Preparation of SRN1-type coupling adducts from aliphatic gem-dinitro compounds in ionic liquids

Article abstract of DOI:10.3390/molecules17054782

S_RN1-type coupling adducts are readily prepared by the reaction between α-sulfonylesters or α-cyanosulfones and gem-dinitro compounds in ionic liquids. The reactions progress smoothly and recovered ionic liquids can be used for several iteratio

Full text of DOI:10.3390/molecules17054782

Molecules 2012, 17, 4782-4790; doi:10.3390/molecules17054782
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Preparation of SRN1-Type Coupling Adducts from Aliphatic
gem-Dinitro Compounds in Ionic Liquids
Akio Kamimura * and Seiichi Toyoshima
Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University,
Ube 755-8611, Japan
* Author to whom correspondence should be addressed; E-Mail: ak10@yamaguchi-u.ac.jp;
Tel./Fax: +81-836-859-231.
Received: 29 February 2012; in revised form: 2 April 2012 / Accepted: 12 April 2012 /
Published: 25 April 2012
Abstract: SRN1-type coupling adducts are readily prepared by the reaction between
-sulfonylesters or -cyanosulfones and gem-dinitro compounds in ionic liquids. The
reactions progress smoothly and recovered ionic liquids can be used for several iterations,
as long as they are washed with water to remove alkali metallic salts. The reaction rate is
slower than the corresponding SRN1 reaction in DMSO, but no acceleration on irradiation
or no inhibition in the presence of m-DNB are observed.
Keywords: SRN1-type adducts; ionic liquids; nitro compounds; kinetics
1. Introduction
The SRN1 reaction is a unique reaction that proceeds via a single electron transfer process [1–3]. The
reaction usually starts with a single electron transfer that generates a radical anion species, which then
gives a radical species via cleavage of the anion radical. Then, the radical reacts with a coupling
partner to form products. The reaction is usually performed in either liquid ammonia or a dipolar
aprotic solvent such as DMSO and HMPA. The reaction progresses through a radical chain mechanism
and the reaction rate are significantly lowered by the presence of small amounts of a radical inhibitor
such as p-dinitrobenzene. The SRN1 reaction is frequently used to construct aromatic compounds [4–15].
The SRN1 reaction between aliphatic compounds produces a new carbon-carbon or carbon-heteroatom
bond between sterically hindered carbons in good yields. This type of bond formation is usually not
easily achieved using any other reactions in organic synthesis. The adducts from an aliphatic SRN1

Molecules 2012, 17
4783
reaction are regarded as precursors for further palladium coupling materials [16] or tri- or
tetrasubstituted alkenes [17–22].
Recently ionic liquids have attracted significant interest in organic synthesis because of their unique
properties such as wide redox windows, high polarities and high solubilities [23–28]. During the
course of our investigation on ionic liquid chemistry [29–31], it occurred to us that ionic liquids could
become a new solvent system for a reaction via electron transfer such as SRN1 reaction. To our best of
knowledge, there have been no reports that employ ionic liquids for such reactions. In this paper, we
demonstrate that the SRN1-type coupling adducts are indeed readily obtained in the reaction in ionic liquids.
2. Results and Discussion
We first examined various ionic liquids for the SRN1-type coupling reaction between gem-dinitro
compounds and -sulfonylesters. gem-Dinitropropane 2a was added to a mixture of tert-BuOK and
-sulfonyl propionic ester 1a in different ionic liquids under photoirradiation produced by a usual
tungsten lamp, and the desired coupling product 3a was isolated (Scheme 1) [32]. Table 1 summarizes
the results.
Scheme 1. SRN1-type coupling reactions between 1a and 2a.
Reagents and conditions: i, tert-BuOK (1.5 eq.), h, ionic liquids, rt.
Table 1. SRN1-type coupling reactions of 1a in various ionic liquids.
