Synthesis of substituted imid(thi)azolidines by [3+2] cycloaddition of aziridines with nitriles(isothiocyanates) via visible light photocatalysis

Article abstract of DOI:10.24820/ark.5550190.p010.246

The [3+2] cycloaddition reaction of aziridines with nitriles (isothiocyanates) has been developed using visible light photocatalysis. Two types of five-membered heterocyclic compounds, imidazolidines and thiazolidines, were synthesized in mild conditions. An oxidative quenching cycle mechanism is probably involved.

Full text of DOI:10.24820/ark.5550190.p010.246

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Arkivoc 2017, part v, 314-326
Organic Chemistry
Synthesis of substituted imid(thi)azolidines by [3+2] cycloaddition of aziridines
with nitriles(isothiocyanates) via visible light photocatalysis
Qianwen Ye,a Xiaoliang Xu,*a Dongping Cheng,*b Baochuan Guan,a Hongfeng Ye,a and Xiaonian Li*a
aCollege of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, P. R. China
bCollege of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, P. R. China
Email: xuxiaoliang@zjut.edu.cn, chengdp@zjut.edu.cn, xnli@zjut.edu.cn
Received 07-02-2017
Accepted 10-22-2017
Published on line 11-19-2017
Abstract
The [3+2] cycloaddition reaction of aziridines with nitriles (isothiocyanates) has been developed using visible
light photocatalysis. Two types of five-membered heterocyclic compounds, imidazolidines and thiazolidines,
were synthesized in mild conditions. An oxidative quenching cycle mechanism is probably involved.
Keywords: Aziridines, nitriles, isothiocyanates, [3+2] cycloaddition, photocatalysis
DOI: https://doi.org/10.24820/ark.5550190.p010.246
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Introduction
Photoredox catalysis by means of visible light is considered an ideal route for green, economic and abundant
chemical synthesis. Different from many conventional reagents, visible light can be used as a type of
renewable source.1-5 Since it was proposed by Ciamician in 1912, this concept has been almost silent for half a
century or more.6 It was not until 2008 that MacMillan firstly reported α-alkylation of aldehydes and ketones
by photocatalysis, which attracted considerable attention from chemists.7 Subsequently, many research
groups have made extensive and outstanding contributions in this field1 and photocatalysis has evolved into
an important means in organic synthesis.
Imidazolines and thiazolines are important heterocyclic systems which have a wide range of applications in
bio-activities8-9 and pharmaceuticals.10-11 Some derivatives are used for the synthesis of anti-inflammatory,
antioxidant, anti-nociceptive and anticarcinogenic drugs. Additionally, imidazolines have been used as metal
complex ligands12 and auxiliary groups13 in asymmetric synthesis.
Many methods have been developed for the synthesis of imidazolines and thiazolines. The traditional
process for imidazolines is the cyclization of 1,2-diamines with carboxylic acids under rigorous conditions.
Unfortunately, 1,2-diamines are not easy to synthesize and the substrate scopes are quite narrow.14 Booker-
Milburn and Zhou reported the preparation of imidazolines from olefins, N-chlorosaccharin (NCSacc) or NBS
(cationic Br as initiator) and a nitrile in two steps under harsh conditions.15-16 In 2016, Xu developed the
synthesis of imidazoline via visible light catalysis from alkenes, an N-Ts-1-aminopyridinium salt and a nitrile but
the transformation was unsuccessful for non-conjugated alkenes.17 Catalyzed by Lewis acid or transition
metals, the [3+2] cycloaddition of aziridines with nitriles can be performed to acquire imidazolines.18-24 For the
synthesis of 2-iminothiazolidines, the [3+2] cycloaddition reaction of aziridines with isothiocayanates could
also be accomplished using several catalysts or stoichiometric reagents.25-26
Results and Discussion
Although many methods have been reported for the synthesis of substituted imidazolidines and thiazolidines,
it is important to find new synthetic methods from the viewpoint of synthetic diversity. In 2014, Xia group
reported the ring opening reaction of aziridines by visible light photocatalysis with Na2S2O8 as an oxidant.27
According to the oxidative quenching cycle mechanism of visible light photocatalysis of this reaction, we
speculated it might be possible to carry out a [3+2] cycloaddition reaction of aziridines and nitriles under these
conditions.
In order to find optimal conditions, the reaction of aziridine 1a and acetonitrile 2a was performed with 1.2
eq of PhN2BF4 in the presence of 1 mol% Ru(bpy)3Cl2·6H2O under air (Table 1). The reaction mixture was
illuminated with a 45W white household lamp at room temperature for four hours monitored by TLC. We
were delighted to find that the desired product 3a could be isolated in 73% yield (entry 1). Extending the
reaction time to five, six, and seven hours respectively, did not increase the yield. The reaction proceeded very
slowly and the yields were very low in the absence of light or photocatalyst (entries 2-3). The yield was
improved slightly when the reaction was carried out under a N2 atmosphere (entry 4). The desired product
could not be obtained without PhN2BF4, which indicated that an oxidant was essential for the reaction (entry
5). All of the tested catalysts promoted the reaction (entries 6-11), but the best yield was obtained using
Ru(bpy)3(BF4)2 as a photocatalyst (entry 8). Using I2, DDQ, NBS, Na2S2O8, K2S2O8, or PhI(OAc)2 as the
substituted oxidant, the reaction failed (entry 12). A 64% yield of the product could be detected by GC analysis
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when (NH4)2S2O8 was used as the oxidant (entry 13). The desired product could not be obtained when
Ir[dF(CF3)ppy]2(dtbbpy)PF6 (E1/2III*/II=+1.21 V vs SCE in CH3CN) or Ru(bpz)3(PF6)2 (E1/2III/II=+1.86V vs SCE in
CH3CN) were tried in the absence of PhN2BF4 (entries 14-15). The yields were 7%, 15%, 30% and 70%
respectively when PhN2BF4 was used at 5%, 10%, 20% and 50%. A small amount of biphenyl was detected by
GC analysis.
Table 1. Optimization of the reaction conditionsa
Ts
Ts
N
1 mol% photocatalyst
oxidant, N2, 45W CFL
N
Me
+ CH3CN
N
Ph
Ph
3a
1a
2a
Entry
1c
Catalyst
Ru(bpy)3Cl2·6H2O
-
Ru(bpy)3Cl2·6H2O
Ru(bpy)3Cl2·6H2O
Ru(bpy)3Cl2·6H2O
EosinY
Oxidant
PhN2BF4
PhN2BF4
PhN2BF4
PhN2BF4
-
Yield(%)b
79(73)
11
2
85(75)
0
37
87
90(83)
83
60
20
0
2d
3e
4f
5
6
7
8
PhN2BF4
PhN2BF4
PhN2BF4
PhN2BF4
PhN2BF4
PhN2BF4
see footnote
(NH4)2S2O8
-
Ir(ppy)3
Ru(bpy)3(BF4)2
Ir(ppy)2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ru(bpz)3(PF6)2
Ru(bpy)3(BF4)2
Ru(bpy)3(BF4)2
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ru(bpz)3(PF6)2
Ru(bpy)3(BF4)2
9
10
11
12g
13
14
15
16h
64
0
0
-
PhN2BF4
see footnote
a1a (0.5 mmol), 2a (40 mmol, 2 mL), oxidant (0.6 mmol, 1.2 eq), photocatalyst (0.005 mmol, 1 mol%), 45 W CFL
(compact fluorescent lamp) irradiation under N2 atmosphere at r.t. for 4 h unless otherwise noted.
c
d
e
bDetermined by GC (yield of isolated product based on 1a in parentheses). Under air. No photocatalyst. No
f
g
h
light. Under N2. Oxidants were I2, DDQ, NBS, PhI(OAc)2, Na2S2O8, K2S2O8. CH3CN (2.5 mmol, 5 eq), various
solvents (2 mL), CH2Cl2, DCE, THF, DMSO, gave yields of 60%, 74%, 0%, 0% respectively.
