Design, synthesis and insecticidal activity of spiro heterocycle containing neonicotinoid analogs

Article abstract of DOI:10.1016/j.cclet.2013.12.004

Spiro heterocycles frequently occur in bioactive molecules. In the pursuit of neonicotinoids with spiro heterocycles, three types of novel neonicotinoids with spirobenzofuranone, spirooxindole or spiroacenaphythylenone framework were designed and synthesized. Insecticidal evaluation showed that some of spirobenzofuranone containing neonicotinoids exhibited moderate activity against cowpea aphid, armyworm or brown planthopper.

Full text of DOI:10.1016/j.cclet.2013.12.004

Chinese Chemical Letters 25 (2014) 197–200
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Original article
Design, synthesis and insecticidal activity of spiro heterocycle
containing neonicotinoid analogs
*
Nan-Yang Chen, Li-Ping Ren, Min-Ming Zou, Zhi-Ping Xu, Xu-Sheng Shao ,
*
Xiao-Yong Xu, Zhong Li
Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Spiro heterocycles frequently occur in bioactive molecules. In the pursuit of neonicotinoids with spiro
heterocycles, three types of novel neonicotinoids with spirobenzofuranone, spirooxindole or
spiroacenaphythylenone framework were designed and synthesized. Insecticidal evaluation showed
that some of spirobenzofuranone containing neonicotinoids exhibited moderate activity against cowpea
aphid, armyworm or brown planthopper.
Received 23 September 2013
Received in revised form 24 November 2013
Accepted 25 November 2013
Available online 7 December 2013
ß 2013 Xu-Sheng Shao and Zhong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All
rights reserved.
Keywords:
Neonicotinoid
Spiro heterocycle
Activity
Insecticide
1. Introduction
AM-400 (400 MHz) spectrometer with DMSO-d6 as the solvent and
TMS as the internal standard. Chemical shifts are reported in
(parts per million) values. High-resolution mass spectra were
recorded under electron impact (70 eV) conditions using
d
Spiro heterocycles often exist in a number of natural or
synthetic molecules [1–3]. A spiro compound in which the spiro
carbon is part of cyclic ring has many unique properties, such as
spiroconjugation, anomeric effect and axial chirality [4–7].
Therefore, spiro heterocyclic scaffolds have broad applications in
many areas [8–12] and are widely used as building blocks for
generating biological and pharmaceutical relevance [13–15].
Neonicotinoid is the largest insecticide now [16–18], but its
superiority is being challenged due to resistance [19] and severe
bee toxicity [20,21]. Thus, there is an urgent need for the
development of novel, effective, neonicotinoid replacements. As
part of a project aiming at exploring functionality of the spiro
heterocycle core in neonicotinoids, we herein report our investi-
gation in spiro heterocycle containing neonicotinoids.
a
MicroMass GCT CA 055 instrument. Analytical thin-layer chroma-
tography (TLC) was carried out on precoated plates (silica gel 60
F254), and spots were visualized with ultraviolet (UV) light.
The general synthetic methods for compounds 8a–d, 9a–g and
10a and 10b are depicted in Schemes 1–3. Unless otherwise noted,
reagents and solvents were used as received from commercial
suppliers. Yields were not optimized. All reactions were carried out
under a protective atmosphere of drying nitrogen or utilizing a
calcium chloride tube.
General syntheticprocedurefor8a–d: Knoevenageladduct2was
synthesized according to the reported procedure [8]. A mixture of
phthalic anhydride (1.480 g, 10 mmol) and malononitrile (0.66 g,
11 mmol) in THF (25 mL) were stirred at room temperature. Then,
diisopropylamine (DIPA) (2.02 g, 20 mmol) was added dropwise.
The resulting mixture was stirred at room temperature for 8 h, and
then was filtered and the precipitate was washed with THF (10 mL)
to afford the white solid. Then, to a solution of the obtained white
solid in 1,2-dichloroethane (20 mL) was added POCl3 (10 mmol)
dropwise at room temperature. After completion, the mixture was
refluxed and the progress of the reaction was monitored by TLC. At
last, the reaction mixture was neutralized by saturated dicarbonate
solution to pH 7, extracted by dichloromethane (30 mL ꢀ 3),
concentrated and the residue was purified by flash chromatography
eluting with dichloromethane to afford compound 2 (yield 40%).
2. Experimental
2.1. Chemistry
Melting points (mp) were recorded on Bu¨chi B540 apparatus
(Bu¨chi Labortechnik AG, Flawil, Switzerland) and are uncorrected.
The 1H NMR and 13C NMR spectra were recorded on Bruker
*
Corresponding authors.
