A predictably selective nitration of olefin with Fe(NO3) 3 and TEMPO

Article abstract of DOI:10.1021/jo400598p

Ferric nitrate with catalytic TEMPO has been identified as a useful reagent for regio- and stereoselective nitration of a wide variety of aromatic, aliphatic, and heteroaromatic olefins. This reaction provided nitroolefins in preparatively useful yields with excellent E-selectivity. Due to its mild nature and operational simplicity, the present protocol is expected to find application in synthetic setup.

Full text of DOI:10.1021/jo400598p

Article
pubs.acs.org/joc
A Predictably Selective Nitration of Olefin with Fe(NO3)3 and TEMPO
Togati Naveen, Soham Maity, Upendra Sharma, and Debabrata Maiti*
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
S
* Supporting Information
ABSTRACT: Ferric nitrate with catalytic TEMPO has been
identified as a useful reagent for regio- and stereoselective nitration
of a wide variety of aromatic, aliphatic, and heteroaromatic olefins.
This reaction provided nitroolefins in preparatively useful yields
with excellent E-selectivity. Due to its mild nature and operational
simplicity, the present protocol is expected to find application in
synthetic setup.
Scheme 2. Nitration of Olefins with Fe(NO3)3
INTRODUCTION
■
Nitro compounds, particularly conjugated nitroolefins, have
great importance in synthetic organic chemistry.1 To obtain
nitroolefins directly from olefins, different nitrating agents such
as HNO3/H2SO4,2a NaNO2/HgCl2,2b AgNO2/I2,2c NO,2d
NO2/O3,2e NaNO2/Cu(II)-I2,2f and AgNO2/CH3COCl2g
have been employed so far.2 However, these methods are
often limited by a number of serious drawbacks: harsh
conditions, limited scope, formation of an undesired mixture
of E/Z isomer, among others. In this context, we recently
reported an efficient nitration of olefins with silver nitrite
(AgNO2) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)
where we circumvented the lack of stereoselectivity issue.3
While performing the screening of different metal nitrates as
potential nitrating agents, we discovered that inexpensive ferric
nitrate could provide (E)-nitrostyrene exclusively in 78% yield,
whereas silver nitrite turned out to be the optimal reagent (99%
yield). In fact, by using a reaction tube of larger volume (o.d. ×
L = 20 × 150 mm vs o.d. × L = 16 × 125 mm) with an
appropriate stir-bar, up to 95% yield was achieved with
Fe(NO3)3. Further, 1-(chloromethyl)-4-(2-nitrovinyl)benzene
(Scheme 1), which failed to produce the desired nitro
in ClCH2CH2Cl at 80 °C can produce nitrostyrene in 95%
yield (Table 1, entry 1).
However, lower yields were observed in the case of other
metal nitrates such as Co(NO3)2 and Na3Co(NO2)6 (Table 1,
entries 3 and 4, respectively), but nitration was not observed in
Table 1. Optimization by Varying Different Nitrating
a
Agents
entry
nitrating agents
GC yield (%)
95
1
2
Fe(NO3)3·9H2O
Fe(NO3)3·9H2O
Co(NO3)2·6H2O
Na3Co(NO2)6
NaNO2
b
78
3
37
22
0
4
Scheme 1. Undesired Nitration Product with AgNO2/
TEMPO
5
6
AgNO3
0
7
Ni(NO3)2·6H2O
Bi(NO3)3·5H2O
Fe(NO3)3·9H2O
Fe(NO3)3·9H2O
Fe(NO3)3·9H2O
0
8
74
c
9
57
d
10
11
19
e
0
a
compound with AgNO2, remained intact under the present
condition while undergoing nitration. Encouraged by these
observations, we decided to explore the scope of the reaction
with Fe(NO3)3 to provide an economic alternative for
stereoselective olefin nitration (Scheme 2).4
Olefin (0.5 mmol), nitrating agent (1 mmol), TEMPO (0.1 mmol), 4
Å MS (150 mg), 80 °C, ClCH2CH2Cl (2 mL), reaction carried out in
borosilicate glass tubes with threaded end: o.d. × L = 20 × 150 mm.
b
Reaction carried out in borosilicate glass tubes with threaded end:
c
d
o.d. × L = 16 × 125 mm. Without molecular sieves. Without
TEMPO. DDQ, chloranil, and anthraquinone were used instead of
e
TEMPO.
RESULTS AND DISCUSSION
■
Styrene was chosen as a model substrate to discover the best
reaction conditions using various nitrating agents and solvents.
We found that 2 equiv of Fe(NO3)3 with 0.2 equiv of TEMPO
Received: March 25, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/jo400598p | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
a
the case of NaNO2 and AgNO3 (Table 1, entries 5 and 6,
respectively). Controlled experiments with or without TEMPO
confirmed its necessity to obtain desired outcome of the
reaction (Table 1, entries 1 and 10, respectively). The nature of
the solvent had a significant effect on the nitration reaction as
less/nonpolar solvents were found to be better compared to
polar solvents (Table 2). The addition of different bases along
with TEMPO was found to have a detrimental effect on the
reaction outcome (Table 3).
