Palladium-catalyzed carbonation-diketonization of terminal aromatic alkenes via carbon-nitrogen bond cleavage for the synthesis of 1,2-diketones

Article abstract of DOI:10.1021/jo201029p

A palladium-catalyzed carbonation-diketonization reaction of terminal alkenes via carbon-nitrogen bond cleavage under an atmosphere of oxygen has been developed. A series of 1,2-diketones were readily prepared from the reaction of aromatic terminal alkenes with nitroalkanes.

Full text of DOI:10.1021/jo201029p

NOTE
pubs.acs.org/joc
Palladium-Catalyzed CarbonationꢀDiketonization of Terminal
Aromatic Alkenes via CarbonꢀNitrogen Bond Cleavage for the
Synthesis of 1,2-Diketones
Azhong Wang, Huanfeng Jiang,* and Xianwei Li
School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, P. R. China
S Supporting Information
b
ABSTRACT: A palladium-catalyzed carbonationꢀdiketoniza-
tion reaction of terminal alkenes via carbonꢀnitrogen bond
cleavage under an atmosphere of oxygen has been developed. A
series of 1,2-diketones were readily prepared from the reaction
of aromatic terminal alkenes with nitroalkanes.
he functionalization of the carbonꢀnitrogen bond is one of
The presence of 10 mol % of 2,20-azobisisobutyronitrile (AIBN)
promoted the yield of 2a to 71% (entry 14). The use of other
frequently employed radical inhibitors in radical reactions,
such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and 2,3-
dichloro-5,6-dicyanobenzoquinone (DDQ), failed to give the
product (entries 15 amd 16). These results suggest that the
reaction may proceed via a radical process. A control experiment
showed that no reaction occurred in the absence of Pd catalyst
(entry 17). Only trace of the desired product was observed in the
absence of a base (entry 18). This indicated that base played an
important role in this process.
To demonstrate the efficiency and generality of this process,
we have examined this transformation with both electron-poor
and electron-rich aromatic terminal alkenes under the optimized
reaction conditions as indicated in entry 14 of Table 1, and the
results obtained are summarized in Table 2. Styrenes bearing
electron-withdrawing and electron-donating para substituents
can be transformed into the corresponding products efficiently
(2bꢀh). A chloride at the meta position slightly affected the
product yield (2i); however, very low yield was obtained when
the chloride group was at the ortho position (2j). 2-Vinylnaphtha-
lene and 4-vinyldiphenyl were also good substrates for this trans-
formation (2k and 2l). The scope of the palladium-catalyzed
carbonationꢀdiketonization reaction was further expanded to a
variety of nitroalkanes. To our delight, nitroethane, 1-nitropropane,
1-nitrobutane, and 2-nitropropane also reacted with styrene to give
the desired products in good yields (2mꢀp). However, an attempt
to react tert-nitrobutane with styrene was unsuccessful.
T
the most challenging targets in modern organic synthesis. As
a result, only a few examples of the activation of CꢀN bond have
been reported.1 However, such transformations would be useful and
powerful methods in synthetic organic chemistry because many
organic molecules contain carbonꢀnitrogen bonds. Recently, some
significant progress in CꢀC bond formation reactions via CꢀN
bond cleavage has been achieved with sulfonamides,2 anilines,3 or
amides4 as the coupling partners. Even so, little attention has been
paid to using nitroalkanes as the coupling partner. To the best of our
knowledge, only one example of stoichiometric CꢀN bond activa-
tion with nitromethane has been reported.5 In connection with our
interest in the search for new alkene oxidations, herein, for the first
time, we present a palladium-catalyzed carbonationꢀdiketonization
reaction of terminal alkenes with molecular oxygen as the oxidant to
synthesize 1,2-diketone derivatives, which are important structural
units and synthetic intermediates in biologically active natural
products and medicinal chemistry.6
The investigation was initiated by using the reaction of styrene
with MeNO2 as a model (Table 1). We were pleased to find that 1,2-
diketone 2a was obtained in the presence of NaOAc or KOAc with
PdCl2 as catalyst, albeit in low yields (entries 1 and 2). It is obvious
that a CꢀN bond cleavage occurred during the process. This
inspirited us to examine optimal reaction conditions for carbona-
tionꢀdiketonization of 1a to 2a in order to obtain more satisfac-
tory results. We first examined the influence of base on the reac-
tion. Among various bases screened (such as CsF, CsOAc, Na2CO3,
K2CO3, Cs2CO3, and Ag2CO3), Na2CO3 was most effective
(entries 3ꢀ8). Subsequently, different palladium species such as
Pd(OAc)2, Pd(CH3CN)2Cl2, [Pd(CH3CN)4]BF4, and Pd(NO3)2
were also tested (entries 9ꢀ12), and Pd(OAc)2 proved to be
the more efficient catalyst in this reaction. It has been reported
that H2O promotes the diketonization of terminal alkynes;7 therefore,
10 equiv of H2O was added in the reaction. In contrast to these
previous studies, water was unable to augment this reaction
(entry 13). We envisioned that a radical process was possibly involved.