E-mail addresses: shaoxusheng@ecust.edu.cn (X.-S. Shao), lizhong@ecust.edu.cn
(Z. Li).
1001-8417/$ – see front matter ß 2013 Xu-Sheng Shao and Zhong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2013.12.004

198
N.-Y. Chen et al. / Chinese Chemical Letters 25 (2014) 197–200
NC
CN
O
O
o
CN
CN
O
DMF or MeCN, 50 or 120
C
1. THF/DIPA
O N
2
CN
O
O
+
NO
2
2. 1,2-dichloroethane/POCl
8a: R = H, n = 1
3
7a: R = H, n = 1
7b: R = H, n = 2
1
1
R
8b: R = H, n = 2
1
1
1
N
N
n
O
O
NH
2
R
1
2
N
NH
n
1
8c: R
=
=
, n = 1
, n = 1
7c: R
=
=
, n = 1
, n = 1
1
Cl
N
1
Cl
N
8a-d
7
8d: R
7d: R
1
1
Scheme 1. Synthetic routes for neonicotinoids containing spiro heterocycles 8a–d.
NC
CN
O
NH
R2
CN
CN
EtOH, reflux
EtOH
O
CN
O
O +
O2N
NO2
N
H
N
piperidine, reflux
H
R1
3a
4
7a: R1 = H, n = 1
7b: R1 = H, n = 2
9a: R1 = H, n = 1
9b: R1 = H, n = 2
N
N
NH2
R1
NH
n
N
n
7c: R1
=
, n = 1
9g: R1
=
, n = 1
9a, 9b and 9g
Cl
N
Cl
N
7
NO2
O
NH
R2
R2
CN
CN
EtOH
piperidine, reflux
+
R1
O
CN
+
O
NH
n
N
O2N
N
N
H
R1
3
9c: R1 = H, n = 1, R2 = NO2
9d: R1 = H, n = 2, R2 = NO2
9e: R1 = H, n = 1, R2 = CH3
9f: R1 = H, n = 2, R2 = CH3
7
N
n
NH2
7a: R1 = H, n = 1
7b: R1 = H, n = 2
3b: R2 = NO2
3c: R2 = CH3
9c-f
Scheme 2. Synthetic routes for neonicotinoids containing spiro heterocycles 9a–g.
Then,
a
solution of compound
2
(0.190 g, 1 mmol) and
General synthetic procedure for 10a and 10b: A mixture of
acenaphthylene-1,2-dione (1.820 g, 10 mmol) and malononitrile
(0.60 g, 10 mmol) in absolute ethanol (20 mL) was refluxed for
30 min. The cooled mixture was filtered and the precipitate was
washed with cold ethanol (10 mL) to afford compound 6 (yield
85%). Then, a solution of compound 6 (0.230 g, 1 mmol) and 7a and
7b (1 mmol) in 5 mL of mixed solvent of dichloromethane and
methanol (4:1, v/v) was stirred for 2 h at room temperature. At last,
the mixture was filtered and the precipitate was washed with
methanol (4 mL) to afford the pure products 10a and 10b.
Analytical data of the target compounds are listed in Supporting
information.
compounds 7a–d (1 mmol) in DMF (4 mL) was heated at
50 8C or 120 8C with the progress of the reaction monitored
by TLC. After completion, the mixture was concentrated and the
residue was purified by recrystallization with ethanol to afford
the pure products 8a–d.
General synthetic procedure for 9a–g: Method 1 (for 9a, 9b and
9g): A mixture of isatin (1.470 g, 10 mmol), malononitrile (0.60 g,
10 mmol) and piperidine (10 mol%) in absolute ethanol (10 mL)
was refluxed for 1 h. The cooled mixture was filtered and the
precipitate was washed with ethanol (4 mL) to afford compound 4
(yield 80%). Then, a solution of compound 4 (0.189 g, 1 mmol) and
compound 7a–c (1 mmol) in ethanol (4 mL) was refluxed for 8 h.
The mixture was filtered and the precipitate washed with cold
ethanol (4 mL) affording the pure products 9a, 9b and 9g. Method 2
(one-pot procedure for 9c–9f): A solution of 3b or 3c (1 mmol),
malononitrile (0.060 g, 1 mmol) and piperidine (10 mol%) was
refluxed in ethanol (4 mL) for 1 h. Then, 7a or 7b was added
simultaneously. The resulted mixture was stirred for 8 h under
refluxing condition with the progress of the reaction monitored by
TLC. After completion, the cooled mixture was filtered and the
precipitate was washed with cold ethanol (4 mL) to afford the
desired products 9c–9f.
