
CN
+
ArCHO
+
PrOH, NaBr
CN
NH2
2a-k
3
4a-k
1
Scheme 1. Electrosynthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones.
All these facts have prompted us to design a convenient
and facile multicomponent synthesis of 1H-pyrazolo[1,2-
b]phthalazine-5,10-diones based on the electrocatalytic
transformation of phthalhydrazide 1, aromatic aldehydes
2a–k, and malononitrile 3 in an undivided cell (Scheme 1).
2PrO + H2
CH(CN)2 + PrOH
Cathode: 2PrOH + 2e
in solution: CH2(CN)2 + PrO
Scheme 2. Formation of propioxide anion at the cathode.
2. Results and discussion
First, to evaluate the synthetic potential of the
procedure proposed and to optimize the electrolysis
conditions, the electrocatalytic multicomponent transfor-
mation of phthalhydrazide 1, 3-nitrobenzaldehydes 2a,
and malononitrile 3 into the corresponding 1H-pyra-
zolo[1,2-b]phthalazine-5,10-dione 4a in n-PrOH in an
undivided cell containing an iron electrode as cathode
and a Pt electrode as anode at constant current in the
presence of sodium bromide as an electrolyte was studied
at room temperature. As it is indicated in Table 1, the
current density 12 mA/cm2 (I = 60 mA, electrode surface
5 cm2) in n-PrOH was found to be the optimum one for the
electrochemically induced chain process and afforded the
highest yield (98%) of 4a. The current density increase up
to 16 mA/cm2 (I = 80 mA) results in a slight decrease of the
reaction yield, which may be connected with the activation
of undesired direct electrochemical processes possible
under these conditions and leading to the oligomerization
of the starting material.
Taking the above results into consideration, the
following mechanism for this electrocatalytic chain
transformation is proposed. As the initiation step of the
catalytic cycle, the deprotonation of an alcohol at the
cathode leads to the formation of propioxide anion. The
subsequent reaction in solution between propioxide anion
and malononitrile gives rise to malononitrile anion
(Scheme 2).
Then, Knoevenagel condensation of malononitrile
anion with aromatic aldehydes 2a–k takes place in
the solution with elimination of hydroxide anion and
formation of arylidene malononitrile 5. The subsequent
propioxide anion promoted Michael addition of phetal-
hydrazide 1 to electron-deficient Knoevenagel adduct 5,
followed by intramolecular cyclization to the correspond-
ing 1H-pyrazolo[1,2-b] phthalazine-5,10-diones 4a-k
(Scheme 3).
Under the optimal conditions (current density 12 mA/
cm2), the electrolysis of phthalhydrazide 1, aromatic
aldehydes 2a–k, and malononitrile 3 in an undivided cell
gives rise to the corresponding 1H-pyrazolo[1,2-b]phtha-
lazine-5,10-diones 4a–k in short reaction times (4–8 min)
and high yields (Table 2). The electronic nature of the
substituent on the aromatic ring showed no particular
effect on the conversion.
3. Conclusions
In conclusion, the use of an EGB in comparison with
conventional chemistry [11] has advantages such as (i) in
situ generation of base, (ii) one-pot reaction in excellent
yields under milder conditions, (iii) avoidance of polluting
or hazardous chemicals or the addition of base or probase;
moreover, its work-up procedure is easy.
Table 1
Electrocatalytic transformation of phthalhydrazide (1), 3-nitrobenzaldehyde (2a) and malononitrile (3) into 3-amino-1-(3-nitrophenyl)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4a)a.
Entry
Alcohol
I
Current density
Time
Electricity passed
(F molÀ1
)
Yield (%)
(mA)
(mAcmÀ2
)
(min)
1
2
3
4
5
EtOH
30
30
50
60
80
6
6
8
8
5
4
3
0.15
0.15
0.15
0.15
0.15
79
85
90
98
93
n-PrOH
n-PrOH
n-PrOH
n-PrOH
10
12
16
a
Phthalhydrazide (1 mmol), 3-nitrobenzaldehyde (1 mmol), malononitrile (1 mmol), NaBr (0.1 mmol), alcohol (10 mL), iron cathode (5 cm2), platinum
anode (5 cm2), room temperature.
Please cite this article in press as: Kefayati H, et al. Electrocatalytic multicomponent assembling of phthalhydrazide,
aldehydes and malononitrile: An efficient approach to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. C. R. Chimie (2014),
http://dx.doi.org/10.1016/j.crci.2013.09.017

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3
Table 2
Electrocatalytic transformation of phthalhydrazide (1), aromatic aldehydes (2a–k), and malononitrile (3) into 1H-pyrazolo[1,2-b]phthalazine-5,10-dione
(4a–k)a.