Entry
Ionic liquids a
[bmim][PF6]
[bmim][BF4]
[bmim][NTf2]
[PP13][NTf2]
[TMPA][NTf2]
[DEME][BF4]
Time (h)
3a; yield (%) b
58 (13)
71 (23)
55 (5)
1
2
3
4
5
6
11
7
7
4
7
66
76
58 (17)
6
a
[bmim]:1-butyl-3-methyimidazolium; [PP13]:1-methyl-1-propylpiperidinium; [TMPA]:
propyltrimethylammonium; [DEME]; N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium;
b Isolated yields. Recovery of 1a is in parentheses.
The coupling reaction between 1a and 2a took place smoothly in ionic liquids to give 3a in good
yield. For example, the reaction in [bmim][PF6] resulted in the formation of the coupling product 3a in
58% yield (entry 1). The reaction was complete after 11 h at room temperature, but some amounts of
the starting material 1a remained and were recovered from the reaction mixture. Although we have
examined many bases such as Me4NOH, DBU and Et3N, none of these amine bases worked well in the
reaction. Starting material 1a was recovered completely. Use of other ionic liquids that contained BF4
and NTf2 as a counter anion were examined (entries 2–6). The reaction progressed smoothly and the
corresponding adduct 3a was isolated in good yield. Thus, ionic liquids were useful solvents for the

Molecules 2012, 17
4784
coupling reaction. The reaction for other starting materials was explored next (Scheme 2). Table 2
summarizes the results. A mixture of 1b and 2,2-dinitropropane (2a) in [TMPA][NTf2], for example,
afforded coupling adduct 3b in 69% yield (entry 1). The reaction was complete within 8 to 24 h.
Coupling with 2,2-dinitrobutane (2b) also gave the products in a 1:1 mixture of two possible
diastereomers (entries 2 and 3). -Cyanosulfonyl compounds also underwent the reaction in ionic
liquid, producing the corresponding coupling products 3e to 3h in moderate to good yields (entries 4–7).
Thus, ionic liquids are useful solvents for promoting the coupling reaction effectively.
Scheme 2. SRN1-type coupling reaction in ionic liquids.
Reagents and conditions: i, tert-BuOK (1.5 eq.), h, [TMPA][NTf2], rt.
Table 2. The coupling reactions with various sulfonyl compounds 1.
Entry
1
R1
Me
Me
Me
Me
Et
R2
R3 Time (h) 3; Yield (%) a
1
2
3
4
5
6
7
1b
1a
1b
1c
1d
1e
CO2Et Me
CO2Me Et
CO2Et
CN
CN
CN
8
3b; 69
3c; 68
3d; 66
3e; 50
3f; 75
3g; 47
3h; 44
22
20
24
24
21
21
Et
Me
Me
Me
Me
C4H9
1f CH2=CH(CH2)3–
CN
a Isolated yields.
The repeated use of ionic liquids was examined for the reaction between 1a and 2a in [bmim][PF6]
(Scheme 3). Table 3 summarizes the results.
Scheme 3. Iteration use of ionic liquids for SRN1-type coupling reaction.
Reagents and conditions: i, tert-BuOK(1.5 eq.), h, [bmim][PF6], rt.
Table 3. Recycling use of [bmim][PF6] for the coupling reaction to give 3a.
Times
Time(h)
3a; Yield (%) a
1
2
3
4
5
11
7
7
7
7
58
62
19
51 b
50 b
a Isolated yields; b The washing treatment of ionic liquid was carried out before the reaction.

