Visible Light Activated Radical Denitrative Benzoylation of β-Nitrostyrenes: A Photocatalytic Approach to Chalcones

Article abstract of DOI:10.1002/adsc.201701559

A metal-free, convenient photocatalytic approach to chalcones from β-nitrostyrenes and benzaldehydes via a radical denitrative benzoylation pathway is reported. The salient features of the protocol include the utilization of visible light as an inexpensive and ecosustainable energy source, N-hydroxyphthalimide (NHPI) as a reusable organophotocatalyst and acetonitrile as an acceptable green solvent to afford chalcones in excellent yields at room temperature in a one-pot procedure. Notably, this is the first application of β-nitrostyrenes as readily available substrates for chalcone synthesis and the first example of photocatalysis in this field. (Figure presented.).

Full text of DOI:10.1002/adsc.201701559

Title: Visible Light Activated Radical Denitrative Benzoylation of β-
Nitrostyrenes: A Photocatalytic Approach to Chalcones
Authors: Shubhangi Tripathi, Ritu Kapoor, and Lal Dhar Yadav
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Adv. Synth. Catal. 10.1002/adsc.201701559
Link to VoR: http://dx.doi.org/10.1002/adsc.201701559

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Visible Light Activated Radical Denitrative Benzoylation of -
Nitrostyrenes: A Photocatalytic Approach to Chalcones
Shubhangi Tripathi, Ritu Kapoor, Lal Dhar S. Yadav *
Green Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad 211002, India; e-mail: ldsyadav@hotmail.com;
Fax: (+91)532-246-0533; Tel.: (+91)532-250-0652.
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.
Abstract:
A
metal-free, convenient photocatalytic
acids/bases catalysed homogeneous and heterogenous
Claisen-Schmidt condensation was used for the
practical synthesis of chalcones.[6] However,
drawbacks of non-appositeness for the substrate
bearing acid/base sensitive groups, slow reaction rate
and very often generation of complex mixture during
the condensation reaction, led to the development of
many superior alternative methods for the synthesis
of chalcones. In this context, different catalytic
systems such as organolithium compounds,[7]
modified phosphates,[8] zinc oxide,[9] KF-Al2O3,[10]
phase transfer catalysts,[11] hydrotalcites and
zeolites[12] have been employed for the synthesis of
chalcones. Again, these processes suffer from the
impediment of difficult catalyst recovery and
purification of the desired products.
approach to chalcones from -nitrostyrenes and
benzaldehydes via a radical denitrative benzoylation
pathway is reported. The salient features of the protocol
include the utilization of visible light as an inexpensive
and ecosustainable energy source, N-hydroxyphthalimide
(NHPI) as a reusable organophotocatalyst and acetonitrile
as an acceptable green solvent to afford chalcones in
excellent yields at room temperature in a one-pot
procedure. Notably, this is the first application of -
nitrostyrenes as readily available substrates for chalcone
synthesis and the first example of photocatalysis in this
field.
Keywords: C-C bond formation; organic catalysis;
photochemistry; radicals; synthetic methods; visible
light.
HO
O
O
O
O
O
O
O
Chalcones constitute
a
privileged family of
O
O
compounds in the perspectives of medicinal and
synthetic chemistry. They exhibit various useful
biological activities such as analgesic, anti-viral, anti-
inflammatory, anti-ulcerative, anti-fungal, anti-
malarial, anti-bacterial and anticancer activities.[1]
Some chalcone-based drugs are in clinical use, for
example, metochalcone, a choleretic drug and
sofalcone as anantiulcer and mucoprotective drug
(Figure 1). Chalcones incorporate a very good
synthon, which renders them valuable intermediates
for the synthesis of flavonoids,[2] flavones[3] and a
diverse range of heterocycles namely, thiazine,
oxazine, isoxazole, pyrazole, diazepine, pyridine and
pyrimidine.[4]
Metochalcone
Sofalcone
Figure 1. Chalcone-based drugs in clinical use.
To overcome the difficulty associated with the
foregoing routes, highly efficient, pioneering and
celebrated cross coupling methodologies such as
Suzuki,[13] Heck[14] and Julia-kocienski[15] cross
couplings have been recently used for the synthesis of
chalcones (Scheme 1a). Though these metal-
catalysed couplings are very effective for chalcone
synthesis, most of them are very expensive and
hazardous to the environment. Thus, the development
Owing to their tremendous chemical and
biological importance, chalcones have been
extensively studied, which is evident from the
appearance of numerous reviews5 thoroughly
covering their synthesis, applications and biological
significances from various angles. Traditionally,
of
a metal-free, environmentally benign, cost
effective and sustainable method for the synthesis of
chalcones is of course a welcome move.