Product
4a
Aldehyde
Current density
Time
Electricity passed
Yield (%)
98
Mp (8C)
Mp (8C)
(lit. [11d])
(mAcmÀ2
)
(min)
(F molÀ1
)
12
4
0.15
269–270
269–271
O2N
CHO
4b
12
6
0.22
98
267–269
265–267
NO2
CHO
4c
4d
4e
12
12
12
5
5
5
0.19
0.19
0.19
85
98
95
228–229
275–277
259–261
228–229
275–276
259–260
O2N
CHO
CHO
OCH3
CHO
4f
12
12
12
7
6
8
0.26
0.22
0.30
91
87
98
249–250
259–261
272–274
248–251
257–259
270–272
H3CO
CHO
4g
4h
Cl
CHO
Cl
CHO
4i
4j
12
12
6
7
0.22
0.26
85
86
267–268
266–268
263–264
Br
N
CHO
–
CHO
4k
12
5
0.19
98
276–278
–
CHO
a
Phthalhydrazide (1 mmol), aromatic aldehydes (1 mmol), malononitrile (1 mmol), NaBr (0.1 mmol), alcohol (10 mL), iron cathode (5 cm2), platinum
anode (5 cm2), room temperature.
Please cite this article in press as: Kefayati H, et al. Electrocatalytic multicomponent assembling of phthalhydrazide,
aldehydes and malononitrile: An efficient approach to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. C. R. Chimie (2014),
http://dx.doi.org/10.1016/j.crci.2013.09.017

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O
NC
NC
O
NC
NC
H
CH(CN)2
CH2(CN)2
Ar
H
-H2O
Ar
Ar
5
2a-k
O
H
N
HN
OPr
The beginning of
Micheal
addition
new catalytic cycle
1
O
N
O
O
NH2
NH
OPr
O
O
O
C
H
N
N
PrOH
N
N
N
N
PrOH
CN
CN
PrO
+
CN
H
Ar
O
Ar
Ar
OPr
4a-k
Scheme 3. Proposed mechanism for the preparation of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones 4a–k.
4. Experimental
124.2, 116.3, 62.8 ppm; IR (KBr):
2160, 1658, 1558, 1515 cmÀ1
y = 3433, 3321, 3076,
.
4.1. General
4.2.2. 3-Amino-1-(2-methoxyphenyl)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4e)
Yellow powder; yield: 95%; mp = 259–261 8C; 1H NMR
All reagents were purchased from Merck and Fluka and
used without further purification. The melting points
were obtained in open capillary tubes and were measured
on an Electrothermal IA 9100 apparatus. IR spectra
were recorded on KBr pellets with a Shimadzu FT-IR
8600 spectrophotometer. 1H and 13C NMR spectra were
determined with a Bruker DRX-400 Avance instrument at
400 and 100 MHz. Elemental analysis were carried out
using a Thermo Finnigan Flash EA 1112 series instrument.
(400 MHz, DMSO-d6): dH 8.30–8.27 (m, 1H), 8.11–8.09 (m,
1H), 8.02 (brs, 2H, NH2), 8.01–7.97 (m, 2H), 7.32–7.27 (m,
2H), 7.04 (d, J = 7.6 Hz, 1H), 6.91 (dt, J = 7.6, 0.8 Hz, 1H), 6.35
(s, 1H), 3.74 (s, 3H, OCH3) ppm; 13C NMR (100 MHz, DMSO-
d6): 157.1, 156.9, 153.7, 151.5, 135.2, 134.2, 129.8, 129.1,
129.0, 127.9, 127.8, 127.2, 126.3, 121.2, 116.5, 112.1, 61.1,
59.4, 56.3 ppm; IR (KBr):
1564, 1379 cmÀ1
y = 3380, 3250, 3184, 2199, 1657,
.
4.2. General procedure for electrochemical synthesis of
pyrazolo[1,2-b]phthalazines
4.2.3. 3-Amino-1-(3-methoxyphenyl)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b] phthalazine-2-carbonitrile (4f)
Yellow powder; yield: 91%; mp = 249–250 8C; 1H NMR
A solution of phthalhydrazide (1.0 mmol), various aryl
aldehydes (1.0 mmol), and malononitrile (1.0 mmol) and
sodium bromide (0.1 mmol) in n-propanol (10 mL) was
electrolyzed in an undivided cell equipped with a magnetic
stirrer, a platinum anode and an iron cathode at room
temperature under a constant current density of 12 mA/
cm2 (I = 60 mA, electrodes square 5 cm2).