Table 4. Stereoselective Nitration of Styrenes
a
Table 2. Optimization with Solvents
entry
solvent
GC yield (%)
1
2
3
4
5
6
7
8
ClCH2CH2Cl
TFT
95
89
62
80
63
68
1
dioxane
benzene
cyclohexane
toluene
THF
a
Olefin (0.5 mmol), Fe(NO3)3 (1 mmol), TEMPO (0.1 mmol), 4 Å
MS (150 mg), 80 °C, ClCH2CH2Cl (2 mL); isolated yield of the E
DMF
43
1
isomer; reaction mixtures were analyzed by GC-MS and/or H NMR
to determine E/Z ratios. GC yield. Yield of E isomer only.
a
Olefin (0.5 mmol), Fe(NO3)3 (1 mmol), TEMPO (0.1 mmol), 4 Å
MS (150 mg), 80 °C, solvent (2 mL).
b
c
a
Table 3. Effect of Various Bases on Nitration Reaction
A 2,4,6-trisubstituted styrene derivative afforded the
corresponding nitration product in an excellent 85% yield
(4m). Slight decreases in yield were observed in the case of α-
and β- substituted styrene (as compared to styrene) probably
owing to the steric effect of the methyl group adjacent to the
reaction center (4q and 4r). In both of these cases, a >7:1 E/Z
mixture was obtained. One of the important findings of the
present protocol is tolerance of the chloromethyl group, which
can be otherwise easily oxidized to the corresponding aldehyde
(4d) (Scheme 1). Notably, 3-nitro-1,2-dihydronaphthalene
(4o) was synthesized in excellent yield. Such an internal
nitroolefin is difficult to access through a traditional Henry
reaction.5
After successful nitration of styrenes, a number of aliphatic
olefins were subjected to nitration (Table 5). Long chain
aliphatic substrates with a terminal olefin produced the desired
nitro product in good yield (5a). Alkenes with internal double
bonds were also nitrated successfully (5b and 5c). Symmetrical
olefin, such as (E)-4-octene, produced the thermodynamically
stable (E)-4-nitrooct-4-ene (5b).
entry
base
GC yield (%)
1
2
3
4
5
6
7
8
9
BaCO3
K2CO3
Na2CO3
CS2CO3
KOtBu
DABCO
pyridine
DBU
71
43
45
40
66
82
65
22
66
K3PO4
a
Olefin (0.5 mmol), Fe(NO3)3 (1 mmol), TEMPO (0.1 mmol), 4 Å
MS (150 mg), 80 °C, ClCH2CH2Cl (2 mL).
Next, the scope and limitations of the reaction were
investigated with the optimized reaction condition. First, we
applied the present protocol on different styrene derivatives of
stereoelectronic variety (Table 4). Notably, only the E isomer
was observed in all these cases in contrast to earlier-reported
methods, which provided E/Z mixtures.2
The electronic nature of the substituents did not have an
impact on reaction outcome as both electron-donating (CH3,
OCH3) and electron-withdrawing (CO2CH3, CN, CHO, and
NO2) substituents provided the desired nitroolefins in good to
excellent yields (4b, 4c, 4g−4j). Different chloro- and bromo-
substituted styrenes were tolerated as well (4e, 4k and 4f, 4l).
These halo-substituted β-nitrostyrenes are useful compounds
for different cross-coupling reactions and other related
transformations.
To investigate the site-selectivity of nitration, we designed a
substrate with two olefins embedded in different electronic
environments. As expected, nitration occurred exclusively at the
distal olefin, which is electron-rich, as compared to the other
part, which is in the vicinity of the electron-withdrawing group
and hence deactivated (5e). On the other hand, selective
nitration at the terminal olefin was observed in the presence of
a terminal alkyne (5g). Ester and halide functional groups on a
distal position of a terminal alkene were also well-tolerated (5d
and 5f).
The present condition is also compatible with heterocyclic
olefins (Table 6). Nitration of 2-vinylbenzothiophene and 3-
vinylbenzothiophene afforded the desired product in good yield
(6a and 6b). Reaction of a vinyl group containing dibenzofuran
proceeded smoothly to generate the nitro product with E-
B
dx.doi.org/10.1021/jo400598p | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Table 5. Regio- and Stereoselective Nitration of Aliphatic
Olefins
Table 7. Regio- and Stereoselective Nitration of Natural
a
a
Product Derived Olefins
a
Olefin (0.5 mmol), Fe(NO3)3 (1.0 mmol), TEMPO (0.1 mmol), 4 Å
MS (150 mg), 80 °C, ClCH2CH2Cl (2 mL); isolated yield of the E
1
isomer; reaction mixtures were analyzed by GC-MS and/or H NMR
to determine E/Z ratios. Isolated as E/Z mixture.
a
Olefin (0.5 mmol), Fe(NO3)3 (1.0 mmol), TEMPO (0.1 mmol), 4 Å
MS (150 mg), 80 °C, ClCH2CH2Cl (2 mL); isolated yield of the E
b
1
isomer; reaction mixtures were analyzed by GC-MS and/or H NMR
a
Table 6. Stereoselective Nitration of Heterocyclic Olefins
to determine E/Z ratios.
Scheme 3. Nitration of 2-Vinylnaphthalene in Gram Scale
CONCLUSION
■
In conclusion, an efficient method for nitration of olefin has
been developed by using inexpensive ferric nitrate and
TEMPO. A wide range of olefins including aromatic, aliphatic,
heteroaromatic, and steroid-derived molecules were studied,
and nitration occurred in excellent yields. The present method
exhibited an excellent E-selectivity for all the observed cases.
This economical alternative is expected to complement our
previous approaches3,13 to generate nitroolefins stereoselec-
tively in everyday synthetic setup.
a
Olefin (0.5 mmol), Fe(NO3)3 (1.0 mmol), TEMPO (0.1 mmol), 4 Å
MS (150 mg), 80 °C, ClCH2CH2Cl (2 mL); isolated yield of the E
isomer; reaction mixtures were analyzed by GC-MS and/or H NMR
to determine E/Z ratios.
1
EXPERIMENTAL SECTION
stereoselectivity (6d). A vinyl pyrazole derivative provided the
nitration product with an excellent 83% isolation yield (6e).
Next, we examined the applicability of this nitration protocol
with steroid-derived molecules to exhibit the applicability of our
method (Table 7). Substrates based on naturally occurring
testosterone were nitrated in synthetically useful yield (7b and
7d). The substrate containing an exo-cyclic double bond was
nitrated with excellent stereoselectivity (7c, 78% yield).
Further, the reaction was successfully scaled-up to 1 g with 2-
vinylnaphthalene (Scheme 3, yield 83%).