Moreover, nitro-olefins are important building
blocks for the synthesis of a wide variety of organic
compounds,[16] possessing various biological and
1
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
pharmaceutical activities.[17] Among nitroalkenes, -
nitrostyrenes were extensively studied[18] because of
their easy preparation (by Henry reaction) and
inherent property to induce different functionalities
via facile ipso-substitution of the nitro group through
radical denitrative addition-elimination reaction.[18]
The literature records very few reports for these
reactions employing photochemical conditions.[18c,g]
Therefore, further research for the fruition of this
stable and easily available intermediate in conjuction
with photocatalysis is highly desirable in organic
synthesis.
Considering the above points and our focus on the
methodology development employing visible light
organophotocatalysts,[23a,23b,24,25] we envisioned that
benzoyl radicals could be easily generated
photochemically from benzaldehydes using NHPI as
catalyst and these could undergo cross coupling with
β-nitrostyrene to afford chalcones (Scheme 1b).
Notably, this is the first chalcone synthesis
employing β-nitrostyrenes as coupling partners and
the work also presents the first application of visible
light photocatalysis to chalcone synthesis.
In recent years, visible light photocatalysis has
become a captivating way for designing and realising
synthetically useful protocols,[19-23] because visible
light is clean, inexpensive and unending natural
energy source. The methodology development in this
area is based on the seminal work of the research
groups of MacMillan,[19] Yoon[20] and Stephenson,[21]
who have demonstrated the powerful visible light
photocatalytic property of Ru(bpy)3Cl2 (bpy = 2,2’-
bipyridine) and Ir(dtbbpy)3Cl2 (dtbbpy = 4,4’-di-tert-
butyl-2,2’-bipyridine). Some organic dyes including
eosin Y, rose Bengal, nile red, rhodamine B, perylene
and fluorescein have also emerged as efficient visible
light photocatalysts.[23] However, the high cost and
potential toxicity of the transition metal-based
photocatalysts makes them incompatible with the
green chemistry demands. Similarly, organic dyes on
prolonged irradiation undergo decomposition and
suffer from the drawback of their tedious recovery for
reuse.[23a] Very recently, our research group has
To realise the envisaged synthetic strategy and
establish the optimal reaction conditions, our study
began with the model reaction of (E)-β-nitrostyrene
1a (1 mmol) with benzaldehyde 2a (1 mmol) in
acetonitrile (3 mL) in the presence of a catalytic
amount of NHPI (10 mol%) under a nitrogen
atmosphere and irradiation with 7 W white LEDs
(White light emitting diodes) at room temperature. To
our delight, the desired product chalcone 3a was
isolated in an excellent yield of 89% within 8 h of
irradiation (Table 1, entry 1).
Encouraged by this initial success, we performed a
series of control and screening experiments to
confirm the requisite reaction parameters. It was
found that there was no product formation when the
reaction was conducted in the dark (Table 1, entry 1
versus 2). Similarly, in the absence of the catalyst
NHPI, the product 3a could not be obtained (Table 1,
entry 1 versus 3). These results established that both
visible light and NHPI are essential to realise the
present protocol. Further, given the significance to
the role of solvent for a chemical transformation, a
series of experiments was performed to choose the
best solvent for the present reaction and the results
revealed that acetonitrile was the best among DCE,
DMF and DMSO (Table 1, entry 1 versus 4, 5 and 6).
Cumulatively, on decreasing the catalyst loading
from 10 mol% to 5 mol%, a significant decrease in
the yield of 3a was observed (Table 1, entry 1 versus
7), while an increase in the catalyst loading from 10
mol% to 15 mol% does not affect the yield of the
product (Table 1, entry 1 versus 8). Moreover, the
catalyst NHPI also works under thermal conditions,
but delivers a considerably lower yield of the desired
disclosed
the
first
utilization
of
N-
hydroxyphthalimide (NHPI) as an efficient visible
light organophotocatalyst,[24] which is free from the
drawbacks of the aforementioned photocatalysts,
hence we opted to use NHPI in the present study.
product 3a (Table 1, entry
1
versus 9).
Advantageously, the catalyst could be recovered in
high yield after the reaction (Table 1, entry 10) and
reused with the same efficiency (Table 1, entry 11).
Besides NHPI, the scope of other N-hydroxy catalysts
was also examined but all of them were far less
effective than NHPI (Table 1, entry 1 versus 12-14).
Having established the optimised reaction
conditions for visible light mediated synthesis of
chalcones, we continued to survey the generality and
scope of the present protocol across a wide range of
Scheme 1. Selected routes to access chalcones.