With the optimal reaction conditions in hand, the substrate scope of the 2-alkyl(aryl)-N-tosylaziridine was
investigated (Table 2). The substituent of the aryl ring of the 2-aryl-N-tosylaziridine, such as F, Cl, Me
generated the cycloaddition products in good yields (3b-e). However, the bromo substituted starting material
gave slightly lower yield (3f). 2-Methyl-2-phenyl-N-tosylaziridine, 2-octyl-N-tosylaziridine, N-
tosylcyclohexanoaziridine, were also suitable for the reaction (3g-i). Next, several alkyl nitriles were examined
and the corresponding products were obtained in moderate yields (3j-n). Only one nitrile group participated in
the reaction when 1,4-dicyanobenzene was used as the substrate (3m).
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Table 2. Cycloaddition reactions of aziridines and nitrilesa
Ts
N
1 mol% Ru(bpy)3(BF4)2
Ts
N
1.2 eq PhN2BF4
R1
R2
R4
R2
R1
R4CN
+
N2, 45W CFL
N
2
3
1
Entry
R1; R2
Ph; H (1a)
R4
CH3 (2a)
2a
Yield(%)b
1
2
3
4
5
6
7
8
9
83 (3a29)
85 (3b)
4-FC6H4; H (1b)
4-ClC6H4; H (1c)
2-ClC6H4; H (1d)
4-MeC6H4; H (1e)
4-BrC6H4; H (1f)
Ph; Me (1g)
2a
2a
2a
2a
2a
2a
2a
84 (3c30)
88 (3d29)
76 (3e29)
54 (3f30)
55 (3g)
C8H17; H (1h)
40 (3h)
57 (3i31)
(1i)
10
11
12
13c
14
1a
1a
1a
1a
1a
Ph (2b)
PhCH2 (2c)
1-naphthyl (2d)
4-NCC6H4 (2e)
4-MeC6H4 (2f)
69 (3j29)
73 (3k29)
43 (3l)
40 (3m)
53 (3n)
a1 (0.5 mmol), 2 (a:40 mmol, b:20 mmol, c:17 mmol, d:14 mmol, f:17 mmol, 2 mL), PhN2BF4 (0.6 mmol, 1.2 eq),
b
c
Ru(bpy)3(BF4)2 (0.005 mmol, 1 mol%), 45W CFL, N2, r.t., 4 h. Yield of isolated product. Nitrile (2.5 mmol, 5 eq),
DCE (2 mL).
To further demonstrate the generality of the [3+2] cycloaddition reaction, we employed isothiocyanates 4
as dipolarophiles to synthesize 2-iminothiazolidines. Based on the reaction of 1a and 2a, the reaction
conditions of 1a and 4a were screened briefly. The reaction did not proceed without light or photocatalyst. A
lower yield was obtained under blue LED illumination perhaps because the six-membered ring dimer was
formed as the by-product.28 Diphenyl was also detected by GC analysis in the reaction mixture. Screening the
solvent, oxidant, etc. showed the optimal conditions were similar to that for the synthesis of 3a (see above).
A series of aryl or alkyl isothiocyanates were surveyed under the optimal conditions (Table 3). The
expected products 5 were obtained in moderate yields. No obvious electronic effect was observed. The yield
was slightly lower when 2-(2-chlorophenyl)-N-tosylaziridine 5d was used as the substrate and the steric effect
may be responsible for this result. 2-Phenyl-1-(phenylsulfonyl)aziridine 5q was also a good candidate and
afforded the corresponding product in 62% yield.
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Table 3. Cycloaddition reactions of aziridines and isothiocyanatesa,b
R3
R3
N
1 mol% Ru(bpy)3(BF4)2
1.2 eq PhN2BF4
NR5
R1
R2
R1
R2
N
R5N C S
+
S
N2, 45W CFL, DCE
5
1
4
Entry
1
2
3
4
5
6
7
8
R1; R2; R3
1a
R5
Ph (4a)
4a
Yield(%)
59 (5a32)
49 (5b33)
55 (5c34)
34 (5d34)
55 (5e34)
58 (5f34)
53 (5g34)
48 (5h)
1b
1e
1d
1f
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
4a
4a
4a
4-MeOC6H4 (4b)
4-FC6H4 (4c)
2-MeC6H4 (4d)
4-BrC6H4 (4e)
4-ClC6H4 (4f)
iPr (4g)
9
47 (5i)
51 (5j)
52 (5k35)
54 (5l34)
52 (5m34)
48 (5n)
49 (5o)
48 (5p33)
62 (5q34)
10
11
12
13
14
15
16
17
cyclohexyl (4h)
C4H9 (4i)
PhCH2 (4j)
1-methylbenzyl (4k)
1-naphthyl (4l)
4a
H; Ph; SO2Ph (1j)
a1 (0.5 mmol), 4 (1.5 mmol, 3 eq), PhN2BF4 (0.6 mmol, 1.2 eq), DCE (3 mL), Ru(bpy)3(BF4)2 (0.005 mmol, 1
mol%), 45 W CFL, N2, r.t., 10 h. bYield of isolated product.
According to the literature16 and the above experimental results, a plausible reaction mechanism is
proposed in Scheme 1. Firstly, under the visible light, the ground state of Ru2+ is excited to provide Ru*2+ which
is oxidized by PhN2BF4 6 to produce Ru3+. Thus, the diazonium salt is reduced to generate the phenyl radical 7
which produces 8 by homo-coupling. The aziridine 1 is oxidized to generate a nitrogen radical cation 9 by Ru3+
which itself is reduced to the original oxidation level, Ru2+. Intermediate 9 is attacked by the dipolarophile,
nitrile 2 or isothiocyanate 4, to give the ion intermediates 10 or 11 via electron exchange with 1 or
intermediate 7, intramolecular cyclization then leading to the imidazoline 3 or thiazolidine 5.
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Scheme 1. A plausible reaction mechanism.
Conclusions
In summary, we have developed a [3+2] cycloaddition of aziridines with nitriles or isothiocyanates by visible
light photocatalysis under simple and mild reaction conditions. The reaction is applicable to aryl and alkyl
nitriles or isothiocyanates and various substituted imidazolines and iminothiazolidines can be prepared with
moderate yields. Visible light as a clean energy source makes this route a good substitute for the existing
synthetic protocols.