■
General Procedures. All solvents, ferric nitrate, TEMPO, and
molecular sieves (4 Å; particle size 2−3 μm) were purchased from
commercial sources. All isolated compounds were characterized on the
basis of 1H NMR and 13C NMR spectroscopic data, gas
chromatography mass spectra (GC-MS), and HRMS data. All 1H
and 13C NMR data were reported in parts per million relative to
tetramethylsilane (δ = 0) and were measured relative to the signals for
1
residual chloroform (7.26 ppm for H and 77.23 ppm for 13C) in the
deuterated solvent. All GC analyses were performed on a GC system
with an FID detector using a J & W DB−1 column (10 m, 0.1 mm
i.d.). As the internal standard, n-decane was used. All GC-MS analysis
was done on a GC system connected with 5975C inert XL EI/CI
MSD (with triple axis detector).
General Procedure for the Synthesis of Nitroolefins. Olefin
(1 mmol), Fe(NO3)3·9H2O (1 mmol, 404 mg), TEMPO (0.1 mmol,
16 mg), and molecular sieves (4 Å, 150 mg) were added to an oven-
dried screw cap test tube (borosilicate glass tubes with threaded end;
o.d. × L = 20 × 150 mm) which was already charged with a magnetic
stir-bar. To start, olefin (if it was liquid) and solvent (ClCH2CH2Cl, 2
mL) were added by microliter and laboratory syringe, respectively.
The tube was placed in a preheated oil bath at 80 °C, and the reaction
In an earlier study with silver nitrite, we postulated about
•
involvement of a nitro radical. Indeed, the nitro radical (NO2 )
can be generated from Fe(NO3)3 under thermal conditions
(Scheme 4),2i following which we have depicted a plausible
mechanism in Scheme 4. The nitro radical would react at the
less-hindered side of the olefin in order to generate a secondary
or benzylic radical. This nitroalkane radical can be converted to
nitroolefin via two pathways. In path 1, TEMPO can abstract a
hydrogen radical, and in path 2, TEMPO may trap and oxidize
a benzylic radical to generate nitroolefin stereoselectively.3
C
dx.doi.org/10.1021/jo400598p | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Scheme 4. Proposed Pathways for Stereoselective Nitration
mixture was stirred vigorously for 12 h. After completion of the
reaction, the reaction mixture was cooled to room temperature and
filtered through a Celite bed with ethyl acetate as the washing solvent.
Finally, organic extract was concentrated and purified by column
chromatography using silica gel (60−120/100−200 mesh size) and
petroleum ether/ethyl acetate as the eluent.
CDCl3) δ (ppm) 7.39−7.44 (m, 2H), 7.57 (d, J = 10.3 Hz, 1H), 7.60
(dd, J = 4.8, 1.7 Hz, 2H), 7.94 (d, J = 13.7 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ (ppm) 127.0, 129.1, 130.5, 132.9, 137.6, 138.0.
(E)-Methyl 4-(2-nitrovinyl)benzoate (Table 4, Entry 4g) (Known
Compound3,7): Light yellow solid (85 mg, 82%), mp 176−178 °C,
1
GC-MS (m/z) 207.1 [M]+; H NMR (400 MHz, CDCl3) δ (ppm)
Procedure for the Synthesis of Nitroolefins in Gram Scale.
To an oven-dried round-bottom (250 mL) flask, which was already
charged with a magnetic stir-bar, were added 2-vinylnaphthalene (6.4
mmol, 1.00 g), Fe(NO3)3·9H2O (12.8 mmol, 5.17 g), TEMPO (1.28
mmol, 0.20 g), and molecular sieves (4 Å, 960 mg), and the solvent
(ClCH2CH2Cl, 26 mL). The flask was then sealed with a rubber
septum, placed in a preheated oil bath at 80 °C, and the reaction
mixture was stirred vigorously for 12 h. After completion of the
reaction, the reaction mixture was cooled to room temperature and
filtered through a Celite bed with ethyl acetate as the washing solvent.
Finally, organic extract was concentrated and purified by column
chromatography using silica gel (100−200 mesh size) and PET-ether/
ethyl acetate as the eluent.
7.30−7.38 (td, J = 7.5, 7.5, 1.4 Hz, 1H), 7.39−7.45 (td, J = 8.0, 7.7, 1.7
Hz, 1H), 7.46−7.51 (dd, J = 8.0, 1.4 Hz, 1H), 7.56−7.61 (m, 2H),
8.36−8.40 (d, J = 13.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
(ppm) 52.7, 129.1, 130.6, 133.2, 134.3, 137.7, 138.8, 166.2.
(E)-4-(2-Nitrovinyl)benzonitrile (Table 4, Entry 4h) (Known
Compound3,6): Light yellow solid (67 mg, 77%), mp 186−187 °C,
1
GC-MS (m/z) 174.1 [M]+; H NMR (400 MHz, CDCl3) δ (ppm)
7.62 (d, J = 13.8 Hz, 1H), 7.67 (d, J = 8.4 Hz, 2H), 7.72−7.80 (m,
2H), 7.99 (d, J = 13.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
(ppm) 115.3, 117.9, 129.5, 133.1, 134.4, 136.7, 139.6.
(E)-3-(2-Nitrovinyl)benzaldehyde (Table 4, Entry 4i) (Known
Compound3): Light yellow solid (69 mg, 78%), mp 91−92 °C, GC-
MS (m/z) 177.1 [M]+; 1H NMR (400 MHz, CDCl3) δ (ppm) 7.62−
7.70 (m, 2H), 7.78−7.85 (m, 1H), 7.97−8.10 (m, 3H), 10.06 (s, 1H);
13C NMR (100 MHz, CDCl3) δ (ppm) 129.7, 130.4, 131.2, 133.0,
(E)-β-Nitrostyrene (Table 4, Entry 4a) (Known Compound2h,3):
Crystalline yellow solid (67 mg, 90%), mp 57−58 °C, GC-MS (m/z)
1
149.1 [M]+; H NMR (400 MHz, CDCl3) δ (ppm) 7.43−7.51 (m,
134.5, 137.3, 137.6, 138.5, 191.2.