To investigate the origin of the oxygen atoms of the 1,2-
diketone products, an isotopic labeling study with 18O2 was
performed (eq 1). The reaction was carried out under 1 atm of
O2 to afford 2n with a MW of 176 when regular O2 was used and
with a MW of 180 when 18O2 was used. The isotopic labeling study
Received: June 14, 2011
Published: July 06, 2011
r
2011 American Chemical Society
6958
dx.doi.org/10.1021/jo201029p J. Org. Chem. 2011, 76, 6958–6961
|

The Journal of Organic Chemistry
NOTE
Table 1. Optimization of Reaction Conditions for the Palla-
Table 2. Palladium-Catalyzed CarbonationꢀDiketonization
dium-Catalyzed CarbonationꢀDiketonazation of Styrenea
of Terminal Alkenes with Nitroalkanesa
entry
base
additive
catalyst
yieldb (%)
1
2
NaOAc
KOAc
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
17
8
3
CsF
0
4
CsOAc
Na2CO3
K2CO3
Cs2CO3
Ag2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
none
trace
36
5
6
9
7
0
8
trace
48
9
Pd(OAc)2
10
11
12
13d
14
15
16
17
18
Pd(CH3CN)2Cl2
[Pd(CH3CN)4]BF4
Pd(NO3)2
Pd(OAc)2
13
trace
26
H2O
trace
71 (67)
0
AIBNe
DDQe
TEMPOe
AIBNe
AIBNe
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
0
none
0
Pd(OAc)2
trace
a Unless otherwise indicated, all reactions were performed with styrene
(1 mmol), Pd cat. (5 mol %), initial pressure of O2 (8 atm), and base
(2 mmol) in 3 mL of MeNO2, 120 °C for 20 h. b Determined by GC analysis
of crude reaction mixture, number in parentheses is yield of isolated product
based on complete alkene consumption. c CuCl2 (10 mol %). d 10 equiv of
H2O was added in the reaction. e 10 mol %.
a Standard reaction conditions: 1 (1 mmol), Pd(OAc)2 (0.05 mmol),
Na2CO3 (2 mmol), AIBN (0.1 mmol), nitroalkanes (3 mL), 120 °C,
initial pressure of O2 (8 atm), 20 h. Yields quoted are isolated yields.
clearly demonstrated that the oxygen atoms of 2n originated from
molecular O2.
Scheme 1. Plausible Reaction Pathways
At this moment, although it is premature to give rationale
behind these reactivities, preliminary reaction pathways for the
reaction of styrene with nitromethane might be proposed, as
shown in Scheme 1. Initially, a methyl radical would be generated
from nitromethane in the presence of Pd(OAc)2 and Na2CO3,8,9
which selectively adds to styrene to produce intermediate A. Inter-
mediate A would be attacked by O2 forming superoxide radical
B.10 The superoxide radical B undergoes [1,4] H abstraction to
generate hydroperoxide C, which subsequently transforms to
ketone radical D. According to the Russell mechanism,11 the
oxidation of ketone radical D with O2 leads to the formation of
R-hydroxy ketone and 1,2-diketone in equal yields (eq 2). The
fact that the R-hydroxy ketone E can be further converted to 2a
under the reaction conditions has been proved (eq 3). It is known
that the oxidation of propiophenone F can also lead to 2a,12 and
we, therefore, suspect that pathway b might be involved in the
6959
dx.doi.org/10.1021/jo201029p |J. Org. Chem. 2011, 76, 6958–6961

The Journal of Organic Chemistry
NOTE
reaction. However, no reaction was observed using propiophe-
none as the substrate (eq 4). Therefore, the participation of
pathway b can be completely excluded. Further studies are
required for the elucidation of detailed mechanism.
