PBr3-mediated [5 + 1] annulation of α-alkenoyl-α-carbamoyl ketene-S,S-acetals: access to substituted pyridine-2,6(1H,3H)-diones

Article abstract of DOI:10.1039/c5ra13498f

A facile and efficient synthesis of substituted pyridine-2,6(1H,3H)-diones via an intramolecular [5 + 1] annulation of readily available α-alkenoyl-α-carbamoyl ketene-S,S-acetals mediated by phosphorus bromide (PBr₃) under very mild conditions is described.

Full text of DOI:10.1039/c5ra13498f

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ARTICLE TYPE
PBr3-Mediated [5+1]Annulation of
S,S-acetals: Access to Substituted Pyridine-2,6(1H,3H)-diones†
α
-Alkenoyl-
α
-Carbamoyl Ketene-
Liping Shi,a Qian Zhang,b Fengjiao Gan,b Rui Zhang,*b Yuanli Ding,b Chun Liu,a and Dewen Dong*b
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
5
Facile and efficient synthesis of substituted pyridineꢀ2,6(1H,3H)ꢀdiones via an intramolecular [5+1] annulation of readily available
carbamoyl keteneꢀS,Sꢀacetals mediated by phosphorus bromide under very mild is developed.
αꢀalkenoylꢀαꢀ
10
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DOIA: 10R.103T9/CI5CRA1L34E98F
PBr3-Mediated [5+1]Annulation of α-Alkenoyl-α-Carbamoyl Ketene-
S,S-acetals: Access to Substituted Pyridine-2,6(1H,3H)-diones†
Liping Shi,a Qian Zhang,b Fengjiao Gan,b Rui Zhang,*b Yuanli Ding,b Chun Liu,a and Dewen Dong*b
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
5
A facile and efficient synthesis of substituted pyridine-2,6(1H,3H)-diones via an intramolecular [5+1]
annulation of readily available α-alkenoyl-α-carbamoyl ketene-S,S-acetals mediated by phosphorus
bromide (PBr3) under very mild conditions is described.
of α-dimethyl aminopropenoyl-α-carbamoyl ketene-S,S-acetals,
40 and examined their reaction behaviours under different conditions.
As a result, we developed a facile one-pot synthesis of substituted
Introduction
pyridine-2,6(1H,3H)-diones from readily available α-alkenoyl-α-
carbamoyl ketene-S,S-acetals mediated by phosphorus tribromide
(PBr3) in dichloromethane (DCM). Herein, we wish to report our
45 results and proposed a mechanism involved in the reactions.
10 Cyclic imide and its derivatives have attracted considerable
research interest since they are distributed in numerous natural
products along with diverse useful bioactivities.1-3 For example,
acetiketal (RK-441S) was isolated from Streptomyces
pulveraceus as a new antibiotic,4 and AG-1 is an agent widely
15 used for the treatment of breast cancer for postmenopausal
patients (Figure 1).5 In addition, the functionalized cyclic imides
have been utilized as versatile intermediates in the synthesis of a
wide variety of six-membered aza-heterocycles, and applied as
disperse dyes in dyestuff industry as well.6 To date, a variety of
20 synthetic approaches have been well established to access to such
cyclic imides and their analogues. The notable approaches
involve the cyclization of dinitriles,7 cyclization of monoamides
with acids,8 condensation of diacids with amines,9 or
[3+3]cycloaddition of α,β- unsaturated esters with acetamides.10
25 Nevertheless, the development of efficient and convenient
synthetic methods for such aza-heterocycles under milder
conditions is still desirable.
