Pd-catalyzed direct c-h bond sulfonylation of azobenzenes with arylsulfonyl chlorides

Article abstract of DOI:10.1021/jo502451k

Pd(II)-catalyzed C-H sulfonylation of azobenzenes with arylsulfonyl chlorides has been developed. The sulfonylazobenzenes were obtained in moderate to excellent yields for 28 examples. This protocol features high efficiency, wide functional group tolerance, and atom economy.

Full text of DOI:10.1021/jo502451k

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Article
Pd-catalyzed Direct C-H Bond Sulfonylation
of Azobenzenes with Arylsulfonyl Chlorides
Duo Zhang, Xiuling Cui, Qianqian Zhang, and Yangjie Wu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo502451k • Publication Date (Web): 05 Jan 2015
Downloaded from http://pubs.acs.org on January 6, 2015
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Pd-catalyzed Direct C-H Bond Sulfonylation of
Azobenzenes with Arylsulfonyl Chlorides
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Duo Zhang,a Xiuling Cui,*a,b Qianqian Zhanga and Yangjie Wu*a
a Department of Chemistry, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key
Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, P.
R. China, Email address: cuixl@zzu.edu.cn; wyj@zzu.edu.cn
b
Xiamen Key Laboratory of Ocean and Gene Drugs, School of Biomedical Sciences, Institute of
Molecular Medicine of Huaqiao University & Engineering Research Centre of Molecular Medicine of
Chinese Education Ministry, Fujian, Xiamen 361021, P. R. China
ABSTACT:
Pd (II) catalyzed CꢀH sulfonylation of azobenzenes with arylsulfonyl chlorides has been developed. The
sulfonylazobenzenes were obtained in moderate to excellent yields for 28 examples. This protocol features
with high efficiency, wide functional group tolerance and atomic economy.
INTRUDUCTION:
The sulfonylazobenzenes are essential components in photosensitive composition,1a color filter,1a chemical
indicator,1b,1c Raman spectroscopy1d and dye.1aꢀ1h They also exist widely in pharmaceuticals1iꢀ1m and natural
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products1n. Two examples are exemplified in Figure 1. Compound A1o and Compound B1p exhibit in
oxidants,1q polymer inhibitors and stabilizers.1r Compound C is used as dye in the textile industry due to its
excellent color stability, high reactivity and ecofriend.1s
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Figure 1. Examples Illustrating the Importance of orthoꢀSulfonylation Azobenzenes
However, building such a structure remains largely unexploited. To the best of our knowledge, only two
procedures were reported. In 1964, Bauer2 obtained the sulfonylazobenzene from diazosulphone, which was
synthesized via the diazotization of 2ꢀaminoazobenzene and sequential sulfonation with benzenesulphinic
acid. Moreover, only sulfonylazobenzene was synthesized. Alexander1h achieved sulfonylazobenzene
derivatives through multiꢀstep reactions, involving diazotization of anilines, orthoꢀsulfonylation and
coupling reaction. These procedures suffered from tedious reaction steps and harsh reaction conditions.
During the past few years, transition metalꢀcatalyzed sulfonylation reactions were proved to a powerful
strategy in organic synthesis for sulfonylated products. These highly efficient catalyst systems have been
developed using sodium benzenesulfinate, thiol
reagent.3
, sulfonylhydrazide, sulfuryl chloride, etc as a sulfonylation
A
rylsulfuryl chlorides were outstanding due to its being easily availability and safety to be handled.
Considering the importance of sulfonylazobenzenes and the drawbacks of the existing methods, the
exploration and development of an efficient and highly regioselective protocol from easily available starting
materials to construct such a desirable frame work is highly desired. Recently, azo as a directing group to
synthesize azobenzene derivatives have attracted a great attention. The transitionꢀmetalꢀcatalyzed
orthoꢀhalogenation,4
orthoꢀacylation,5
orthoꢀarylation,6
orthoꢀalkoxylation,7
orthoꢀacyloxyation8
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orthoꢀamidation9 and cyclization10 of azobenzenes have been developed recently. Herein, we disclose a
simple and efficient procedure for various orthoꢀsulfonylation azobenzenes via palladiumꢀcatalyzed direct
crossꢀcoupling of azobenzenes with aryl sulfonyl chlorides.