Experimental Section
General. All of the commercial reagents were used without further purification unless otherwise specified and
were purchased from Aladdin, Macklin, Energy or Bide Pharmatech. All of the chemical reactions and
manipulations were implemented in oven-dried glassware under an atmosphere of N2 using standard Schlenk
technique. The solvents were made absolutely anhydrous and freshly distilled prior to use. Reactions were
monitored by thin-layer chromatography (TLC) on GF254 Silica plates, visualizing with UV-light (254 nm) or I2
stain. 1H NMR and 13C NMR spectra were recorded in ppm at 500 MHz and 125 MHz using CDCl3 as solvent and
TMS as internal standard using a Bruker AVANCE III 500MHz Nuclear Magnetic Resonance Spectrometer. Low-
resolution MS (Varian 1200 Mass Spectrum Analyzer) and HRMS (Bruker ApexIII Fourier Transform Ion
Cyclotron Resonator) were obtained using ESI ionization. Elemental analyses were performed on a vario Micro
cube. GC spectra were measured using an Agilent 7890B. Melting points were measured using a SGW® X-4.
General experimental procedure for synthesis of 3a-n
An 25 mL oven-dried Schlenk tube was equipped with a stirring bar, an aziridine 1 (0.5 mmol), PhN2BF4 (0.6
mmol, 1.2 eq), and Ru(bpy)3(BF4)2 (0.005 mmol, 1 mol%). The mixture was degassed by using standard Schlenk
techniques with an oil pump. Then a nitrile 2a-d, 2f (a: 40mmol, b: 20mmol, c: 17mmol, d: 14mmol, f: 17mmol,
2 mL) or nitrile 2e (2.5 mmol, 5 eq) and DCE (2 mL) were injected into the reaction tube. The reaction mixture
was allowed to stir for 4 h under irradiation of 45 W CFL (compact fluorescent lamp) (FSL, YPZ220/45-S,
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Luminous Flux (2580Lm) at rt, the distance fof the reaction vessel from the light bulb being about 5 cm. After
the reaction was completed (TLC), to the mixture was added distilled water (10 mL) and product extracted
with CH2Cl2 (3 × 30 mL) in a separatory funnel. The combined organic layers were dried (anhydrous Na2SO4).
Afterwards, the organic solution was concentrated under reduced pressure using a rotary evaporator and
purified by column chromatography on silica gel (200-300 mesh) (PE:EtOAc = 5-10:1) to give the pure product
3.
1
2-Methyl-4-phenyl-1-tosyl-4,5-dihydro-1H-imidazole (3a). White solid, mp 97-98 °C (lit. 100-102 °C)29; H
NMR (500 MHz, CDCl3) δ 7.77-7.76 (m, 2H, Ph in Ts), 7.37 (d, J 8.0 Hz, 2H, Ph in Ts), 7.30-7.25 (m, 3H, Ph), 7.07-
7.05 (m, 2H, Ph), 5.03-4.99 (m, 1H, CH2), 4.21-4.17 (m, 1H, CH2), 3.65 (dd, J 9.8, 7.9 Hz, 1H, CHN=), 2.48 (s, 3H,
Me in Ts), 2.42, 2.41 (ss, 3H, 2-Me). 13C NMR (125 MHz, CDCl3) δ 156.5, 144.8, 141.5, 135.2, 130.1, 128.7,
127.7, 127.3, 126.4, 66.6, 55.5, 21.6, 16.8. MS (ESI): ([M+H]+) 315.1.
1
2-Methyl-4-(4-fluorophenyl)-1-tosyl-4,5-dihydro-1H-imidazole (3b). Colorless gum; H NMR (500 MHz, CDCl3)
δ 7.76 (d, J 8.3 Hz, 2H, Ph in Ts), 7.37 (d, J 8.2 Hz, 2H, Ph in Ts), 7.05-7.01 (m, 2H, Ph), 6.98-6.95 (m, 2H, Ph),
5.01-4.98 (m, 1H, CH2), 4.20-4.16 (m, 1H, CH2), 3.61 (dd, J 9.9, 7.8 Hz, 1H, CHN=), 2.48 (s, 3H, Me in Ts), 2.421,
2.418 (ss, 3H, 2-Me). 13C NMR (125 MHz, CDCl3) δ 163.2, 161.3, 157.1, 145.0, 137.3, 135.1, 130.2, 129.8, 128.0,
128.1, 127.3, 127.1, 115.7, 115.5, 65.7, 55.6, 21.6, 16.8. MS (ESI): ([M+H]+) 333.1. HRMS (ESI) calculated for
C17H19FN2O2S ([M+H]+) 333.0995, found 333.1068. El. Anal. calculated for C17H18FN2O2S: C, 61.43; H, 5.16; N,
8.43; found C, 61.29; H, 5.45; N, 8.52.
2-Methyl-4-(4-chlorophenyl)-1-tosyl-4,5-dihydro-1H-imidazole (3c). White solid, mp 173-174 °C (lit. 170-172
1
°C)30; H NMR (500 MHz, CDCl3) δ 7.75 (d, J 8.3 Hz, 2H, Ph in Ts), 7.36 (d, J 8.1 Hz, 2H, Ph in Ts), 7.26-7.23 (m,
2H, Ph), 7.01-6.99 (m, 2H, Ph), 5.01-4.96 (m, 1H, CH2), 4.20-4.16 (m, 1H, CH2), 3.59 (dd, J 9.9, 7.8 Hz, 1H,
CHN=), 2.48 (s, 3H, Me in Ts), 2.413, 2.412 (ss, 3H, 2-Me,). 13C NMR (125 MHz, CDCl3) δ 157.0, 144.9, 140.1,
135.1, 133.5, 130.2, 128.8, 127.8, 127.2, 65.8, 55.4, 21.6, 16.8. MS (ESI): ([M+H]+) 349.1.
2-Methyl-4-(2-chlorophenyl)-1-tosyl-4,5-dihydro-1H-imidazole (3d). White solid, mp 133-135 °C (EtOAc-PE)29;
1H NMR (500 MHz, CDCl3) δ 7.74 (d, J 8.3 Hz, 2H, Ph in Ts), 7.36-7.33 (m, 3H, Ph and Ph in Ts), 7.23-7.16 (m, 2H,
Ph), 7.12-7.10 (m, 1H, Ph), 5.35-5.32 (m, 1H, CH2), 4.34-4.30 (m, 1H, CH2), 3.55 (dd, J 10.0, 7.7 Hz, 1H, CHN=),
2.452, 2.448 (ss, 6H, 2-Me). 13C NMR (125 MHz, CDCl3) δ 157.7, 144.8, 139.5, 135.3, 132.3, 130.1, 129.4, 128.7,
127.5, 127.2, 127.1, 63.7, 54.8, 21.6, 16.9. MS (ESI): ([M+H]+) 349.1.
