One-pot synthesis of symmetric 1,7-dicarbonyl compounds via a tandem radical addition-elimination-addition reaction

Article abstract of DOI:10.1039/c3ra42932f

A novel approach to synthesize symmetric 1,7-dicarbonyl compounds via a tandem radical addition-elimination-addition reaction of S-carbonylmethyl xanthates with allylmethylsulfone and its analogues has been developed. Radicals were produced from S-carbonylmethyl xanthates by adding dilauroyl peroxide and reacted with allylmethylsulfone or analogues to generate terminal olefins as intermediates. The excessive radicals reacted with the intermediate olefins immediately to give adducts of symmetric 1,7-dicarbonyl compounds. This is an efficient method to synthesize 1,7-dicarbonyl compounds under mild conditions. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ra42932f

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One-pot synthesis of symmetric 1,7-dicarbonyl
compounds via a tandem radical addition–elimination–
addition reaction3
Cite this: RSC Advances, 2013, 3,
15114
Zhongyan Huang and Jiaxi Xu*
A novel approach to synthesize symmetric 1,7-dicarbonyl compounds via a tandem radical addition–
elimination–addition reaction of S-carbonylmethyl xanthates with allylmethylsulfone and its analogues has
been developed. Radicals were produced from S-carbonylmethyl xanthates by adding dilauroyl peroxide
and reacted with allylmethylsulfone or analogues to generate terminal olefins as intermediates. The
excessive radicals reacted with the intermediate olefins immediately to give adducts of symmetric 1,7-
dicarbonyl compounds. This is an efficient method to synthesize 1,7-dicarbonyl compounds under mild
conditions.
Received 19th March 2013,
Accepted 25th June 2013
DOI: 10.1039/c3ra42932f
www.rsc.org/advances
Compounds with a xanthate group are useful intermediates
in organic synthesis because the xanthate group is generally
Introduction
maintained after reactions with olefins.11 Meanwhile, the
xanthate group can be converted to hydrogen,12 thiol,13
sulfonic acid,14 halogen, or azide, which can be further
converted to an amino group.15 It has been reported that the
reactions of xanthates with allylalkylsulfones15a,16 or vinylalk-
yl(phenyl)sulfones17 generate terminal olefins or olefins,
respectively, via a radical addition and a subsequent radical
rearrangement and elimination of alkanesulfonyl or benzene-
sulfonyl radicals. It is well-known that xanthates readily
undergo the radical addition with various terminal olefins.11,18
To the best of our knowledge, no example has been reported
on the tandem radical addition–elimination–addition of two
molecules of xanthates with allylmethylsulfone and analogues
to construct symmetric organic compounds. Herein, we
designed and present a tandem radical addition–elimina-
tion–addition reaction of S-carbonylmethylxanthates with
allylmethylsulfone and its analogues to prepare symmetric
1,7-dicarbonyl derivatives.
Symmetric 1,7-dicarbonyl compounds are key intermediates in
the synthesis of natural compounds and drug candidates in
medicinal chemistry. Some symmetric 1,7-dicarbonyl com-
pounds and analogues show anticancer,1 antitumor,2 antith-
rombosis,3 and neuroprotection activities.4 Symmetric 1,7-
dicarbonyl compounds have been widely applied in the
synthesis of cycloheptene derivatives via intramolecular
reductive coupling5a or via acetalization and disproportatio-
nation,5b in the synthesis of cyclohexanone derivatives via the
intramolecular Dieckmann condensation,6 and in the synth-
esis of seven-membered cyclic ketones7a and eight-membered
cyclic diketones.7b As a result, several methods to synthesize
1,7-dicarbonyl compounds have been developed. Pioneering
works on the synthesis of 1,7-dicarbonyl compounds involved
Michael addition reactions of nitroalkanes, aliphatic ketones,
or esters with a,b-unsaturated carbonyl compounds,8 coupling
reactions of 1,5-dihaloalkane bis-Grignard reagents (or bis-
zinc reagents) with acyl chlorides or benzimidazolium salts,9
and Friedel–Crafts acylation of pentanedioic chloride with
arenes.10 However, these methods showed some drawbacks
such as harsh reaction conditions, limited group tolerance, or
low regioselectivity in the Friedel–Crafts acylation. Thus, it is
important to develop a more facile method to prepare 1,7-
dicarbonyl compounds.
