Yb(OTf)3: An efficient catalyst for the synthesis of 11-Aryl-7H-cyclopenta[b][4,7]phenanthrolin-10(11H)-One derivatives

Article abstract of DOI:10.1002/jhet.977

A mild and efficient method for the synthesis of 8,9-dihydro-11-aryl-7H- cyclopenta[b][4,7]phenanthrolin-10(11H)-one derivatives via three-component reaction of aromatic aldehyde, quinolin-6-amine and cyclopentane-1,3-dione is described catalyzed by Yb(OTf)₃. The features of this procedure are mild reaction conditions, good to high yields, and operational simplicity.

Full text of DOI:10.1002/jhet.977

November 2012
Yb(OTf)3: An Efficient Catalyst for the Synthesis of 11-Aryl-7H-
cyclopenta[b][4,7]phenanthrolin-10(11H)-One Derivatives
1439
Bai-Xiang Du,a Ming-Yue Yin,a Mei-Mei Zhang,b Yu-Ling Li,a
a
*
and Xiang-Shan Wang
aSchool of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional
Materials, Xuzhou Normal University, Xuzhou Jiangsu 221116, People’s Republic of China
bThe Key Laboratory of Biotechnology on Medical Plant of Jiangsu Province, Xuzhou Normal
University, Xuzhou Jiangsu 221116, People’s Republic of China
*
E-mail: xswang1974@yahoo.com
Received February 15, 2011
DOI 10.1002/jhet.977
View this article online at wileyonlinelibrary.com.
A mild and efficient method for the synthesis of 8,9-dihydro-11-aryl-7H-cyclopenta[b][4,7]phenanthrolin-10
(11H)-one derivatives via three-component reaction of aromatic aldehyde, quinolin-6-amine and cyclopentane-
1,3-dione is described catalyzed by Yb(OTf)3. The features of this procedure are mild reaction conditions, good
to high yields, and operational simplicity.
J. Heterocyclic Chem., 49, 1439 (2012).
INTRODUCTION
of 1 mol % Yb(OTf)3, afforded the corresponding 8,9-
dihydro-11-aryl-7H-cyclopenta[b][4,7]phenanthrolin-10
(11H)-one derivatives 4 in good to high yields (Scheme 1).
Using the conversion of 2-fulorobenzaldehyde 1a,
quinolin-6-amine and cyclopentane-1,3-dione as a model,
several parameters were explored as shown in Table 1.
The yield of 4a was moderate at reflux in the absence
of Yb(OTf)3 (62%, Table 1, entry 1) and much greater
in the presence of various quantities of the catalyst,
reaching a maximum of 87% yield with 1 mol % Yb
(OTf)3 (Table 1, entries 2–11). The yield of 4a was also
dependent on temperature (entries 2, 5, and 6), proceed-
ing smoothly at reflux. Different solvents were also
tested and THF appeared to be the best medium for this
transformation (entry 2 vs. 13–14).
Over the past few years, Yb(OTf)3 has emerged as a
powerful catalyst for various organic transformations to
afford the products in good to excellent yields. Owing
to several advantages such as inexpensive, nontoxic,
ecofriendly nature, Yb(OTf)3 has been used as a catalyst
in the investigation of different organic reactions [1].
Phenanthrolines are important core structures found in
a variety of biologically important molecules [2]. It is
reported that metallic complexes possess a wide range
of biological activities, which confer applications as
anticancer [3], antiinflammatory [4], antitumor [5], anti-
microbial [6], and antibacterial agents [7]. Therefore,
much attention is devoted to the synthesis of these
active frameworks in recent years [8].
To the best of our knowledge, there is no report con-
cerning the synthesis of cyclopenta[b][4,7]phenanthrolin-
10(11H)-one derivatives. Such variations may contribute
to the bioactivity differences and enrich the phenanthroline
library for biomedical screening. As a continuation of our
research devoted to the development of new methods for
the preparation of heterocycles catalyzed by Yb(OTf)3
[9], herein, we would like to synthesize of 8,9-dihydro-
11-aryl-7H-cyclopenta[b][4,7] phenanthrolin-10(11H)-one
by a reaction of aromatic aldehyde, quinolin-6-amine, and
cyclopentane-1,3-dione catalyzed by Yb(OTf)3.