2.2. Biological assay
All bioassays were performed on representative test organisms
grown in the laboratory. The bioassay was repeated at (25 ꢁ 1) 8C
according to statistical requirements. All compounds were dissolved
in N,N-dimethylformamide (AP, Shanghai Chemical Reagent Co., Ltd.,
Shanghai, China) and diluted with distilled water containing Triton X-
100 (0.1 mg Lꢂ1) to obtain a series of concentrations of 500.0, 250.0,
125.0 mg Lꢂ1 and others for bioassays. The results of bioassay are
depicted in Table 1.
NO
2
NC
R
1
O
O
O
CN
NH
n
N
O
O N
2
CN
NH
CN
CN
7a: R = H, n = 1
1
EtOH
7
7b: R = H, n = 2
1
+
R
1
N
N
reflux, 30 min
2
CH Cl /MeOH, r.t.
2
2
n
10a: R = H, n = 1
1
10b: R = H, n = 2
10a-b
5
6
1
Scheme 3. Synthetic routes for neonicotinoids containing spiro heterocycles 10a–b.

N.-Y. Chen et al. / Chinese Chemical Letters 25 (2014) 197–200
199
Table 1
affording tetrahydroimidazo[1,2-a]pyridine derivatives as high
active neonicotinoids [25]. Enlightened by this, the spiro hetero-
cycle might be embodied in parental neonicotinoid by the
corresponding spirocyclization using cyclic KAs. Therefore, cyclic
Insecticidal activity of compounds 8a–d, 9a–g and 10a and b against cowpea aphis
(Aphis craccivora), armyworm (Mythimna separata) and brown planthopper
(Nilaparvata lugens).
Compound
Mortality (%, 500 mg Lꢂ1
)
KAs 2,
4 and 6 were prepared here by condensation of
Aphis craccivora
Mythimna separata
Nilaparvata lugens
malononitrile and cyclic ketones according to reported procedures
[8,26].
8a
0
0
100
20
0
0
0
Reactions of 7 with KAs 2, 4 and 6 afforded spirobenzofuranones
8a–d, spirooxindoles 9a–g and spiroaceraphthylenones 10a and
10b, respectively, as spiro heterocycle containing neonicotinoids.
In further studies, we found that compounds 9a–g could be easily
obtained in high yields by a one-pot method from nitroeamine 7,
ketone 3 and malononitrile. The reaction solvents of 7a with 6 were
screened. The reaction proceeded very well in the mixed solvent of
dichloromethane and methanol (4:1), while no reactions were
detected in the single solvents, such as dichloromethane, metha-
nol, ethanol, pyridine and acetonitrile. Spirocyclization of 7c with 6
was unsuccessful probably due to steric effects. Attempts to
synthesize corresponding products using other cyclic KAs 2-(2,3-
dihydro-1H-inden-1-ylidene)malononitrile and 2-cyclohexylide-
nemalononitrile failed in varied solvents, such as acentonitrile,
dichloromethane, methanol and DMF.
8b
8c
90
0
95
0
8d
80
0
9a
0
0
9b
0
0
0
9c
0
0
0
9d
0
0
0
9e
0
0
0
9f
0
0
0
9g
0
0
0
10a
0
0
0
10b
0
0
0
Imidacloprid
100
–
100
Insecticidal test for cowpea aphids (Aphis craccivora): The
activities of insecticidal compounds against cowpea aphids were
tested by leaf-dip method. The leaves of the horsebean plant with
40–60 apterous adults were dipped in diluted solutions of the
chemicals containing Triton X-100 (0.1 mg Lꢂ1) for 5 s and the
excess solution was sucked out with filter paper, and the burgeons
were placed in the conditioned room ((25 ꢁ 1) 8C, 50% RH). Water
containing Triton X-100 (0.1 mg Lꢂ1) was used as a control. The
mortality rates were evaluated 24 h after treatment. Each treatment
had three repetitions and the data were adjusted and subjected to
probit analysis as before.
Insecticidal test for Armyworm (Mythimna separata): The
insecticidal activity against armyworm was tested by foliar
application. Individual corn (Zea mays) leaves were placed on
moistened pieces of filter paper in Petri dishes. The leaves were
then sprayed with the sample solutions and exposed to dry. The
dishes were infested with 10 s-instar larvae and placed in the
conditioned room. The mortality rates were evaluated 48 h after
treatment. Each treatment had three repetitions and the data were
adjusted and subjected to probit analysis as before.
Insecticidal test for brown planthopper (Nilaparvata lugens):
The activities of insecticidal compounds against Nilaparvata lugens
were tested using the dipping method. Rice plants at tillering to
booting stage were pulled out and the rice stems (about 10 cm
lengths) with roots were cut and air dried to remove excess water.