3H), 7.54−7.57 (m, 2H), 7.57−7.61 (d, J = 13.7 Hz, 1H), 7.99−8.04
(d, J = 13.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 129.3,
129.6, 130.2, 132.3, 137.3, 139.3.
(E)-1-Nitro-3-(2-nitrovinyl)benzene (Table 4, Entry 4j) (Known
Compound3,8): Light yellow solid (81 mg, 83%), mp 125−126 °C,
1
GC-MS (m/z) 194.1 [M]+; H NMR (400 MHz, CDCl3) δ (ppm)
(E)-1-Methyl-4-(2-nitrovinyl)benzene (Table 4, Entry 4b) (Known
Compound3,6): Yellow solid (72 mg, 88%), mp 106−107 °C, GC-MS
(m/z) 163.1 [M]+; 1H NMR (400 MHz, CDCl3) δ (ppm) 2.36−2.49
(s, 3H), 7.25−7.30 (d, J = 2.5 Hz, 2H), 7.44−7.47 (d, J = 8.2 Hz, 2H),
7.56−7.60 (d, J = 13.7 Hz, 1H), 7.98−8.02 (d, J = 13.7 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 21.8, 127.4, 129.3, 130.3, 136.4,
139.3, 143.3.
(E)-1-Methoxy-4-(2-nitrovinyl)benzene (Table 4, Entry 4c)
(Known Compound2h,3): Yellow solid (75 mg, 84%), GC-MS (m/z)
179.1 [M]+; 1H NMR (400 MHz, CDCl3) δ (ppm) 3.87 (s, 3H), 6.96
(d, J = 8.8 Hz, 2H), 7.49−7.55 (m, 3H), 7.98 (d, J = 13.6 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 55.7, 115.1, 122.7, 131.3, 135.2,
139.2, 163.1.
7.66−7.72 (m, 2H), 7.89 (d, J = 7.9 Hz, 1H), 8.06 (d, J = 13.8 Hz,
1H), 8.34−8.37 (ddd, J = 8.2, 2.2, 1.0 Hz, 1H), 8.43 (t, J = 2.0, 2.0 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 123.6, 126.3, 130.8,
131.9, 134.6, 136.4, 139.4, 148.9.
(E)-1-Chloro-2-(2-nitrovinyl)benzene (Table 4, Entry 4k) (Known
2h
1
Compound ): Yellow liquid (74 mg, 81%); H NMR (400 MHz,
CDCl3) δ (ppm) 7.30−7.36 (td, J = 7.5, 7.5, 1.4 Hz, 1H), 7.39−7.45
(td, J = 8.0, 7.7, 1.7 Hz, 1H), 7.46−7.50 (dd, J = 8.0, 1.4 Hz, 1H),
7.56−7.61 (m, 2H), 8.38 (d, J = 13.7 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 127.6, 128.6, 128.7, 130.8, 133.0, 135.2, 136.1, 138.9.
(E)-1-Bromo-2-(2-nitrovinyl)benzene (Table 4, Entry 4l) (Known
Compound3,9): Crystalline light yellow solid (88 mg,77%), mp 88−89
°C, GC-MS (m/z) 228.1 [M]+; 1H NMR (400 MHz, CDCl3) δ (ppm)
7.31−7.40 (dtd, J = 19.3, 7.5, 7.5, 1.6 Hz, 2H), 7.50−7.59 (m, 2H),
7.67 (d, J = 8.1 Hz, 1H), 8.35−8.39 (dd, J = 13.7, 2.8 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 126.4, 128.2, 128.6, 130.4, 133.1,
134.1, 137.7, 138.9.
(E)-1-(Chloromethyl)-4-(2-nitrovinyl)benzene (Table 4, Entry 4d):
1
Yellow solid (75 mg, 76%); H NMR (400 MHz, CHCl3) δ (ppm)
4.61 (s, 2H), 7.48 (d, J = 8.3 Hz, 2H), 7.53−7.61 (m, 3H), 7.99 (d, J =
13.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 45.4, 129.6,
129.7, 130.2, 137.6, 138.4, 141.7; ESI-MS calcd for C9H8ClNNaO2
220.01, found 219.91. Anal. Calcd for C9H8ClNO2: C, 54.70; H, 4.08;
N, 7.09. Found: C, 54.84; H, 3.93; N, 7.30.
(E)-1,3,5-tri-Methyl-2-(2-nitrovinyl)benzene (Table 4, Entry 4m)
(Known Compound3): Yellow solid (81 mg, 85%), mp 123−124 °C,
1
GC-MS (m/z) 191.1 [M]+; H NMR (400 MHz, CDCl3) δ (ppm)
(E)-1-Chloro-4-(2-nitrovinyl)benzene (Table 4, Entry 4e) (Known
Compound2h,3): Crystalline light yellow solid (78 mg, 85%), mp 113−
2.31 (s, 3H), 2.38 (s, 6H), 6.95 (s, 2H), 7.24−7.34 (m, 1H), 8.26 (d, J
= 13.9 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 21.3, 21.7,
125.8, 130.0, 136.7, 138.6, 139.8, 141.0.
1
114 °C, GC-MS (m/z) 183.1 [M]+; H NMR (400 MHz, CDCl3) δ
(ppm) 7.40−7.47 (m, 2H), 7.46−7.53 (m, 2H), 7.56 (d, J = 13.7 Hz,
1H), 7.96 (d, J = 13.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
(ppm) 128.7, 129.9, 130.4, 137.6, 137.9, 138.5.