13C NMR (CDCl3, 100 MHz) δ 200.0, 189.9, 132.4, 132.0, 130.8, 130.4,
26.4; MS (EI, 70 eV) m/z 226 (M+, 2), 183 (100), 155 (59), 75 (53).
1-(4-(Trifluoromethyl)phenyl)propane-1,2-dione (2e): 1H NMR
(CDCl3, 400 MHz) δ 8.13 (d, J = 8.0 Hz, 2 H), 7.73 (d, J = 8.0 Hz, 2
H), 2.53 (s, 3 H); 13C NMR (CDCl3, 100 MHz) δ 199.4, 189.6, 135.7
(q, J = 32.5 Hz), 134.9, 131.0, 126.0 (q, J = 3.7 Hz), 123.6 (q, J = 27.1
Hz), 26.3; MS (EI, 70 eV) m/z 216 (M+, 1), 173 (100), 145 (73), 95
(24), 43 (92).
1
1-(4-Cyanophenyl)propane-1,2-dione (2f): H NMR (CDCl3, 400
MHz) δ 8.13 (d, J = 8.0 Hz, 2 H), 7.77 (d, J = 7.6 Hz, 2 H), 2.53 (s, 3 H);
13C NMR (CDCl3, 100 MHz) δ 199.0, 188.9, 135.3, 132.7, 131.0, 117.9,
117.7, 26.2; MS (EI, 70 eV) m/z 173 (M+, 1), 130 (100), 102 (64), 75
(18), 43 (49).
1
1-p-Tolylpropane-1,2-dione (2g): H NMR (CDCl3, 400 MHz) δ
7.88 (d, J = 8.0 Hz, 2 H), 7.27 (d, J = 8.0 Hz, 2 H), 2.48 (s, 3 H), 2.41 (s, 3
H); 13C NMR (CDCl3, 100 MHz) δ 201.1, 191.4, 146.1, 130.6, 129.8,
129.4, 26.6, 22.1; MS (EI, 70 eV) m/z 162 (M+, 1), 119 (100), 91 (82),
65 (37).
1
1-(4-tert-Butylphenyl)propane-1,2-dione (2h): H NMR (CDCl3,
400 MHz) δ 7.93 (d, J = 8.4 Hz, 2 H), 7.58 (d, J = 8.4 Hz, 2 H), 2.49 (s, 3
H), 1.33 (s, 9 H); 13C NMR (CDCl3, 100 MHz) δ 201.1, 191.4, 158.9,
130.5, 129.4, 126.1, 35.5, 31.2, 26.6; MS (EI, 70 eV) m/z 204 (M+, 1),
161 (100), 146 (18), 118 (23).
1
In summary, we have developed an unprecedented protocol
for the synthesis of 1,2-diketones from alkenes and nitroalkanes
through palladium-catalyzed cleavage of CꢀN bond. A variety of
functional groups are compatible with the reaction conditions. The
success of the present studies not only provides a powerful method
for the construction of new carbonation reactions but also suggests a
new strategy for CꢀN bond activation. Future work will include
further elucidation of the mechanism and utilizing nitroalkanes as
coupling partners for CꢀC bond formation.
1-(3-Chlorophenyl)propane-1,2-dione (2i): H NMR (CDCl3, 400
MHz) δ 7.87ꢀ7.98 (m, 2 H), 739ꢀ7.58 (m, 2 H), 2.50 (s, 3 H); 13C
NMR (CDCl3, 100 MHz) δ 199.7, 189.6, 135.3, 134.6, 133.6, 130.4,
130.3, 128.7, 26.4; MS (EI, 70 eV) m/z 182 (M+, 1), 139 (72), 111
(100), 75 (68). Anal. Calcd for C9H7ClO2: C, 59.20; H, 3.86. Found: C,
59.31; H, 3.79.
1
1-(2-Chlorophenyl)propane-1,2-dione (2j): H NMR (CDCl3, 400
MHz) δ 7.35ꢀ7.40 (m, 2 H), 746ꢀ7.48 (m, 1 H), 7.62ꢀ7.64 (m, 1 H),
2.55 (s, 3 H); 13C NMR (CDCl3, 100 MHz) δ 198.7, 193.2, 134.1, 134.0,
133.3, 131.5, 130.2, 127.5, 25.1; MS (EI, 70 eV) m/z 182 (M+, 1), 139
(100), 111 (65), 75 (53), 43 (69). Anal. Calcd for C9H7ClO2: C, 59.20;
H, 3.86. Found: C, 59.33; H, 3.78.