Scheme 1 Synthesis of Substituted Pyridine-2,4(1H,3H)-diones.13
O
SR1
SR1
O
O
O
O
DMFDMA
DMF, 60 o
DMF
NHR
NHR
(1)
125 OC
C
SR1
R1S
N
R
O
SR1
R1S
Me2N
S
O
O
S
O
S
O
S
O
DMFDMA
DMFDMA
S
NHR
NHR
(2)
DMF
120 OC
DMF
60 O
N
R
O
S
Me2N
C
Results and discussion
The substrates, α-aminopropenoyl-α-carbamoyl ketene-S,S-
acetals 1 were prepared from α-acyl-α-carbamoyl ketene-S,S-
acetals with N,N-dimethyl formamide dimethylacetal (DMFDMA)
50 in high yields according to our published procedure.13 Recently,
we investigated the reaction behaviors of 2-arylamino-3-acetyl-
5,6-dihydro-4H-pyrans and 1-carbamyl-1-oximyl cyclopropanes
toward Vilsmeier reagent, e.g. POCl3/DMF, and POCl3 in DCM,
respectively.14 These obtained results suggested that POCl3
55 showed different reaction behaviour when employed with or
without DMF. Thus, in the present work, the reaction of 2-
[bis(methylthio)methylene]-5-(dimethylamino)-3-oxo-N-phenyl
pent-4-enamide 1a and POCl3 (1.0 equiv.) was first attempted in
DCM at room temperature. The reaction could proceed as
60 indicated by TLC result, and furnished a product after workup
and purification by silica column chromatography, which was
characterized as 3-[bis(methylthio)methylene]-1-phenylpyridine-
2,6(1H,3H)-dione 2a on the basis of its spectral and analytical
data (Table 1, entry 1). It was observed that the variation of
Figure 1
During the course of our studies on the chemistry of α-oxo
ketene-S,S-acetals, we successfully developed novel strategies for
30 the synthesis of highly valuable six-membered carbocycles11 and
heterocycles,12 relying upon the utilization of α-alkenoyl ketene-
S,S-acetals as a five carbon 1,5-dielectrophilic species in the
formal [5+1] annulation with various nucleophiles. Also, we
achieved facile and efficient synthesis of substituted pyridine-
35 2,4(1H,3H)-diones via an intramolecular [5+1] annulations of α-
aminopropenoyl ketene-S,S-acetals (Scheme 1).13 In connection
with our previous work and our continuing interest in the
synthesis of functionalized heterocycles, we synthesized a series
This journal is © The Royal Society of Chemistry [year]
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Under the conditions as for 2a in entry 4, Table 1, a series of
Table 1 Screening of reaction conditions a.
reactions of α-alkenoyl ketene-S,S-acetals 1 were carried out, and
some of the results are listed in Table 2. It was foundVtiehwatArtthiceleαO-nline
DOI: 10.1039/C5RA13498F
25 aminopropenoyl-α-carbamoyl ketene-S,S-acetals 1b-f bearing
varied aryl groups or benzyl group R1 could proceed efficiently to
afford the corresponding pyridine-2,6(1H,3H)-diones 2b-f in
good to high yields (Table 2, entries 2-6). The versatility of this
pyridine-2,6(1H,3H)-dione synthesis was further evaluated by
30 performing 1g-l bearing varied aryl groups or alkyl group R1 and
ethyl or benzyl groups R2 under the identical conditions (entries
7-13). The structure of 2i was further confirmed by X-ray single
crystal analysis and its spectral and analytical data (Figure 2).
The results shown above demonstrate the efficiency and synthetic
35 value of the cyclization reaction of a variety of α-alkenoyl
ketene-S,S-acetals 1. It should be noted that the richness of the
functionality of substituted pyridine-2,6(1H,3H)-diones 2 may
render them versatile as synthons in further synthetic
transformations, e.g. selective reduction of C-C double bond or
40 carbonyl groups,17 Michael addition,18 and nucleophilic vinylic
substitution (SNV) reactions.19
Entry
Reagent
(equiv.)
Solvent Temp.
(oC)
Time
(h)
Yieldb
(%)
1
2
3
4
5
6
7
8
POCl3 (1.0)
POCl3 (1.2)
POCl3 (2.0)
PBr3 (1.2)
PBr3 (1.2)
PBr3 (1.2)
PBr3 (1.2)
PBr3 (1.2)
DCM
DCM
DCM
DCM
DCM
DCM
toluene
DMF
r t
r t
r t
r t
0
9.0
7.0
5.0
6.0
6.0
3.5
6.0
6.0
48
52
53
75
nr c
45
r t
r t
67
mixture
nr
a
b
Reagents and conditions: 1a (1.0 mmol), solvent (15 mL);
Isolated yield; c No reaction.