This process can tolerate both electron-donating (alkyl
and alkoxy) and electron-withdrawing (halogen) sub-
stituents on the aromatic aldehydes (Table 2). In all
cases, the reactions proceeded efficiently in THF at
reflux to afford the corresponding 7H-cyclopenta[b]
[4,7]phenanthrolin-10(11H)-one 4a-l in high yields.
1
All the compounds were characterized by H NMR, IR,
and HRMS.
The formation of 4 is likely to proceed via initial
condensation of aldehyde 1 with cyclopentane-1,3-dione
2 to afford 2-benzylidenecyclopentane-1,3-dione 5, which
further undergoes Michael addition with quinolin-6-amine
3 to furnish 6. Intramolecular nucleophilic reaction of its
isomer 7 could afford the compound 8, which could
eliminate one molecule of H2O to afford title product 4
(Scheme 2). The role of the catalyst Yb(OTf)3 is activating
the carbonyl groups in intermediate products 5 and 7.
RESULTS AND DISCUSSION
Treatment of aromatic aldehyde, quinolin-6-amine,
and cyclopentane-1,3-dione in reflux THF in the presence
© 2012 HeteroCorporation

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B.-X. Du, M.-Y. Yin, M.-M. Zhang, Y.-L. Li, and X.-S. Wang
Vol 49
Scheme 1. The reaction of 1, 2, and 3 catalyzed by Yb(OTf)3.
Scheme 2. Reaction mechanism of 1, 2, and 3 catalyzed by Yb(OTf)3.
Table 1
Synthesis of 4a at different reaction conditions.a
Entry
T (°C)
Solvent
Cat. (mol %)
Yieldb (%)
1
2
3
4
5
6
7
8
Reflux
Reflux
Reflux
Reflux
r.t
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
CH3CN
Benzene
DMF
0
62
87
86
87
Trace
73
83
80
78
85
Yb(OTf)3 (1)
Yb(OTf)3 (5)
Yb(OTf)3 (10)
Yb(OTf)3 (1)
Yb(OTf)3 (1)
AgOTf (1)
Cu(OTf)2 (1)
Zn(OTf)2 (1)
Y(OTf)3 (1)
Fe(OTf)2 (1)
Yb(OTf)3 (1)
Yb(OTf)3 (1)
Yb(OTf)3 (1)
10(11H)-one derivatives via three-component reaction of
aromatic aldehyde, quinolin-6-amine, and cyclopentane-1,3-
dione catalyzed by Yb(OTf)3. The features of this procedure
are mild reaction conditions, good to high yields, and opera-
tional simplicity.
50
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
80
9
10
11
12
13
14
79
85
84
80
EXPERIMENTAL
aReaction condition: 10 mL solvent, 2-fluorobenzaldehyde (0.248 g,
2.0 mmol), quinolin-6-amine (0.288 g, 2.0 mmol), cyclopentane-1,3-
dione (0.196 g, 2.0 mmol).
Melting points were determined in open capillaries and are
uncorrected. IR spectra were recorded on a Tensor 27 spec-
trometer in KBr pellet. 1H NMR spectra was obtained from a so-
lution in DMSO-d6 with Me4Si as internal standard using a
Bruker-400 spectrometer. HRMS analyses were carried out
using a Bruker-micro-TOF-Q-MS analyzer.
bIsolated yields.
Table 2
General procedure for the synthesis of 7H-cyclopenta
[b][4,7]phenanthrolin- 10(11H)-one derivatives 4.