2
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
(E)-β-nitrostyrenes and benzaldehydes, incorporating
various functionalities like Me, OH, OMe, F, NO2 or
the electronic and steric properties of substrates, they
produce the desired chalcones 3 in 76-96% yields.
Electronically, (E)-β-nitrostyrenes 2 bearing an
electron-withdrawing substituent on the aromatic
nucleus appear to react faster and afford slightly
higher yields in comparison to those possessing an
electron-donating substituent (Table 2, product 3g
versus 3k). However, benzaldehydes 1 with an
electron-donating group on aromatic ring appear to
react faster to afford marginally higher yields than
those having an electron-withdrawing group (Table 2,
products 3b, 3c, 3e, 3n versus 3d, 3f, 3o). The
method also works well with heterocyclic aldehydes
(Table 2, products 3l, 3m).
Table 1. Optimisation of reaction conditions a
H
O
NO2
O
(White LEDs, 7 W)
(E)
(E)
catalyst (mol%)
solvent, N2, rt, 8-16 h
1a
2a
3a
O
O
O
N
N
OH
N
N
OH
N
OH
N
S
O
O
O
OH
O
4
5
6
7
NHPI and related catalysts 4-7
Table 2. Substrate scope for the synthesis of chalcones a
Entry
1
Reaction conditions
Time Yield
(h)
8
(%)b
89
O
O
NO2
(white LEDs, 7 W)
4 (10 mol%), CH3CN, white
(E)
H
Ar
(E)
Ar
Ar
Ar
NHPI (10 mol%)
CH3CN, N2, rt, 8-16 h
LEDs
1
2
3b
(76-96%)c
2
4 (10 mol%), CH3CN, in the
16
16
8
n.d.
n.d.
58
dark
3
No catalyst, CH3CN, white
O
O
O
LEDs
H3CO
4
4 (10 mol%), DCE, white
CH3
LEDs
3a, 89%, 8 h
3b, 92%, 8 h
3c, 90%, 8 h
5
4 (10 mol%), DMF, white
8
67
LEDs
O
O
O
6
4 (10 mol%), DMSO, white
LEDs
8
72
H3CO
tBu
F
O
7
4 (5 mol%), CH3CN, white
LEDs
8
53
3d
, 79%, 12 h
3e
, 94%, 8 h
3f
, 76%, 12 h
8
4 (15 mol%), CH3CN, white
8
89
O
O
O
LEDs
9
4 (10 mol%), CH3CN, in the
dark
4 (10 mol%), CH3CN, white
LEDs
4 (10 mol%), CH3CN, white
LEDs
5 (10 mol%), CH3CN, white
8
69c
89d
89e
35
H3
C
tBu
H2
N
OCH3
H2
N
NO2
3g, 87%,12 h
3h, 84%, 12 h
3i, 96%, 8 h
10
11
12
13
14
8
O
O
O
HO
8
O
O2N
H3
C
F
H2N
8
3j
3k
3l
, 94%, 8 h
, 93%, 8 h
, 87%, 12 h
LEDs
O
O
O
6 (10 mol%), CH3CN, white
LEDs
7 (10 mol%), CH3CN, white
8
21
S
H3CO
H2
N
8
58
3m
, 91%, 12 h
3n
3o
LEDs
, 85%, 16 h
, 83%, 16 h
[a]
Reaction conditions: 1a (1.0 mmol), 2a (1.0 mmol),
OCH3
O
O
O
NHPI (5-15 mol%), in a 3 mL solvent irradiated under a
nitrogen atmosphere at rt using high power white LEDs (7
W) for 8-16 h.
H3CO
OCH3
3p
, 0%, 16 h
3q
3r
, 85%, 12 h
, 0%, 16 h
[b]
Isolated yield of the pure product 3a (For general
procedure, see experimental section); n.d.= not detected.
[c] Reaction was conducted at 80 oC in the dark.
[d] Catalyst was recovered in 94% yield.
[a] For general procedure, see Experimental section.
[b]
All compounds are known and were characterised by
comparison of their spectral data with those reported in the
literature (see SI).
[e] Recovered catalyst was used.
[c] Isolated yield of purified products 3.
NH2 (Table 2). The study reveals the splendid
tolerance of both electron-donating and electron-
withdrawing groups and regardless of differences in
Unfortunately, aliphatic nitroalkenes such as (E)-1-
nitro-1-butene and 1-nitrocyclohex-1-ene do not react
3
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
Scheme 2. Preliminary mechanistic investigations.
with an aliphatic aldehyde, butyraldehyde to give the
desired products (3p and 3q) under the present
reaction conditions. This is probably due to the
significantly lower stability of alkyl and aliphatic acyl
radicals than benzyl and benzoyl radicals. We also
prepared a choleretic drug, metochalcone (3r) which
further improves the appeal of our designed protocol.