Table 2 Synthesis of substituted pyridine-2,6(1H,3H)-diones 2 a.
addition amount of POCl3 had significant influence on the
reaction time and yield of 2a (Table 1, entries 2 and 3). When the
reaction of 1a was performed with PBr3 (1.2 equiv) in DCM, 2a
could be obtained in 75% yield. The results suggested that PBr3
was more effective than the previously investigated POCl3 for the
transformation of 1a to 2a (Table 1, entry 4). However, no
reaction occurred when the reaction temperature was decreased to
0 °C (Table 1, entry 5). By increasing the reaction temperature to
45 °C, the reaction could be complete within 3.5 h as indicated by
10 TLC along with 67 % yield of 2a (Table 1, entry 6). Subjecting
1a and PBr3 (1.2 equiv) to toluene at room temperature, a
complex mixture was formed, in which no main product could be
isolated (Table 1, entry 7). It is should be mentioned that no
reaction was observed when 1a was treated with PBr3 (1.2 equiv)
15 in DMF at room temperature (Table 1, entry 8), whereas 4-
bromo-pyridin-2(1H)-ones were obtained in Chen’s work by
subjecting α-acyl ketene-S,S-acetals to Vilsmeier conditions at
100 °C (Scheme 2a).15 It should also be noted that 4-halo-pyridin-
2(1H)-ones could be obtained by the reaction of 1-
20 aminopropenoyl-1-carbamoyl cyclopropanes with POCl3 or PBr3
at room temperature (Scheme 2b).16
Entry
1
R1
R2
2
Yield(%)b
1
1a
1b
1c
1d
1e
1f
Ph
Me
Me
Me
Me
Me
Me
Et
2a
2b
2c
2d
2e
2f
75
83
80
87
76
82
86
85
79
76
78
84
77
5
2
4-MeC6H4
4-ClC6H4
4-MeOC6H4
2-MeOC6H4
Bn
3
4
5
6
7
1g
1h
1i
Ph
2g
2h
2i
8
4-MeC6H4
4-ClC6H4
4-MeOC6H4
Ph
Et
9
Et
10
11
12
1j
Et
2j
1k
1l
Bn
Bn
Et
2k
2l
4-MeC6H4
13
1m Me
2m
a
Reagents and conditions: 1a (1.0 mmol), PBr3 (1.2 equiv.),
CH2Cl2 (15 mL), rt, 5.0-7.0 h; b Isolated yield.
Scheme 2 Synthesis of 4-Halo-pyridin-2(1H)-ones.15, 16
Figure 2 ORTEP drawing of 2i.
2
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+
Shimadzu FTIR-8400S spectrophotometer in the range of 400-
4000 cm-1.
NMe2
NHR1
O
R1
O
PBr3
-Br
HN
View Article Online
Me2N
DOI: 10.1039/C5RA13498F
Br2PO
R2S
Typical procedure for the synthesis of 2 (2a as an examples)
O
R2S
SR2
SR2
35
To a solution of 1a (336 mg, 1.0 mmol) in CH2Cl2 (15 mL)
was added PBr3 (325 mg, 1.2 mmol) at 0 °C. Then the reaction
mixture was allowed to warm to room temperature and stirred for
6.0 h. After the reaction was completed, the resulting mixture was
poured into saturated aqueous NaCl (100 mL), which was
40 extracted with dichloromethane (3×30 mL). The organic extracts
were washed with water, dried over MgSO4, filtered and
concentrated in vacuo. Purification was carried out by flash silica
gel chromatography using petroleum ether: ethyl acetate (9:1, v/v)
as eluent to give product 2a (218 mg, 75%).