Synthetic results of 4 in THF catalyzed by Yb(OTf)3.a
A dry
50-mL-flask was charged with aromatic aldehyde (2.0 mmol),
quinolin-6-amine (2.0 mmol, 0.288 g), and cyclopentane-1,3-
dione (2.0 mmol, 0.196 g), THF (10 mL) and Yb(OTf)3 (0.02
mmol, 0.012 g). The reaction mixture was stirred at reflux for
12–16 h, after completion of the reaction as indicated by TLC,
another portion of THF was added to the mixture until all the
yellow solid was dissolved. The desired products 4 were
obtained as yellow powder by filtration, when the mixture was
cooled to room temperature.
Time
(h)
Isolated Yields
(%)
Entry
Ar
Products
1
2
3
4
5
6
7
8
9
2-FC6H4
2-ClC6H4
4-ClC6H4
3-BrC6H4
4-BrC6H4
4-CH3C6H4
3-CH3OC6H4
3,4-Cl2C6H3
3,4-(CH3)
2C6H3
4a
4b
4c
4d
4e
4f
4g
4h
4i
12
12
14
14
16
16
16
10
16
87
88
92
82
86
90
92
86
83
11-(2-Fluorophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]phe-
nanthrolin-10(11H)-one 4a. 1H NMR (DMSO-d6, 400 MHz): δH
2.21–2.32 (m, 2H, CH2), 2.67–2.76 (m, 2H, CH2), 5.81 (s, 1H,
CH), 6.90–7.19 (m, 4H, ArH), 7.41(s, 1H, ArH), 7.50
(d, J = 8.0 Hz, 1H, ArH), 7.90 (d, J = 8.0 Hz, 1H, ArH), 8.18
(d, J = 7.6 Hz, 1H, ArH), 8.65 (s, 1H, ArH), 10.50 (s, 1H,
NH). IR (KBr): ν 3242, 3173, 3092, 3040, 2923, 1668, 1624,
1609, 1576, 1530, 1487, 1416, 1399, 1342, 1272, 1241, 1219,
10
3,4-
4j
16
86
OCH2OC6H3
2,3-Cl2C6H3
2,4-Cl2C6H3
11
12
4k
4l
12
12
90
89
aReagents and conditions: 1 (2.0 mmol), 2 (0.288 g, 2.0 mmol), 3
(0.196 g, 2.0 mmol), THF (10 mL). Yb(OTf)3 (0.012 g, 0.02 mmol).
831, 756, 699 cm−1
.
HRMS (ESI, m/z): Calcd for
C21H16FN2O (M + H+) 331.1247, found 331.1232.
11-(2-Chlorophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4b. 1H NMR (DMSO-d6, 400
MHz): δH 2.19–2.31 (m, 2H, CH2), 2.67–2.72 (m, 2H, CH2),
5.93 (s, 1H, CH), 7.06–7.12 (m, 3H, ArH), 7.31 (d, J = 7.6
Hz, 1H, ArH), 7.39 (dd, J = 8.4Hz, J′ = 4.4 Hz, 1H, ArH),
7.50 (d, J = 8.8 Hz, 1H, ArH), 7.91 (d, J = 8.8 Hz, 1H,
CONCLUSION
In conclusion, we found a mild and efficient method for the
synthesis of 11-aryl-7H-cyclopenta[b][4,7]phenanthrolin-
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

November 2012
Yb(OTf)3: An Efficient Catalyst for the Synthesis of 11-Aryl-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one Derivatives
1441
ArH), 8.16 (d, J = 8.4 Hz, 1H, ArH), 8.64 (s, 1H, ArH),
10.50 (s, 1H, NH). IR (KBr): ν 3245, 3180, 3098, 3040, 2971,
2921, 1682, 1629, 1577, 1530, 1468, 1416, 1394, 1273, 1218,
1051, 1034, 834, 746, 699 cm−1. HRMS (ESI, m/z): Calcd. for
C21H16ClN2O (M + H+) 347.0951, found 347.0953.
11-(4-Chlorophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4c. 1H NMR (DMSO-d6, 400
MHz): δH 2.27–2.34 (m, 2H, CH2), 2.67–2.74 (m, 2H, CH2),
5.70 (s, 1H, CH), 7.18–7.24 (m, 4H, ArH), 7.36 (dd, J = 8.4
Hz, J′ = 4.4 Hz, 1H, ArH), 7.55 (d, J = 8.8 Hz, 1H, ArH),
7.95 (d, J = 8.8 Hz, 1H, ArH), 8.18 (d, J = 8.4 Hz, 1H, ArH),
8.68 (dd, J = 4.4 Hz, J′ = 1.6 Hz, 1H, ArH), 10.45 (s, 1H, NH).