Results and discussion
We designed a reaction of S-carbonylmethylxanthates and
allylmethylsulfone that would generate 3-butenylcarbonyl
intermediates, which would further react with the second
molecule of S-carbonylmethylxanthates to give rise to sym-
metric 1,7-dicarbonyl compounds. To achieve the tandem
reaction, O-ethyl S-2-phenyl-2-oxoethylxanthate (1a) and allyl-
methylsulfone (2a) were first selected to optimize the reaction
conditions. When the reaction was initiated by dilauryl
peroxide (DLP), xanthate 1a and sulfone 2a reacted in a molar
State Key Laboratory of Chemical Resource Engineering and Department of Organic
Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing
100029, China. E-mail: jxxu@mail.buct.edu.cn; Fax: 86 10 6443 5565;
Tel: 86 10 6443 5565
Electronic supplementary information (ESI) available: Analytic data of known
3
compounds 1 and 2, copies of 1H and 13C NMR spectra of unknown
intermediates of 1 and 2, and products 3. See DOI: 10.1039/c3ra42932f
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Table 1 Optimization of the reaction of xanthate 1a with allylmethylsulfone (2a) and its analogues
Entry
2
R
Molar ratio 1a : 2
Initiator (equiv. vs. 1a)
Solvent
Isolated yield (%)
1
2
3
4
5
6
7
8
2a
2a
2a
2a
2a
2a
2a
2b
2c
2d
2e
2f
MeSO2
MeSO2
MeSO2
MeSO2
MeSO2
MeSO2
MeSO2
EtSO2
PhSO2
n-BuSO
PhSO
2 : 1
2.2 : 1
3 : 1
DLP (0.45)
DLP (0.45)
DLP (0.45)
BPO (0.50)
AIBN (1.0)
DLP (0.45)
DLP (0.45)
DLP (0.45)
DLP (0.70)
DLP (0.45)
DLP (0.45)
DLP (0.45)
DLP (0.45)
DLP (0.45)
DCE
DCE
DCE
DCE
DCE
EA
C6H5Cl
DCE
DCE
DCE
DCE
DCE
DCE
DCE
75
81
78
36
trace
75
75
75
65
60
40
49
27
50
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
2.2 : 1
9
10
11
12
13
14
n-BuS
PhS
AcS
2g
2h
ratio of 2 : 1 in refluxing 1,2-dichloroethane (DCE) to produce
the expected product O-ethyl-S-(1,7-diphenyl-1,7-dioxoheptan-
4-yl) xanthate (3a) in a yield of 75% (Table 1, entry 1). The yield
was improved to 81% when the molar ratio was increased to
2.2 : 1 (Table 1, entry 2). Further increasing the molar ratio to
3 : 1 resulted in the decrease of the yield to 78% (Table 1, entry
3). However, benzoyl peroxide (BPO) and azodiisobutyronitrile
(AIBN) diminished the yield (Table 1, entries 4 and 5). The
solvent screening revealed that dichloroethane (DCE) shows
better efficiency than ethyl acetate (EA) and chlorobenzene
(Table 1, entries 2, 6, and 7). To evaluate the effect of the
substituent in the allylsulfones, allyl ethylsulfone (2b) and allyl
phenylsulfone (2c) were prepared and tested as the olefin
precursors instead of sulfone 2a. Both sulfones 2b and 2c gave
rise to xanthate 3a in lower yields than the sulfone 2a (Table 1,
entries 8 and 9). When allyl phenylsulfone (2c) was used, the
reaction consumed more DLP (Table 1, entry 9). To extend the
tandem reaction, a variety of sulfone analogues, including
representative aliphatic and aromatic allylsulfoxides (2d and
2e), allylthioethers (2f and 2g), and allyl thioacetate (2h), were
tested (Table 1, entries 10–14). The adduct xanthate 3a was
obtained in low to satisfactory yields. The results indicate that
all allylic sulfur derivatives can be used as the precursors of the
C3 moiety in the tandem radical reaction for the synthesis of
the 1,7-dicarbonyl compound. But allylsulfones, especially
allylmethylsulfone (2a), are more efficient precursors than
allylsulfoxides, allylthioethers, and allyl thioacetate.
compounds under the optimal conditions (Table 2). The
results indicate that 1,7-dicarbonyl compounds, including 1,7-
diketones (Table 2, entries 1–4), 1,7-heptanedioates (Table 2,
entries 5–9), 1,7-heptanediamides (Table 2, entries 10–12), and
1,7-heptanedinitrile (Table 2, entry 13), were obtained in
satisfactory to good yields except for di(4-nitrophenyl) 1,7-
heptanedioate (3h) and N,N,N9,N9-tetraphenyl 1,7-heptanedia-
mide (3j) (Table 2, entries 8 and 10), which were obtained in
relatively low yields.
Table 2 Synthesis of symmetric 1,7-dicarbonyl compounds via tandem radical
reactions
Entry
Xanthate
R
Time (h)
Isolated yield (%)
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
PhCO
4-MeOC6H4CO
MeCO
ClCH2CO
EtO2C
PhO2C
4-ClC6H4O2C
4-O2NC6H4O2C
BnO2C
Ph2NCO
Ph(Ms)NCO
15
15
15
15
8
8
8
20
8
20
15
15
81
78
72
65
71
69
84
40
69
35
69
79
9
Different xanthates 1 were readily obtained via the reaction
of potassium O-ethyl xanthate and the corresponding halo-
methylcarbonyl compounds, including representative alipha-
tic and aromatic bromo/chloromethyl ketones, chloroacetates,
chloroacetamides, and chloroacetonitrile.19–24 They reacted
with the best precursor of the C3 moiety, allylmethylsulfone
(2a), to afford the corresponding symmetric 1,7-dicarbonyl
10
11
12
1j
1k
1l
13
1m
CN
15
51
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reactive radical and reacts with the xanthate 1 to give rise to
the stable product xanthate 3 and the radical B as well. During
the tandem reaction, all S-alkyl O-ethyl xanthates 3, 4, and 6
are inert byproducts or products, while all simple aliphatic
radicals (methyl radical, undecyl radical A and the radical C)
are highly reactive and show short half-lives. They are readily
captured by the sulfur atom in the xanthate group. The alkyl
radicals are nucleophilic radicals and only react with electron-
deficient acceptors rather than with electron-rich olefins 2a
and 5, whilst carbonylmethyl radicals B have an electrophilic
character and thus are reactive to nucleophilic radical
acceptors, such as simple alkenes. They can undergo radical
addition with olefins 2a and 5. This reactivity difference
determines the selectivity of the radical.25 This is the reason
why the radical tandem addition–elimination–addition reac-
tion can be realized successfully.
Conclusion
Scheme 1 Possible mechanism of the tandem radical addition–elimination–
In summary, we developed a one-pot tandem radical addition–
elimination–addition reaction to synthesize symmetric 1,7-
dicarbonyl compounds from S-carbonylmethyl xanthates with
allylmethylsulfone and analogues, including allylalkyl/arylsul-
fones, allylalkyl/arylsulfoxides, allylalkyl/arylthioethers, and
allyl thioacetate. The method shows several advantages, such
as mild and efficient protocols, readily available and inexpen-
sive starting materials, and the non-use of toxic transition
metals.
addition reaction.
Previous reports show that it is harmful for the radical
addition of xanthates with olefins when the molecules contain
an amino group. The common solution to the problem is to
protect the amino group.11 When the protecting group is
diphenyl, the reaction gives the product in a low yield.
However, when changing the protecting group to a methane-
sulfonyl or alkoxycarbonyl group, the yields increase obviously,
revealing that the electron-withdrawing protecting groups are
beneficial for the tandem reaction. These decrease the
alkalinity of the nitrogen atom, resulting in an increase of
the electrophilicity of the aminocarbonylmethyl radicals
(Table 2, entries 10–12).