1
2-Methyl-4-(p-tolyl)-1-tosyl-4,5-dihydro-1H-imidazole (3e). Colorless liquid29; H NMR (500 MHz, CDCl3) δ
7.76 (d, J 8.3 Hz, 2H, Ph in Ts), 7.36 (d, J 8.1 Hz, 2H, Ph in Ts), 7.08 (d, J 7.9 Hz, 2H, Ph), 6.95 (d, J 8.0 Hz, 2H, Ph),
4.98-4.95 (m, 1H, CH2), 4.19-4.15 (m, 1H, CH2), 3.62 (dd, J 9.7, 8.0 Hz, 1H, CHN= ), 2.48 (s, 3H, Me in Ts), 2.401,
2.398 (ss, 3H, 2-Me), 2.32 (s, 3H, CH3 in tolyl). 13C NMR (125 MHz, CDCl3) δ 156.2, 144.7, 138.6, 137.3, 135.2,
130.1, 129.3, 127.2, 126.3, 66.4, 55.5, 21.6, 21.1, 16.8. MS (ESI): ([M+H]+) 329.1.
1
2-Methyl-4-(4-bromophenyl)-1-tosyl-4,5-dihydro-1H-imidazole (3f). Colorless liquid30; H NMR (500 MHz,
CDCl3) δ 7.74 (d, J 8.3 Hz, 2H, Ph), 7.41-7.38 (m, 2H, Ph in Ts), 7.36 (d, J 8.2 Hz, 2H, Ph in Ts ), 6.96-6.93 (m, 2H,
Ph), 4.99-4.95 (m, 1H, CH2), 4.21-4.16 (m, 1H, CH2), 3.58 (dd, J 9.9, 7.8 Hz, 1H, CHN=), 2.48 (s, 3H, Me in Ts),
2.412, 2.409 (ss, 3H, 2-Me). 13C NMR (125 MHz, CDCl3) δ 157.0, 145.0, 140.6, 135.1, 131.8, 130.2, 128.1, 127.2,
121.6, 65.9, 55.4, 21.6, 16.8. MS (ESI): ([M+H]+) 395.0.
1
2,4-Dimethyl-4-phenyl-1-tosyl-4,5-dihydro-1H-imidazole (3g). White solid, mp 82-83°C (EtOAc-PE); H NMR
(500 MHz, CDCl3) δ 7.72 (d, J 8.3 Hz, 2H, Ph in Ts), 7.32-7.22 (m, 7H, Ph and Ph in Ts), 3.93 (d, J 9.6 Hz, 1H, CH2),
3.81 (d, J 9.6 Hz, 1H, CH2), 2.44 (s, 3H, Me in Ts), 2.39 (s, 3H, 2-Me), 1.47 (s, 3H, 4-Me). 13C NMR (125 MHz,
CDCl3) δ 154.2, 146.3, 144.6, 135.4, 130.0, 128.5, 127.1, 126.9, 125.0, 69.6, 61.1, 29.6, 21.6, 16.9. MS (ESI):
([M+H]+) 329.1. HRMS (ESI) calculated for C18H21N2O2S ([M+H]+): 329.1318, found: 329.1245. El. Anal.
calculated for C18H20N2O2S: C, 65.83; H, 6.14; N, 8.53; found C, 65.72; H, 6.37; N, 8.69.
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1
2-Methyl-4-n-octyl-1-tosyl-4,5-dihydro-1H-imidazole (3h). Viscous oil; H NMR (500 MHz, CDCl3) δ 7.75 (d, J
8.3 Hz, 2H, Ph), 7.36 (d, J 8.1 Hz, 2H, Ph), 3.86-3.81 (m, 2H, CH2N), 3.34 (dd, J 8.2, 6.3 Hz, 1H, CHN=), 2.46 (s, 3H,
Me in Ts), 2.29 (s, 3H, 2-Me), 1.29-1.23 (m, 14H, 7-CH2), 0.88 (t, J 7.0 Hz, 3H, CH3 in n-octyl). 13C NMR (125
MHz, CDCl3) δ 155.0, 144.6, 135.4, 130.0, 127.2, 63.6, 53.2, 35.8, 31.8, 29.5, 29.4, 29.2, 25.6, 22.6, 21.6, 16.8,
14.1; MS (ESI): ([M+H]+) 351.2. HRMS (ESI) calculated for C19H31N2O2S ([M+H]+) 351.2101, found 351.2028. El.
Anal. calculated for C19H30N2O2S: C, 65.11; H, 8.63; N, 7.99; found C, 65.32; H, 8.59; N, 8.21.
2-Methyl-1-tosyl-3a,4,5,6,7,7a-hexahydro-1H-benzimidazole (3i). White solid, mp 112-113 °C (lit. 115-117
1
°C)31; H NMR (500 MHz, CDCl3) δ 7.71 (d, J 8.3 Hz, 2H, Ph), 7.36 (d, J 8.2 Hz, 2H, Ph), , 3.13-3.07 (m, 1H,
CHNTs), 2.88-2.82 (m, 1H, CH2), 2.57-2.54 (m, 1H, CH2), 2.46 (s, 3H, Me in Ts), 2.32, 2.31 (ss, 3H, 2-Me), 2.26-
2.23 (m, 1H, CH2), 1.88-1.78 (m, 2H, CH2), 1.68-1.60 (m, 1H, CHN=), 1.37-1.22 (m, 3H, CH2). 13C NMR (125 MHz,
CDCl3) δ 158.2, 144.6, 135.0, 130.0, 127.4, 70.2, 69.3, 30.56, 30.55, 25.0, 24.6, 21.6, 17.9. MS (ESI): ([M+H]+)
293.1.
1
2,4-Diphenyl-1-tosyl-4,5-dihydro-1H-imidazole (3j). White solid, mp 164-165 °C (EtOAc-PE)29; H NMR (500
MHz, CDCl3) δ 7.80-7.78 (m, 2H, 2-Ph), 7.56-7.53 (m, 1H, Ph in Ts), 7.47-7.41 (m, 4H, Ph in Ts and 2-Ph), 7.25-
7.21 (m, 5H, Ph in Ts and 4-Ph), 6.70-6.98 (m, 2H, 4-Ph), 5.03-4.99 (m, 1H, CHN=), 4.48-4.43 (m, 1H, CH2), 3.90-
3.86 (m, 1H, CH2), 2.44 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 159.9, 144.7, 141.5, 134.5, 131.2, 130.1,
129.9, 129.8, 128.6, 127.7, 127.6, 127.4, 126.4, 67.8, 56.9, 21.6. MS (ESI): ([M+H]+) 377.1.
2-Benzyl-4-phenyl-1-tosyl-4,5-dihydro-1H-imidazole (3k). Colorless liquid29; 1H NMR (500 MHz, CDCl3) δ 7.43-
7.40 (m, 4H, Ph in Ts), 7.38-7.25 (m, 6H, 4-Ph and 2-Ph), 7.21-7.18 (m, 2H, 2-Ph), 7.04-7.7.03 (m, 2H, 2-Ph),
5.08-5.05 (m, 1H, CHN=), 4.20-4.14 (m, 3H, CH2 and CH2 in benzyl), 3.62-3.59 (m, 1H, CH2 in benzyl), 2.42 (s, 3H,
Me). 13C NMR (125 MHz, CDCl3) δ 158.3, 144.5, 141.7, 135.4, 134.9, 129.9, 129.4, 128.7, 128.5, 127.6, 127.3,
127.0, 126.4, 66.9, 55.5, 35.7, 21.5. MS (ESI): ([M+H]+) 391.1.
2-(1-Naphthalenyl)-4-phenyl-1-tosyl-4,5-dihydro-1H-imidazole (3l). White solid, mp 152-153 °C (EtOAc-PE);
1H NMR (500 MHz, CDCl3) δ 7.98 (d, J 8.2 Hz, 1H), 7.91 (d, J 8.4 Hz, 1H), 7.86 (d, J 8.1 Hz, 1H), 7.73 (d, J 6.8 Hz,
1H), 7.56-7.52 (m, 1H), 7.51-7.47 (m, 1H), 7.43-7.40 (m, 1H), 7.37-7.23 (m, 7H), 7.02 (d, J 8.1 Hz, 2H, Ph), 5.36
(dd, J 9.9, 8.8 Hz, 1H, CH2), 4.62-4.58 (m, 1H, CH2), 4.05 (dd, J 10.5, 8.4 Hz,1H, CHN=), 2.34 (s, 3H, Me in Ts). 13C
NMR (125 MHz, CDCl3) δ 157.7, 144.5, 141.6, 134.6, 133.2, 131.4, 130.8, 129.4, 128.8, 128.3, 127.7, 127.6,
127.3, 126.7, 126.5, 125.9, 125.2, 124.4, 68.2, 55.8, 21.5. MS (ESI): ([M+H]+) 427.2; HRMS (ESI) calculated for
C26 H23N2O2S ([M+H]+) 427.1494, found 427.1475. El. Anal. calculated for C26H22N2O2S: C, 73.21; H, 5.20; N,
6.57; found C, 73.11; H, 5.36; N, 6.79.
2-(p-Benzonitrile)-4-phenyl-1-tosyl-4,5-dihydro-1H-imidazole (3m). White solid, mp 151-153 °C (EtOAc-PE);
1H NMR (500 MHz, CDCl3) δ 7.92 (d, J 8.3 Hz, 2H, 2-Ph), 7.75 (d, J 8.3 Hz,, 2H, Ph in Ts), 7.42 (d, J 8.2 Hz, 2H, Ph
in Ts), 7.27-7.23 (m, 5H, 4-Ph), 6.97-6.95 (m, 2H, 2-Ph), 5.07-5.03 (m, 1H, CH2), 4.47-4.43 (m, 1H, CH2), 3.88
(dd, J 11.4, 8.1 Hz, 1H, CHN=), 2.46 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 158.4 145.2, 140.9, 134.7, 134.1,
132.8, 131.6, 130.5, 130.0, 128.7, 127.7, 127.6, 126.3, 118.2, 114.7, 68.4, 56.8, 21.6. MS (ESI): ([M+H]+) 402.1;
HRMS (ESI) calculated for C23H20N3O2S ([M+H]+) 402.1259, found 402.1271. El. Anal. calculated for C23H19N3O2S:
C, 68.81; H, 4.77; N, 10.47; found C, 68.92; H, 4.78; N, 10.32.
1
4-Phenyl-2-(p-tolyl)-1-tosyl-4,5-dihydro-1H-imidazole (3n). Colorless liquid; H NMR (500 MHz, CDCl3) δ 7.71
(d, J 8.1 Hz, 2H, Ph in Ts), 7.43 (d, J 8.3 Hz, 2H, Ph in Ts), 7.28-7.26 (m, 2H, 2-Ph), 7.24-7.20 (m, 5H, 4-Ph), 6.98-
6.96 (m, 2H, 2-Ph), 4.96 (dd, J 9.5, 8.4 Hz, 1H, CHN=), 4.43 (dd, J 11.4, 10.0 Hz, 1H, CH2), 3.85 (dd, J 11.5, 8.1 Hz,
1H, CH2), 2.45(s, 3H, Me in Ts), 2.44 (s, 3H, Me in tolyl). 13C NMR (125 MHz, CDCl3) δ 160.0, 144.6, 141.7, 141.6,
134.5, 129.9, 129.8, 128.9, 128.54, 128.45, 127.6, 127.4, 127.3, 127.2, 127.0, 126.3, 67.8, 56.9, 21.63, 21.59.
MS (ESI): ([M+H]+) 391.2; HRMS (ESI) calculated for C23H23N2O2S ([M+H]+) 391.1492, found 391.1475. El. Anal.
calculated for C23H22N2O2S: C, 70.74; H, 5.68; N, 7.17; found C, 70.58; H, 5.77; N, 7.33.
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General experimental procedure for synthesis of 5a-q
An 25 mL oven-dried Schlenk tube was equipped with a stirring bar, an aziridine 1 (0.5 mmol), PhN2BF4 (0.6
mmol, 1.2 eq), and Ru(bpy)3(BF4)2 (0.005 mmol, 1 mol%). The mixture was degassed by using standard Schlenk
techniques with the oil pump. Then isothiocyanate 4 (1.5 mmol, 3 eq), and DCE (3 mL) were injected into the
reaction tube. The reaction mixture was allowed to stir for 10 h under irradiation of 45 W CFL (FSL, YPZ220/45-
S, Luminous Flux (2580Lm) at rt, the distance from the light bulb to the reaction vessel being about 5 cm. After
the reaction was complete (TLC), the tot he mixture was added distilled water (10 mL) and product extracted
with CH2Cl2 (3 × 30 ml) in separatory funnel. The combined the organic layers were dried (Na2SO4), the organic
solution was concentrated under reduced pressure using a rotary evaporator and the residue purified by
column chromatography on silica gel (200-300 mesh) (PE:EtOAc = 5-10:1) to give the pure product 5.
1
N,5-Diphenyl-3-tosylthiazolidin-2-imine (5a). White solid, mp 129-131 °C (lit. 132-133 °C)32; H NMR (500
MHz, CDCl3) δ 8.00 (d, J 8.4 Hz, 2H, Ph in Ts), 7.38-7.33 (m, 7H, Ph in Ts and 5-Ph), 7.28-7.26 (m, 2H, PhN=),
7.08 (t, J 7.4 Hz,1H, PhN=), 6.81-6.79 (m, 2H, PhN=), 4.82 (dd, J 8.6, 6.5 Hz, 1H, CH2), 4.62 (dd, J 10.4, 6.5 Hz, 1H,
CH2), 4.07 (dd, J 10.4, 8.6 Hz, 1H, CHS), 2.50 (s, 3H, -Me). 13C NMR (125 MHz, CDCl3) δ 152.1, 150.1, 144.9,
136.5, 134.7, 129.24, 129.20, 129.05, 128.97, 128.8, 127.5, 124.3, 120.8, 56.8, 47.0, 21.7. MS (ESI): ([M+H]+)
409.1.