Molecules 2012, 17
4785
The recycling of the ionic liquids was performed in the following way: after the first reaction was
completed, we performed a usual work-up. Thus, product 3a was isolated in 58% yield by direct
extraction with ether from the ionic liquid and the remaining [bmim][PF6] was used directly for the
next reaction. The second run worked well and 3a was prepared in 62% yield. The third run, however,
occurred sluggishly, and the desired product 3a was isolated in only 19% yield. We thought this might
be due to accumulating side products such as sodium nitrite. Therefore, [bmim][PF6] was washed with
water to remove salts and other water-soluble impurities that had accumulated during the reaction. The
ionic liquid was recovered without significant loss. After drying, we used the recovered [bmim][PF6]
for the reaction and obtained 3a in 51% yield. When we used it for the fifth time, [bmim][PF6] worked
well and product 3a was isolated in 50% yield. Thus, the present procedure allowed us to use the ionic
liquid several times. We examined iterative use of ionic liquids [TMPA][NTf2] for the reaction and
successfully obtained 3a in good to moderate yields (Table 4). High yields of 3a were achieved until
six times use, when 3a was obtained in 60%, after then the yields decreased to less than 40%.
Table 4. Coupling reactions of compounds 1a with iterative use of [TMPA][NTf2].
Times
1
2
3
4
5
6
7
8
9
10
3a; Yield (%) a
86 87 80 78 68 60 40 32 30 24
a Isolated yields. The washing treatment of ionic liquid was carried out for each time.
To explore the reaction profile, we examined the reaction kinetics. Figure 1 shows the comparison
of the reaction between 1a and 2a under classical conditions employing DMSO as a solvent and under
the present conditions using [TMPA][NTf2] as a solvent.
Figure 1. Time course of the SRN1 reaction of 1a and 2a.
Kinetic measurements were performed for the reaction on a 0.2 M scale. Thus, the mixture of
0.6 mmol of -tosylpropionate 1a and 2,2-dinitropropane (2a) in DMSO or [TMPA][NTf2] (2.5 mL)
was used for the kinetic measurements. We detected product 3a by HPLC analyses and estimated it
using the curve fitting method. The reaction in DMSO progressed very fast to give 3a almost
quantitatively within a minute, while the reaction in [TMPA][NTf2] progressed much slowly, and the
yield of 3a increased to greater than 80% after about 40 minutes. This difference in the reaction rate

Molecules 2012, 17
4786
should arise from the difference in viscosity because ionic liquids usually possess greater viscosities
than any other usual organic solvent [33].
Scheme 4. Photo irradiation and additive effects.
Reagents and conditions: i, tert-BuOK (1.5 eq.), [TMPA][NTf2], rt.
It is noteworthy that the coupling reaction in ionic liquids showed no inhibition by additives or
acceleration by photoirradiation. Scheme 4 summarizes the results in which the reaction progress was
almost the same even on addition of m-dinitrobenzene or with irradiation from a tungsten lamp. These
results are in sharp contrast with the conventional SRN1 reaction in which inhibition by adding
aromatic nitro compounds and acceleration with photo irradiation have been clearly observed [32].
3. Experimental
General
1
All H- and 13C-NMR spectra were measured in CDCl3 and recorded on a JEOL Lamda-500
1
spectrometer (at 500 MHz for H and 126 MHz for 13C). All reactions were performed under a
nitrogen atmosphere unless otherwise mentioned. DMSO was dried over CaH2 and distilled under
reduced pressure before use. Ionic liquids, except for [DEME][NTf2], were purchased from Kanto
Chemical Co. Ltd. [DEME][NTf2] was supplied by Nisshinbo Co. Ltd. Photoirradiation was carried
out by a standard 40 W tungsten lamp. Elemental analyses and high-resolution mass spectra were
measured at Tokiwa Instrumental Analysis Center, Yamaguchi University, Ube, Japan.