Experimental
General method
Melting points were determined with
a melting point
apparatus and are uncorrected. 1H NMR spectra were recorded
at 400 MHz in CDCl3 with TMS as the internal standard. 13C
NMR spectra were recorded at 100 MHz in CDCl3. IR spectra
were determined directly. HRMS spectra were recorded with an
LC/MSD TOF mass spectrometer. TLC analysis was performed
on glass plate pre-coated with silica gel (10–40 mm). Spots were
visualized with UV light or iodine. Column chromatography
was performed on silica gel (200–300 mesh) with a mixture of
petroleum ether and ethyl acetate as the eluent. Allylthioethers
2f and 2g,26 and allyl thioacetate (2h)27 were prepared by
referring to the previously reported methods.
The cyano group is a potential carbonyl group, a precursor
of the carbonyl, carboxylic acid, carboxylate, or amide groups.
Thus, introducing the cyano group into the molecule is very
important in organic synthesis. When submitting xanthate 1m
to the tandem reaction, we successfully produced the target
product S-(1,5-dicyanopentan-3-yl) O-ethyl carbonodithioate
(3m) in a moderate yield of 51% (Table 2, entry 13).
The proposed mechanism of the tandem reaction is shown
in Scheme 1. DLP dissociates into the undecyl radical (A) via
homolysis and subsequently releases carbon dioxide under
heating. The radical A attacks a xanthate 1 to form stable
O-ethyl S-undecyl xanthate 4 and a carbonylmethyl radical B,
which undergoes a radical addition with allylmethylsulfone
(2a) followed by a subsequent radical rearrangement to
generate a terminal olefin 5 and methylsulfonyl radical. The
methylsulfonyl radical further decomposes to sulfur dioxide
and a methyl radical. The highly reactive methyl radical
attacks xanthate 1 as well to regenerate the radical B and
another stable O-ethyl S-methyl xanthate 6. The radical B
further undergoes a radical addition with the terminal olefin 5
to produce a secondary radical C, which is also a highly
General procedure for the synthesis of xanthates 1 (except for
1d)
Potassium O-ethyl xanthate (841 mg, 5.25 mmol) was added
portion-wise to a solution of carbonylmethyl chloride (5 mmol;
for the synthesis of 1a–c, carbonylmethyl bromides were used)
in 20 mL of acetone in an ice-water bath while stirring. The
resulting solution was further stirred for 2 h at room
temperature. After removal of the solvent the residue was
purified using silica gel column chromatography (petroleum
ether–ethyl acetate = 20/1 to 1/1, v/v) to give xanthate 1.
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= 7.1 Hz, 3H, CH3), 3.48 (s, 3H, CH3), 3.75 (s, 2H, CH2), 4.61 (q,
J = 7.1 Hz, 2H, CH2), 7.42–7.44 (m, 2H, ArH), 7.53–7.55 (m, 3H,
ArH). 13C NMR (CDCl3, 100 MHz) (d, ppm) 13.7 (CH3), 41.3
(CH2), 42.1 (CH3), 71.1 (CH2), 130.0 (CH), 130.2 (CH), 130.6
(CH), 134.8 (C), 167.5 (CLO), 213.0 (CLS). IR (neat) n = 3035,
O-Ethyl S-[2-oxo-2-phenylethyl] carbonodithioate (1a). Pale
yellow solid, yield: 1.08 g, 90%, m.p. 32–33 uC, lit.19 m.p. 31–32
uC.
O-Ethyl S-[2-(4-methoxyphenyl)-2-oxoethyl] carbonodithioate
(1b). Pale yellow solid, yield: 1.20 g, 89%, m.p. 69–70 uC, lit.19
m.p. 68–69 uC.
2982, 2932, 2854, 1710, 1491, 1355, 1231, 1150, 1048 cm21
.
HRMS (ESI) calcd. for C12H15NNaO4S3 [M+Na]+ m/z = 356.0061;
found 356.0051.
O-Ethyl S-(2-oxopropyl) carbonodithioate (1c)17b. Pale yellow
liquid, yield: 0.81 g, 91%.
S-(2-Ethoxyl-2-oxoethyl) O-ethyl carbonodithioate (1e)20. Pale
yellow liquid, yield: 0.92 g, 88%.
O-Ethyl S-[2-oxo-2-(oxazolidin-2-on-3-yl)ethyl] carbonodithio-
ate (1l). Pale yellow solid, yield: 1.11 g, 89%, m.p. 100–101 uC,
lit.22 m.p. 96 uC.
O-Ethyl S-(2-oxo-2-phenoxyethyl) carbonodithioate (1f)21
.
S-(Cyanomethyl) O-ethyl carbonodithioate (1m)23. Pale
yellow liquid, yield: 0.71 g, 88%.
Pale yellow liquid, yield: 1.18 g, 92%.
S-[2-(4-Chlorophenoxy)-2-oxoethyl] O-ethyl carbonodithioate
(1g). Rf = 0.35 (petroleum ether–ethyl acetate = 10/1, v/v). Pale
yellow solid, yield: 1.37 g, 95%, m.p. 50–51 uC. 1H NMR (CDCl3,
400 MHz) (d, ppm) 1.44 (t, J = 7.1 Hz, 3H, CH3), 4.13 (s, 2H,
CH2), 4.68 (q, J = 7.1 Hz, 2H, CH2), 7.07 (d, J = 8.7 Hz, 2H, ArH),
7.35 (d, J = 8.7 Hz, 2H, ArH). 13C NMR (CDCl3, 100 MHz) (d,
ppm) 13.7 (CH3), 37.9 (CH2), 70.9 (CH2), 122.6 (CH), 129.5
(CH), 131.5 (C), 149.0 (C), 166.4 (CLO), 212.4 (CLS). IR (neat) n
Synthesis of S-(3-chloro-2-oxopropyl) O-ethyl carbonodithio-
ate (1d). 1,3-Dichloro-2-propanone (957 mg, 7.54 mmol) was
added to a solution of potassium O-ethyl xanthate (1.21 g, 7.54
mmol) in water (10 mL) portion-wise under stirring at 0 uC.