(400 MHz, DMSO-d6): dH 8.25–8.27 (m, 1H), 8.08–8.10 (m,
3H, NH2, H), 7.95–7.99 (m, 2H), 7.28 (t, J = 7.6 Hz, 1H),
6.99–7.01 (m, 2H), 6.89 (dd, J = 8.0, 1.6 Hz, 1H), 6.10 (s, 1H),
3.74 (s, 3H, OCH3) ppm; 13C NMR (100 MHz, DMSO-d6):
159.8, 157.1, 154.1, 151.1 138.1, 134.2, 130.1, 129.5, 129.3,
129.1, 127.3, 127.1, 124.2, 119.2, 113.8, 113.1, 64.0,
The progress of the reaction was monitored by thin
layer chromatography. After completion of the reaction (4–
8 minutes), the obtained precipitate was filtered, and the
filter cake was washed with ethanol to yield pure products
(4a–k).
55.6 ppm; IR (KBr):
1566 cmÀ1
y = 3361, 3259, 3056, 2190, 1654,
.
4.2.4. 3-Amino-1-(2-chlorophenyl)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4g)
Yellow powder; yield: 87%; mp = 259–261 8C; 1H NMR
4.2.1. 3-Amino-1-(4-nitrophenyl)-5,10-dioxo-5,10-dihydro-
1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4c)
(400 MHz, DMSO-d6): dH 8.29–8.27 (m, 1H), 8.14 (brs, 2H,
NH2), 8.11–8.07 (m, 1H), 8.01–7.96 (m, 2H), 7.60 (dd,
J = 7.0, 2.0 Hz, 1H), 7.48–7.46 (m, 1H), 7.38–7.31 (m, 2H),
6.46 (s, 1H) ppm; 13C NMR (100 MHz, DMSO-d6): 157.1,
154.0, 151.6, 135.8, 135.2, 134.3, 131.7, 130.4, 130.2,
129.5, 129.2, 128.8, 128.3, 127.8, 127.2, 116.2, 61.1,
Yellow powder; yield: 85%; mp = 228–229 8C; 1H NMR
(400 MHz, DMSO-d6): dH 8.27–8.29 (m, 1H), 8.22 (d,
J = 8.6 Hz, 2H), 8.20 (brs, 2H, NH2), 8.08–8.10 (m, 1H),
7.97–7.99 (m, 2H), 7.81 (d, J = 8.6 Hz, 2H), 6.30 (s, 1H) ppm;
13C NMR (100 MHz, DMSO-d6): 157.2, 154.2, 151.4, 151.3,
147.8, 146.3, 135.1, 134.3, 129.4, 128.9, 128.5, 127.8, 127.2,
60.2 ppm; IR (KBr):
1568, 1379 cmÀ1
y = 3367, 3232, 3171, 2206, 1655,
.
Please cite this article in press as: Kefayati H, et al. Electrocatalytic multicomponent assembling of phthalhydrazide,
aldehydes and malononitrile: An efficient approach to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. C. R. Chimie (2014),
http://dx.doi.org/10.1016/j.crci.2013.09.017

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5
4.2.5. 3-Amino-1-(4-chlorophenyl)-5,10-dioxo-5,10-
1560 cmÀ1; Anal. calcd. for C22H14N4O2: C, 72.12; H, 3.85;
N, 15.29. Found: C, 72.71; H, 3.50; N, 15.52.
dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4h)
Yellow powder; yield: 98%; mp = 272–274 8C; 1H NMR
(400 MHz, DMSO-d6): dH 8.27-8.24 (m, 1H), 8.13 (brs, 2H,
NH2), 8.10–8.06 (m, 1H), 7.99–7.94 (m, 2H), 7.52 (d,
J = 8.8 Hz, 2H), 7.43 (d, J = 8.8 Hz, 2H), 6.15 (s, 1H) ppm; 13
NMR (100 MHz, DMSO-d6): 157.1, 154.1, 151.2, 151.1,
Acknowledgements
C
Financial support for this work by the research council
of Islamic Azad University, Rasht Branch is gratefully
acknowledged.
137.1, 135.1, 134.2, 133.3, 129.3, 129.4, 129.0, 128.1, 127.7,
127.1, 116.4, 62.7 ppm; IR (KBr):
2196, 1656, 1566 cmÀ1
y = 3371, 3257, 3114,
.
References
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4.2.6. 3-Amino-1-(4-Bromophenyl)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4i)
Yellow powder; yield: 85%; mp = 267–268 8C; 1H NMR
(400 MHz, DMSO-d6): dH 8.27-8.25 (m, 1H), 8.13 (brs, 2H,
NH2), 8.10-8.07 (m, 1H), 7.98–7.96 (m, 2H), 7.56 (d,
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(b) D. O’Hagan, J. Fluorine Chem. 131 (2010) 1071.
J = 8.8 Hz, 2H), 7.46 (d, J = 8.8 Hz, 2H), 6.13 (s, 1H) ppm; 13
C
NMR (100 MHz, DMSO-d6): 157.1, 154.1, 151.2, 138.4,
135.1, 134.2, 131.9, 129.6, 129.3, 129.0, 127.7, 127.1, 121.9,
[5] F. Al-Assar, K.N. Zelenin, E.E. Lesiovskaya, I.P. Bezhan, B.A. Chakchir,
Pharm. Chem. J. 36 (2002) 598.