IR (KBr): ν 3273, 3179, 3095, 3052, 2969, 2931, 1668,
1625, 1578, 1517, 1489, 1466, 1388, 1338, 1272, 1242, 1218,
1087, 1013, 957, 832, 790, 768, 689 cm−1. HRMS (ESI, m/z):
Calcd for C21H15ClN2ONa (M + Na+) 369.0771, found 369.0790.
m/z): Calcd for C22H18N2O2Na (M + Na+) 365.1266, found
365.1259.
11-(3,4-Dichlorophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4h. 1H NMR (DMSO-d6, 400
MHz): δH 2.29–2.34 (m, 2H, CH2), 2.67–2.73 (m, 2H, CH2),
5.76 (m, 1H, CH), 7.03 (dd, J = 8.4 Hz, J′ = 2.0 Hz, 1H, ArH),
7.37–7.42 (m, 2H, ArH), 7.54 (d, J = 2.0 Hz, 1H, ArH), 7.56 (d,
J = 9.2 Hz, 1H, ArH), 7.97 (d, J = 9.2 Hz, 1H, ArH), 8.21 (d,
J = 8.4 Hz, 1H, ArH), 8.69(dd, J = 4.0 Hz, J′ = 1.6 Hz,
1H, ArH), 10.53 (s, 1H, NH). IR (KBr): ν 3177, 3083, 3053,
3020, 2962, 2927, 1668, 1624, 1590, 1511, 1465, 1415, 1388,
1342, 1273, 1241, 1218, 1187, 1132, 1029, 1014, 993, 956, 883,
832, 791, 728, 691 cm−1. HRMS (ESI, m/z): Calcd for
C21H15Cl2N2O (M + H+) 381.0561, found 381.0574.
8,9-Dihydro-11-(3,4-dimethylphenyl)-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4i. 1H NMR (DMSO-d6, 400
MHz): δH 2.04 (s, 6H, 2CH3), 2.21–2.33(m, 2H, CH2),
2.61–2.72 (m, 2H, CH2), 5.55 (s, 1H, CH), 6.83–6.75 (m, 3H,
ArH), 7.35 (dd, J = 8.0 Hz, J′ = 4.0 Hz, 1H, ArH), 7.52
(d, J = 8.8 Hz, 1H, ArH), 7.91 (d, J = 8.8 Hz, 1H, ArH), 8.20
(d, J = 8.0 Hz, 1H, ArH), 8.65 (s, 1H, ArH), 10.39 (s, 1H,
NH). IR (KBr): ν 3237, 3166, 3087, 3034, 2921, 2856, 1665,
1625, 1607, 1576, 1467, 1415, 1396, 1272, 1242, 1215, 1150,
1125, 1112, 1061, 1041, 1012, 990, 957, 828, 803, 781, 760,
719, 700 cm−1. HRMS (ESI, m/z): Calcd for C23H20N2ONa
(M + Na+) 363.1473, found 363.1484.
11-(3-Bromophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4d. 1H NMR (DMSO-d6, 400
MHz): δH 2.25–2.35 (m, 2H, CH2), 2.64–2.77 (m, 2H, CH2), 5.71
(s, 1H, CH), 7.11 (d, J = 6.4 Hz, 2H, ArH), 7.24 (d, J = 6.4 Hz,
1H, ArH), 7.36–7.40 (m, 2H, ArH), 7.55 (d, J = 8.8 Hz, 1H, ArH),
7.95 (d, J = 8.8 Hz, 1H, ArH), 8.20 (d, J = 8.4 Hz, 1H, ArH), 8.68
(d, J = 3.2 Hz, 1H, ArH), 10.51 (s, 1H, NH). IR (KBr): ν 3281,
3199, 3117, 3067, 3032, 2918, 1672, 1627, 1607, 1520, 1466,
1392, 1323, 1272, 1214, 1174, 1162, 1116, 1073, 1011, 839, 801,
787, 753, 685 cm−1. HRMS (ESI, m/z): Calcd for C21H16BrN2O
(M + H+) 391.0446, found 391.0448.