The resulting solution was further stirred for 1 h at the same
temperature and then filtered. The solid was washed with
water and dried in the air to give xanthate 1d as a white solid,
yield: 1.12 g, 70%, m.p. 52–53 uC, lit.24 49–50 uC.
= 3096, 3064, 2981, 2922, 2854, 1758, 1485, 1225, 1045 cm21
.
HRMS (ESI) calcd. for C11H12ClO3S2 [M+H]+ m/z = 290.9916;
found 290.9902.
Synthesis of sodium ethanesulphinate
Diethyl disulfide (1.83 g, 15 mmol) was added dropwise to a
mixture of NCS (16.02 g, 120 mmol), 2 M HCl (7.2 mL) and
MeCN (41 mL) in a 10 uC water bath. The mixture was further
stirred at room temperature for 30 min. After removal of the
MeCN, 100 mL of ether was added. The resulting mixture was
washed with water and brine. The organic phase was dried
over anhydrous Na2SO4 and concentrated under reduced
pressure to afford the pale yellow liquid ethanesulfonyl
chloride 3.10 g (80%),28 which was used directly in the next
step.
Ethanesulfonyl chloride (3.10 g, 24 mmol) was added
dropwise to a solution of sodium bicarbonate (4.05 g, 48
mmol) and sodium sulfide (6.08 g, 48 mmol) in water (30 mL)
at 75–80 uC. The mixture was further stirred at the same
temperature for 2 h. After removal of the water, the resulting
solid was extracted with absolute ethanol (5 6 30 mL). White
solid sodium ethanesulphinate (2.70 g, 96%) was obtained
following the subsequent evaporation of ethanol.
O-Ethyl S-[2-(4-nitrophenoxy)-2-oxoethyl] carbonodithioate
(1h). Rf = 0.23 (petroleum ether–ethyl acetate = 5/1, v/v). Pale
yellow solid, yield: 1.40 g, 93%, m.p. 56–57 uC. 1H NMR (CDCl3,
400 MHz) (d, ppm) 1.45 (t, J = 7.1 Hz, 3H, CH3), 4.18 (s, 2H,
CH2), 4.69 (q, J = 7.1 Hz, 2H, CH2), 7.32 (d, J = 9.0 Hz, 2H, ArH),
8.28 (d, J = 9.0 Hz, 2H, ArH). 13C NMR (CDCl3, 100 MHz) (d,
ppm) 13.7 (CH3), 37.9 (CH2), 71.1 (CH2), 122.2 (CH), 125.2
(CH), 145.5 (C), 155.1 (C), 165.8 (CLO), 212.3 (CLS). IR (neat) n
= 3114, 3081, 2981, 2923, 2854, 1770, 1524, 1205, 1045 cm21
.
HRMS (ESI) calcd. for C11H11NNaO5S2 [M+Na]+ m/z = 323.9976;
found 323.9959.
S-(2-Benzyloxy-2-oxoethyl) O-ethyl carbonodithioate (1i). Rf =
0.31 (petroleum ether–ethyl acetate = 10/1, v/v). Pale yellow
1
liquid, yield: 1.25 g, 93%. H NMR (CDCl3, 400 MHz) (d, ppm)
1.36 (t, J = 7.1 Hz, 3H, CH3), 3.95 (s, 2H, CH2), 4.60 (q, J = 7.1
Hz, 2H, CH2), 5.19 (s, 2H, CH2), 7.36 (s, 5H, ArH). 13C NMR
(CDCl3, 100 MHz) (d, ppm) 13.6 (CH3), 37.8 (CH2), 67.5 (CH2),
70.6 (CH2), 128.3 (CH), 128.4 (CH), 128.5 (CH), 135.2 (C), 167.7
(CLO), 212.3 (CLS). IR (neat) n = 3065, 3032, 2980, 2928, 2856,
1741, 1450, 1215, 1048 cm21
. HRMS (ESI) calcd. for
Synthesis of allylsulfones 2
C12H14NaO3S2 [M+Na]+ m/z = 293.0282; found 293.0275.
S-(2-Diphenylamino-2-oxoethyl) O-ethyl carbonodithioate
(1j). Rf = 0.20 (petroleum ether–ethyl acetate = 3/1, v/v). Pale
yellow solid, yield: 1.52 g, 92%, m.p. 112–113 uC. 1H NMR
(CDCl3, 400 MHz) (d, ppm) 1.38 (t, J = 7.1 Hz, 3H, CH3), 3.92 (s,
2H, CH2), 4.60 (q, J = 7.1 Hz, 2H, CH2), 7.33 (s, 10H, ArH). 13C
NMR (CDCl3, 100 MHz) (d, ppm) 13.7 (CH3), 40.6 (CH2), 70.4
(CH2), 125.9 (CH), 128.8 (CH), 129.9 (CH), 142.1 (C), 166.4
(CLO), 213.7 (CLS). IR (neat) n = 3065, 2980, 2923, 2854, 1681,
1488, 1379, 1296, 1217, 1052 cm21. HRMS (ESI) calcd. for
C17H17NNaO2S2 [M+Na]+ m/z = 354.0598; found 354.0591.
O-Ethyl S-[2-(N-methanesulfonyl-N-phenylamino)-2-
oxoethyl] carbonodithioate (1k). Rf = 0.24 (petroleum ether–
ethyl acetate = 1/1, v/v). Pale yellow solid, yield: 1.58 g, 95%,
m.p. 109–110 uC. 1H NMR (CDCl3, 400 MHz) (d, ppm) 1.41 (t, J
A mixture of sodium methanesulphinate (10.21 g, 0.1 mol) [or
sodium ethanesulphinate (2.50 g, 21.5 mmol) or sodium
benzenesulfinate (16.42 g, 0.1 mol)] and allyl bromide (15.7 g,
0.13 mol) [3.38 g, 28 mmol for sodium ethanesulphinate] was
stirred at 60 uC for 4 h in PEG-400 (40 mL). After removal of the
excess allyl bromide, the reaction mixture was poured into
water (300 mL). The resulting mixture was extracted with ethyl
acetate (3 6 100 mL). The combined organic phase was dried
over anhydrous Na2SO4. After removal of the solvent the
residue was purified using silica gel column chromatography
(petroleum ether–ethyl acetate = 3/1, v/v) to produce allylsul-
fone 2.
Allyl methylsulfone (2a)29. Colorless liquid, yield: 10.5 g,
87%.
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Allyl ethylsulfone (2b)28b. Colorless liquid, from sodium
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= 5/1, v/v). White solid, yield: 360 mg, 78%, m.p. 60–61 uC. H
NMR (CDCl3, 400 MHz) (d, ppm) 1.36 (t, J = 7.1 Hz, 3H, CH3),
2.08 (dddd, J = 14.5, 8.5, 6.3, 6.0 Hz, 2H in 2CH2), 2.27 (dddd, J
= 14.5, 8.5, 6.7, 5.0 Hz, 2H in 2CH2), 3.06–3.20 (m, 4H, 2CH2),
3.86 (s, 6H, 2CH3), 3.93 (tt, J = 8.5, 5.0 Hz, 1H, CH), 4.57 (q, J =
7.1 Hz, 2H, CH2), 6.92 (d, J = 8.8 Hz, 4H, ArH), 7.94 (d, J = 8.8
Hz, 4H, ArH). 13C NMR (CDCl3, 100 MHz) (d, ppm) 13.6 (CH3),
29.0 (CH2), 35.3 (CH2), 50.8 (CH), 55.4 (CH3), 69.9 (CH2), 113.6
(CH), 129.8 (CH), 130.2 (C), 163.4 (C), 197.6 (CLO), 213.9 (CLS).
IR (neat) n = 3073, 2930, 2839, 1675, 1599, 1575, 1509, 1456,
1257, 1169, 1048 cm21. HRMS (ESI) calcd. for C24H29O5S2
[M+H]+ m/z = 461.1456; found 461.1450.
S-(1,7-Dioxononan)-5-yl O-ethyl carbonodithioate (3c). Rf =
0.18 (petroleum ether–ethyl acetate = 5/1, v/v). Pale yellow
liquid, yield: 199 mg, 72%. 1H NMR (CDCl3, 400 MHz) (d, ppm)
1.43 (t, J = 7.1 Hz, 3H, CH3), 1.83 (dddd, J = 14.7, 8.5, 7.7, 6.7
Hz, 2H in 2CH2), 2.04 (dddd, J = 14.7, 8.5, 7.5, 5.0 Hz, 2H in
2CH2), 2.14 (s, 6H, 2CH3), 2.59 (ddd, J = 15.0, 7.7, 6.7 Hz, 2H in
2CH2), 2.63 (dt, J = 15.0, 7.5 Hz, 2H in 2CH2), 3.71 (tt, J = 8.5,
5.0 Hz, 1H, CH), 4.64 (q, J = 7.1 Hz, 2H, CH2). 13C NMR (CDCl3,
100 MHz) (d, ppm) 13.7 (CH3), 28.2 (CH2), 30.0 (CH3), 40.5
(CH2), 50.5 (CH), 70.1 (CH2), 207.6 (CLO), 214.1 (CLS). IR (neat)
n = 2982, 2926, 2853, 1718, 1364, 1215, 1047 cm21. HRMS (ESI)
calcd. for C12H21O3S2 [M+H]+ m/z = 277.0932; found 277.0924.
S-(1,7-Dichloro-1,7-dioxononan)-5-yl O-ethyl carbonodithio-
ate (3d). Rf = 0.21 (petroleum ether–ethyl acetate = 5/1, v/v).
White solid, yield: 225 mg, 65%, m.p. 83–84 uC. 1H NMR
(CDCl3, 400 MHz) (d, ppm) 1.43 (t, J = 7.1 Hz, 3H, CH3), 1.90
(dddd, J = 14.6, 8.5, 7.7, 6.9 Hz, 2H in 2CH2), 2.12 (dddd, J =
14.6, 8.5, 7.5, 5.0 Hz, 2H in 2CH2), 2.71–2.85 (m, 4H, 2CH2),
3.74 (tt, J = 8.5, 5.0 Hz, 1H, CH), 4.09 (s, 4H, 2CH2), 4.65 (q, J =
7.1 Hz, 2H, CH2). 13C NMR (CDCl3, 100 MHz) (d, ppm) 13.7
(CH3), 28.2 (CH2), 36.8 (CH2), 48.1 (CH2), 50.2 (CH), 70.4 (CH2),
201.6 (CLO), 213.8 (CLS). IR (neat) n = 2925, 2853, 1732, 1399,
1219, 1046 cm21. HRMS (ESI) calcd. for C12H19Cl2O3S2 [M+H]+
m/z = 345.0153; found 345.0148.
ethanesulphinate (2.50 g, 21.5 mmol), yield: 1.75 g, 60%.
Allyl phenylsulfone (2c)30. Colorless liquid, yield: 15.6 g,
85%.
Synthesis of allylsulfoxides 2d and 2e
30% H2O2 (1.36 g, 20 mmol) was added dropwise to a solution
of allyl thioether (10 mmol) and thiourea (38 mg, 0.5 mmol) in
dichloromethane (10 mL) under stirring at room temperature.
The resulting mixture was further stirred at the same
temperature for 24 h. After removal of the solvent the residue
was purified using silica gel column chromatography (petro-
leum ether–ethyl acetate = 3/1, v/v) to produce allylsulfoxide.
Allyl butylsulfoxide (2d). Rf = 0.32 (petroleum ether–ethyl
acetate = 3/1, v/v). Colorless liquid, yield: 0.72 g, 49%. 1H NMR
(CDCl3, 400 MHz) (d, ppm) 0.96 (t, J = 7.2 Hz, 3H, CH3), 1.43–
1.55 (m, 2H, CH2), 1.71–1.89 (m, 2H, CH2), 2.65–2.77 (m, 2H,
CH2), 3.44 (dd, J = 12.8, 7.6 Hz, 1H in CH2), 3.52 (dd, J = 12.8,
7.6 Hz, 1H in CH2), 5.39 (d, J = 17.2 Hz, 1H in CH2), 5.44 (d, J =
10.2 Hz, 1H in CH2), 5.84–5.95 (m, 1H, CH). 13C NMR (CDCl3,
100 MHz) (d, ppm) 13.5 (CH3), 21.9 (CH2), 24.3 (CH2), 50.5
(CH2), 55.5 (CH2), 123.3 (CH2), 125.7 (CH). IR (neat) n = 3439,
3235, 3085, 3013, 2959, 2932, 2873, 1637, 1316, 1132, 1031
cm21. HRMS (ESI) calcd. for C7H15OS [M+H]+ m/z = 147.0844;
found 147.0838.