Methyl 2,3-dimethyl-3-nitro-2-tosylbutanoate (3a): Under a nitrogen atmosphere, t-BuOK (102.2 mg,
0.91 mmol) was added to a solution of 1a (147.9 mg, 0.61 mmol) in [TMPA][NTf2] (2.5 mL) at room
temperature. Then 2,2-dinitropropane (91.0 mg, 0.68 mmol) was added and the reaction mixture was
stirred at room temperature for 7 h under irradiation by a fluorescent light (365 nm). The reaction
mixture was extracted with ether (3 mL  30) and the combined organic phase was washed with 1 M
HCl (10 mL) and saturated NaCl (20 mL). The organic phase was dried over Na2SO4, filtered, and
concentrated in vacuo. The residue was purified by flash chromatography (silica gel, 10:1, 8:1, and
then 5:1 hexane-EtOAc) to give 3a (153.3 mg, 465.4 mmol, 76%) as a white solid; mp. 101.5–102.5 °C;
1H-NMR (CDCl3) δ 7.70 (dd, 2 H, J = 13.4, 8.5 Hz), 7.29 (dd, 2 H, J = 10.9, 4.7 Hz), 3.80–3.42 (m, 3 H),
13
2.44 (s, 3 H), 2.26 (s, 3 H), 1.97 (s, 3 H), 1.66 (s, 3 H); C-NMR (CDCl3) δ 166.85, 146.21, 133.53,
130.90, 129.59, 93.80, 76.20, 53.40, 26.44, 25.23, 21.83, 18.25; Anal. Calcd. for C14H19NO6S: C,
51.05; H, 5.81; N, 4.25%. Found: C, 50.91; H, 5.85; N, 4.32%.

Molecules 2012, 17
4787
1
Ethyl 2,3-dimethyl-3-nitro-2-tosylbutanoate (3b): Isolated as an oil (175.2 mg, 69%); H-NMR (CDCl3).
7.68 (d, 2 H, J = 8.4 Hz), 7.31 (d, 2 H, J = 8.6 Hz), 4.13–3.94 (m, 2 H), 2.42 (s, 3 H), 2.26 (s, 3 H),
1.95 (s, 3 H), 1.66 (s, 3 H), 1.12 (t, 3 H, J = 7.2 Hz); 13C-NMR (CDCl3). 166.23, 146.13, 133.56,
130.97, 129.50, 93.69, 76.11, 62.87, 26.36, 25.44, 21.79, 18.35, 13.57; HRMS (ESI+ M+NH4)+ m/z
361.1438. Calcd. for C15H25N2O6S 361.1433.
Methyl 2,3-dimethyl-3-nitro-2-tosylpentanoate (3c): Isolated as a white solid (116.9 mg, 68%, 1:1
1
inseparable diastereomeric mixture); mp. 136–137 °C; H-NMR (CDCl3). 7.72 (dd, 2 H for one
isomer, J = 8.4, 1.8 Hz), 7.67 (dd, 2 H for another isomer, J = 8.3, 1.6 Hz), 7.35–7.30 (m, 2 H for both
isomers), 3.66 (s, 3 H for one isomer), 3.51 (s, 3 H for 1 isomer), 2.85 (dq, 1 H for one isomer,
J = 14.6, 7.3 Hz), 2.68 (dq, 1 H for another isomer, J = 14.9, 7.4 Hz), 2.44–2.40 (m, 1 H for another
isomer), 2.44 (s, 3 H for one isomer), 2.43 (s, 3 H for another isomer), 2.35 (dq, 1 H for one isomer,
J = 14.2, 7.0 Hz), 2.20 (s, 3 H one isomer), 1.94 (s, 3 H for another isomer), 1.78 (s, 3 H for one
isomer), 1.61 (s, 3 H for another isomer), 0.95 (t, 3 H for one isomer, J = 7.2 Hz), 0.83 (t, 3 H for
another isomer, J = 6.4 Hz); 13C-NMR (CDCl3). 166.92, 166.35, 146.19, 146.06, 133.93, 133.90,
130.99, 129.64, 129.47, 98.47, 96.10, 77.16, 76.90, 53.48, 53.38, 29.91, 29.89, 21.82, 20.29, 18.86,
18.53, 17.53, 9.21, 8.78; HRMS (ESI+ M+NH4) m/z = 361.1437. Calcd. for C15H25N2O6S 361.1433.
Ethyl 2,3-dimethyl-3-nitro-2-tosylpentanoate (3d): Isolated as an oil (135.4 mg, 66%, 1:1 inseparable
diastereomeric mixture); 1H-NMR (CDCl3). 7.74 (d, 2 H for one isomer, J = 8.4 Hz), 7.69 (d, 2 H for
another isomer, J = 8.4 Hz), 7.34 (dd, 2 H for one isomer, J = 3.7, 0.6 Hz), 7.32 (d, 2 H for another
isomer, J = 3.7 Hz), 4.19–4.08 (m, 2 H for one isomer), 4.00–3.89 (m, 2 H for another isomer), 2.95–2.83
(m, 1 H for one isomer), 2.69 (dq, 1 H for another isomer, J = 14.9, 7.4 Hz), 2.45 (s, 3 H for one isomer),
2.44 (s, 3 H for another isomer), 2.44–2.37 (m, 1 H for one isomer), 2.37–2.28 (m, 1 H for another
isomer), 2.23 (s, 3 H for one isomer), 1.95 (s, 3 H for another isomer), 1.78 (s, 3 H for one isomer),
1.62 (s, 3 H for another isomer), 1.20 (t, 3 H for one isomer, J = 7.2 Hz), 1.06 (t, 1 H for one isomer,
J = 7.2 Hz), 0.95 (t, 3 H for another isomer, J = 7.3 Hz), 0.84 (t, 3 H for another isomer,
J = 7.4 Hz); 13C-NMR (CDCl3). 166.38, 165.72, 146.07, 145.97, 134.04, 133.87, 131.13, 131.09,
129.53, 129.40, 98.46, 96.01, 77.63, 77.08, 63.16, 62.74, 30.19, 29.85, 21.82, 21.80, 20.33, 19.02,
18.57, 17.50, 13.60, 13.55, 9.21, 8.79; HRMS (ESI+ M+H) m/z = 375.1569. Calcd. for C16H27N2O6S
375.1590.
2,3-Dimethyl-3-nitro-2-tosylbutanenitrile (3e): Isolated as a white solid (174.1 mg, 50%) mp. 75–76 °C;
1H-NMR (CDCl3). 7.92 (d, 2 H, J = 8.4 Hz), 7.44 (d, 2 H, J = 8.0 Hz), 2.50 (s, 3 H), 2.15 (s, 3 H), 1.98
(s, 3 H), 1.69 (s, 3 H); 13C-NMR (CDCl3). 147.66, 131.54, 130.11, 130.09, 116.13, 90.97, 66.61,
25.82, 22.43, 22.00, 19.27; Anal. Calcd. for C13H16N2O4S: C, 52.69; H, 5.44; N, 9.45%. Found: C,
52.74; H, 5.38; N, 9.11%.
2-(2-Nitropropan-2-yl)-2-tosylhexanenitrile (3f): Isolated as a white solid (142.5 mg, 75%); mp. 68–70 °C;
1H-NMR (CDCl3). 7.89 (d, 2 H, J = 8.3 Hz), 7.43 (d, 2 H, J = 8.1 Hz), 2.49 (s, 3 H), 2.36 (dq, 1 H,
J = 15.0, 7.5 Hz), 2.09 (s, 3 H), 1.95 (s, 3 H), 1.91 (dq, 1 H, J = 15.1, 7.5 Hz), 0.87 (t, 3 H,
13
J = 7.5 Hz); C-NMR (CDCl3). 147.51, 132.70, 131.43, 130.11, 114.90, 91.81, 72.66, 25.81, 25.22,
23.29, 22.00, 11.50; HRMS (ESI+ M+NH4) m/z = 328.1360. Calcd. for C14H21N3O4S 328.1331.

Molecules 2012, 17
4788
2-Ethyl-3-methyl-3-nitro-2-tosylbutanenitrile (3g): Isolated as a white solid (110.8 mg, 47%); mp.