11-Methylenedioxophenyl-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4j. 1H NMR (DMSO-d6, 400
MHz): δH 2.28–2.31 (m, 2H, CH2), 2.67–2.71 (m, 2H, CH2),
5.60 (s, 1H, CH), 5.88 (d, J = 11.6 Hz, 2H, CH2), 6.53
(dd, J = 8.0 Hz, J′ = 1.6 Hz, 1H, ArH), 6.67 (d, J = 8.0 Hz,
1H, ArH), 6.78 (d, J = 1.6 Hz, 1H, ArH), 7.38 (dd, J = 8.4
Hz, J′ = 4.4 Hz, 1H, ArH), 7.53 (d, J = 9.2 Hz, 1H, ArH),
7.92 (d, J = 8.8 Hz, 1H, ArH), 8.24 (d, J = 8.4 Hz, 1H, ArH),
8.66–8.67 (m, 1H. ArH), 10.45 (s, 1H, NH). IR (KBr): ν 3237,
3165, 3086, 3036, 2924, 2853, 1665, 1610, 1536, 1502, 1488,
1467, 1397, 1363, 1254, 1216, 1180, 1036, 922, 829, 810,
792 cm−1. HRMS (ESI, m/z): Calcd for C22H17N2O3 (M + H+)
357.1239, found 357.1243.
11-(4-Bromophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4e. 1H NMR (DMSO-d6, 400
MHz): δH 2.27–2.34(m, 2H, CH2), 2.67–2.73 (m, 2H, CH2),
5.69 (s, 1H, CH), 7.12–7.16 (m, 2H, ArH), 7.37–7.38 (m, 3H,
ArH), 7.55 (d, J = 9.2 Hz, 1H, ArH), 7.95 (d, J = 8.8 Hz, 1H,
ArH), 8.18 (d, J = 8.4 Hz, 1H, ArH), 8.68 (dd, J = 4.0 Hz,
J′ = 1.6 Hz, 1H, ArH), 10.48 (s, 1H, NH). IR (KBr): ν 3172,
3092, 3049, 2968, 2929, 2856, 1667, 1624, 1575, 1518, 1465,
1415, 1387, 1336, 1271, 1217, 1181, 1157, 1111, 1069, 1010,
956, 832, 788, 767, 729, 687 cm−1. HRMS (ESI, m/z): Calcd
for C21H16BrN2O (M + H+) 391.0446, found 391.0443.
8,9-Dihydro-11-p-tolyl-7H-cyclopenta[b][4,7]phenanthrolin-
10(11H)-one 4f. 1H NMR (DMSO-d6, 400 MHz): δH 2.14
(s, 3H, CH3), 2.21–2.33 (m, 2H, CH2), 2.68–2.70 (m, 2H,
CH2), 5.61 (s, 1H, CH), 6.95 (d, J = 7.6 Hz, 2H, ArH), 7.06
(d, J = 8.0 Hz, 2H, ArH), 7.34 (dd, J = 8.4 Hz, J′ = 4.4 Hz,
1H, ArH), 7.54 (d, J = 9.2 Hz, 1H, ArH), 7.92 (d, J = 9.2 Hz,
1H, ArH), 8.20 (d, J = 8.4 Hz, 1H, ArH), 8.66 (dd, J = 8.0 Hz,
J′ = 1.6 Hz, 1H, ArH), 10.40 (s, 1H, NH). IR (KBr): ν 3178,
3093, 3044, 3017, 2929, 2854, 1669, 1625, 1586, 1516, 1466,
1416, 1387, 1272, 1219, 1111, 1012, 957, 828, 790, 776,
690 cm−1. HRMS (ESI, m/z): Calcd for C21H19N2O (M + H+)
327.1497, found 327.1495.