On addition of TEMPO (2,2,6,6-tetramethyl-1-
piperidinyloxyl), a traditional radical scavenger, the
reaction was quenched (Scheme 2a); indicating that it
might follow a radical pathway. The formation of
benzoyl-TEMPO adduct during quenching was
confirmed by its isolation and MS (HRMS (EI) calcd
for C16H23NO2: 261.1729, found 261.1726). To gain
further insight into the mechanism of the reaction,
electron paramagnetic resonance (EPR) experiments
were also conducted. A complicated spectrum,
displaying a resonance characteristic of organic
radical, was recorded on the addition of 5,5-dimethyl-
1-pyrroline N-oxide (DMPO) to the reaction mixture
of benzaldehyde (1.0 mmol), (E)--nitrostyrene (1.0
mmol) and NHPI (10 mol%) under the standard
reaction conditions (Scheme 2b). Both the results
established the involvement of radical species in the
reaction.
Moreover, an intermolecular competing kinetic
isotope effect (KIE) experiment was also carried out
which gives a prominent KIE with kH/kD = 5.2,
suggesting thereby the activation of aldehydic C-H
bond in the rate determining step (Scheme 2c). In
addition, an on/off experiment was conducted to
check the role of visible light in promoting the
process and the graph thus obtained establishes the
necessity of continuous irradiation with visible light
to realise the present protocol (Scheme 2d). The UV-
vis specrtum
a) Trapping Experiment
H
O
white LEDs, 7 W
NHPI (10 mol%)
NO2
O
CH3CN, N2, rt, 8 h
TEMPO (1 equiv)
1a
2a
3a was not
observed
b) Electron Paramagnetic Resonance (EPR) Experiment
c) Kinetic Isotope Effect (KIE) Experiment
H
O
O
white LEDs, 7 W
NHPI (10 mol%)
NO2
3a
1a
CH3CN, N2, rt, 8 h
D
D
O
D
D
D
2a
D
D
D
D
O
D
3a'
D
1a'
d) Evidence in support of continuous irradiation
Scheme 3. Plausible reaction mechanism for NHPI
catalysed synthesis of chalcones.
of the catalyst NHPI is also given in see SI for ready
reference.
In accordance with our observations and the
literature precedents,[18,24,25b] a plausible mechanistic
pathway for visible light-mediated synthesis of
chalcones is depicted in Scheme 3. On irradiation
with visible light using 7 W white LEDs under a
nitrogen atmosphere, H atoms of NHPI migrate from
O to the carbonyl groups of the imide chromophore
and by that process liberate the reactive O radical A
4
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
comparison of their spectral data with those reported in the
literature. [14c,d,26,27,28]
for hydrogen transfer from aldehyde 1. This forms
acyl radical 8 along with radical B. The radical 8
reacts with (E)-β-nitrostyrene 2 to generate the
benzylic radical 9. Subsequently, the radical 9 easily
Acknowledgements
.
eliminates the stable NO2 radical to afford the desired
.
Acknowledgements We sincerely thank SAIF, Punjab University,
Chandigarh, for providing microanalyses and spectra. S.T. is
grateful to the UGC, New Delhi, for the award of a Junior
Research Fellowship (File No. 21/06/2015(i)EU-V). R.K is
grateful to the DST-SERB, New Delhi, for the award of a Start-
Up-Grant project (Ref no. CS-271/2014) and financial assistance.
product 3. The NO2 radical abstracts a hydrogen atom
from B to give NHPI to complete the catalytic cycle.
In summary, we have disclosed a convenient,
metal-free one-pot photocatalytic approach to
chalcones through visible light activated radical cross
coupling of β-nitrostyrenes and aromatic aldehydes.
The protocol presents the first application of
nitrostyrenes as readily available substrates and the
first example of photocatalysis in chalcone synthesis.
Its desirable features include the utilization of visible
light as a clean, inexpensive and ecosustainable
References
[1] a) C. J. Zheng, S. M. Jiang, Z. H. Chen, Archiv der
Pharmazie. 2011, 344, 689; b) B. A. Bhat, K. L.
Dhar, S.C Puri, Bioorg. Med. Chem. Lett. 2005, 15,
3177; c) Y. M. Lin, Y. Zhou, M. T. Flavin, Bioorg.
Med. Chem. 2002, 10, 2795; d) Y. Xia, Z. Y. Yang,
P. Xia, Bioorg. Med. Chem. Lett. 2000, 10, 699; e)
J. J. Ares, P. E. Outt, J. L. Randall, Bioorg. Med.
Chem. Lett. 1996, 6, 995; f) R. J. Anto, K.