Three rice stems were dipped in appropriate solutions of tested
compound for 30 s. After rice stems had been air dried, the rice
roots was wrapped with moistened cotton and then placed into a
tumbler. Thirty N. lugens were introduced into the tumbler with
3.2. Insecticidal activity
The insecticidal activity of the target compounds against cowpea
aphids (A. craccivora), armyworm (M. sepatara) and brown
planthopper (N. lugens) was evaluated. Spirobenzofuranone analogs
8a, 8b and 8d have some activity against armyworm with 100%, 20%
and 80% mortality, respectively, while 8c showed moderate activity
to hemipterainsectssuch ascowpea aphidsand brownplanthopper.
The other two types of spiro heterocyclic neonicotinoids 9a–g and
10a and 10b were inactive to these three tested insects. The poor
activity of these compounds might be caused by their low solubility
in water and the large size of the spirocycles which made it difficult
to bind within the receptor pocket.
4. Conclusion
The first introduction of a spiro heterocycle into the neonico-
tinoid molecule was accomplished. Using cyclic KAs, neonicoti-
noids
bearing
spirobenzofuranone,
spirooxindole
and
spiroacenaphythylenone were successfully constructed and their
insecticidal activity was screened. Some compounds had moderate
insecticidal activity, and ongoing research is focused on improving
the efficacy through further analog generation. These novels
compounds are expected to provide a basis for designing new spiro
heterocycle containing neonicotinoids.
the treated insects were maintained at
a temperature of
Acknowledgments
(27 ꢁ 1) 8C. Only distilled water only was used as control for each
tested chemical. Each process was repeated for 3 times and the
mortality rates were evaluated 48 h after treatment. The data were
adjusted and subjected to probit analysis as before.
This work was financial supported by National Basic Research
Program of China (973 Program, No. 2010CB126100), National
High Technology Research Development Program of China (863
Program, No. 2011AA10A207), Key Projects in the National Science
3. Results and discussion
&
Technology Pillar Program (No. 2011BAE06B05), National
Natural Science Foundation of China (No. 21372079), Shanghai
Education Committee (No. 12ZZ057) and the Fundamental
Research Funds for the Central Universities. This work was also
partly supported by Australia DC Foundation.
3.1. Synthesis
The introduction of a spiro heterocycle into neonicotinoid
molecule was accomplished by reactions of nitroenamine 7, a
neonicotinoid precusor, and Knoevenagel adducts (KAs) 2, 4 and 6.
Nitroenamines have highly polarized push–pull ethylene systems,
making them reactive intermediates with a vast variety of
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.cclet.2013.12.004.
electrophiles [22–24]. In
nitroenamine could react with KAs benzylidenemalononitriles
a previous study, we found that

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N.-Y. Chen et al. / Chinese Chemical Letters 25 (2014) 197–200
[13] S. Rapposelli, M.C. Breschi, V. Calderone, et al.,A. Balsamo, Synthesis and biologi-
References
cal evaluation of 5-membered spiro heterocycle-benzopyran derivatives against
myocardial ischemia, Eur. J. Med. Chem. 46 (2011) 966–973.
[1] R. Rios, Enantioselective methodologies for the synthesis of spiro compounds,
Chem. Soc. Rev. 41 (2012) 1060–1074.
[14] C.W. Lee, R. Lira, J. Dutra, K. Ogilvie, et al., Stereoselective synthesis of spiropi-
peridines as BACE-1 aspartyl protease inhibitors via late stage N-arylation of a
1,8-diazaspiro[4.5]dec-3-en-2-one pharmacophore, J. Org. Chem. 78 (2013)
2661–2669.
[15] M. Rottmann, C. McNamara, B.K.S. Yeung, et al., Spiroindolones, a potent com-
pound class for the treatment of malaria, Science 329 (2010) 1175–1180.
[16] A. Elbert, M. Schindler, R. Nauen, P. Jeschke, Overview of the status and global
strategy for neonicotinoids, J. Agric. Food Chem. 59 (2011) 2897–2908.
[17] S. Kagabu, Discovery of imidacloprid and further developments from strategic
molecular designs, J. Agric. Food Chem. 59 (2011) 2887–2896.
[2] T. Jin, M. Himuro, Y. Yamamoto, Triflic acid catalyzed synthesis of spirocycles via
acetylene cations, Angew. Chem. Int. Ed. 48 (2009) 5893–5896.
[3] G.S. Singh, Z.Y. Desta, Isatins as privileged molecules in design and synthesis of
spiro-fused cyclic frameworks, Chem. Rev. 112 (2012) 6104–6155.