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RESULTS AND DISCUSSION:
Initially, the crossꢀcoupling of azobenzene (1a) with p-tolysulfonylchloride (2a) was chosen as a model
reaction to optimize the reaction parameters. The reaction gave the desired crossꢀcoupling product 3a in 48%
yield using Pd(OAc)2 (10 mol%) as a catalyst in the presence of K2S2O8 (1.1 equiv) under air for 24 hours
(entry 1, Table 1). Inspired by this result, various catalysts, such as Pd(TFA)2, Pd(CH3CN)2Cl2 and PdCl2
were screened (entries 1ꢀ4, Table 1). Pd(OAc)2 was proved to be best palladium reagent (entry 1,Table 1).
Among the oxidants examined, including Ag2O, AgCl, AgOTf, K2S2O8 and Ag2CO3, K2S2O8 was the best
choice (entry 1 vs entries 5ꢀ8, Table 1). The yield of 3a could reach 70% and 79% when the temperature of
oil bath increased to 110 ˚C and 120 ˚C, respectively (entries 9ꢀ10, Table 1). Higher temperature disfavored
this transformation (entry 11, Table 1). No desired product was observed in the absence of the catalyst (entry
12, Table 1). The solvents, such as 1, 4ꢀdioxane, toluene, THF, DMF, DMSO and DCE were screened. DCE
was found to be superior to others (entries 10, 13ꢀ17, Table 1). Prolonging the reaction time to 36 hours, the
85% yield of 3a was achieved (entry 18, Table 1). When the catalyst loading was reduced to 5 mol% and the
reaction time was 36 h, the product 3a was obtained in 90% yield (entry 19, Table 1). When increasing the
loading of pꢀtolylsulfonyl chloride (2a) to 4 equiv, the yield was not improved significantly (entry 20, Table
1). However, reducing its loading resulted in decreasing the yield of the desired product. The optimized
reaction conditions were identified as follows: Pd(OAc)2 (5 mol%), K2S2O8 (1.1 equiv), ratio of 1a and 2a is
1: 3 in DCE at 120 ˚C oil bath under air for 36 hours (entry 19, Table 1). The structure of 3a was confirmed
by single crystal Xꢀray diffraction11, and was shown in Figure 1 in the Supporting Information
.
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Table 1. Optimizing Reaction Conditions for PdꢀCatalyzed orthoꢀSulfonylation of Azobenzene with
pꢀTolylsulfonyl Chlorides.a
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entry
1
PdX2
oxidant
K2S2O8
K2S2O8
K2S2O8
K2S2O8
Ag2O
solvent yield(%)b
Pd(OAc)2
Pd(TFA)2
Pd(CH3CN)2Cl2
PdCl2
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
48
2
35
3
15
4
Trace
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5
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
ꢀꢀ
6
AgCl
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AgOTf
Ag2CO3
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
5
8
Trace
70
9c
10d
11e
12d
13d
14d
79
65
n.r.
Pd(OAc)2
Pd(OAc)2
Dioxane 25
Toluene 72
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15d
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
THF
Nr
16d
DMF
DMSO
DCE
DCE
DCE
trace
N.R
85
17d
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18d,f
19d,f,g
90
20d,f,g,h Pd(OAc)2
91
aReaction conditions: azobenzene (1a) (0.2 mmol),
pꢀtolylsulfonyl chloride (2a) (3.0 equiv), catalyst (10 mol%),
º
oxidant (1.1 equiv), solvent (2.0 mL), under air, 100 C, 24 h.
bIsolated yield based on 1a. c110 ºC. 120 ºC. e130 ºC. f36 h.