Allyl phenylsulfoxide (2e)31. Colorless liquid, yield: 0.83 g,
50%.
General procedure for the synthesis of symmetric 1,7-
dicarbonyl compounds 3
A solution of allylmethylsulfone or analogs 2 (1 mmol) and
xanthate 1 (2.2 mmol) in 1,2-dichloroethane (1.5 mL) was
degassed by vacuum, then filled with nitrogen. After the
solution was heated to reflux, dilauroyl peroxide (DLP) (44 mg,
0.11 mmol) was added portion-wise. DLP (88 mg, 0.22 mmol)
was added portion-wise every 1 h until 0.99 mmol of DLP was
added. The reaction mixture was further refluxed for another
3–15 h until the starting material disappeared. After evapora-
tion of the solvent, the residue was purified using silica gel
column chromatography (petroleum ether–ethyl acetate = 15/1
to 1/2, v/v) to afford the adduct xanthate 3.
S-(1,7-Diethoxyl-1,7-dioxoheptan)-4-yl O-ethyl carbono-
dithioate (3e). Rf = 0.25 (petroleum ether–ethyl acetate = 10/
1, v/v). Pale yellow liquid, yield: 240 mg, 71%. 1H NMR (CDCl3,
400 MHz) (d, ppm) 1.25 (t, J = 7.1 Hz, 6H, 2CH3), 1.42 (t, J = 7.1
Hz, 3H, CH3), 1.93 (ddt, J = 14.3, 8.9, 6.5 Hz, 2H in 2CH2), 2.09
(dddd, J = 14.3, 8.5, 7.2, 5.1 Hz, 2H in 2CH2), 2.45 (ddd, J =
15.5, 8.5, 6.5 Hz, 2H in 2CH2), 2.49 (ddd, J = 15.5, 7.2, 6.5 Hz,
2H in 2CH2), 3.81 (tt, J = 8.9, 5.1 Hz, 1H, CH), 4.13 (q, J = 7.1
Hz, 4H, 2CH2), 4.64 (q, J = 7.1 Hz, 2H, CH2). 13C NMR (CDCl3,
100 MHz) (d, ppm) 13.7 (CH3), 14.1 (CH3), 29.5 (CH2), 31.5
(CH2), 50.2 (CH), 60.4 (CH2), 70.0 (CH2), 172.7 (CLO), 213.7
(CLS). IR (neat) n = 2981, 2930, 2856, 1735, 1446, 1215, 1050
cm21. HRMS (ESI) calcd. for C14H25O5S2 [M+H]+ m/z =
337.1143; found 337.1135.
S-(1,7-Dioxo-1,7-diphenylheptan)-4-yl O-ethyl carbonodithio-
ate (3a). Rf = 0.15 (petroleum ether–ethyl acetate = 15/1, v/v).
1
Pale yellow solid, yield: 325 mg, 81%, m.p. 72–73 uC. H NMR
(CDCl3, 400 MHz) (d, ppm) 1.36 (t, J = 7.1 Hz, 3H, CH3), 2.09
(dddd, J = 14.8, 8.9, 7.2, 6.5 Hz, 2H in 2CH2), 2.31 (dddd, J =
14.8, 8.5, 6.8, 4.9 Hz, 2H in 2CH2), 3.16 (ddd, J = 15.0, 8.5, 6.5
Hz, 2H in 2CH2), 3.23 (ddd, J = 15.0, 7.2, 6.8 Hz, 2H in 2CH2),
3.96 (tt, J = 8.9, 4.9 Hz, 1H, CH), 4.57 (q, J = 7.1 Hz, 2H, CH2),
7.46 (dd, J = 7.6, 7.2 Hz, 4H, ArH), 7.56 (t, J = 7.2 Hz, 2H, ArH),
7.95 (d, J = 7.6 Hz, 4H, ArH). 13C NMR (CDCl3, 100 MHz) (d,
ppm) 13.6 (CH3), 28.9 (CH2), 35.7 (CH2), 50.7 (CH), 70.0 (CH2),
128.0 (CH), 128.5 (CH), 133.1 (CH), 136.7 (C), 199.1 (CLO),
213.8 (CLS). IR (neat) n = 3057, 2980, 2926, 2853, 1685, 1448,
1214, 1048 cm21. HRMS (ESI) calcd. for C22H24NaO3S2 [M+Na]+
m/z = 423.1065; Ffound 423.1057.
S-(1,7-Dioxo-1,7-diphenoxyheptan)-4-yl O-ethyl carbono-
dithioate (3f). Rf = 0.25 (petroleum ether–ethyl acetate = 10/1,
1
v/v). Pale yellow oil, yield: 299 mg, 69%. H NMR (CDCl3, 400
MHz) (d, ppm) 1.42 (t, J = 7.1 Hz, 3H, CH3), 2.09 (ddt, J = 14.8,
8.5, 6.5 Hz, 2H in 2CH2), 2.27 (dddd, J = 14.8, 8.5, 7.6, 5.0 Hz,
2H in 2CH2), 2.71–2.83 (m, 4H, 2CH2), 4.00 (tt, J = 8.5, 5.0 Hz,
1H, CH), 4.66 (q, J = 7.1 Hz, 2H, CH2), 7.08 (d, J = 7.8 Hz, 4H,
ArH), 7.22 (t, J = 7.5 Hz, 2H, ArH), 7.36 (dd, J = 7.8, 7.5 Hz, 4H,
S-[1,7-Dioxo-1,7-di(4-methoxyphenyl)heptan]-4-yl O-ethyl
carbonodithioate (3b). Rf = 0.20 (petroleum ether–ethyl acetate
15118 | RSC Adv., 2013, 3, 15114–15120
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ArH). 13C NMR (CDCl3, 100 MHz) (d, ppm) 13.7 (CH3), 29.7
(CH2), 31.6 (CH2), 50.4 (CH), 70.3 (CH2), 121.5 (CH), 125.8
(CH), 129.4 (CH), 150.6 (C), 171.3 (CLO), 213.7 (CLS). IR (neat)
n = 3064, 3042, 2980, 2925, 2855, 1747, 1592, 1492, 1214, 1044
cm21. HRMS (ESI) calcd. for C22H24NaO5S2 [M+Na]+ m/z =
455.0963; found 455.0957.
1216, 1050 cm21. HRMS (ESI) calcd. for C34H35N2O3S2 [M+H]+
m/z = 583.2089; found 583.2082.
S-[1,7-Di(methanesulfonylphenylamino)-1,7-dioxoheptan]-4-
yl O-ethyl carbonodithioate (3k). Rf = 0.21 (petroleum ether–
ethyl acetate = 1/1, v/v). Pale yellow solid, yield: 407 mg, 69%,
m.p. 136–137 oC. 1H NMR (CDCl3, 400 MHz) (d, ppm) 1.37 (t, J
= 7.1 Hz, 3H, CH3), 1.76 (dddd, J = 14.3, 8.5, 7.3, 7.0 Hz, 2H in
2CH2), 2.01 (dddd, J = 14.3, 8.2, 6.3, 5.0 Hz, 2H in 2CH2), 2.19
(ddd, J = 15.0, 8.2, 7.3 Hz, 2H in 2CH2), 2.23 (ddd, J = 15.0, 7.5,
6.3 Hz, 2H in 2CH2), 3.44 (s, 6H, 2CH3), 3.63 (tt, J = 8.5, 5.0 Hz,
1H, CH), 4.57 (q, J = 7.1 Hz, 2H, CH2), 7.23–7.26 (m, 4H, ArH),
7.43–7.47 (m, 6H, ArH). 13C NMR (CDCl3, 100 MHz) (d, ppm)
13.7 (CH3), 29.1 (CH2), 33.8 (CH2), 42.0 (CH3), 49.9 (CH), 70.2
(CH2), 129.7 (CH), 129.9 (CH), 130.1 (CH), 135.1 (C), 173.1
(CLO), 213.6 (CLS). IR (neat) n = 3060, 3032, 2980, 2922, 2847,
1701, 1490, 1352, 1218, 1152, 1047 cm21. HRMS (ESI) calcd. for
S-[1,7-Di(4-chlorophenoxy)-1,7-dioxoheptan]-4-yl O-ethyl car-
bonodithioate (3g). Rf = 0.32 (petroleum ether–ethyl acetate =
10/1, v/v). Pale yellow oil, yield: 422 mg, 84%. 1H NMR (CDCl3,
400 MHz) (d, ppm) 1.42 (t, J = 7.1 Hz, 3H, CH3), 2.06 (ddt, J =
14.8, 8.5, 6.5 Hz, 2H in 2CH2), 2.25 (dddd, J = 14.8, 8.5, 7.6, 5.1
Hz, 2H in 2CH2), 2.70–2.83 (m, 4H, 2CH2), 3.99 (tt, J = 8.5, 5.1
Hz, 1H, CH), 4.66 (q, J = 7.1 Hz, 2H, CH2), 7.03 (d, J = 8.6 Hz,
4H, ArH), 7.33 (d, J = 8.6 Hz, 4H, ArH). 13C NMR (CDCl3, 100
MHz) (d, ppm) 13.8 (CH3), 29.7 (CH2), 31.5 (CH2), 50.4 (CH),
70.4 (CH2), 122.9 (CH), 129.4 (CH), 131.2 (C), 149.0 (C), 171.1
(CLO), 213.7 (CLS). IR (neat) n = 3097, 3070, 2980, 2925, 2855,
C
24H30N2NaO7S4 [M+Na]+ m/z = 609.0834; found 609.0832.
S-[1,7-Dioxo-1,7-di(2-oxooxazolidin-3-yl)heptan]-4-yl O-ethyl
1758, 1486, 1201, 1050 cm21
. HRMS (ESI) calcd. for
C22H22Cl2NaO5S2 [M+Na]+ m/z = 523.0183; found 523.0180.
S-[1,7-Di(4-nitrophenoxy)-1,7-dioxoheptan]-4-yl O-ethyl car-
bonodithioate (3h). Rf = 0.20 (petroleum ether–ethyl acetate =
carbonodithioate (3l). Rf = 0.26 (petroleum ether–ethyl acetate
= 1/2, v/v). Pale yellow oil, yield: 332 mg, 79%. 1H NMR (CDCl3,
400 MHz) (d, ppm) 1.43 (t, J = 7.1 Hz, 3H, CH3), 2.01 (dddd, J =
14.5, 8.5, 7.1, 6.8 Hz, 2H in 2CH2), 2.17 (dddd, J = 14.5, 8.5, 7.5,
5.0 Hz, 2H in 2CH2), 3.07 (ddd, J = 15.5, 8.5, 7.1 Hz, 2H in
2CH2), 3.12 (ddd, J = 15.5, 7.5, 6.8 Hz, 2H in 2CH2), 3.80–3.87
(m, 1H, CH), 4.02 (t, J = 8.0 Hz, 4H, 2CH2), 4.41 (t, J = 8.0 Hz,
4H, 2CH2), 4.63 (q, J = 7.1 Hz, 2H, CH2). 13C NMR (CDCl3, 100
MHz) (d, ppm) 13.6 (CH3), 28.8 (CH2), 32.4 (CH2), 42.4 (CH2),
49.8 (CH), 62.0 (CH2), 70.1 (CH2), 153.4 (CLO), 172.4 (CLO),
213.9 (CLS). IR (neat) n = 3532, 3366, 2984, 2922, 2862, 1771,
1696, 1389, 1223, 1113, 1043 cm21. HRMS (ESI) calcd. for
1
5/1, v/v). Pale yellow oil, yield: 210 mg, 40%. H NMR (CDCl3,
400 MHz) (d, ppm) 1.44 (t, J = 7.1 Hz, 3H, CH3), 2.10 (ddt, J =
14.8, 9.0, 7.2 Hz, 2H in 2CH2), 2.30 (ddt, J = 14.8, 5.0, 7.2 Hz,
2H in 2CH2), 2.84 (t, J = 7.2 Hz, 4H, 2CH2), 4.03 (tt, J = 9.0, 5.0
Hz, 1H, CH), 4.68 (q, J = 7.1 Hz, 2H, CH2), 7.29 (d, J = 8.5 Hz,
4H, ArH), 8.26 (d, J = 8.5 Hz, 4H, ArH). 13C NMR (CDCl3, 100
MHz) (d, ppm) 13.8 (CH3), 29.6 (CH2), 31.5 (CH2), 50.4 (CH),
70.6 (CH2), 122.4 (CH), 125.2 (CH), 145.3 (C), 155.2 (C), 170.4
(CLO), 213.7 (CLS). IR (neat) n = 3115, 3082, 2980, 2926, 2855,
1762, 1592, 1522, 1346, 1209, 1119, 1050 cm21. HRMS (ESI)
calcd. for C22H22N2NaO9S2 [M+Na]+ m/z = 545.0664; found
545.0662.