(E)-5-Nitro-6-(2-nitrovinyl)benzo[d][1,3]dioxole (Table 4, Entry
4n) (Known Compound3): Yellow solid (85 mg, 71%), mp 110−
1
111°C, GC-MS (m/z) 238.1 [M]+; H NMR (400 MHz, CDCl3) δ
(E)-1-Bromo-4-(2-nitrovinyl)benzene (Table 4, Entry 4f) (Known
Compound2h): Light yellow solid (96 mg, 84%); 1H NMR (400 MHz,
(ppm) 6.14 (s, 2H), 6.85 (s, 1H), 7.28 (d, J = 13.5 Hz, 1H), 7.57 (s,
D
dx.doi.org/10.1021/jo400598p | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
1H), 8.42 (d, J = 13.5 Hz, 1H);13C NMR (100 MHz, CDCl3) δ (ppm)
100.1, 104.1, 106.6, 107.8, 122.5, 135.8, 139.4, 150.5, 152.5.
3-Nitro-1,2-dihydronaphthalene (Table 4, Entry 4o) (Known
Compound ): Greenish yellow liquid (76.2, 87%); H NMR (400
MHz, CDCl3) δ (ppm) 2.94−2.97 (m, 2H), 2.98−2.99 (t, J = 1.3, 1.3
Hz, 1H), 3.02−3.03 (t, J = 1.1, 1.1 Hz, 2H), 7.28−7.31 (m, 2H),
7.31−7.34 (dd, J = 4.6, 1.7 Hz, 1H), 7.34−7.37 (dd, J = 7.3, 1.8 Hz,
1H), 7.78−7.90 (d, J = 1.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
(ppm) 22.5, 28.0, 127.4, 128.06, 130.2, 130.3, 131.4, 131.7, 136.5,
148.0.
(E)-Prop-2-yn-1-yl 11-nitroundec-10-enoate (Table 5, Entry 5g):
Yellow liquid (89.5 mg, 67%); 1H NMR (400 MHz, CDCl3) δ (ppm)
1.28−1.37 (m, 9H), 1.47−1.70 (m, 5H), 2.24−2.31 (qd, J = 7.4, 7.4,
7.4, 1.5 Hz, 2H), 2.32−2.39 (t, J = 7.5, 7.5 Hz, 2H), 2.47−2.50 (t, J =
2.5, 2.5 Hz, 1H), 4.64−4.70 (d, J = 2.5 Hz, 2H), 6.95−7.04 (m, 1H),
7.22−7.34 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 24.7,
27.7, 28.4, 28.9, 29.0, 29.0, 33.9, 51.8, 74.8, 77.8, 139.6, 142.8, 172.9;
HRMS (ESI) calcd for C14H21NNaO4 290.1368, found 290.1360.
(E)-(2-Nitrovinyl)cyclohexane (Table 5, Entry 5h) (Known
Compound3,6): Yellow liquid 56 mg, 72%); 1H NMR (400 MHz,
CDCl3) δ (ppm) 1.14−1.40 (m, 5H), 1.57−1.59 (s, 2H), 1.68−1.75
(dddd, J = 11.7, 5.0, 3.2, 1.6 Hz, 1H), 1.78−1.84 (m, 2H), 2.20−2.31
(ddtd, J = 11.0, 7.4, 3.9, 3.5, 1.3 Hz, 1H), 6.91−6.96 (dd, J = 13.5, 1.4
Hz, 1H), 7.20−7.26 (dd, J = 13.5, 7.2 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 25.6, 25.8, 31.6, 37.7, 138.4, 147.5.
(E)-2-(2-Nitrovinyl)benzo[b]thiophene (Table 6, Entry 6a): Green-
ish yellow solid (71 mg, 69%); 1H NMR (400 MHz, CDCl3) δ (ppm)
1.54−1.63 (s, 1H), 7.39−7.52 (m, 3H), 7.68−7.70 (s, 1H), 7.82−7.85
(m, 1H), 8.20−8.26 (dd, J = 13.3, 0.6 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 122.8, 125.2, 125.6, 127.7, 132.9, 133.2, 133.8, 137.2,
139.3, 141.27; HRMS (ESI) calcd for C10H8NO2S 206.0276, found
206.0282.
10
1
(E)-2-(2-Nitrovinyl)naphthalene (Table 4, Entry 4p) (Known
Compound2c,3): Yellow solid (88 mg, 88%), mp 128−130 °C, GC-
1
MS (m/z) 199.1 [M]+; H NMR (400 MHz, CDCl3) δ (ppm) 7.54−
7.62 (m, 3H), 7.70 (d, J = 13.6 Hz, 1H), 7.86−7.91 (m, 3H), 8.01−
8.02 (m, 1H), 8.16 (d, J = 13.7 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 123.5, 127.4, 127.7, 128.1, 128.6, 129.0, 129.5, 132.5,
133.3, 135.1, 137.3, 139.4.
(E)-(1-Nitroprop-1-en-2-yl)benzene (Table 4, Entry 4q) (Known
Compound3,11): Yellow liquid (51 mg, 62%), GC-MS (m/z) 163.1
[M]+; 1H NMR (400 MHz, CDCl3) δ (ppm) 2.65 (d, J = 1.5 Hz, 3H),
7.31 (q, J = 1.5, 1.4, 1.4 Hz, 1H), 7.45 (m, 5H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 18.8, 127.0, 129.2, 130.5, 136.5, 138.4, 150.2.
(Z)-(2-Nitroprop-1-enyl)benzene (Table 4, Entry 4r) (Known
Compound3,11): Yellow liquid (49 mg, 60%), GC-MS (m/z) 163.1
(E)-3-(2-Nitrovinyl)benzo[b]thiophene (Table 6, Entry 6b) (Known
3
1
Compound ): Greenish yellow solid (74 mg, 72%); H NMR (400
MHz, CDCl3) δ (ppm) 7.46−7.56 (m, 2H), 7.76 (d, J = 12.0 Hz, 1H),
7.92−7.98 (m, 3H), 8.29 (d, J = 12.0 Hz, 1H);13C NMR (100 MHz,
CDCl3) δ (ppm) 122.2, 123.5, 125.9, 127.2, 131.3, 133.1, 136.6, 136.8,
140.7.