1
72.8–73.0 °C; H-NMR (CDCl3). 7.91 (d, 2 H, J = 8.4 Hz), 7.43 (d, 2 H, J = 8.1 Hz), 2.49 (s, 3 H),
2.23 (ddd, 1 H, J = 15.2, 12.4, 4.3 Hz), 2.10 (s, 3 H, s), 1.96 (3 H, s), 1.79 (1 H, ddd, J 15.2, 12.6, 5.0),
13
1.38–1.08 (3 H, m), 0.93–0.82 (1 H, m) and 0.77 (3 H, t, J 7.3); C-NMR (CDCl3). 147.53, 132.63,
131.44, 130.05, 115.04, 92.03, 71.90, 31.11, 29.01, 25.97, 23.04, 22.66, 21.99 and 13.53. Anal. Calcd.
for C16H22N2O4S: C, 56.78; H, 6.55; N, 8.28%. Found: C, 56.86; H, 6.44; N, 8.27%.
2-(2-Nitropropan-2-yl)-2-tosylhept-6-enenitrile (3h): Isolated as a white solid (115.9 mg, 44%); mp.
1
74–75 °C; H-NMR (CDCl3). 7.90 (d, 2 H, J = 8.4 Hz), 7.42 (d, 2 H, J = 8.1 Hz), 5.55 (ddt, 1 H,
J = 17.0, 10.3, 6.7 Hz), 4.96 (dt, 1 H, J = 10.9, 1.7 Hz), 4.93 (dq, 1 H, J = 17.2, 1.6 Hz), 2.49 (s, 3 H), 2.23
(ddd, 1 H, J = 15.3, 12.6, 4.4 Hz), 2.09 (s, 3 H), 1.95 (s, 3 H), 1.99–1.95 (m, 1 H), 1.93–1.85 (m, 1 H),
13
1.79 (ddd, 1 H, J = 15.3, 12.6, 5.0 Hz), 1.50–1.38 (m, 1 H), 1.10–0.94 (m, 1 H); C-NMR (CDCl3).
147.59, 136.60, 132.53, 131.48, 130.08, 116.30, 115.00, 92.02, 71.81, 33.23, 30.66, 26.00,
25.93, 23.07, 21.99. Anal. Calcd. for C17H22N2O4S: C, 58.27; H, 6.33; N, 7.99%. Found: C, 58.20; H,
6.30; N, 7.94%.
4. Conclusions
We have demonstrated the first examples of SRN1-type coupling reactions in an ionic liquid, which
not only possesses high polarity but is also regarded as a good solvent for promoting the electron
transfer process. The ionic liquids [bmim][PF6] and [TMPA][NTf2] were useful for the efficient
progress of the reaction. Although amine base was not effective for the progress of the reaction,
t-BuOK was a useful base to enhance the reactions. Although the reaction rate in the SRN1 reaction was
not as fast as that in the conventional SRN1 reaction in DMSO, ionic liquids have an advantage over the
conventional method because of the reusability of the solvent if it was washed with water; a simple
manipulation that enabled the ionic liquid to be reused for another reaction. A notable contrast from
the conventional SRN1 reaction in DMSO was the fact that the reaction was not impeded by the
presence of m-DNB, and the coupling products were obtained in a similar yield. The use of ionic
liquids for other reactions is now under investigation in our laboratory.
Supplementary Materials
Supplementary materials can be accessed at: http://www.mdpi.com/1420-3049/17/5/4782/s1.
Acknowledgments
The authors are grateful for the financial support by a Grant-in-Aid for Scientific Research on
Priority Areas (Science of Ionic Liquids, 2005–2009) from The Ministry of Education, Culture, Sports,
Science and Technology, Japan. A financial aid from Yamaguchi University based on The YU
Strategic Program for Fostering Research Activities (2010–2011) is also acknowledged.
References and Notes
1. Rossi, R.A.; Pierini, A.B.; Santiago, A.N. Aromatic substitution by the SRN1 reaction. Org. React.
1999, 54, 1–271.