11-(2,3-Dichlorophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4k. 1H NMR (DMSO-d6, 400
MHz): δH 2.20–2.34 (m, 2H, CH2), 2.89 (s, 2H, CH2), 6.01
(s, 1H, CH), 7.13–7.17 (m, 2H, ArH), 7.35 (d, J = 8.8 Hz, 1H,
ArH), 7.42 (dd, J = 8.8 Hz, J′ = 4.4 Hz, 1H, ArH), 7.53
(d, J = 9.2 Hz, 1H, ArH), 7.92–7.95 (m, 1H, ArH), 8.06
(d, J = 8.4 Hz, 1H, ArH), 8.67 (d, J = 3.6 Hz, 1H, ArH),
10.59 (s, 1H, NH). IR (KBr): ν 3233, 3165, 3082, 3015, 2928,
2860, 1673, 1625, 1594, 1523, 1464, 1417, 1389, 1270, 1240,
1219, 1174, 1155, 1086, 1042, 1013, 957, 827, 738, 709, 635
cm−1. HRMS (ESI, m/z): Calcd for C21H15Cl2N2O (M + H+)
381.0561, found 381.0565.
8,9-Dihydro-11-(3-methoxyphenyl)-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4g. 1H NMR (DMSO-d6, 400
MHz): δH 2.34–2.35 (m, 2H, CH2), 2.63–2.73 (m, 2H,
CH2), 3.64 (s, 3H, CH3O), 5.63 (s, 1H, CH), 6.61–6.66 (m,
2H, ArH), 6.80 (s, 1H, ArH), 7.04–7.07 (m, 1H, ArH), 7.37
(dd, J = 8.4 Hz, J′ = 4.0 Hz, 1H, ArH), 7.55 (d, J = 8.8
Hz, 1H, ArH), 7.93 (d, J = 8.8 Hz, 1H, ArH), 8.22 (d, J =
8.4 Hz, 1H, ArH), 8.67 (d, J = 3.6 Hz, 1H, ArH), 10.46 (s,
1H, NH). IR (KBr): ν 3238, 3170, 3091, 3028, 2930, 2835,
1668, 1627, 1606, 1528, 1487, 1465, 1438, 1394, 1311,
1259, 1217, 1143, 1046, 1013, 831, 689 cm−1. HRMS (ESI,
11-(2,4-Dichlorophenyl)-8,9-dihydro-7H-cyclopenta[b][4,7]
phenanthrolin-10(11H)-one 4l. 1H NMR (DMSO-d6, 400 MHz):
δH 2.19–2.34 (m, 2H, CH2), 2.73 (m, 2H, CH2), 5.92 (s, 1H, CH),
7.14 (d, J = 8.0 Hz, 1H, ArH), 7.22 (dd, J = 8.4 Hz, J′ = 1.6 Hz,
1H, ArH), 7.41 (dd, J = 8.4 Hz, J′ = 4.4 Hz, 1H, ArH), 7.48 (d,
J = 1.6 Hz, 1H, ArH), 7.51 (d, J = 8.8 Hz, 1H, ArH), 7.92
(d, J = 8.8 Hz, 1H, ArH), 8.07 (d, J = 8.8 Hz, 1H, ArH),
8.66–8.67 (m, 1H, ArH), 10.56 (s, 1H, NH). IR (KBr): ν 3238,
3172, 3095, 3028, 2961, 2920, 1670, 1625, 1598, 1526,
1466, 1437, 1390, 1269, 1239, 1221, 1097, 1044, 1013, 957,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1442
B.-X. Du, M.-Y. Yin, M.-M. Zhang, Y.-L. Li, and X.-S. Wang
Vol 49
845, 827, 769, 690, 645 cm−1. HRMS (ESI, m/z): Calcd for
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Acknowledgment. The authors are grateful to the National Natural
Science foundation of China (20802061), the Natural Science
foundation (08KJD150019), and Qing Lan Project (08QLT001) of
Jiangsu Education Committee for financial support.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet