Facile access to nitroalkanes: Nitration of alkanes by selective C[sbnd]H nitration using metal nitrate, catalyzed by in-situ generated metal oxide

Article abstract of DOI:10.1016/j.catcom.2020.106035

Direct C ? H functionalization of inactive alkanes is an important strategy to streamline the preparation of functional molecules. Herein, we describe an operationally simple and effective alkane C ? H nitration reaction to access versatile nitroalkanes without cleavage of the C ? C skeleton. Nontoxic and inexpensive metal nitrate (Fe(NO₃)₃·9H₂O) plays a dual role as catalyst precursors as well as nitro sources for the transformation. Experimental evidence and theoretical modeling have shown the formation of iron oxide as a key catalytic species for the alkane C ? H and NO₂ activation, which favors a stepwise radical mechanism with initial alkyl radical formation.

Full text of DOI:10.1016/j.catcom.2020.106035

CatalysisCommunications142(2020)106035
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
Facile access to nitroalkanes: Nitration of alkanes by selective CeH nitration
using metal nitrate, catalyzed by in-situ generated metal oxide
Ling Penga, Haoyu Penga, Na Lia, Wenzhou Zhonga,⁎, Liqiu Maoa,⁎, Kuiyi Youb, Dulin Yina
a National & Local United Engineering Laboratory for New Petrochemical Materials & Fine Utilization of Resources, Key Laboratory of Chemical Biology Traditional
Chinese Medicine Reserach Ministry of Education, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, PR China
b College of Chemical Engineering, Xiangtan University, Xiangtan 411105, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Alkane
Nitroalkane
Metal nitrate
Nitration
Direct C − H functionalization of inactive alkanes is an important strategy to streamline the preparation of
functional molecules. Herein, we describe an operationally simple and effective alkane C − H nitration reaction
to access versatile nitroalkanes without cleavage of the C − C skeleton. Nontoxic and inexpensive metal nitrate
(Fe(NO3)3·9H2O) plays a dual role as catalyst precursors as well as nitro sources for the transformation.
Experimental evidence and theoretical modeling have shown the formation of iron oxide as a key catalytic
species for the alkane C − H and NO2 activation, which favors a stepwise radical mechanism with initial alkyl
radical formation.
1. Introduction
methods for the selective nitration of C − H bonds is highly desirable,
since nitrocyclohexane and nitrocyclohexene are easily by reduction to
Nitro compounds are regarded as key building blocks [1,2] and
ideal intermediates [3] for the generation of pharmaceuticals, dyes,
explosives and materials in synthetic chemistry. In contrast to the easy
nitration of aromatic C − H bonds, the preparation of nitroalkanes by
the selective nitration of aliphatic C − H bonds is very challenging and
much less investigated because of the difficulty of activation of alkane
CeH bond. Currently, nitration of alkanes relies on harsh methodolo-
gies involving excess nitrogen dioxide or nitric acid under forced re-
action conditions (250–450 °C) to generate thermally alkyl radicals by
the alkane CeH bond scission [4,5]. Under such conditions, alkanes
undergo the undesired CeC skeleton cleavage, exhibiting poor ni-
troalkane selectivity. Therefore, this vapor-phase approach present a
number of critical drawbacks in terms of reactant structure, which is
only limited to the nitration of methane, ethane and propane [4,6,7].
Thus, vapor-phase nitration of higher molecular weight hydrocarbons
such as cycloalkane is in a less satisfactory state [8,9], since there are
reactions which compete the thermal isomerization of the cycloalkane
to alkenes with the further formation of the undesirable lower ni-
troalkanes. In the last few decades, although some strategies including
ozone-promoted or laser-induced nitration with nitrogen dioxide and
either nitration with unstable NO2BF4 have provided access to ni-
trocycloalkane, there has been a notable lack of recent progress in the
selective nitration CeH bonds of cycloalkane (Scheme S1) [10–13].