Molecules 2012, 17
4789
2. Rossi, R.A.; Pierini, A.B.; Penenory, A.B. Nucleophilic substitution reactions by electron transfer.
Chem. Rev. 2003, 103, 71–167.
3. Galli, C.; Rappoport, Z. Unequivocal SRN1 route of vinyl halides with a multitude of competing
pathways: Reactivity and structure of the vinyl radical intermediate. Acc. Chem. Res. 2003, 36,
580–587.
4. Baumgartner, M.T.; Lotz, G.A.; Palacios, S.M. Diastereoselective C-arylation of prochiral
enolates by the SRN1 reaction. Chirality 2004, 16, 212–219.
5. Layman, W.J.T., Jr.; Greenwood, D.; Downey, A.L.; Wolfe, J.F. Synthesis of 2H-1,2-benzothiazine
1,1-dioxides via heteroannulation reactions of 2-iodobenzenesulfonamide with ketone enolates
under SRN1 conditions. J. Org. Chem. 2005, 70, 9147–9155.
6. Wu, K., Jr.; Dolbier, W.R.; Battiste, M.A.; Zhai, Y. The SRN1 chemistry of 4-iodo-
1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane. Mendeleev Commun. 2006, 16, 146–147.
7. Barolo, S.M.; Teng, X.; Cuny, G.D.; Rossi, R.A. Syntheses of aporphine and homoaporphine
alkaloids by intramolecular ortho-arylation of phenols with aryl halides via SRN1 reactions in
liquid ammonia. J. Org. Chem. 2006, 71, 8493–8499.
8. Guastavino, J.F.; Barolo, S.M.; Rossi, R.A. One-pot synthesis of 3-substituted isoquinolin-1-(2H)-
ones and fused isoquinolin-1-(2H)-ones by SRN1 reactions in DMSO. Eur. J. Org. Chem. 2006,
3898–3902.
9. Bude, M.E.; Rossi, R.A. Syntheses of phenanthridines and benzophenanthridines by
intramolecular ortho-arylation of aryl amide ions with aryl halides via SRN1 reactions.
Tetrahedron Lett. 2007, 48, 8739–8742.
10. Roydhouse, M.D.; Walton, J.C. Formation of a tetracyclic isoquinoline derivative by
rearrangement of a [(bromophenyl)butyryl]oxazolidinone. Eur. J. Org. Chem. 2007, 1059–1063.
11. Marshall, L.J.; Roydhouse, M.D.; Slawin, A.M.Z.; Walton, J.C. Effect of chain length on radical
to carbanion cyclo-coupling of bromoaryl alkyl-linked oxazolines: 1,3-Areneotropic migration of
oxazolines. J. Org. Chem. 2007, 72, 898–911.
12. Szabo, R.; Crozet, M.D.; Vanelle, P. Original SRN1 reactions on new non-nitrated heterocyclic
system. Synlett 2008, 2836–2840.
13. Vaillard, V.A.; Buden, M.E.; Martin, S.E.; Rossi, R.A. Synthesis of novel fused azaheterocycles
by photostimulated intramolecular SRN1 reactions with nitrogen nucleophiles. Tetrahedron Lett.
2009, 50, 3829–3832.
14. Buden, M.E.; Vaillard, V.A.; Martin, S.E.; Rossi, R.A. Synthesis of carbazoles by intramolecular
arylation of diarylamide anions. J. Org. Chem. 2009, 74, 4490–4507.
15. Argüello, J.E.; Schmidt, L.C.; Peñéñory, A.B. “One-pot” two-step synthesis of aryl sulfur
compounds by photoinduced reactions of thiourea anion with aryl halides. Org. Lett. 2003, 5,
4133–4136.
16. Corsico, E.F.; Rossi, R.A. Sequential reactions of trimethylstannyl anions with vinyl chlorides and
dichlorides by the SRN1 mechanism followed by palladium-catalyzed cross-coupling processes.