116.4, 62.8, 61.3 ppm; IR (KBr):
1655, 1560 cmÀ1
y = 3371, 3257, 3193, 2194,
[6] R.P. Jain, J.C. Vederas, Bioorg. Med. Chem. Lett. 14 (2004) 3655.
[7] R.W. Carling, K.W. Moore, L.J. Street, D. Wild, C. Isted, P.D. Leeson, S.
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[9] Y. Nomoto, H. Obase, H. Takai, M. Teranishi, J. Nakamura, K.C. Kubo,
Chem. Pharm. Bull. 38 (1990) 2179.
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[11] (a) M.R. Nabid, S.J.T. Rezaei, R. Ghahremanzadeh, A. Bazgir, Ultrason.
Sonochem. 17 (2010) 159;
.
4.2.7. 3-Amino-1-(pyridine carbaldehyde)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b]phthalazine-2-carbonitrile (4j)
Yellow powder; yield: 86%; mp = 266–268 8C; 1H NMR
(400 MHz, DMSO-d6): dH 8.73 (d, J= 1.6 Hz, 1H), 8.54 (dd,
J = 4.8, 1.2 Hz, 1H), 8.27–8.25 (m, 1H), 8.17 (brs, 2H, NH2),
8.10–8.08 (m, 1H), 7.99–7.96 (m, 2H), 7.94–7.92 (m, 1H),
7.40 (dd, J = 7.8, 4.4 Hz, 1H), 6.22 (s, 1H) ppm; IR (KBr):
y
= 3364, 3259, 3193, 2189, 1652, 1569, 1383 cmÀ1; Anal.
(b) R. Ghahremanzadeh, G.I. Shakibaei, A. Bazgir, Synlett 8 (2008)
1129;
(c) D.S. Raghuvanshi, K.N. Singh, Tetrahedron Lett. 52 (2011) 5702;
(d) H.R. Shaterian, M. Mohammadnia, J. Mol. Liq. 173 (2012) 55;
(e) G. Karthikeyana, A. Pandurangan, J. Mol. Catal. A: Chem. 361–362
(2012) 58.
calcd. for C17H11N5O2: C, 64.35; H, 3.49; N, 22.07. Found: C,
64.66; H, 3.27; N, 21.55.
4.2.8. 3-Amino-1-(1-naphtalen-1-yl)-5,10-dioxo-5,10-
dihydro-1H-pyrazolo[1,2-b] phthalazine-2-carbonitrile (4k)
Yellow powder; yield: 98%; mp = 276–278 8C; 1H NMR
[12] (a) M.N. Elinson, A.I. Ilovaisky, V.M. Merkulova, D.V. Demchuk, P.A.
Belyakov, Y.N. Ogibin, G.I. Nikishin, Electrochim. Acta 53 (2008) 8346;
(b) M.N. Elinson, V.M. Merkulova, A.I. Ilovaisky, A.O. Chizhov, P.A.
Belyakov, F. Barba, B. Batanero, Electrochim. Acta 55 (2010) 2129;
(c) M.N. Elinson, V.M. Merkulova, A.I. Ilovaisky, F. Barba, B. Batanero,
Electrochim. Acta 56 (2011) 8219;
(400 MHz, DMSO-d6): dH 8.30–8.28 (m, 1H), 8.16 (brs, 2H,
NH2), 7.89–8.08 (m, 7H), 7.53–7.60 (m, 3H), 6.30 (s, 1H)
ppm; 13C NMR (100 MHz, DMSO-d6): 157.2, 154.2, 151.1,
151.0 136.3, 135.1, 134.2, 133.3, 133.1, 129.3, 129.1, 128.9,
128.3, 128.1, 127.8, 127.1, 126.9, 126.8, 126.5, 124.8, 116.6,
(d) M.N. Elinson, A.I. Ilovaisky, V.M. Merkulova, T.A. Zaminovskaya, G.I.
Nikishin, Mendeleev Commun. 21 (2011) 122;
(e) M.N. Elinson, A.I. Ilovaisky, A.S. Dorofeev, V.M. Merkulova, N.O.
Stepanov, F.M. Miloserdov, Y.N. Ogibin, G.I. Nikishin, Tetrahedron 63
(2007) 10543.
63.7 ppm; IR (KBr):
y = 3365, 3255, 3193, 2190, 1652,
Please cite this article in press as: Kefayati H, et al. Electrocatalytic multicomponent assembling of phthalhydrazide,
aldehydes and malononitrile: An efficient approach to 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. C. R. Chimie (2014),
http://dx.doi.org/10.1016/j.crci.2013.09.017