1
[M]+; H NMR (400 MHz, CDCl3) δ (ppm) 2.45−2.48 (d, J = 1.1
Hz, 3H), 7.42−7.47 (m, 5H), 8.10−8.11 (m, 1H); 13C NMR (100
MHz, CDCl3) δ (ppm) 14.2, 128.1, 129.1, 130.1, 130.1, 132.6, 133.7.
(E)-1-Nitrooct-1-ene (Table 5, Entry 5a) (Known Compound3,12):
(E)-2-(1-Nitroprop-1-en-2-yl)benzofuran (Table 6, Entry 6c).
1
Yellow liquid (62 mg, 79%); H NMR (400 MHz, CDCl3) δ (ppm)
1
Yellow solid (66 mg, 65%); H NMR (400 MHz, CDCl3) δ (ppm)
0.86−0.92 (m, 3H), 1.21−1.39 (m, 6H), 1.46−1.56 (m, 2H), 2.23−
2.30 (qd, J = 7.5, 7.5, 7.4, 1.6 Hz, 2H), 6.96−7.01 (dt, J = 13.4, 1.6, 1.6
Hz, 1H), 7.24−7.32 (m, 1H);13C NMR (100 MHz, CDCl3) δ (ppm)
14.2, 22.6, 27.8, 28.6, 28.9, 31.6, 139.7, 143.0.
2.64 (d, J = 1.4 Hz, 3H), 7.26 (s, 1H), 7.24−7.33 (m, 1H), 7.40−7.44
(ddd, J = 8.4, 7.2, 1.3 Hz, 1H), 7.48−7.51 (dd, J = 8.4, 1.0 Hz, 1H),
7.63 (d, J = 8.1 Hz, 1H), 7.89 (d, J = 1.5 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ (ppm) 14.9, 111.7, 112.3, 122.1, 123.9, 127.7, 128.1,
135.1, 136.6, 152.3, 155.6; HRMS (ESI) calcd for C11H10NO3
204.0661, found 204.0652.
(E)-4-(2-Nitrovinyl)dibenzo[b,d]furan (Table 6, Entry 6d) (Known
Compound3): Light yellow solid (94.4 mg, 79%), mp 123−124 °C; 1H
NMR (400 MHz, CDCl3) δ (ppm) 7.39−7.44 (tdd, J = 7.7, 7.7, 2.6,
0.8 Hz, 2H), 7.51−7.57 (m, 2H), 7.65−7.68 (dd, J = 8.3, 0.9 Hz, 1H),
7.96−7.99 (m, 1H), 8.04−8.07 (dt, J = 7.7, 0.9, 0.9 Hz, 1H), 8.15−
8.20 (dd, J = 13.7, 0.9 Hz, 1H), 8.30−8.35 (dd, J = 13.6, 0.9 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ (ppm) 112.2, 115.5, 121.1, 123.2,
(E)-4-Nitrooct-4-ene (Table 5, Entry 5b) (Known Compound3,12):
1
Yellow liquid (44 mg, 56%); H NMR (400 MHz, CDCl3) δ (ppm)
0.91−1.00 (dt, J = 13.2, 7.4, 7.4 Hz, 6H), 1.23−1.26 (s, 1H), 1.49−
1.57 (ddt, J = 11.5, 7.5, 3.9, 3.9 Hz, 3H), 2.17−2.25 (q, J = 7.6, 7.6, 7.6
Hz, 2H), 2.53−2.60 (m, 2H), 7.07−7.13 (t, J = 8.0, 8.0 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 13.8, 14.0, 21.4, 22.0, 28.3, 30.1,
76.9, 77.2, 77.5, 100.1, 136.6.
(E)-2-Nitrohex-2-ene (Table 5, Entry 5c) (Known Compound3):
1
Yellow liquid (42 mg, 65%); H NMR (400 MHz, CDCl3) δ (ppm)
0.92−1.00 (dt, J = 10.2, 7.4, 7.4 Hz, 3H), 1.24−1.27 (d, J = 9.0 Hz,
0H), 1.49−1.60 (td, J = 14.8, 14.8, 7.4 Hz, 3H), 1.87−1.90 (dt, J = 7.4,
0.7, 0.7 Hz, 1H), 2.15−2.24 (m, 4H), 2.54−2.60 (m, 1H), 7.11−7.23
(m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 12.7, 13.7, 14.0, 21.1,
21.8, 28.0, 30.2, 131.8, 136.4.
123.6, 123.8, 124.5, 125.5, 128.3, 130.7, 134.4, 139.9, 154.5, 156.2;
HRMS (ESI) calcd for C14H10NO3 240.0661, found 240.0668.
(E)-3-Methyl-4-(2-nitrovinyl)-1-phenyl-1H-pyrazole (Table 6,
Entry 6e) (Known Compound3): Greenish yellow solid (95 mg,
83%), mp 143−144 °C; 1H NMR (400 MHz, CDCl3) δ (ppm) 2.40−
2.54 (s, 2H), 7.32−7.37 (td, J = 7.5, 7.3, 1.2 Hz, 1H), 7.44−7.50 (m,
3H), 7.64−7.69 (dd, J = 8.7, 1.1 Hz, 2H), 8.00−8.04 (d, J = 13.7 Hz,
1H), 8.15−8.16 (s, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm)
122.8, 125.2, 125.6, 127.7, 132.9, 133.2, 133.8, 137.2, 139.3, 141.2;
HRMS (ESI) calcd for C12H12N3O2 230.0930, found 230.0923.