’ EXPERIMENTAL SECTION
1-(Naphthalen-3-yl)propane-1,2-dione (2k): 1H NMR (CDCl3, 400
MHz) δ 8.54 (s, 1 H), 8.01 (d, J = 8.8 Hz, 1 H),7.91 (d, J = 8.4 Hz, 1 H),
7.87 (d, J = 8.8 Hz, 1 H), 7.83 (d, J = 8.4 Hz, 1 H), 7.60 (t, J = 8.0 Hz, 1
H), 7.52 (t, J = 8.0 Hz, 1 H), 2.56 (s, 3 H); 13C NMR (CDCl3, 100 MHz)
δ 200.9, 191.5, 136.3, 133.4, 132.4, 130.1, 129.6, 129.0, 128.0, 127.2,
124.4, 26.7; MS (EI, 70 eV) m/z 198 (M+, 3), 155 (76), 127 (100), 77
(14), 43 (35).
General Procedure. The reactions were carried out in a 15 mL
autoclave. Pd(OAc)2 (11.2 mg, 0.05 mmol), Na2CO3 (212 mg, 2 mmol),
AIBN (16.4 mg, 0.1 mmol), nitroalkane (3 mL), and alkene (1 mmol) were
added into a 15 mL autoclave in sequence. O2 was pumped into the
autoclave to reach the desired pressure, and the autoclave was then heated
by oil bath under magnetic stirring for the desired reaction time. After the
reaction finished, the autoclave was allowed to cool to room temperature.
O2 was vented, and the surplus was extracted with EtOAc (30 mL). The
organic layer was dried over anhydrous MgSO4 and concentrated under
reduced pressure to give crude product. The crude product was purified by
chromatography on a silica gel column using light petroleum ether/ethyl
acetate (10:1) as eluent.
1
1ꢀ10-Biphenyl-4-ylpropane-1,2-dione (2l): H NMR (CDCl3, 400
MHz) δ 8.08 (d, J = 8.4 Hz, 2 H), 7.69 (d, J = 8.0 Hz, 2 H), 7.61 (d, J =
7.6 Hz, 2 H), 7.46 (t, J = 7.6 Hz, 2 H), 7.40 (t, J = 7.2 Hz, 1 H), 2.54 (s, 3
H); 13C NMR (CDCl3, 100 MHz) δ 200.8, 191.0, 147.3, 139.6, 131.1,
130.6, 129.2, 128.7, 127.6, 127.5, 26.6; MS (EI, 70 eV) m/z 224 (M+, 1),
181 (100), 152 (58), 76 (23), 43 (42). Anal. Calcd for C15H12O2: C,
80.34; H, 5.39. Found: C, 80.45; H, 5.33.
1
1-Phenylpropane-1,2-dione (2a): H NMR (CDCl3, 400 MHz) δ
7.99 (d, J = 7.2 Hz, 2 H), 7.62 (t, J = 7.2 Hz, 1 H), 7.47 (t, J = 7.6 Hz, 2 H),
2.50 (s, 3 H); 13C NMR (CDCl3, 100 MHz) δ 200.9, 191.3, 135.1, 131.8,
130.8, 128.6, 26.5; MS (EI, 70 eV) m/z 148 (M+, 2), 105 (100), 77 (83),
51 (36).
1
1-Phenylbutane-1,2-dione (2m): H NMR (CDCl3, 400 MHz) δ
7.96 (d, J = 7.6 Hz, 2 H), 7.62 (t, J = 7.6 Hz, 1 H), 7.47 (t, J = 7.6 Hz, 2 H),
2.89 (t, J = 7.2 Hz, 2 H), 1.18 (t, J = 7.2 Hz, 3 H); 13C NMR (CDCl3, 100
MHz) δ 204.0, 192.8, 134.8, 132.2, 130.3, 129.1, 32.3, 7.0; MS (EI, 70
eV) m/z 162 (M+, 1), 105 (100), 77 (73), 51 (34).
1-(4-Fluorophenyl)propane-1,2-dione (2b): 1H NMR (CDCl3, 400
MHz) δ 8.03ꢀ8.07 (m, 2 H), 7.11ꢀ7.16 (m, 2 H), 2.49 (s, 3 H); 13C
NMR (CDCl3, 100 MHz) δ 200.3, 189.5, 166.8 (d, J = 256.3 Hz), 133.5
(d, J = 9.6 Hz), 128.5 (d, J = 3 Hz), 116.3 (d, J = 21.9 Hz), 26.4; MS (EI,
70 eV) m/z 166 (M+, 1), 123 (93), 95 (100), 75 (24).