N-Phenyl-5-(4-fluorophenyl)-3-tosylthiazolidin-2-imine (5b). Viscous liquid33; 1H NMR (500 MHz, CDCl3) δ 8.00
(d, J 8.3 Hz, 2H, Ph in Ts), 7.38-7.33 (m,4H, Ph in Ts and 5-Ph), 7.29-7.26 (m, 2H, PhN=), 7.10-7.07 (m, 1H,
PhN=), 7.05-7.02 (m, 2H, 5-Ph), 6.80-6.79 (m, 2H, PhN=), 4.79 (dd, J 8.1, 6.5 Hz, 1H, CH2), 4.58 (dd, J 10.5, 6.4
Hz, 1H, CH2), 4.04 (dd, J 10.3, 8.3 Hz, 1H, CHS), 2.50 (s, 3H, -Me). 13C NMR (125 MHz, CDCl3) δ 163.7, 161.7,
151.8, 150.0, 145.0, 134.6, 132.5, 129.3, 129.24, 129.21, 129.15, 129.0, 124.4, 120.7, 116.1, 115.9, 56.8, 46.2,
21.7. MS (ESI): ([M+H]+) 427.1; HRMS (ESI) calculated for C22H20FN2O2S2 ([M+H]+) 427.0945, found 427.0953.
1
N-Phenyl-5-(4-methylphenyl)-3-tosylthiazolidin-2-imine (5c). White solid, mp 115-117 °C (EtOAc-PE)34; H
NMR (500 MHz, CDCl3) δ 8.01-7.99 (m, 2H, Ph in Ts), 7.37 (d, J 8.0 Hz, 2H, Ph in Ts), 7.28-7.24 (m, 4H, PhN= and
5-Ph), 7.15 (d, J 8.0 Hz, 2H, 5-Ph), 7.10-7.06 (m, 1H, PhN=), 6.81-6.79 (m, 2H, PhN=), 4.79 (dd, J 8.8, 6.5 Hz, 1H,
CH2), 4.60 (dd, J 10.4, 6.4 Hz, 1H, CH2), 4.03 (dd, J 10.4, 8.8 Hz, 1H, CHS), 2.50 (s, 3H, Me in Ts), 2.35 (s, 3H,
Me). 13C NMR (125 MHz, CDCl3) δ 152.3, 150.1, 144.9, 138.7, 134.7, 133.4, 129.7, 129.2, 129.1, 128.9, 127.4,
124.3, 120.8, 56.8, 46.9, 21.7, 21.1. MS (ESI): ([M+H]+) 423.1; HRMS (ESI) calculated for C23H23N2O2S2 ([M+H]+)
423.1195, found 423.1195.
1
N-Phenyl-5-(2-chlorophenyl)-3-tosylthiazolidin-2-imine (5d). Viscous yellow liquid34; H NMR (500 MHz,
CDCl3) δ 7.98 (d, J 8.3 Hz, 2H, Ph in Ts), 7.59-7.57 (m, 1H, 5-Ph), 7.42-7.36 (m, 3H, Ph in Ts and PhN=), 7.30-7.27
(m, 4H, PhN= and 5-Ph), 7.09 (t, J 7.4 Hz, 1H, PhN=), 6.81-6.79 (m, 2H, PhN=), 5.21-5.19 (m, 1H, CH2), 4.52 (dd,
J 10.6, 6.5 Hz, 1H, CH2), 4.29 (dd, J 10.6, 5.4 Hz, 1H, CHS), 2.50 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 151.7,
150.0, 145.0, 135.4, 134.6, 133.5, 129.9, 129.7, 129.24, 129.19, 129.0, 128.0, 127.6, 124.4, 120.7, 55.2, 43.5,
42.7, 21.7. MS (ESI): ([M+H]+) 443.1; HRMS (ESI) calculated for C22H20ClN2O2S2 ([M+H]+) 443.0649, found
443.0652.
1
N-Phenyl-5-(4-bromophenyl)-3-tosylthiazolidin-2-imine (5e). Colorless liquid34; H NMR (500 MHz, CDCl3) δ
7.98 (d, J 8.3 Hz, 2H, 5-Ph), 7.49-7.46 (m, 2H, Ph in Ts), 7.37 (d, J 8.2 Hz, 2H, Ph in Ts), 7.30-7.22 (m, 4H, 5-Ph
and PhN=), 7.09 (t, J 7.4 Hz, 1H, PhN=), 6.79 (d, J 7.4 Hz, 2H, PhN=), 4.76-4.73 (m, 1H, CH2), 4.58 (dd, J 10.4, 6.4
Hz, 1H, CH2), 4.05 (dd, J 10.4, 7.9 Hz, 1H, CHS), 2.50 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 151.6, 149.9,
145.0, 135.9, 134.6, 132.2, 129.3, 129.2, 129.0, 124.5, 122.7, 120.7, 56.6, 46.3, 21.7. MS (ESI): ([M+H]+) 489.0;
HRMS (ESI) calculated for C22H20BrN2O2S2 ([M+H]+) 487.0144, found 487.0162.
1
N-(4-Methoxyphenyl)-5-phenyl-3-tosylthiazolidin-2-imine (5f). Yellow liquid34; H NMR (500 MHz, CDCl3) δ
8.00 (d, J 8.2 Hz, 2H, Ph in Ts), 7.37-7.34 (m, 7H, Ph in Ts, PhN= and 5-Ph), 6.82-6.77 (dd, J 8.8, 8.9 Hz, 4H, PhN=
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and 5-Ph), 4.81 (dd, J 8.3, 6.6 Hz, 1H, CH2), 4.60 (dd, J 10.3, 6.4 Hz, 1H, CH2), 4.06 (dd, J 10.2, 8.7 Hz, 1H, CHS),
3.78 (s, 3H, OMe), 2.49 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 156.6, 151.7, 144.8, 143.4, 136.7, 134.9,
129.2, 129.0, 128.7, 127.5 121.9, 114.2, 56.7, 55.4, 47.0, 21.7. MS (ESI): ([M+H]+) 439.4; HRMS (ESI) calculated
for C23H23N2O3S2 ([M+H]+) 439.1145, found 439.1162.
1
N-(4-Fluorophenyl)-5-phenyl-3-tosylthiazolidin-2-imine (5g). Colorless liquid34; H NMR (500 MHz, CDCl3) δ
7.98 (d, J 8.3 Hz, 2H, Ph in Ts), 7.38-7.34 (m, 7H, Ph in Ts and 5-Ph), 6.98-6.94 (m, 2H, PhN=), 6.778-6.75 (m, 2H,
PhN=), 4.82 (dd, J 8.5, 6.5 Hz, 1H, CH2), 4.61 (dd, J 10.4, 6.5 Hz, 1H, CH2), 4.08 (dd, J 10.4, 8.5 Hz, 1H, CHS), 2.50
(s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 160.7, 158.8, 152.4, 146.1, 145.0, 144.5, 136.4, 134.7, 129.3, 129.2,
129.1, 128.8, 127.5, 122.2, 122.1, 115.7, 115.6, 56.8, 47.1, 21.7. MS (ESI): ([M+H]+) 427.2; HRMS (ESI)
calculated for C22H20FN2O2S2 ([M+H]+) 427.0945, found 427.0964.