In an industrial context, the development of mild and efficient
cyclohexanone oxime, which is a starting material for the manufacture
of nylon-6 polymers [14–17]. Recently, Ishii and his co-workers
[12,18,19] discovered that N-hydroxyphthalimide (NHPI) can serve a
key catalyst for the nitration of low-carbon cycloalkanes under mild
conditions, by the use of HNO3 or NO2 as a nitro reagent. However,
most of NHPI was decomposed to phthalic acid and other products, and
a large amount of NHPI catalyst (> 10 mol%) was required to achieve
high conversion [13]. And later on, Yamaguchi et al. developed a [VO
(H2O)5]H[PMo12O40] -catalyzed method for the nitration of various
alkanes using nitric acid in acetic acid [20]. Nitration of cyclohexane is
reported to give a 10% nitrocyclohexane yield with 90% selectivity, but
the increase of conversion is still difficult issues. At present, all of the
above-mentioned nitration reactions associated with the use of excess
mineral HNO3 or NO2 as nitrating agents, which present a number of
critical drawbacks with the difficulty of its handling and toxicity in
terms of environmental impact [21]. Thus, a search for user-friendly
and selective nitrating agents is a good research goal for the direct
C − H activation in the C − N bond formation. Iron compounds have
recently attracted great attention in organic transformation as nontoxic
and inexpensive green elements [22]. Thermal decomposition of Fe
(NO3)3·9H2O is well known to in-situ generate nitrogen dioxide [23],
which is a radical species, but no attention has been paid to direct al-
kane C − H functionalization of this method. Herein, we developed an
efficient and facile radical nitration of various alkanes and
⁎ Corresponding authors.
E-mail addresses: zwenz79@163.com (W. Zhong), mlq1010@126.com (L. Mao).
https://doi.org/10.1016/j.catcom.2020.106035
Received 15 February 2020; Received in revised form 7 April 2020; Accepted 2 May 2020
Availableonline05May2020
1566-7367/©2020ElsevierB.V.Allrightsreserved.

L. Peng, et al.
CatalysisCommunications142(2020)106035
Table 1
Table 2
Effect of different metal nitrate as nitrating agent on nitration of cyclohexane.a
Nitration of different substrates with ferric nitrate.a
Entry
Nitrating agent
Conv. (%)
Sel. (%)b
Yield (%)c
Entry
Substrate
Conv. (%)
Sel.(%)
Product
A
B
C
D
1
2
3
4
5
6
7
8
LiNO3
KNO3
AgNO3
Pb(NO3)2
3.6
3.6
1.2
1.7
5.2
3.3
0.6
1.3
37.0
41.6
48.0
53.7
29.9
60.9
53.1
17.3
38.5
64.5
49.7
75.1
45.5
54.3
43.2
53.3
78.8
89.1
92.4
92.1
88.1
83.1
93.1
74.4
–
–
–
–
–
–
–
–
5.4
7.7
4.2
4.3
8.5
4.3
3.0
9.5
21.5
15.3
29.2
14.9
13.4
16.2
21.7
20.5
4.6
–
–
–
–
1.9
–
7.7
8.8
21.2
10.0
9.1
9.0
19.4
26.2
5.7
–
–
3.6
–
1.5
2.5
8.7
1.4
2.3
0.6
1.3
2.4
1.8
0.3
0.7
29.2
37.0
44.3
49.5
26.3
50.6
49.5
12.9
1
Cyclopentane
Cyclohexane
Cycloheptane
42.1
53.7
37.6
97.0
NO2
2
NO2
NO2
92.1 4.3
3b
Co(NO3)2·6H2O
Ni(NO3)2·6H2O
Mg(NO3)2·6H2O
La(NO3)3·nH2O
Al(NO3)3·9H2O
Bi(NO3)3·5H2O
Cr(NO3)3·9H2O
Fe(NO3)3·9H2O
Zr(NO3)4·5H2O
Fe(NO3)3·9H2O
Fe(NO3)3·9H2O
Fe(NO3)3·9H2O
76.9
NO2
NO2
4b
5
Cyclooctane
3-Methylpentane
N-hexane
29.6
27.5
29.9
66.1
9
NO2
10
11
12
13
14d
15e
16f
42.8 16.7
50.9 49.1
NO2
O2N
6
NO2
NO2
7
8b
N-heptane
N-octane
23.0
36.2
24.1
35.0
44.3
30.8
31.6
NO2
–
a
Reaction conditions: alkane (1.78 mmol), PhCF3 (5 mL), ferric nitrate
(5.35 mmol), 145 °C, 3 h.
a
Reaction conditions: cyclohexane (1.78 mmol), PhCF3 (5 mL), nitrate salts
b
(5.35 mmol), 145 °C, 3 h.
Reaction time 24 h at 110 °C.
b
A
= nitrocyclohexane, B = nitrocyclohexene, C = cyclohexanol,
D = cyclohexanone.
slower than in trifluorotoluene but provided exclusively the desired
nitrocyclohexane and nitrocyclohexene products. Use of halogenated
solvents noticeably decreased the conversion and selectivity of this
reaction. In contrast, by employing the reactions in CH3CN and DMF
produced little nitro product. Screening of the parameter of tempera-
ture indicated that 145 °C was a more suitable temperature for the
reaction (Table S2). A decrease in temperature to 125 °C resulted in a
slower reaction that required more time (8 h) to reach similar results.
By increasing the amount of nitrite, we were able to convert cyclo-
hexane to the desired nitro product in virtually quantitative yield. The
optimal amount of nitrite with 3.0 equiv. of cyclohexane in catalytic
system is essential to the outcome of the reaction (Table S3), and the
excess nitrate can be recycled by simple filtration. Under the optimized
condition, a gram-scale (2 g) reaction resulted in 44% isolated yield of
the desired nitro product.
With the optimal conditions in hand, the scope of the protocol was
explored for the reactions of a series of alkanes with Fe(NO3)3·9H2O to
nitro compounds, and representative results are summarized in Table 2
and Table S4. First, nitration reactions of cyclic alkanes were examined.
In Table 2, the conversion is 42.1% and selectivity is 97.0%, which is
higher than that for cyclohexane in terms of selectivity though lower in
terms of conversion. On the other hand, seven-membered cycloheptane
or eight-membered cyclooctane was difficult to nitrate selectively, and
gave slightly lower yield (37.6% conversion with 76.9% selectivity for
cycloheptane; 29.6% conversion with 66.1% selectivity for cyclooc-
tane) because of the formation of ketone byproducts. Next, several
aliphatic hydrocarbons were subjected to the nitration under these re-
action conditions. The nitration of 3-methylpentane occurred at the
tertiary position in preference to the methylene group, giving 3-methyl-
3-nitropentane and 3-methyl-2-nitropentane, in 42.8% and 16.7% se-
lectivity, respectively. Treatment of n-hexane with Fe(NO3)3·9H2O at
145 °C led to an approximate 1:1 regioisomeric mixture of 2-ni-
trohexane and 3-nitrohexane at 29.9% conversion. The same preference
was observed as well in the case of n-heptane with 100% nitroalkane
product, whereas n-octane having a longer carbon chain was less se-
lective giving 65.8% selectivity, respectively. Finally, the protocol was
extended for the reaction of various alkylbenzenes with Fe(NO3)3·9H2O
(Table S5). Toluene was difficult to nitrate selectively on the methyl
group, giving the (nitromethyl)benzene product in less than 6.5% se-
lectivity, along with benzene ring substituted products such as p-ni-
trotoluene (60.9%) and o-nitrotoluene (21.6%). Actually, nitration of
aromatic ring was also observed for benzene under these reaction
conditions. It is noted that the nitration of ethylbenzene only occurred
c
Yields are average values obtained from several runs and are based on
cyclohexane used.
d
Pure oxygen atmosphere.
Nitrogen atmosphere.
A combination of HNO3 and a small amount (0.04 mmol) of Fe(NO3)3.
e
f
alkylbenzenes using Fe(NO3)3·9H2O to give nitro-compounds from the
viewpoints of safety and economy. Moreover, it enables the ni-
trocycloalkanes formation that cannot be accessed effectively by other
means so far, most notably nitrocyclohexane compounds (Scheme S1).
2. Results and discussion
We initiated our investigation by exploring the nitration of cyclo-
hexane with simple, readily available Fe(NO3)3·9H2O in PhCF3 for the
method development studies, where product selectivity (i.e., nitration
versus oxidation or isomerization) may be problematic. Remarkably
clean and smooth conversion (53.7%) to nitrocyclohexane was
achieved Fe(NO3)3·9H2O with under the conditions employed (Table 1,
entry 12), affording nitrocyclohexane (92.1%) and nitrocyclohexene
(4.3%) along with oxygenated products, cyclohexanone (3.6%). Other
nitrated and oxidized products caused by the C − C skeleton cleavage
of cyclohexane were not detected at our reaction conditions. In a set of
nitro sources screened, it is noteworthy that both Cr(NO3)3·9H2O and Bi
(NO3)3·5H2O (entries 10 and 11) also show significant activity similar
to that of Fe(NO3)3·9H2O, though slightly lower. Under similar condi-
tions as for Al(NO3)3·9H2O and Zr(NO3)4·5H2O also demonstrated
comparable efficiency but with a lower conversion and selectivity
(entries 9 and 13), thus asserting the importance of the metal ion in
nitration process. In contrast, other metal nitrate salts proved in-
effective for this nitration reaction (entries 1–8), which could be at-
tributed to the fact that in situ generation of NO2 would be difficult for
thermal decomposition of metal nitrate salts, as in the latter transfor-
mation. On the other hand, the nitration of cyclohexane with a com-
bination of HNO3 and a small amount of Fe(NO3)3 (as catalyst) led to
nitrocyclohexane in poor yield (entry 16). The reaction under nitrogen
atmosphere instead of oxygen performed well and produced ni-
trocyclohexane with a slightly higher selectivity (entries 12, 14–15).
Among the solvents examined (Table S1), trifluorotoluene was found to
be a good solvent. Meanwhile, Fe(NO3)3·9H2O and self-decomposition
iron oxide were almost insoluble in trifluorotoluene, which is easy to
separate and reuse in a more practical nitration procedure. In other
solvents such as CH3COOH and CF3COOH, the reaction was noticeably
2

L. Peng, et al.
CatalysisCommunications142(2020)106035
Table 3
exact nature of these species for the CeH bond activation under reac-
tion conditions is critically important. In Fig. S2B, cyclohexane dis-
sociately adsorbs on the surface of Fe2O3 (001) with an adsorption
energy of −0.83 eV. The H atom of cyclohexane binds with the O atom
of FeeO sites with the distance of 3.565 Å (which is further supported
by charge density difference, as shown in Fig. S3B), and the C − H bond
of cyclohexane elongates from 1.107 Å (free cyclohexane) to 1.112 Å.
Additionally, the H 1 s and O 2p bands are smearing upon a wide range
of energy levels through the valence band between −7.5 to −2.5 eV
from state-by-state atom-projected density of states (PDOS) (Fig. 1),
without strong anti-bonding above the Fermi level. Thus, the lowest
unoccupied molecular orbitals (LUMO) in a low-spin, FeeO sites are
expected to be the two orthogonal p* orbitals, which would direct the
approach of the CeH bond to a bent p*-approach trajectory [25]. This
markedly reduces the energy barrier for the first CeH band homolytic
pathway. In Fig. S2C, NO2 adsorbs on Fe atom of Fe2O3 with the FeeO
distance of 1.870 Å and the N]O bond length obviously changes from
1.234 Å (free NO2) to 1.384 Å. The O–N–O angle (decreased by 20°) is
in this case 112° and the adsorption energy −2.04 eV. Meanwhile, as
the LUMO level of NO2 becomes occupied (Fig. 1), the adsorbate con-
stitutes a system with an even number of electrons, which leads to the
broadening of 2p* band with an edge near the Fermi level and the
significant charge-transfer (about 0.23 electron) from the surface Fe
atom to the adsorbed NO2 molecule (the charging of NO2 is more ef-
ficient in the presence of a backing metal, as shown in Fig. S3). Thus,
Effect of different isolated metal oxides as cataysts on nitration of cyclohexane.a
Entry Cata.
Nitrating agent Conv.(%) Sel. (%)b
Yield (%)
A
B
C
D
3
Fe2O3 Al(NO3)3·9H2O 58.3
86.0 5.7 1.5
84.9 4.4 2.1
83.0 9.7 1.1
81.9 8.1 1.2
89.8 5.2 0.3
2.6
2.9
1.6
3.9
2.4
50.1
40.3
44.8
40.0
46.7
4c
5
Fe2O3 Al(NO3)3·9H2O 47.5
Cr2O3 Al(NO3)3·9H2O 53.9
Bi2O3 Al(NO3)3·9H2O 48.9
Fe2O3 Al(NO3)3·9H2O 52.0
6
7
8
Fe2O3 AgNO3
0.5
55.1
42.2
–
–
31.7 13.2 0.3
18.0 16.8 0.5
9
10
Fe2O3 Co(NO3)2·6H2O 1.3
Fe2O3 Zr(NO3)4·5H2O 49.5
88.2 6.6 0.5
1.2
43.6
a
Reaction conditions: 0.02 mmol isolated metal oxide, cyclohexane
(1.78 mmol), PhCF3 (5 mL), nitrate salts (5.35 mmol), 145 °C, 3 h.
b
A
=
nitrocyclohexane,
B = nitrocyclohexene, C = cyclohexanol,
D = cyclohexanone.
c
Using 0.02 mmol Fe2O3 (prepared) as catalyst. Yields are average values
obtained from several runs and are based on cyclohexane used.
on the ethyl side-chain group to give 96.8% nitro-compound selectivity,
with the benzene ring remaining intact. This can be attributed to a
lower CeH bond energy of ethyl group in ethylbenzene. Furthermore,
tetrahydronaphthalene was also nitrated to only give the alkyl mono-
nitrated product, and no nitration of benzene ring was detected.
To probe the possibility of the ferric oxide species acting as a cat-
alyst, the ferric oxide from the Fe(NO3)3·9H2O decomposition was
isolated by filtrating and washing with ethanol after the reaction, and
the α-Fe2O3 structure was confirmed by the XRD analysis (Fig. S1) [24].
Employing the isolated ferric oxide (1.1 mol%) as an additive, the ni-
tration of cyclohexane with Al(NO3)3·9H2O or Zr(NO3)4·5H2O as the
nitrating agent showed higher activity than that of Al(NO3)3·9H2O or Zr
(NO3)4·5H2O alone (Table 3, entry 3), and the conversion of cyclo-
hexane was improved from 37.0% to 58.3%. When other metal oxides
such as Bi2O3 and Cr2O3 were used as a additive, the nitration of cy-
clohexane with Al(NO3)3·9H2O was efficiently promoted and the ac-
tivity was similar to that of Fe2O3. These results implied that the self-
decomposition metal oxide might be the active catalyst in the current
catalytic nitration reaction. To gain further insight, density functional
theory (DFT) is employed to understand the influence of ferric oxide on
the reaction in the catalysis (Fig.S2 and Fig. 1). First, adsorption of
cyclohexane molecules takes place on FeeO sites, understanding the
the NO2 radical molecule as a resonance hybrid (
) is partially bent via its polarization to more (I) with electron-rich
oxygen by the effect of Fe2O3 species, CeH attraction reaction can
ensue. Consequently, partial metal nitrate can act as an active nitrating
agent for unreactive alkanes.
To gain insights on the reaction pathway, additional experiments
were performed (Scheme S2). First, an intermolecular competition ex-
periment between cyclohexane and benzene showed 56.7% ni-
trocyclohexane and 2.5% nitrobenzene, which is also supported by the
fact that no benzene ring substituted process occurred in an in-
tramolecular competition experiment using cyclohexylbenzene sub-
strate. Furthermore, no nitrocyclohexane product was observed when
the reaction with Fe(NO3)3·9H2O was performed in the presence of
radical scavengers, such as TEMPO and BHT. These results indicate that
alkane nitration might involved a radical process. Second, deuterium
kinetic isotope effect (KIE) was evaluated by the reaction of a 1:1
Fig. 1. Electronic density of states of cyclohexane (A) and NO2 (B) adsorption on α-Fe2O3 (001).
3

L. Peng, et al.
CatalysisCommunications142(2020)106035
Fig. 2. Proposed mechanism for self-decomposition metal oxide-catalyzed CeH nitration reactions.
mixture of deuterated cyclohexane and cyclohexane, producing an in-
termolecular competitive KIE of 2.3. This large value suggests that cy-
clohexane CeH bond cleavage is the rate-determining step of the ni-
tration. Finally, we conducted the dynamics of spectral changes during
the nitration of cyclohexane with time (Fig. S4). The UV–Vis spectra of
reaction mixture containing 0.02 M cyclohexane, recorded shortly
(5–10 min) after reaction, exhibits a strong absorbance at 290 nm,
which indicated the evolution of nitrogen dioxide. After the reaction for
40 min, a significant blue shift (280 nm) is observed in the reaction
mixture spectrum, which was indicative of the formation of the ni-
trocyclohexane product. Particularly, this spectral intensity at 280 nm
became much stronger upon prolonging the reaction time from 40 min
to 60 min, which confirmed that there should be an obvious induction
period for cyclohexane nitration. This is further explained by reaction
profiles of the nitration of cyclohexane in Fig.S5.
cyclohexene with further nitration.
3. Conclusion
In summary, we reported the first a new set of nitrating reagents for
highly selective nitration reaction of alkanes. Various alkanes and alkyl
side-chain of aromatic compounds were nitrated in excellent yields, by
the use of cheap and easy-to-handle metal nitrate compared with NO2
and nitric acid. Under the present conditions, carbon-carbon bond
cleavage reactions for cyclohexane nitration hardly proceed, affording
nitrocyclohexane (92.1%) and nitrocyclohexene (4.3%) along with
oxygenated products, cyclohexanone (3.6%).
Declaration of Competing Interest
On the basis of the experiments above and literature precedents
[13,18,26], a plausible mechanism for Fe2O3-catalyzed sp3 C − H ni-
tration of cyclohexane is proposed (Fig. 2). The NO2 radical and ferric
oxide as catalytic species are first formed from thermal decomposition
of Fe(NO3)3·9H2O under reaction conditions. The active ferric oxide
species plays a dual role, as the polarization of NO2 to bent NO2 mo-
lecule with electron-rich oxygen and the activation of cyclohexane.
Subsequently, H-atom abstraction reaction of activated cyclohexane by
bent NO2 molecule gives a cyclohexyl radical and HNO2. Thus, the
radical traps another NO2 to give nitrocyclohexane. It is reported that
HNO2 can be converted into NO2 and H2O under heating conditions
[13,27], and the generated NO2 is reused in the present nitration, which
is the reason why this reaction can be performed without addition of
O2. In addition, the possibility that the direct formation of cyclohexyl
radical on Fe2O3 species by H-atom abstraction (or single electron
transfer), followed by the reaction with NO2 to nitrocyclohexane as
another path cannot be ruled out, because the nitration of cyclohexane
proceeded with an shorter induction period (20 min) in the presence of
Fe2O3 species. A small amount of nitrocyclohexene product provides
support for the generation of cyclohexyl radical intermediate, which is
obtained by elimination of hydrogen atom with NO2 to give
The authors declare that they have no known competing financia-
linterestsor personal relationships that could have appeared to influ-
ence the work reported in this paper.
Acknowledgments
This work was supported by the Natural Science Foundation of
China (Grant No. 21576078, 21878074 and 21978078).
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.catcom.2020.106035.
References
[1] N. Ono, The Nitro Group in Organic Synthesis, Wiley-VCH, New York, 2001.
[2] G. Cheng, X. Duan, X. Qi, C. Lu, Catal.Commun. 10 (2008) 201–204.