Sukumaran, G. Kuttan, Cancer Lett. 1995, 97, 33;
g) R. Li, X. Chen, B. Gong, J. Med. Chem. 1995,
38, 5031; h) J. F. Ballesteros, M. J Sanz, A. Ubeda,
J. Med. Chem. 1995, 38, 2794.
energy source and NHPI as
a
reusable
organophotocatalyst to afford the desired product in
excellent yields at room temperature.
Experimental Section
General Remarks
All commercially available reagents were obtained from
commercial suppliers and used without further purification.
Solvents were purified by the usual methods and stored
over molecular sieves. All reactions were performed using
oven-dried glass ware. Organic solutions were
concentrated using a Buchi rotary evaporator. Flash
chromatography was carried out over silica gel (Merck
200–300 mesh) and TLC was performed using silica gel
GF254 (Merck) plates. Melting points were determined by
open glass capillary method and are uncorrected. 1H NMR
(400 MHz) and 13C NMR (100 MHz) spectra were
recorded on a Bruker AVII spectrometer in CDCl3 using
TMS as internal reference with chemical shift values being
reported in ppm. All coupling constants (J) are reported in
Hertz (Hz). MS (EI) spectra were recorded on double
focusing mass spectrometer. Luxeon Rebel high power
white LEDs (7 W) were used as visible light source.
[2] R. A. Dixon, N. L. Paiva, Plant Cell, 1995, 7, 1085.
[3] J. Li, Name Reactions in Heterocyclic Chemistry,
Wiley-Interscience Publication, 2005, pp. 262.
[4] a) N. A. Al-Jaber, A. S. Bougasim, M. S. Karah, J.
Saudi Chem. Soc. 2012, 16 , 45; b) R. Kalirajan, S.
U. Sivakumar, S. Jubie, Int. J. Chem. Res. 2009, 1,
27.
[5] For reviews on chalcones, see: a) C. Zhuang, W.
Zhang, C. Sheng, W. Zhang, C. Xing, Chem. Rev.
2017, 117, 7762; b) M. Das, K. Manna, J. Toxicol.
2016, 2016, 7651047; c) D. K. Mahapatra, S. K.
Bharti, Life Sci. 2016, 148, 154; d) M. J. Matos, S.
Vazquez-Rodriguez, E. Uriarte, L. Santana, Expert
Opin. Ther. Pat. 2015, 25, 351; e) A. J. Leon-
Gonzalez, N. Acero, D. Munoz-Mingarro, I.
Navarro, C. Martin-Cordero, Curr. Med. Chem.
2015, 22, 3407; f) D. K. Mahapatra, V. Asati, S. K.
Bharti, Eur. J. Med. Chem. 2015, 92, 839; g) D. K.
Mahapatra, S. K. Bharti, V. Asati, Eur.J. Med.
Chem. 2015, 101, 496; h) D. K. Mahapatra, S. K.
Bharti, V. Asati, Eur. J. Med. Chem. 2015, 98, 69; i)
B. Zhou, C. Xing, Med. Chem. 2015, 5, 388; j) P.
Singh, A. Anand, V. Kumar, Eur. J. Med. Chem.
2014, 85, 758; k) D. Kumar, M. Kumar, A. Kumar,
S. K. Singh, Med. Chem. 2013, 13, 2116; l) S. N.
Bukhari, S. G. Franzblau, I. Jantan, M. Jasamai,
Med. Chem. 2013, 9, 897; m) A. Kamal, M. K.
Reddy, A. Viswanath, Expert Opin. Drug
Discovery. 2013, 8, 289; n) V. Sharma, V. Kumar,
P. Kumar, Med. Chem. 2013, 13, 422; o) N. K.
Sahu, S. S. Balbhadra, J. Choudhary, D. V. Kohli,
Curr. Med. Chem. 2012, 19, 209; p) N. Abbas, S. N.
Bukhari, M. Jasamai, I. Jantan, Med. Chem. 2012,
12, 1394; q) A. Boumendjel, X. Ronot, J.
General procedure for the synthesis of chalcones 3a-o
A mixture of an aromatic aldehyde 1 (1 mmol), β-
nitrostyrene 2 (1 mmol) and CH3CN (3 mL) was taken in a
round bottom flask and stirred under a nitrogen atmosphere
and irradiation with white LEDs, at rt for 8-16 h (Table 2).
After the completion of reaction (as indicated by TLC), it
was quenched with saturated aqueous sodium hydrogen
carbonate (5 mL) and extracted with ethyl acetate (3 × 10
mL). The combined organic phases were dried over anhyd.