J. Org. Chem. 2004, 69, 6427–6432.
17. Kornblum, N.; Boyd, S.D.; Pinnick, H.W.; Smith, R.G. New synthesis of olefins. J. Am. Chem.
Soc. 1971, 93, 4316–4318.

Molecules 2012, 17
4790
18. Kornblum, N.; Cheng, L. The synthesis of functionalized tetrasubstituted olefins. Calcium
amalgam—A novel reducing agent. J. Org. Chem. 1977, 42, 2944–2945.
19. Ono, N.; Tamura, R.; Eto, H.; Hamamoto, I.; Nakatsuka, T.; Hayami, J.; Kaji, A. A new olefin
synthesis. Synchronous elimination of nitro and ester groups or nitro and keto groups from -nitro
esters or -nitro ketones. J. Org. Chem. 1983, 48, 3678–3684.
20. Beugelmans, R.; Lechevallier, A.; Rousseau, H. Substitution nucleophile radicalaire en chaine
(SRN1): 11ème mémoire. Substrats et nucleophiles derives de nitroalcanes aliphatiques
fonctionnalises. Tetrahedron Lett. 1983, 24, 1787–1790.
21. Russell, G.A.; Mudryk, B.; Jawdosiuk, M. α-Alkylidene derivatives of β-diketones and β-keto
esters; 2-Chloro-2-nitropropane as an acetone equivalent in controlled cross-aldol-type processes.
Synthesis 1981, 1, 62–64.
22. Ono, N.; Miyake, H.; Tamura, R.; Hamamoto, I.; Kaji, A. Free radical chain elimination reaction
(ERC1). Conversion of vicinal dinitro compounds or β-nitro sulfones to olefins with tributyltin
hydride. Chem. Lett. 1981, 10, 1139.
23. Gu, Y.; Li, G. Ionic liquids-based catalysis with solids: State of the art. Adv. Synth. Cat. 2009,
351, 817–847.
24. Chowdhury, S.; Mohanb, R.S.; Scott, J.L. Reactivity of ionic liquids. Tetrahedron 2007, 63,
2363–2389.
25. Ohno, H. Functional design of ionic liquids. Bull. Chem. Soc. Jpn. 2006, 79, 1665–1680.
26. Miao, W.; Chan, T.H. Ionic-liquid-supported synthesis: A novel liquid-phase strategy for organic
synthesis. Acc. Chem. Res. 2006, 39, 897–908.
27. Lévêque, J.-M.; Cravotto, G. Microwaves, power ultrasound, and ionic liquids. A new synergy in
green organic synthesis. Chimia 2006, 60, 313–320.
28. Welton, T. Room-temperature ionic liquids. Solvents for synthesis and catalysis. Chem. Rev.
1999, 99, 2071–2084.
29. Kamimura, A.; Yamamoto, S. An efficient method to depolymerize polyamide plastics: A new
use of ionic liquids. Org. Lett. 2007, 9, 2533–2235.
30. Kamimura, A.; Yamamoto, S. A novel depolymerization of nylons in ionic liquids. Polym. Adv.
Technol. 2008, 19, 1391–1395.
31. Yamamoto, S.; Kamimura, A. Preparation of novel functionalized ammonium salts that effectively
catalyze depolymerization of nylon-6 in ionic liquids. Chem Lett. 2009, 39, 1016–1017.
32. Ono, N.; Tamura, R.; Nakatsuka, T.; Hayami, J.; Kaji, A. Substitution and elimination reactions
via one electron transfer process. A new olefin synthesis from β-nitro sulfones. Bull. Chem. Soc.
Jpn. 1980, 53, 3295–3300.
33. Froeba, A.P.; Kremer, H.; Leipertz, A. Density, refractive index, interfacial tension, and viscosity
of ionic liquids [EMIM][EtSO4], [EMIM][NTf2], [EMIM][N(CN)2], and [OMA][NTf2] in
dependence on temperature at atmospheric pressure. J. Phys. Chem. B 2008, 112, 12420–12430.
Sample Availability: Not available.
© 2012 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/3.0/).