C
16H23N2O7S2 [M+H]+ m/z = 419.0947; found 419.0937.
S-(1,5-Dicyanopentan-3-yl) O-ethyl carbonodithioate (3m). Rf
= 0.13 (petroleum ether–ethyl acetate = 5/1, v/v). Pale brown
liquid, yield: 124 mg, 51%. 1H NMR (CDCl3, 400 MHz) (d, ppm)
1.46 (t, J = 7.1 Hz, 3H, CH3), 2.01 (dddd, J = 14.5, 8.5, 7.5, 7.0
Hz, 2H in 2CH2), 2.17 (dddd, J = 14.5, 8.5, 6.5, 5.0 Hz, 2H in
2CH2), 2.54 (ddd, J = 15.0, 8.5, 7.5 Hz, 2H in 2CH2), 2.63 (ddd, J
= 15.0, 7.5, 6.5 Hz, 2H in 2CH2), 3.94 (tt, J = 8.5, 5.0 Hz, 1H,
CH), 4.68 (q, J = 7.1 Hz, 2H, CH2). 13C NMR (CDCl3, 100 MHz)
(d, ppm) 13.6 (CH3), 14.9 (CH2), 30.4 (CH2), 48.9 (CH), 70.9
(CH2), 118.5 (CN), 211.3 (CLS). IR (neat) n = 2982, 2932, 2868,
S-(1,7-Dibenzyloxy-1,7-dioxoheptan)-4-yl O-ethyl carbono-
dithioate (3i). Rf = 0.27 (petroleum ether–ethyl acetate = 10/1,
1
v/v). Pale yellow oil, yield: 318 mg, 69%. H NMR (CDCl3, 400
MHz) (d, ppm) 1.37 (t, J = 7.1 Hz, 3H, CH3), 1.93 (ddt, J = 14.8,
9.0, 6.5 Hz, 2H in 2CH2), 2.10 (dddd, J = 14.8, 8.5, 7.2, 5.0 Hz,
2H in 2CH2), 2.49 (ddd, J = 15.0, 8.5, 6.5 Hz, 2H in 2CH2), 2.54
(ddd, J = 15.0, 7.2, 6.5 Hz, 2H in 2CH2), 3.81 (tt, J = 9.0, 5.0 Hz,
1H, CH), 4.59 (q, J = 7.1 Hz, 2H, CH2), 5.10 (s, 4H, 2CH2), 7.31–
7.37 (m, 10H, ArH). 13C NMR (CDCl3, 100 MHz) (d, ppm) 13.7
(CH3), 29.6 (CH2), 31.5 (CH2), 50.3 (CH), 66.4 (CH2), 70.1 (CH2),
128.2 (CH), 128.5 (CH), 135.8 (C), 172.5 (CLO), 213.6 (CLS). IR
(neat) n = 3065, 3033, 2980, 2928, 2856, 1731, 1455, 1215, 1049
cm21. HRMS (ESI) calcd. for C24H28NaO5S2 [M+Na]+ m/z =
483.1276; found 483.1269.
S-{[1,7-Di(diphenylamino)-1,7-dioxo]heptan}-4-yl O-ethyl
carbonodithioate (3j). Rf = 0.15 (petroleum ether–ethyl acetate
= 3/1, v/v). Pale yellow oil, yield: 205 mg, 35%. 1H NMR (CDCl3,
400 MHz) (d, ppm) 1.34 (t, J = 7.1 Hz, 3H, CH3), 1.88 (dddd, J =
14.5, 8.5, 6.8, 6.5 Hz, 2H in 2CH2), 2.11 (dddd, J = 14.5, 8.5, 7.8,
5.0 Hz, 2H in 2CH2), 2.31–2.43 (m, 4H, 2CH2), 3.71 (tt, J = 8.5,
5.0 Hz, 1H, CH), 4.55 (q, J = 7.1 Hz, 2H, CH2), 7.22–7.33 (m,
20H, ArH). 13C NMR (CDCl3, 100 MHz) (d, ppm) 13.7 (CH3),
30.0 (CH2), 32.5 (CH2), 50.5 (CH), 69.7 (CH2), 126.3 (CH), 127.6
(CH), 129.1 (CH), 142.6 (C), 172.0 (CLO), 213.9 (CLS). IR (neat)
n = 3060, 3032, 2980, 2923, 2854, 1671, 1593, 1491, 1377, 1288,
2247, 1447, 1224, 1045 cm21
10H14N2NaOS2 [M+Na]+ m/z = 265.0445; found 265.0442.
. HRMS (ESI) calcd. for
C
Acknowledgements
The project was supported by the National Basic Research
Program of China (No. 2013CB328900), the National Natural
Science Foundation of China (Nos. 21172017, and 20972013),
and the specialized Research Fund for the Doctoral Program of
Higher Education, Ministry of Education of China (No.
20110010110011).
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