1
A
-H+
NMe2
NMe2
NMe2
N
R1
O
R1
R1
H+
N
N
Br2PO
R2S
Br2PO
R2S
Br2PO
R2S
O
O
H
SR2
B'
SR2
SR2
C
B
-HOPBr2
+
NMe2
N
NMe2
O
R1
45 Analytical data of 2
R1
R1
O
N
H2O
N
3-[Bis(methylthio)methylene]-1-phenylpyridine-2,6(1H,3H)-
dione (2a)
O
O
-HNMe2
R2S
SR2
R2S
SR2
R2S
SR2
D'
+
Yellow solid; mp 149-150 °C. ¹H NMR (300 MHz, CDCl3): δ
2.54 (s, 3 H), 2.67 (s, 3H), 6.24 (d, J = 10.0 Hz, 1 H), 7.18-7.21
50 (m, 2 H), 7.47-7.49 (m, 3 H), 8.07 (d, J = 10.2 Hz, 1 H). 13C
NMR (100 MHz, CDCl3): δ 174.1, 164.6, 162.9, 138.6, 135.2,
129.2, 128.6, 128.4, 123.2, 116.3, 21.6, 19.8. IR (KBr, cm-1) 3446,
2918, 1677, 1639, 1592, 1491, 1452, 1411, 1178, 782. Anal.
Calcd for C14H13NO2S2: C, 57.71; H, 4.50; N, 4.81. Found: C,
55 57.48; H, 4.43; N, 4.87
2
D
Scheme 3 Plausible mechanism for the reaction of α-alkenoyl-
α-carbamoyl ketene-S,S-acetal 1 with PBr3.
On the basis of the above experimental results together with
some literatures, a mechanism for the synthesis of pyridine-
2,6(1H,3H)-dione 2 is proposed as depicted in Scheme 3. In the
presence of PBr3, α-aminopropenoyl-α-carbamoyl ketene-S,S-
acetal 1 is transformed into iminium ion intermediate A, which
undergoes an intramolecular cyclization to afford intermediate B
and its tautomer B’. 20,21 The protonation of the C-C double bond
of B’ gives carbocation C,15 followed by elimination of HOPBr2
to form carbocation D and its tautomer iminium ion D’. The latter
3-[Bis(methylthio)methylene]-1-p-tolylpyridine-2,6(1H,3H)-
dione (2b)
5
Yellow solid; mp 142-143 °C. ¹H NMR (300 MHz, CDCl3): δ
60 2.39 (s, 3 H), 2.52 (s, 3H), 2.66 (s, 3H), 6.24 (d, J = 10.0 Hz, 1 H),
7.06 (d, J = 8.0 Hz,, 2 H), 7.28 (d, J = 8.0 Hz, 2 H), 8.05 (d, J =
10.2 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 174.0, 164.7,
163.0, 138.5, 138.3, 132.4, 130.0, 128.2, 123.1, 116.3, 21.6, 21.2,
19.8. IR (KBr, cm-1) 3446, 2919, 1686, 1637, 1513, 1449, 1408,
65 1187, 841. Calcd for C15H15NO2S2: C, 58.99; H, 4.95; N, 4.59.
Found: C, 58.68; H, 5.06; N, 4.50.
10 is hydrolyzed to the final product pyridine-2,6(1H,3H)-dione 2
during the workup process under acidic conditions.14b, 21
Conclusions
3-[Bis(methylthio)methylene]-1-(4-chlorophenyl)pyridine-
2,6(1H,3H)-dione (2c)
In summary, an efficient synthesis of substituted pyridine-
2,6(1H,3H)-diones via an intramolecular [5+1] annulation of
15 readily available α-alkenoyl-α-carbamoyl ketene-S,S-acetals 1
mediated by phosphorus bromide (PBr3) is developed. This
protocol is associated with readily available starting materials,
mild conditions, high yields, a wide range of substrate scope, and
rich functionalities and important synthetic potential of the
20 products.
70 Yellow solid; mp 137-139 °C. ¹H NMR (300 MHz, CDCl3): δ
2.54 (s, 3 H), 2.68 (s, 3 H), 6.22 (d, J = 10.2 Hz, 1 H), 7.12-7.15
(m, 2 H), 7.43-7.53 (m, 2 H), 8.06 (d, J = 10.2 Hz, 1 H). 13C
NMR (100 MHz, CDCl3): δ 175.0, 164.5, 162.7, 138.9, 134.4,
133.7, 130.0, 129.5, 122.8, 116.0, 21.7, 19.9. IR (KBr, cm-1) 3421,
75 2956, 1685, 1645, 1603, 1505, 1469, 1453, 1186, 839. Anal.