1
N-(2-Methylphenyl)-5-phenyl-3-tosylthiazolidin-2-imine (5h). Viscous liquid; H NMR (500 MHz, CDCl3) δ 7.98
(d, J 8.3 Hz, 2H, Ph in Ts), 7.39-7.34 (m, 7H, Ph in Ts and 5-Ph), 7.14-7.08 (m, 2H, 2-Ph), 7.01-6.98 (m, 1H, 2-Ph),
6.69 (d, J 7.7 Hz, 1H, 2-Ph), 4.82 (dd, J 8.2, 6.5 Hz, 1H, CH2), 4.65 (dd, J 10.4, 6.4 Hz, 1H, CH2), 4.14 (dd, J 10.3,
8.3 Hz, 1H, CHS), 2.48 (s, 3H, Me in Ts), 1.95 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 151.7, 149.2, 144.7,
136.8, 135.2, 130.3, 129.4, 129.3, 129.0, 128.9, 128.7, 127.4, 126.3, 124.3, 119.6, 57.0, 46.8, 21.6, 17.4. MS
(ESI): ([M+H]+) 423.1; HRMS (ESI) calculated for C23H23N2O2S2 ([M+H]+) 423.1195, found 423.1184. El. Anal.
calculated for C23H22N2O2S2: C, 65.38; H, 5.25; N, 6.63; found C, 65.29; H, 5.37; N, 6.89.
1
N-(4-Bromophenyl)-5-phenyl-3-tosylthiazolidin-2-imine (5i). Viscous liquid; H NMR (500 MHz, CDCl3) δ 7.97
(d, J 8.2 Hz, 2H, Ph in Ts), 7.43-7.34 (m, 9H, Ph in Ts, 5-Ph and 2-Ph), 6.68 (d, J 8.6 Hz, 2H, 2-Ph), 4.83 (dd, J 8.5,
6.5 Hz, 1H, CH2), 4.62 (dd, J 10.4, 6.5 Hz, 1H, CH2), 4.08 (dd, J 10.3, 8.6 Hz, 1H, CHS), 2.50 (s, 3H, Me). 13C NMR
(125 MHz, CDCl3) δ 152.8, 148.9, 145.1, 136.3, 134.6, 132.0, 129.3, 129.14, 129.11, 128.9, 127.5, 122.6, 117.4,
56.8, 47.1, 21.7. MS (ESI): ([M+H]+) 487.0; HRMS (ESI) calculated for C22H20BrN2O2S2 ([M+H]+) 487.0144, found
487.0124. El. Anal. calculated for C22H19BrN2O2S2: C, 54.21; H, 3.93; N, 5.75; found C, 54.25; H, 3.68; N, 5.68.
1
N-(4-Chlorophenyl)-5-phenyl-3-tosylthiazolidin-2-imine (5j). Viscous liquid; H NMR (500 MHz, CDCl3) δ 7.97
(d, J 8.3 Hz, 2H, Ph in Ts), 7.38-7.33 (m, 7H, Ph in Ts, 5-Ph and 2-Ph), 7.24-7.22 (m, 2H, 5-Ph), 6.75-6.72 (m, 2H,
2-Ph), 4.83 (dd, J 8.5, 6.5 Hz, 1H, CH2), 4.62 (dd, J 10.3, 6.5 Hz, 1H, CH2), 4.08 (dd, J 10.4, 8.5 Hz, 1H, CHS), 2.50
(s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 152.8, 148.5, 145.1, 136.3, 134.6, 129.6, 129.3, 129.14, 129.10,
129.05, 128.9, 127.5, 122.2, 56.8, 47.1, 21.7. MS (ESI): ([M+H]+) 443.1; HRMS (ESI) calculated for
C22H20ClN2O2S2 ([M+H]+) 443.0649, found 443.0635. El. Anal. calculated for C22H19ClN2O2S2: C, 59.65; H, 4.32; N,
6.32; found C, 59.38; H, 4.60; N, 6.34.
N-(Isopropyl)-5-phenyl-3-tosylthiazolidin-2-imine (5k). White solid, mp 134-136 °C (EtOAc-PE)35; 1H NMR (500
MHz, CDCl3) δ 7.93 (d, J 8.3 Hz, 2H, Ph in Ts), 7.39-7.34 (m, 5H, Ph in Ts and 5-Ph), 7.31-7.28 (m, 2H, 5-Ph), 4.78
(dd, J 8.5, 6.4 Hz, 1H, CH2), 4.47 (dd, J 10.3, 6.3 Hz, 1H, CH2), 3.87 (dd, J 10.2, 8.7 Hz, 1H, CHS), 3.11-3.07 (m, 1H,
CH in isopropyl), 2.47 (s, 3H, Me in Ts), 1.14 (d, J 6.2 Hz, 3H, Me), 1.08 (d, J 6.2 Hz, 3H, Me). 13C NMR (125 MHz,
CDCl3) δ 147.2, 144.4, 137.0, 134.9, 129.3, 129.0, 128.9, 128.6, 127.6, 57.7, 56.0, 46.9, 23.6, 23.4, 21.7. MS
(ESI): ([M+H]+) 375.1;
1
N-Cyclohexyl-5-phenyl-3-tosylthiazolidin-2-imine (5l). White solid, mp 152-154 °C (EtOAc-PE)34; H NMR (500
MHz, CDCl3) δ 7.93 (d, J 8.3 Hz, 2H, Ph in Ts), 7.39-7.28 (m, 7H, Ph in Ts and 5-Ph), 4.78 (dd, J 8.5, 6.3 Hz, 1H,
CH2), 4.47 (dd, J 10.3, 6.3 Hz, 1H, CH2), 3.89 (dd, J 10.2, 8.5 Hz, 1H, CHS), 2.79-2.77 (m, 1H, CH in cyclohexyl),
2.46 (s, 3H, Me), 1.74-1.56 (m, 6H, cyclohexyl), 1.30-1.24 (m, 4H, cyclohexyl). 13C NMR (125 MHz, CDCl3) δ
147.1, 144.3, 137.1, 135.0, 129.2, 129.0, 128.9, 128.6, 127.6, 56.0, 46.9, 33.5, 33.3, 25.7, 24.4, 21.7. MS (ESI):
([M+H]+) 415.3; HRMS (ESI) calculated for C22H27N2O2S2([M+H]+) 415.1508, found 415.1510.