[4] H. Diirr, R. Gleiter, Spiroconjugation, Angew. Chem. Int. Ed. 17 (1978) 559–569.
[5] B. Gleiter, H. Hoffmann, H. Irngartinger, M. Nixdorf, Donor–acceptor spiro-com-
pounds-syntheses, structures and electronic properties, Chem. Ber. 127 (1994)
2215–2224.
[6] J. Sun, Y.J. Xie, C.G. Yan, Construction of dispirocyclopentanebisoxindoles via self-
domino michael-aldol reactions of 3-phenacylideneoxindoles, J. Org. Chem. 78
(2013) 8354–8365.
[7] K. Murai, H. Komatsu, R. Nagao, H. Fujioka, Oxidative rearrangement of spiro
cyclobutane cyclic aminals: efficient construction of bicyclic amidines, Org. Lett.
14 (2012) 772–775.
[18] M. Tomizawa, J.E. Casida, Molecular recognition of neonicotinoid insecticides: the
determinants of life or death, Acc. Chem. Res. 42 (2009) 260–269.
[19] R. Nauen, I. Denholm, Resistance of insect pests to neonicotinoid insecticides:
current status and future prospects, Arch. Insect. Biochem. Physiol. 58 (2005)
200–215.
´
[20] M. Henry, M. Beguin, F. Requier, et al., A common pesticide decreases foraging
[8] W.Y. Xu, Y.M. Jia, J.K. Yang, Z.T. Huang, C.Y. Yu, Reactions of heterocyclic detene
aminals with 2-[3-oxoisobenzofuran-1(3H)-ylidenne]malononitrile: synthesis of
novel polyfunctionalized 1,4-dihydropyridine-fused 1,3-diazaheterocycles, Syn-
lett 11 (2010) 1682–1684.
[9] F. Shi, G.J. Xing, R.Y. Zhu, W. Tan, S.J. Tu, A catalytic asymmetric isatin-involved
povarov reaction: diastereo- and enantioselective construction of spiro[indolin-
3,20-quinoline] scaffold, Org. Lett. 15 (2013) 1128–1131.
[10] S. Pal, M.N. Khan, S. Karamthulla, S.J. Abbas, L.H. Choudhury, One pot four-
component reaction for the efficient synthesis of spiro[indoline-3,40-pyr-
ano[2,3-c]pyrazole]-30-carboxylate derivatives, Tetrahedron Lett. 54 (2013)
5434–5440.
[11] F.Y. Miyake, K. Yakushijin, D.A. Horne, Preparation and synthetic applications of
2-halotryptamines: synthesis of elacomine and isoelacomine, Org. Lett. 6 (2004)
711–713.
success and survival in honey bees, Science 336 (2012) 348–350.
[21] S.A. Cameron, J.D. Lozier, J.P. Strange, et al., Patterns of widespread decline in
North American bumble bees, Proc. Natl. Acad. Sci. U.S.A. 108 (2011) 662–667.
[22] X.S. Shao, P.W. Lee, Z.W. Liu, et al., cis-Configuration: a new tactic/rationale for
neonicotinoid molecular design, J. Agric. Food Chem. 59 (2011) 2943–2949.
[23] X.S. Shao, Z. Li, X.H. Qian, X.Y. Xu, Design, synthesis and insecticidal activities of
novel analogues of neonicotinoids: replacement of nitromethylene with nitro-
conjugated system, J. Agric. Food Chem. 57 (2009) 951–957.
[24] X.S.Shao,H.Fu,X.Y.Xu,etal.,Divalentandoxabridgedneonicotinoidsconstructedby
dialdehydes and nitromethylene analogues of imidacloprid: design, synthesis, crys-
tal structure, and insecticidal activities, J. Agric. Food Chem. 58 (2010) 2696–2702.
[25] W.W. Zhang, X.B. Yang, W.D. Chen, et al., Design, multicomponet synthesis, and
bioactivities of novel neonicotinoid analogues with 1,4-dihydropyridine scaffold,
J. Agric. Food Chem. 58 (2010) 2741–2745.
[12] B. Tan, N.R. Candeias, C.F. Barbas III, Construction of bispirooxindoles containing
[26] A. Alizadeh, T. Firuzyar, A. Mikaeili, Efficient one-pot synthesis of spirooxindole
derivatives containing 1,4-dihydropyridine-fused-1,3-diazaheterocycle frag-
ments via four-component reaction, Synthesis 22 (2010) 3913–3917.
three quaternary stereocentres in
a cascade using a single multifunctional
organocatalyst, Nat. Chem. 3 (2011) 473–477.