[3] J. Gui, C.M. Pan, Y. Jin, T. Qin, J.C. Lo, B.J. Lee, S.H. Spergel, M.E. Mertzman,
W.J. Pitts, T.E. La Cruz, M.A. Schmidt, N. Darvatkar, S.R. Natarajan, P.S. Baran,
Science 348 (2015) 886–891.
[4] S.B. Markofsky, Ullmann’s Encyclopedia of Industrial Organic Chemicals, 6 Wiley-
4

L. Peng, et al.
CatalysisCommunications142(2020)106035
[16] X. Wang, N. Perret, M.A. Keane, Appl. Catal. A Gen. 467 (2013) 575–584.
[17] W. Zhong, L. Mao, W. Yi, S.R. Kirk, D. Yin, A. Zheng, H. Luo, Catal.Commun. 56
(2014) 148–152.
VCH, Weinheim, 1999, pp. 3487–3501.
[5] K. You, J. Jian, H. Xiao, P. Liu, Q. Ai, H. Luo, Catal. Commun. 28 (2012) 174–178.
[6] G.B. Bachman, B.H. Hass, M.L. Addison, J. Organomet. Chem. 17 (1952) 914–927.
[7] H.B. Hass, J. Dorsky, E.B. Hodge, Ind. Eng. Chem. 33 (1941) 1138–1143.
[8] G.A. Olah, P. Ramaiah, G.K.S. Prakash, Proc. Natl. Acad. Sci. 94 (1997)
11783–11785.
[18] S. Sakaguchi, Y. Nishiwaki, T. Kitamura, Y. Ishii, Angew. Chem. 113 (2001)
228–230.
[19] Y. Nishiwaki, S. Sakaguchi, Y. Ishii, J. Organomet. Chem. 67 (2002) 5663–5668.
[20] K. Yamaguchi, S. Shinachi, N. Mizuno, Chem. Commun. 4 (2004) 424–425.
[21] R. Calvo, K. Zhang, A. Passera, D. Katayev, Nat. Commun. 10 (2019) 1–8.
[22] a) C. Bolm, J. Legros, J. LePaih, L. Zani, Chem. Rev. 104 (2004) 6217–6254.
[23] T. Taniguchi, T. Fujii, H. Ishibashi, J. Organomet. Chem. 75 (2010) 8126–8132.
[24] Y.E.I. Mendili, J.F. Bardeau, N. Randrianantoandro, F. Grasset, J.M. Greneche, J.
Phys. Chem. C 116 (2012) 23785–23792.
[9] G.A. Olah, R. Malhotra, S.C. Narahg, Nitration: Methods and Mechanism, VCH, New
York, 1989.
[10] G.A. Olah, P. Ramaiah, C.B. Rao, G. Sandford, J.A. Olah, J. Am. Chem. Soc. 115
(1993) 7246–7249.
[11] A.E. Stanley, J.M. Bonicamp, S.E. Godbey, L.M. Ludwick, J. Photoch. Photobio. A
91 (1995) 33–52.
[12] Y. Isozaki, S. Nishiwaki, Y. Sakaguchi, Ishii, Chem. Commun. 15 (2001) 1352–1353.
[13] S. Shinachi, H. Yahiro, K. Yamaguchi, N. Mizuno, Chem. Eur. J. 10 (2004)
6489–6496.
[25] W. Liu, X. Huang, M.J. Cheng, R.J. Nielsen, W.A. Goddard III, J.T. Groves, Science
337 (2012) 1322–1325.
[26] Y. Liu, J.L. Zhang, R.J. Song, P.C. Qian, J.H. Li, Angew. Chem. Int. Ed. 53
(2014) 1–5.
[14] Y. Yan, S. Liu, F. Hao, P. Liu, Catal. Commun. 50 (2014) 9–12.
[15] P. Serna, M. Lopez-Haro, J.J. Calvino, A. Corma, J. Catal. 263 (2009) 328–334.
[27] J.J. Carberry, Chem. Eng. Sci. 9 (1959) 189–194.
5