(8S,9S,10R,13R,14S,17R)-10,13-dimethyl-17-((R)-6-methylheptan-
2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclo-
penta[a]phenanthren-3-yl 4-((E)-2-nitrovinyl)benzoate (Table 7,
Entry 7a): Bright yellowish solid (230 mg, 82%); 1H NMR (400
MHz, CDCl3) δ (ppm) 0.68−0.70 (s, 2H), 0.84−2.07 (m, 21H),
2.39−2.57 (d, J = 7.7 Hz, 1H), 4.79−4.99 (tdd, J = 9.2, 9.2, 7.6, 4.5 Hz,
1H), 5.37−5.50 (m, 1H), 7.60−7.65 (m, 2H), 8.00−8.05 (d, J = 13.8
Hz, 1H), 8.09−8.13 (d, J = 8.4 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 12.0, 18.9, 19.5, 21.2, 22.7, 23.0, 24.0, 24.5, 28.0,
28.2, 28.4, 32.0, 32.1, 36.0, 36.4, 36.8, 37.2, 38.3, 39.7, 39.9, 42.5, 50.2,
56.3, 56.8, 75.48 123.2, 129.1, 130.6, 133.9, 134.1, 137.9, 138.7, 139.6,
159.8, 165.4; ESI-MS calcd for C36H51NO4 561.38, found 561.39 and
562.41.
(E)-Methyl-11-nitroundec-10-enoate (Table 5, Entry 5d) (Known
Compound3): Light yellow liquid (83 mg, 68%), GC-MS (m/z) 212.1
1
[M]+; H NMR (400 MHz, CDCl3) δ (ppm) 1.29−1.36 (m, 9H),
1.46−1.63 (m, 4H), 2.22−2.32 (m, 4H), 3.66 (s, 3H), 6.95−6.99 (dt, J
= 13.4, 1.6, 1.6 Hz, 1H), 7.23−7.30 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 24.9, 27.8, 28.5, 29.1, 29.1, 29.1, 29.1, 34.1, 51.6,
139.7, 142.9, 174.3.
(E)-3-Nitroallyl-undec-10-enoate (Table 5, Entry 5e) (Known
Compound3): Light yellow liquid (82 mg, 61%); 1H NMR (400 MHz,
CDCl3) δ (ppm) 1.24−1.66 (m, 12H), 2.21−2.38 (m, 3H), 4.55−4.60
(d, J = 5.7 Hz, 1H), 5.20−5.37 (m, 1H), 5.85−6.00 (ddt, J = 17.2,
10.4, 5.7, 5.7 Hz, 1H), 6.95−7.01 (m, 1H), 7.23−7.33 (m, 1H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 25.0, 27.9, 28.6, 29.2, 29.2, 29.2,
29.9, 34.4, 65.1, 118.3, 132.5, 139.7, 142.9, 173.6.
(E)-10-Bromo-1-nitrodec-1-ene (Table 5, Entry 5f) (Known
Compound3): Yellow liquid (77 mg, 58%); 1H NMR (400 MHz,
CDCl3) δ (ppm) 1.24−1.35 (m, 7H), 1.35−1.44 (m, 2H), 1.49 (p, J =
7.5, 7.5, 7.3, 7.3 Hz, 2H), 1.74−1.90 (m, 2H), 2.17−2.31 (qd, J = 7.4,
7.4, 7.4, 1.5 Hz, 2H), 3.38 (t, J = 6.8, 6.8 Hz, 2H), 6.88−7.03 (dd, J =
13.4, 1.5 Hz, 1H), 7.17−7.34 (dt, J = 13.7, 7.4, 7.4 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ (ppm) 27.8, 28.2, 28.6, 28.7, 29.1, 29.2, 32.9,
34.1, 139.7, 142.9.
(8R,9S,10R,13S,14S,17S)-10,13-Di-methyl-3-oxo-2,3,6,-
7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]-
phenanthren-17-yl-4-((E)-2-nitrovinyl)benzoate (Table 7, Entry 7b)
3
1
(Known Compound ): Light yellow solid (185 mg, 80%); H NMR
(400 MHz, CDCl3) δ (ppm) 0.95−1.32 (m, 9H), 1.38−1.50 (m, 2H),
E
dx.doi.org/10.1021/jo400598p | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
1.57−1.80 (m, 6H), 1.84−1.92 (m, 2H), 2.00−2.07 (m, 1H), 2.26−
2.48 (m, 4H), 4.04−4.20 (d, J = 7.1 Hz, 1H), 4.83−4.91 (dd, J = 9.2,
7.7 Hz, 1H), 5.72−5.76 (m, 1H), 7.61−7.65 (m, 3H), 8.01−8.04 (d, J
= 13.8 Hz, 1H), 8.09−8.11 (d, J = 8.4 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 12.5, 17.6, 20.7, 23.8, 27.8, 31.6, 32.9, 34.1, 35.6,
35.9, 36.9, 38.8, 43.1, 50.4, 53.8, 83.7, 124.2, 129.1, 130.5, 133.7, 134.2,
137.8, 138.8, 165.5, 170.9, 199.6.
Prateeptongkum, S.; Jackstell, R.; Vogl, N.; Weckbecker, C.; Beller, M.
Adv. Synth. Catal. 2008, 350, 2493. (i) Taniguchi, T.; Fujii, T.;
Ishibashi, H. J. Org. Chem. 2010, 75, 8126.
(3) Maity, S.; Manna, S.; Rana, S.; Naveen, T.; Mallick, A.; Maiti, D. J.
Am. Chem. Soc. 2013, 3355.
(4) (a) Bolm, C.; Legros, J.; Paith, J. L.; Zani, L. Chem. Rev. 2004,
104, 6217. (b) Sherry, B. D.; Furstner, A. Acc. Chem. Res. 2008, 41,
1500. (c) Enthaler, S.; Junge, K.; Beller, M. Angew. Chem. 2008, 120,
3363; Angew. Chem., Int. Ed. 2008, 47, 3317. (d) Correa, A.; Mancheo,
O. G.; Bolm, C. Chem. Soc. Rev. 2008, 37, 1108. (e) Morris, R. H.
Chem. Soc. Rev. 2009, 38, 2282.