Calcd for C14H12ClNO2S2: C, 51.61; H, 3.71; N, 4.30. Found: C,
51.81; H, 3.79; N, 4.18.
Experimental
General
3-[Bis(methylthio)methylene]-1-(4-methoxyphenyl)pyridine-
80 2,6(1H,3H)-dione (2d)
Yellow solid; mp 166-168°C. ¹H NMR (300 MHz, CDCl3): δ
2.53 (s, 3 H), 2.67 (s, 3 H), 3.83 (s, 3H), 6.23 (d, J = 10.2 Hz, 1
H), 7.00 (d, J = 8.7, 2 H), 7.11 (d, J = 8.7, 2 H), 8.05 (d, J = 10.2
Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 174.0, 164.8, 163.1,
85 159.3, 138.5, 129.4, 127.6, 123.2, 116.3, 114.6, 55.4, 21.6, 19.8.
Anal. Calcd for C15H15NO3S2: C, 56.05; H, 4.70; N, 4.36. Found:
C, 56.33; H, 4.82; N, 4.45.
All reagents were purchased from commercial sources and
used without treatment, unless otherwise indicated. The products
25 were purified by column chromatography over silica gel. 1H
NMR spectra and 13C NMR spectra were obtained at 25 °C at 300
MHz (or 400 MHz) and 100 MHz, respectively, on a Bruker
AV300 (or AV 400) spectrometer using CDCl3 (otherwise
indicated) as solvent and TMS as internal standard. Mass spectra
30 were recorded on a Bruker autoflex III( smartbeam MALDI-TOF)
mass spectrometer. IR spectra (KBr) were recorded on a
3-[Bis(methylthio)methylene]-1-(2-methoxyphenyl)pyridine-
90 2,6(1H,3H)-dione (2e)
Yellow solid; mp 142-143°C.¹H NMR (300 MHz, CDCl3): δ 2.53
(s, 3 H), 2.65 (s, 3 H), 3.76 (s, 3 H), 6.22 (d, J = 10.2 Hz, 1 H),
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7.01-7.07 (m, 2 H), 7.12-7.15 (m, 1 H), 7.37-7.42 (m, 1 H), 8.06
3.83(s, 3 H), 6.22 (d, J = 10.2 Hz, 1 H), 6.98 (d, J = 9.0 Hz, 2 H),
(d, J = 10.2 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 173.3, 65 7.09 (d, J = 9.0 Hz, 2 H), 8.07 (d, J = 10.2 Hz, 1 H). 13C NMR
View Article Online
164.3, 162.5, 154.9, 138.6, 130.0, 129.9, 124.0, 123.3, 120.9,
116.4, 111.9, 55.7, 21.5, 19.8. IR (KBr, cm-1) 3446, 1683, 1642,
1600, 1500, 1451, 1410, 1192, 759. Anal. Calcd for C15H15NO3S2:
C, 56.05; H, 4.70; N, 4.36. Found: C, 56.31; H, 4.56; N, 4.29.
(100 MHz, CDCl3): δ 171.6, 164.9, 163.2, 159.3, 138.7, 129.5,
127.7, 123.9, 116.3, 114.6, 55.4, 34.0, 30.7, D1O4.I8: ,101.310.93.9/ICR5R(KA1B34r,98F
cm-1) 3441, 1693, 1647, 1454, 1412, 1190, 674. Anal. Calcd for
C17H19NO3S2: C, 58.43; H, 5.48; N, 4.01. Found: C, 58.77; H,
70 5.57; N, 4.10.