MgSO4, filtered and concentrated under reduced pressure
to yield the crude product, which was purified by silica gel
column chromatography using a mixture of ethyl acetate-
hexane to afford an analytically pure sample of 3. All the
products are known compounds and were characterised by
5
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
Boutonnat, Curr. Drug. Targets. 2009, 10, 363; r)
H. J. Steinfelder, Biochem. Pharmacol. 2003, 65,
603; d) J. H. Kim, J. H. Kim, G. E. Lee, J. E. Lee, I.
K. Chung, Mol. Pharmacol. 2003, 63, 1117; e) Y.
Meah, V. Massey, Proc. Natl. Acad. Sci. 2000, 97,
10733; f) T. A. Alston, D. J. T. Porter, H. J. Bright,
Bioorg. Chem. 1985, 13, 375; g) P. Talalay, M. J.
De Long, H. J. Prochaska, Proc. Natl. Acad. Sci.
1988, 85, 8261.
C. Kontogiorgis, M. Mantzanidou, D. Hadjipavlou-
Litina, Med. Chem. 2008, 8, 1224; s) M. L. Go, X.
Wu, X. L. Liu, Curr. Med. Chem. 2005, 12, 483; t)
J. R. Dimmock, D. W. Elias, M. A. Beazely, N. M.
Kandepu, Curr. Med. Chem. 1999, 6, 1125.
[6] a) V. Calvino, M. Picallo, A. J. Lopez-Peinado, R.
M. Martın-Aranda, C. J. Duran-Valle, Appl. Surf.
Sci. 2006, 252, 6071; b) L. Claisen, A. Claparꢀde,
Ber. Dtsch. Chem. Ges. 1881, 14, 2460.
[7] J. B. Daskiewicz, G. Comte, D. Barron, A. D.
Pietro, F. Thomasson, Tetrahedron Lett. 1999, 40,
7095.
[8] S. Sebti, A. Solhy, R. Tahir, S. Boulaajaj, J. A.
Mayoral, J. M. Fraile, A. Kossir, H. Oumimoun,
Tetrahedron Lett. 2001, 42, 7953.
[9] S. Saravanamurugan, M. Palanichamy, B.
Arabindoo, V. Murugesan, Catal. Commun. 2005,
6, 399.
[18]a) A. K. Yadav, K. N. Singh, New J. Chem. 2017,
DOI: 10.1039/C7NJ02997G; b) T. Keshari, R.
Kapoor, L. D. S. Yadav, Eur. J. Org. Chem. 2016,
2695; c) N. Zhang, Z. -J. Quan, Z. Zhang, Y. -X.
Da, X. -C. Wang, Chem. Commun. 2016, 52, 14234;
d) S.-R. Guo, Y. -Q. Yuan, Synlett 2015, 26, 1961;
e) J. -F. Xue, S. -F. Zhou, Y. -Y. Liu, X. Pan, J. -P.
Zou, O. T. Asekun, Org. Biomol. Chem. 2015, 13,
4896; f) S. Guo, Y. Yuan, J. Xiang, New J. Chem.
2015, 39, 3093; g) P. Schroll, D. P. Hari, B. König,
ChemistryOpen 2012, 1, 130; h) Y. -J. Jang, Y. -K.
Shih, J. -Y. Liu, W. -Y. Kuo, C. -F. Yao, Chem.
Eur. J. 2003, 9, 2123.
[10]J. T. Li, W. Z. Yang, Z. X. Wang, S. H. Li, T.S. Li,
Ultrason. Sonochem. 2002, 9, 237.
[11]J. Yang, G. Ji, H. Liu, Y. Lian, Chem. Abstr. 2013,
160, 33884.
[12]M. J. Climent, A. Corma, S. Iborra, J. Primo, J.
Catal. 1995, 151, 60.
[13]a) K. R. Buszek, N. Brown, Org. Lett. 2007, 9, 707;
b) S. Eddarir, N. Cotelle, Y. Bakkour, C. Rolando,
Tetrahedron Lett. 2003, 44, 5359; c) N. A.
Bumagin, D. N. Korolev, Tetrahedron Lett. 1999,
40, 3057; d) M. Haddach, J. R. McCarthy,
Tetrahedron Lett. 1999, 40, 3109.
[19]a) A, Noble, D. W. C. MacMillan, J. Am. Chem.
Soc. 2014, 136, 11602; b) J. A. Terrett, M. D. Clift,
D. W. C. MacMillan, J. Am. Chem. Soc. 2014, 136,
6858; c) M. T. Pirnot, D. A. Rankic, D. B. C.