1
N-(n-Butyl)-5-phenyl-3-tosylthiazolidin-2-imine (5m). Viscous liquid34; H NMR (500 MHz, CDCl3) δ 7.92-7.90
(m, 2H, Ph in Ts), 7.40-7.34 (m, 5H, Ph in Ts and 5-Ph), 7.31 (d, J 8.3 Hz, 2H, 5-Ph), 4.79 (dd, J 8.4, 6.3 Hz, 1H,
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CH2), 4.50 (dd, J 10.3, 6.3 Hz, 1H, CH2), 3.93 (dd, J 10.2, 8.4 Hz, 1H, CHS), 3.24-3.19 (m, 1H, CH2 in butyl), 3.11-
3.07 (m, 1H, CH2 in butyl), 2.46 (s, 3H, Me in Ts), 1.53-1.49 (m, 2H, CH2 in butyl), 1.22-1.17 (m, 2H, CH2 in
13
butyl), 0.88 (t, J 7.4 Hz, 3H, Me). C NMR (125 MHz, CDCl3) δ 149.3, 144.4, 137.0, 135.1, 129.1, 129.0, 128.6,
127.6, 56.3, 55.9, 46.9, 32.8, 21.6, 20.4, 13.9. MS (ESI): ([M+H]+) 389.3; HRMS (ESI) calculated for C20H25N2O2S2
([M+H]+) 389.1352, found 389.1346.
N-Benzyl-5-phenyl-3-tosylthiazolidin-2-imine (5n). White solid, mp 120-122 °C (EtOAc-PE); 1H NMR (500 MHz,
CDCl3) δ 7.86 (d, J 8.2 Hz, 2H, Ph in Ts), 7.42-7.35 (m, 5H, Ph in benzyl), 7.29-7.24 (m, 3H, Ph in Ts and 5-Ph),
7.19 (d, J 8.1 Hz, 2H, 5-Ph), 7.16-7.14 (m, 2H, 5-Ph), 4.86 (dd, J 8.2, 6.5 Hz, 1H, CH2), 4.56 (dd, J 10.3, 6.3 Hz, 1H,
CH2), 4.44 (d, J 15.2 Hz, 1H, CHS), 4.36 (d, J 15.2 Hz, 1H, CH2-Ph), 4.01 (dd, J 10.2, 8.4 Hz, 1H, CH2-Ph), 2.43 (s,
3H, Me). 13C NMR (125 MHz, CDCl3) δ 151.2, 144.4, 139.4, 136.8, 135.1, 129.2, 129.1, 129.0, 128.8, 128.1,
127.6, 127.5, 126.6, 59.4, 56.5, 47.2, 21.6. MS (ESI): ([M+H]+) 423.3; HRMS (ESI) calculated for C23H23N2O2S2
([M+H]+) 423.1195, found 423.1195. El. Anal. calculated for C23H22N2O2S2: C, 65.38; H, 5.25; N, 6.63 found C,
65.41; H, 5.32; N, 6.49.
1
N-(α-Methylbenzyl)-5-phenyl-3-tosylthiazolidin-2-imine (5o). Viscous liquid; H NMR (500 MHz, CDCl3) δ 7.96
(d, J 8.3 Hz, 1/4×2H), 7.90 (d, J 8.2 Hz, 3/4×2H), 7.40-7.32 (m, 5H), 7.30-7.20 (m, 5+1/4×2H), 7.18-7.17 (m,
3/4×2H), 4.85-4.75 (m, 1H), 4.55-4.49 (m, 1H), 4.14-4.10 (m, 1H), 3.98-3.92 (m, 1H), 2.46 (s, 1/4×3H), 2.44 (s,
3/4×3H), 1.43 (d, J 6.5 Hz, 3/4×3H), 1.38 (d, J 6.5 Hz, 1/4×3H). 13C NMR (125 MHz, CDCl3) δ 148.9, 145.1, 145.0,
144.4, 144.3, 136.9, 136.7, 135.3, 129.2, 129.05, 129.00, 128.9, 128.7, 128.6, 128.2, 128.1, 127.6, 127.5, 126.6,
126.57, 126.5, 126.4, 65.5, 65.4, 56.2, 56.0, 47.3, 47.1, 25.1, 24.6, 21.6. MS (ESI): ([M+H]+) 437.1; HRMS (ESI)
calculated for C24H25N2O2S2 ([M+H]+) 437.1352, found 437.1350. El. Anal. calculated for C24H24N2O2S2: C, 66.03;
H, 5.54; N, 6.42 found C, 65.88; H, 5.31; N, 6.25.
N-(α-Naphthyl)-5-phenyl-3-tosylthiazolidin-2-imine (5p). Yellow solid, mp 133-135 °C (EtOAc-PE)33; δ 8.03 (d,
J 8.3 Hz, 2H, naphthyl), 7.80 (d, J 8.2 Hz, 1H, Ph in Ts), 7.58 (d, J 8.3 Hz, 1H, Ph in Ts), 7.49-7.45 (m, 2H), 7.39-
7.30 (m, 9H, 5-Ph, Ph in Ts and naphthyl), 6.87 (d, J 7.1 Hz, 1H, 5-Ph), 4.84 (dd, J 8.3, 6.5 Hz, 1H, CH2), 4.72 (dd,
J 10.4, 6.4 Hz, 1H, CH2), 4.21 (dd, J 10.3, 8.4 Hz, 1H, CHS), 2.52 (s, 3H, Me). 13C NMR (125 MHz, CDCl3) δ 152.4,
146.9, 144.8, 136.6, 135.4, 134.1, 129.5, 129.13, 129.05, 128.8, 127.7, 127.5, 126.2, 125.7, 125.3, 124.5, 123.9,
114.7, 56.9, 46.9, 21.7. MS (ESI): ([M+H]+) 459.1; HRMS (ESI) calculated for C26H23N2O2S2([M+H]+) 459.1195,
found 459.1203.
N,5-Diphenyl-3-(phenylsulfonyl)thiazolidin-2-imine (5q). Viscous liquid34; 1H NMR (500 MHz, CDCl3) δ 8.12 (d,
J 7.5 Hz, 2H, Ph in Ts), 7.71 (t, J 7.5 Hz, 1H, Ph in Ts), 7.59 (t, J 7.8 Hz, 2H, Ph in Ts), 7.37-7.34 (m, 5H, 5-Ph),
7.29-7.25 (m, 2H, PhN=), 7.08 (t, J 7.4 Hz, 1H, PhN=), 6.78 (d, J 7.6 Hz, 2H, PhN=), 4.83 (dd, J 8.4, 6.5 Hz, 1H,
CH2), 4.64 (dd, J 10.4, 6.4 Hz, 1H, CH2), 4.11 (dd, J 10.4, 8.5 Hz, 1H, CHS). 13C NMR (125 MHz, CDCl3) δ 152.1,
149.9, 137.7, 136.5, 133.9, 129.14, 129.07, 128.98, 128.8, 128.6, 127.5, 124.4, 120.7, 56.8, 47.1. MS (ESI):
([M+H]+) 395.1.
Acknowledgements
This work was supported by the Natural Science Foundation of Zhejiang Provincial (LY15B020004), the Natural
Science Foundation of China (21602197) and the Open Research Fund Program of Collaborative Innovation
Center of Membrane Separation and Water Treatment (2016YB07).
Supplementary Material
Copies of 1H and 13C NMR spectra for all isolated compounds.
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