5
1-Benzyl-3-[bis(methylthio)methylene]pyridine-2,6(1H,3H)-
dione (2f)
3-[Bis(benzylthio)methylene)-1-phenylpyridine-2,6(1H,3H)-
dione (2k)
Yellow solid; mp 165-166 °C.¹H NMR (300 MHz, CDCl3): δ
10 Yellow solid: mp 98-100 oC; 1H NMR (400 MHz, CDCl3): δ 2.53
(s, 3 H), 2.72 (s, 3 H), 5.21(s, 2 H), 6.21 (d, J = 10.4 Hz, 1 H),
7.28-7.30 (m, 1 H), 7.32-7.36 (m, 2 H),7.52 (d, J = 7.6 Hz, 2 H), 75 4.05 (s, 2 H), 4.29 (s, 2 H), 6.09 (d, J = 10.2 Hz, 1 H), 7.15-7.49
8.01 (d, J = 10.4 Hz, 1 H); 13C NMR (100 MHz, CDCl3):δ172.2,
163.6, 161.6, 137.0, 136.3, 127.9, 127.2, 126.2, 122.3, 115.2,
15 41.9, 20.6, 18.7; Anal. Calcd for C15H15NO2S2: C, 58.99; H, 4.95;
N, 4.59; Found: C, 58.76; H, 4.99; N, 4.72. MS (MALDI): calcd
for C15H16NO2S2 [M+H]+ 306.1, found 306.1
(m, 15 H), 7.81 (d, J = 10.2 Hz, 1 H). 13C NMR (100 MHz,
CDCl3): δ 169.0, 164.4, 163.0, 138.5, 135.6, 135.1, 135.0, 129.4,
129.2, 128.9, 128.8, 128.7, 128.6, 128.5, 128.3, 127.7, 124.6,
116.6, 43.9, 41.4. IR (KBr, cm-1): 3445, 2923, 2853, 1658, 1557,
80 1540, 1487, 1350, 1260, 748. Anal. Calcd for C26H21NO2S2: C,
70.40; H, 4.77; N, 3.16. Found: C, 70.69; H, 4.70; N, 3.07.
3-[Bis(ethylthio)methylene]-1-phenylpyridine-2,6(1H,3H)-
dione (2g)
20 Yellow solid; mp 119-120 °C.¹H NMR (300 MHz, CDCl3): δ
3-[Bis(benzylthio)methylene]-1-(p-tolyl)pyridine-2,6(1H,3H)-
1.32-1.39 (m, 6 H), 2.96-3.03 (m, 2 H), 3.18-3.26 (m, 2 H), 6.23
dione (2l)
(d, J = 10.2 Hz, 1 H), 7.18-7.21 (m, 1 H), 7.38-7.51 (m, 4 H), 85 Yellow solid; mp 166-168 °C.¹H NMR (300 MHz, CDCl3): δ
8.09 (d, J = 10.2 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 171.8,
164.6, 163.0, 138.8, 135.2, 129.2, 128.6, 126.3, 123.9, 116.3,
25 34.1, 30.8, 14.8, 13.9. IR (KBr, cm-1) 3442, 2924, 1686, 1641,
1593, 1493, 1453, 1413, 1190, 698. Anal. Calcd for C16H17NO2S2:
C, 60.16; H, 5.36; N, 4.38. Found: C, 60.35; H, 5.28; N, 4.50.
2.37 (s, 3 H), 4.04 (s, 2 H), 4.29 (s, 2 H), 6.09 (d, J = 10.2 Hz, 1
H), 7.03 (d, J = 7.8 Hz, 2 H), 7.22-7.32 (m, 12 H), 7.79 (d, J =
10.2 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 168.9, 164.5,
163.1, 138.4, 135.7, 135.2, 132.3, 130.0, 129.4, 128.9, 128.8,
90 128.7, 128.3, 128.2, 127.7, 124.6, 116.6, 43.9, 41.1, 21.2. IR
(KBr, cm-1) 3446, 2935, 1692, 1644, 1600, 1511, 1493, 1454,
1191, 820. Anal. Calcd for C27H23NO2S2: C, 70.87; H, 5.07; N,
3.06. Found: C, 70.66; H, 5.13; N, 2.98.
3-[Bis(ethylthio)methylene]-1-p-tolylpyridine-2,6(1H,3H)-
30 dione (2h)
Yellow solid; mp 115-117 °C.¹H NMR (300 MHz, CDCl3): δ
1.27-1.37 (m, 6 H), 2.39 (s, 3H), 2.96-2.99 (m, 2 H), 3.19-3.22
(m, 2 H), 6.22 (d, J = 10.0 Hz, 1 H), 7.06-7.08 (m, 2 H), 7.26-
7.29 (m, 2H), 8.08 (d, J = 10.0 Hz, 1 H). 13C NMR (100 MHz,
35 CDCl3): δ 171.7, 164.7, 163.0, 138.7, 138.2, 132.4, 129.9, 128.2,
123.8, 116.2, 34.0, 30.7, 21.2, 14.7, 13.8. Anal. Calcd for
C17H19NO2S2: C, 61.23; H, 5.74; N, 4.20. Found: C, 61.48; H,
5.88; N, 4.31.