Martin, D. W. C. MacMillan, Science 2013, 339,
1593; d) D. A. Nagib, M. E. Scott, D. W. C.
MacMillan, J. Am. Chem. Soc. 2009, 131, 10875; e)
D. A. Nicewicz, D. W. C. MacMillan, Science
2008, 322, 77.
[20]a) J. Du, T. P. Yoon, J. Am. Chem. Soc. 2009, 131,
14604; b) M. A. Ischay, M. E. Anzovino, J. Du, T.
P. Yoon, J. Am. Chem. Soc. 2008, 130, 12886.
[21]a) M. D. Konieczynska, C. Dai, C. R. J.
Stephenson, Org. Biomol. Chem. 2012, 10, 4509; b)
C. Dai, J. M. R. Narayanam, C. R. J. Stephenson,
Nat. Chem. 2011, 3, 140; c) A. G. Condie, J. C.
Gonzâlez-Gólez, C. R. J. Stephenson, J. Am. Chem.
Soc. 2010, 132, 1464; d) J. W. Tucker, J. M. R.
Narayanam, S. W. Krabbe, C. R. J. Stephenson,
Org. Lett. 2010, 12, 368; e) J. M. R. Narayanam, J.
W. Tucker, C. R. J. Stephenson, J. Am. Chem. Soc.
2009, 131, 8756.
[22]For leading reviews on visible light photocatalysis,
see: a) C. K. Prier, D. A. Rankic, D. W.
C. MacMillan, Chem. Rev. 2013, 113, 5322; b) Y.
Xi, H. Yia, A. Lei, Org. Biomol. Chem. 2013, 11,
2387; c) J. Xuan, W. -J. Xiao, Angew. Chem. Int.
Ed. 2012, 51, 6828; d) J. M. R. Narayanam, C. R.
J. Stephenson, Chem. Soc. Rev. 2011, 40, 102; e) F.
Collect. Teply, Czech. Chem. Commun. 2011, 76,
859; f) T. P. Yoon, M. A. Ischay, J. Du, Nat. Chem.
2010, 2, 527; g) K. Zeitler, Angew. Chem. Int.
Ed. 2009, 48, 9785; h) J. K. Kochi, Angew. Chem.
Int. Ed. 1988, 27, 1227; i) R. G. Salomon, J. K.
Kochi, J. Am. Chem. Soc. 1974, 96, 1137; j) R.
Srinivasan, J. Am. Chem. Soc. 1963, 85, 3048.
[23]For recent examples using organic dyes as the
photocatalyst, see: a) V. P. Srivastava, A. K. Yadav,
L. D. S. Yadav, Synlett 2014, 25, 665; b) A. K.
Yadav, V. P. Srivastava, L. D. S. Yadav, RSC Adv.
2014, 4, 4181; c) X. -J. Yang, B. Chen, L. -Q.
[14]a) X. F. Wu, H. Neumann, M. Beller, Chem. Asian
J. 2012, 7, 282; b) P. Hermange, T. M. Gogsig, A.
T. Lindhardt, R. H. Taaning, T. Skrydstrup, Org.
Lett. 2011, 13, 2444; c) X. F. Wu, H. Neumann, A.
Spannenberg, T. Schulz, H. Jiao, M. Beller, J. Am.
Chem. Soc. 2010, 132, 14596; d) X. F. Wu, H.
Neumann, M. Beller, Angew. Chem. Int. Ed. 2010,
49, 5284; e) G. Zou, J. P. Guo, Z. Y. Wang, W.
Huang, J. Tang, Dalton T. 2007, 28, 3055; f) A.
Bianco, C. Cavarischia, M. Guiso, Eur. J. Org.
Chem. 2004, 13, 2894; g) R. F. Heck, J. P. Nolley,
J. Org. Chem. 1972, 37, 2320; h) T. Mizoroki, K.
Mori, A. Ozaki, Bull. Chem. Soc. 1971, 44, 581.
[15]A. Kumar, S. Sharma, V. D. Tripathi, S. Srivastava,
Tetrahedron 2010, 66, 9445.
[16]a) L. Q. Lu, J. R. Chen, W. J. Xiao, Acc. Chem. Res.
2012, 45, 1278; b) M. A. Reddy, N. Jain, D. Yada,
C. Kishore, J. R. Vangala, R. P. Surendra, A.
Addlagatta, S. V. Kalivendi, B. Sreedhar, J. Med.
Chem. 2011, 54, 6751; c) H. Uehara, R. Imashiro,
G. Hernandez Torres, C. F. Barbas, Proc. Natl.
Acad. Sci. 2010, 107, 20672; d) H. Feuer, A.