1
1-Phenylpentane-1,2-dione (2n): H NMR (CDCl3, 400 MHz) δ
7.96 (d, J = 7.6 Hz, 2 H), 7.62 (t, J = 7.6 Hz, 1 H), 7.48 (t, J = 7.6 Hz, 2 H),
2.84 (t, J = 7.2 Hz, 2 H), 1.67ꢀ1.77 (m, 2 H), 0.99 (t, J = 7.2 Hz, 3 H); 13C
NMR (CDCl3, 100 MHz) δ 203.6, 192.8, 134.8, 132.2, 130.4, 129.1, 40.9,
16.7, 13.9; MS (EI, 70 eV) m/z 176 (M+, 1), 105 (100), 77 (58), 51 (27).
1-(4-Chlorophenyl)propane-1,2-dione (2c): 1H NMR (CDCl3,
400 MHz) δ 7.94 (d, J = 8.0 Hz, 2 H), 7.42 (d, J = 8.4 Hz, 2 H), 2.48
(s, 3 H); 13C NMR (CDCl3, 100 MHz) δ 200.0, 189.7, 141.4, 131.9,
130.3, 129.3, 26.4; MS (EI, 70 eV) m/z 182 (M+, 1), 139 (100), 111
(73), 75 (64), 43 (52).
1
3-Methyl-1-phenylbutane-1,2-dione (12o): H NMR (CDCl3, 400
MHz) δ 7.91 (d, J = 7.6 Hz, 2 H), 7.44ꢀ7.62 (m, 3 H), 3.33 (q, J = 6.8
Hz, 1 H), 1.18 (q, J = 6.8 Hz, 6 H); 13C NMR (CDCl3, 100 MHz) δ
206.8, 194.3, 134.8, 132.8, 130.1, 129.1, 128.8, 128.5, 36.7, 17.1; MS (EI,
70 eV) m/z 176 (M+, 1), 105 (100), 77 (93), 51 (69), 43 (94).
1-(4-Bromophenyl)propane-1,2-dione (2d): 1H NMR (CDCl3, 400
MHz) δ 7.88 (d, J = 8.8 Hz, 2 H), 7.61 (d, J = 8.8 Hz, 2 H), 2.50 (s, 3 H);
6960
dx.doi.org/10.1021/jo201029p |J. Org. Chem. 2011, 76, 6958–6961

The Journal of Organic Chemistry
NOTE
1-Phenylhexane-1,2-dione (2p): 1H NMR (CDCl3, 400 MHz) δ 7.95
(d, J = 7.6 Hz, 2 H), 7.63 (t, J = 7.6 Hz, 1 H), 7.48 (t, J = 7.6 Hz, 2 H), 2.86
(t, J = 7.2 Hz, 2 H), 1.63ꢀ1.70 (m, 2 H), 1.34ꢀ1.41 (m, 2 H), 0.92 (t, J=7.2
Hz, 3 H); 13C NMR (CDCl3, 100 MHz) δ 203.5, 192.6, 134.6, 132.0, 130.2,
128.9, 38.5, 24.9, 22.3, 13.8; MS (EI, 70 eV) m/z 190 (M+, 1), 105 (100),
77 (74), 57 (48).
(11) (a) Miyamoto, S.; Martinez, G. R.; Medeiros, M. H. G..; Mascio,
P. D. J. Am. Chem. Soc. 2003, 125, 6172. (b) Sheldon, R. A.; Kochi, J. K.
Metal-Catalyzed Oxidations of Organic Compounds; Academic Press:
New York, 1981.
(12) (a) Lee, J. C.;Park, H.-J.;Park,J. Y.Tetrahedron Lett. 2002, 43, 5661.
(b) Wasserman, H. H.; Ives, J. L. J. Org. Chem. 1985, 50, 3573.
’ ASSOCIATED CONTENT
S
Supporting Information. Full experimental details and
b
copies of NMR spectral data. This material is available free of
charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: jianghf@scut.edu.cn.
’ ACKNOWLEDGMENT
We are grateful to the National Natural Science Foundation of
China (20932002), National Basic Research Program of China
(973 Program) (2011CB808600), Doctoral Fund of Ministry of
Education of China (20090172110014), and Guangdong Natural
Science Foundation (10351064101000000) for financial support.