3-[Bis(ethylthio)methylene]-1-methylpyridine-2,6(1H,3H)-
95 dione (2m)
Yellow oil. ¹H NMR (300 MHz, CDCl3): δ 1.31 (t, J = 7.5 Hz, 3
H), 1.37 (t, J = 7.5 Hz, 3 H), 2.93 (q, J = 7.5 Hz, 2 H), 3.22 (q, J
= 7.5 Hz, 2 H), 3.33 (s, 3H), 6.12 (d, J = 10.2 Hz, 1 H), 7.97 (d, J
= 10.2 Hz, 1 H); 13C NMR (100 MHz, CDCl3): δ 14.0, 14.6, 26.2,
100 30.6, 33.9, 116.0, 124.0, 137.8, 163.1, 164.8, 170.5; Anal. Calcd
for C11H15NO2S2: C, 51.33; H, 5.87; N, 5.44. Found: C, 51.60; H,
5.72; N, 5.37. MS (MALDI): calcd for C11H16NO2S2 [M+H]+
258.1, found 258.1.
40 3-[Bis(ethylthio)methylene]-1-(4-chlorophenyl)pyridine-
2,6(1H,3H)-dione (2i)
Yellow solid; mp 122-123 °C.¹H NMR (300 MHz, CDCl3): δ
1.32-1.39 (m, 6 H), 2.96-3.04 (m, 2 H), 3.19-3.24 (m, 2 H), 6.21
(d, J = 10.2 Hz, 1 H), 7.13 (d, J = 8.4 Hz, 2 H), 7.43 (J = 8.4 Hz,
45 2 H), 8.09 (d, J = 10.2 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ
172.7, 164.4, 162.8, 139.0, 134.3, 133.7, 130.1, 129.4, 123.5,
115.9, 34.1, 30.9, 14.8, 13.9. IR (KBr, cm-1) 3443, 1679, 1647,
1598, 1493, 1454, 1407, 1190, 783, 695. Anal. Calcd for
C16H16ClNO2S2: C, 54.30; H, 4.56; N, 3.96. Found: C, 53.94; H,
50 4.45; N, 4.09.
105 Acknowledgements
Financial support of this research by the National Natural
Science Foundation of China (21172211) and Jilin Provincial
Science and Technology Development (201205027) is greatly
110 acknowledged.
Crystal data for 2i: C16H16ClNO2S2, colourless crystal, M = 352.9,
Monoclinic, P2(1)/n, a = 12.739(5) Å, b = 5.382(2) Å, c =
24.848(10) Å, α = 90.00 º, β = 103.362(6) º, γ = 90.00 º, V =
1657.3(11) Å3, Z = 4, T = 273(2), F000 = 736.0, R1 = 0.0636,
55 wR2 = 0.1423. CCDC deposition number: 1058034. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic
Data Center, 12 Union Road, Cambridge CB21EZ, UK; fax:
(+44)1223-336-033; or deposit@ccdc.cam.ac.uk).
Notes and references
a College of Chemistry and Biology, Beihua University, Jilin, 132013,
China.
b Key Laboratory of Synthetic Rubber, Changchun Institute of Applied
115
Chemistry, Chinese Academy of Sciences, Changchun 130022,
China.
E-mail: ariel@ciac.ac.cn; dwdong@ciac.ac.cn
60 3-[Bis(ethylthio)methylene]-1-(4-methoxyphenyl)pyridine-
2,6(1H,3H)-dione (2j)
Yellow solid; mp 118-120 °C.¹H NMR (300 MHz, CDCl3): δ
† Electronic Supplementary Information (ESI) available: crystallographic
120 data in CIF for 2i, and copies of NMR spectra for compounds 2. See
DOI: 10.1039/b000000x/
1.31-1.38 (m, 6 H), 2.95-3.02 (m, 2 H), 3.18-3.25 (m, 2 H),
4
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