Nielsen, Nitro Compounds: Recent Advances in
Synthesis and Chemistry, VCH, New York, 1990; e)
A. G. M. Barrett, G. G. Graboski, Chem. Rev. 1986,
86, 751.
[17]a) J. Zheng, D. Wang, S. Cui, Org. Lett. 2015, 17,
4572; b) P. Cheng, Z. Y. Jiang, R. R. Wang, X. M.
Zhang, Q. Wang, Y. T. Zheng, J. Zhou, J. J. Chen,
Bioorg. Med. Chem. Lett. 2007, 17, 4476; c) S.
Kaap, I. Quentin, D. Tamiru, M. Shaheen, K. Eger,
6
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
Zheng, L. -Z. Wu, C. -H Tung, Green Chem. 2014,
2016, 52, 10621.
16, 1082; d) Y. C. Teo, Y. Pan, C. H. Tan,
ChemCatChem. 2013, 5, 235; e) D. -T. Yang, Q. -Y.
Meng, J. -J. Zhong, M. Xiang, Q. Liu, L. -Z. Wu,
Eur. J. Org. Chem. 2013, 7528; f) M. Rueping, C.
Vila, T. Bootwicha, ACS Catal. 2013, 3, 1676; g) Y.
-Q. Zou, J. -R. Chen, X. -P. Liu, L. -Q. Lu, R. L.
Davis, K. A. Jørgensen, W. -J. Xiao, Angew. Chem.
Int. Ed. 2012, 51, 784; h) D. P. Hari, P. Schroll, B.
König, J. Am. Chem. Soc. 2012, 134, 2958; i) D. P.
Hari, T. Hering, B. König, Org. Lett. 2012, 14,
5334; j) T. Hering, D. P. Hari, B. König, J. Org.
Chem. 2012, 77, 10347; k) Q. Li, Y. -N. Li, H. -H.
Zhang, B. Chen, C. -H. Tung, L. -Z. Wu, Chem. -
Eur. J. 2012, 18, 620; l) K. Fidaly, C. Ceballos, A.
Falguieres, M. S. -I. Veitia, A. Guy, C. Ferroud,
Green Chem. 2012, 14, 1293; m) J. Yu, L. Zhang,
G. Yan, Adv. Synth. Catal. 2012, 354, 2625; n) M.
Neumann, S. Fuldner, B. König, K. Zeitler, Angew.
Chem. Ins. Ed. 2011, 50, 951; o) D. P. Hari, B.
König, Org. Lett. 2011, 13, 3852; p) Y. Pan, C. W.
Kee, L. Chen, C. -H. Tan, Green Chem. 2011, 13,
2658; q) Y. Pan, S. Wang, C. W. Kee, E.
Dubbuisson, Y. K. Yang, P. Loha, C.-H. Tan, Green
Chem. 2011, 13, 3341.
[25]a) R. Kapoor, S. Tripathi, S. N. Singh, T. Keshari,
L. D. S. Yadav, Tetrahedron Lett. 2017, 58, 3814;
b) A. K. Yadav, L. D. S. Yadav, Tetrahedron Lett.
2017, 58, 552; c) S. Tripathi, S. N. Singh, L. D. S.
Yadav, RSC Adv. 2016, 6, 14547; d) A. K. Yadav,
L. D. S. Yadav, Green Chem. 2016, 18, 4240; e) V.
K. Yadav, V. P. Srivastava, L. D. S. Yadav,
Tetrahedron Lett. 2016, 57, 155.
[26]K. C. Bharadwaj, Tetrahedron 2017, 73, 5690.
[27]T. Narender, K. P. Reddy, Tetrahedron Lett. 2007,
48, 3177.
[28]M. B. Santos, V. C. Pinhanelli, M. A. R. Garcia, G.
Silva, S. J. Baek, S. C. França, A. L. Fachin, M.
Marins, L. O. Regasini, Eur. J. Med. Chem. 2017,
138, 884.
[24]A. K. Yadav, L. D. S. Yadav, Chem. Commun.
7
This article is protected by copyright. All rights reserved.

10.1002/adsc.201701559
Advanced Synthesis & Catalysis
COMMUNICATION
Visible Light Activated Radical Denitrative
Benzoylation of -nitrostyrenes: A Photocatalytic
Approach to Chalcones
O
O
NO2
(white LEDs, 7 W)
H
(E)
(E)
Ar
Ar
Ar
Ar
NHPI (10 mol%)
Adv. Synth. Catal. Year, Volume, Page – Page
CH3CN, N2, rt, 8-16 h
1
2
3
Up to 96% yields
15 examples
Shubhangi Tripathi, Ritu Kapoor, L. D. S. Yadav*
8
This article is protected by copyright. All rights reserved.