’ REFERENCES
(1) (a) Guo, S.; Qian, B.; Xie, Y.; Xia, C.; Huang, H. Org. Lett. 2011,
13, 522. (b) Kuninobu, Y.; Nishi, M.; Takai, K. Chem. Commun. 2010,
46, 8860. (c) Kok, G. B.; Pye, C. C.; Singer, R. D.; Scammells, P. J. J. Org.
Chem. 2010, 75, 4806. (d) Sabiah, S.; Lee, C.-S.; Hwang, W.-S.; Lin,
I. J. B. Organometallics 2010, 29, 290. (e) Liu, C.-R.; Li, M.-B.; Cheng,
D.-J.; Yang, C.-F.; Tian, S.-K. Org. Lett. 2009, 11, 2543. (f) Hollmann, D.;
B€ahn, S.; Tillack, A.; Beller, M. Angew. Chem., Int. Ed. 2007, 46, 8291.
(g) Nechab, M.; Kumar, D. N.; Philouze, C.; Einhorn, C.; Einhorn, J.
Angew. Chem., Int. Ed. 2007, 46, 3080. (h) Zacuto, M. J.; Xu, F. J. Org.
Chem. 2007, 72, 6298.
(2) Liu, C.-R.; Yang, F.-L.; Jin, Y. Z.; Ma, X.-T.; Cheng, D.-J.; Li, N.;
Tian, S.-K. Org. Lett. 2010, 12, 3832.
(3) (a) Anbarasan, P.; Neumann, H.; Beller, M. Angew. Chem., Int.
Ed. 2011, 50, 519. (b) Jiang, T. S.; Li, J. H. Chem. Commun. 2009, 7236.
(c) Ueno, S.; Chatani, N.; Kakiuchi, F. J. Am. Chem. Soc. 2007, 129, 6098.
(4) Liu, Z.; Larock, R. C. J. Am. Chem. Soc. 2005, 127, 13112.
(5) Golisz, S. R.; Hazari, N.; Labinger, J. A.; Bercaw, J. E. J. Org.
Chem. 2009, 74, 8441.
(6) (a) Ozkay, Y.; Isikdaꢀg, I.; Incesu, Z.; Akalin, G. Eur. J. Med. Chem.
)
2010, 45, 3320. (b) Deng, X.; Mani, N. S. Org. Lett. 2006, 8, 269.
(c) Wadkins, R. M.; Hyatt, J. L.; Wei, X.; Yoon, K. J. P.; Wierdl, M.;
Edwards, C. C.; Morton, C. L.; Obenauer, J. C.; Damodaran, K.;
Beroza, P.; Danks, M. K.; Potter, P. M. J. Med. Chem. 2005, 48, 2906.
(d) Wolkenberg, S. E.; Wisnoski, D. D.; Leister, W. H.; Wang, Y.; Zhao,
Z.; Lindsley, C. W. Org. Lett. 2004, 6, 1453.
(7) (a) Zhang, C.; Jiao, N. J. Am. Chem. Soc. 2010, 132, 28. (b) Ren,
W.; Xia, Y.; Ji, S.-J.; Zhang, Y.; Wan, X.; Zhao, J. Org. Lett. 2009, 11, 1841.
(8) For radical reactions on nitroalkanes, see: (a) Tanner, D. D.;
Harrison, D. J.; Chen, J.; Kharrat, A.; Wayner, D. D. M.; Griller, D.;
McPhee, D. J. J. Org. Chem. 1990, 55, 3321. (b) Ono, N.; Miyake, H.;
Kamimura, A.; Hamamoto, I.; Tamura, R.; Kaji, A. Tetrahedron 1985,
41, 4013. (c) Ono, N.; Miyake, H.; Tamura, R.; Kaji, A. Tetrahedron Lett.
1981, 22, 1705. (d) Tanner, D. D.; Blackburn, E. V.; Diaz, G. E. J. Am.
Chem. Soc. 1981, 103, 1557.
(9) For cleavage of the CꢀN bond in nitromethane by palladium
complexes, see ref 5. The role of palladium and AIBN is not clear at the
present stage.
(10) Nakayama, H.; Itoh, A. Tetrahedron Lett. 2007, 48, 1131.
6961
dx.doi.org/10.1021/jo201029p |J. Org. Chem. 2011, 76, 6958–6961