(8R,9S,10S,13R,14S,17R,E)-10,13-Dimethyl-17-((R)-6-methyl-
heptan-2-yl)-3-(nitromethylene)hexadecahydro-1H-cyclopenta[a]-
phenanthrene (Table 7, Entry 7c) (Known Compound3): Creamy
1
white solid (168 mg, 78%); H NMR (400 MHz, CDCl3) δ (ppm)
0.64−0.75 (d, J = 30.0 Hz, 6H), 0.84−0.94 (m, 15H), 0.95−1.21 (m,
7H), 1.20−1.42 (m, 8H), 1.47−1.62 (m, 2H), 1.65−2.01 (m, 5H),
2.08−2.27 (m, 1H), 2.28−2.40 (m, 1H), 4.73−4.87 (s, 1H), 6.82−
6.96 (d, J = 2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) 18.9,
21.4, 22.7, 23.0, 24.0, 24.4, 28.2, 28.4, 30.3, 31.5, 32.0, 32.1, 35.5, 36.0,
36.3, 39.3, 39.7, 40.0, 42.7, 47.3, 48.3, 54.2, 54.3, 56.4, 56.5, 132.4,
156.1.
(5) (a) Kurti, L.; Czako, B. Strategic Applications of Named Reactions
in Organic Synthesis; Elsevier Academic Press: Philadelphia, PA, 2005.
(b) Fioravanti, S.; Pellacani, L.; Tardella, P. A.; Vergari, M. C. Org.
Lett. 2008, 10, 1449.
(6) Yoshida, M.; Kitamikado, N.; Ikehara, H.; Hara, S. J. Org. Chem.
2011, 76, 2305.
(7) Campos, P. J.; Garcia, B.; Rodriguez, M. A. Tetrahedron Lett.
2000, 41, 979.
(8) Neelakandeswari, N.; Sangami, G.; Emayavaramban, P.;
Karvembu, R.; Dharmaraj, N.; Kim, H. Y. Tetrahedron Lett. 2012,
53, 2980.
(9) Chang, C.-F.; Huang, C.-Y.; Huang, Y.-C.; Lin, K.-Y.; Lee, Y.-J.;
Wang, C. J. Synth. Commun. 2010, 40, 3452.
(10) Sreekumar, R.; Padmakumar, R.; Rugmini. Tetrahedron Lett.
1998, 39, 2696.
(E)-(8R,9S,10R,13S,14S,17S)-10,13-Dimethyl-3-oxo-
2,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta-
[a]phenanthren-17-yl 11-nitroundec-10-enoate (Table 7, Entry 7d):
1
Light yellow liquid (162 mg, 65%); H NMR (400 MHz, CDCl3) δ
(ppm) 0.79−1.24 (m, 11H), 1.24−1.44 (m, 10H), 1.44−1.89 (m, 6H),
1.99−2.06 (m, 1H), 2.12−2.48 (m, 9H), 4.56−4.65 (dd, J = 9.2, 7.8
Hz, 1H), 5.71−5.75 (m, 1H), 6.96−7.01 (dt, J = 13.4, 1.6, 1.6 Hz,
1H), 7.08−7.15 (m, 1H), 7.22−7.34 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 12.2, 17.5, 20.6, 23.6, 25.17, 27.6, 27.8, 28.6, 29.1,
29.2, 31.6, 32.9, 34.1, 34.6, 35.5, 35.8, 36.8, 38.7, 42.6, 50.3, 53.8, 82.3,
124.1, 139.7, 142.9, 171.2, 173.9, 199.6; HRMS (ESI) calcd for
C30H45NNaO5 522.3190, found 522.3186.
(11) Fryszkowska, A.; Fisher, K.; Gardiner, J. M.; Stephens, G. M. J.
Org. Chem. 2008, 73, 4295.
(12) Motokura, K.; Tomita, M.; Tada, M.; Iwasawa, Y. Chem.Eur. J.
2008, 14, 4017.
(13) Manna, S.; Jana, S.; Saboo, T.; Maji, A.; Maiti, D. Chem.
Commun. 2013, 49, 5286.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Figures of H and 13C NMR spectra for all products. This
material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: dmaiti@iitb.ac.in.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This activity is supported by DST, India. Financial support
received from CSIR-India (fellowship to T.N. and S.M.) and
DST-India (fellowship to U.S. under Fast Track Scheme) is
gratefully acknowledged.
REFERENCES
■
(1) (a) Ono, N. The Nitro Group in Organic Synthesis; Wiley-VCH:
Weinheim, Germany, 2001. (b) Feuer, H.; Nielsen, A. T. Nitro
Compounds; VCH Publishers, Inc.: New York, 1990. (c) Barrett, A. G.
M.; Graboski, G. G. Chem. Rev. 1986, 86, 751. (d) Rosini, G.; Ballini,
R. Synthesis 1988, 833. (e) Tamura, R.; Kamimura, A.; Ono, N.
Synthesis 1991, 423. (f) Carruthers, W. Cycloaddition Reactions in
Organic Synthesis; Pergamon Press:Oxford, U.K., 1990. (g) Perlmutter,
P. Conjugate Addition Reactions in Organic Synthesis; Pergamon Press:
Oxford, U.K., 1992. (h) Ballini, R.; Bosica, G.; Fiorini, D.; Palmieri, A.;
Petrini, M. Chem. Rev. 2005, 105, 933.
(2) (a) Tinsley, S. W. J. Org. Chem. 1961, 26, 4723. (b) Corey, E. J.;
Estreicher, H. J. Am. Chem. Soc. 1978, 100, 6294. (c) Sy, W. W.; By, A.
W. Tetrahedron Lett. 1985, 26, 1193. (d) Mukaiyama, T.; Hata, E.;
Yamada, T. Chem. Lett. 1995, 505. (e) Suzuki, H.; Mori, T. J. Org.
Chem. 1997, 62, 6498. (f) Campos, P. J.; Garcia, B.; Rodriguez, M. A.
Tetrahedron Lett. 2000, 41, 979. (g) Kancharla, P. K.; Reddy, Y. S.;
Dharuman, S.; Vankar, Y. D. J. Org. Chem. 2011, 76, 5832. (h) Jovel, I.;
F
dx.doi.org/10.1021/jo400598p | J. Org. Chem. XXXX, XXX, XXX−XXX