d
gPd(OAc)2 (5 mol%), h2a (4.0 equiv)
With the optimized reaction conditions in the hand, the scope of the arylsulfonyl chlorides was firstly
examined (Scheme 1). These results demonstrated that the reactions of arylsulfonyl chlorides bearing
electronꢀdonating or electronꢀwithdrawing groups with azobenzene(1a) could proceed smoothly, affording
the orthoꢀsulfonylation azobenzenes in moderate to excellent yields (3aꢀ3m Scheme 1). When arylsulfonyl
chlorides were substituted by electronꢀdonating groups, such as ꢀMe, ꢀOMe, ꢀtBu at the paraꢀposition, the
desired products were afforded in 90%, 79% and 82% yields, respectively (3aꢀ3c Scheme 1). Arylsulfonyl
chlorides with electronꢀwithdrawing substituents were also suitable substrates. For example, 4ꢀCF3, 4ꢀF, 4ꢀCl
and 4ꢀBr phenyl sulfonyl chlorides gave the corresponding products in 90%, 89%, 73% and 57% yields,
respectively (3d-3g Scheme 1). Phenylsulfonyl chloride provided the product in 92% yield (3h Scheme 1).
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Benzene sulfonyl chloride substituted with Cl, CN and CH3 at 2ꢀposition could also react with azobenzene
smoothly and provided the desired product in 67%, 71% and 45% yields, respectively (3i-3k Scheme 1). In
addition, 3ꢀmethyl benzene sulfonyl chloride and 2ꢀnaphthol sulfonyl chloride were also tolerated in this
reaction system and afforded the desired products in 80% and 87% yields, respectively (3l and 3m, Scheme
1). The results obtained above indicated that the electron density in the arylsulfonyl chlorides did not affect
this transformation significantly. However, the slight influence of the steric hindrance was observed. Then,
the scope and generality of azobenzene was explored under the standard reaction conditions (3n-3t Scheme
1). In general, electronꢀrich azobenzenes were more suitable substrates and gave higher yields than
electronꢀdeficient azobenzenes. 4ꢀMethyl azobenzene and 3ꢀmethoxyl azobenzene provided the products in
85% and 84% yields, respectively (3n, 3r Scheme 1). While, 4ꢀtrifluoromethoxyl, 4ꢀfluoro and 4ꢀethyl
carbonyl azobenzene provided 54%, 43% and 65% yields of the corresponding products, respectively (3o-3q
Scheme 1). The steric effect substituents of the azobenzene were wellꢀtolerated. 2, 5ꢀDimethyl and 2ꢀmethyl
azobenzene could deliver the desired products in 60% and 55% yields, respectively (3s-3t Scheme 1). The
reactions of unsymmetrical azobenzenes could also proceed smoothly and gave the products in good to
excellent yields. However, the regioselectivity was poor. Two isolable isomers were obtained (3u-3x and
3u’-3x’ Scheme 1).
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Scheme 1. Palladium Catalyzed CꢀH Sulfonylation of Azobenzene.a
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aReaction conditions: azobenzene (1a) (0.2 mmol), pꢀtolylsulfonyl chloride (2a)
(3.0 equiv), Pd(TFA)2 (5 mol%), oxidant(1.1 equiv), solvent (2.0 mL), under
air, 120 ºC, 36 h, isolated yield based on 1a. b48 h.
To clarify the reaction mechanism, some controlled experiments were carried out under the optimized
conditions as follows: (1) Adding a radical scavenger (BHT) to the reaction mixture, this reaction was
inhibited. And 3a was no detected (eq. 1, Scheme 2); (2) The pꢀtolylsulfonyl radical was captured by BHT in
(eq. 2, Scheme 2), perhaps because K2S2O8 and high temperature helped to activate the pꢀtolylsulfonyl
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radical.12 Based on the results obtained and literatures,13 a radical process was suggested to be involved in
this catalytic system. The possible reaction pathway was proposed and described in Scheme 2. Azobenzene
1a firstly reacted with Pd(OAc)2 to form palladacycle I through the orthoꢀC–H bond insertion, which
accounted for the high regioselectivity in the reactions. Then, the palladacycle I reacted with the
pꢀtolylsulfonyl radical and generated Pd(IV) or Pd(III) species II. 5a,14 Subsequently, the species II underwent
reductive elimination to afford the sulfonylation product 3a. Pd(II) was regenerated for the next catalytic
cycle.
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Scheme 2. Proposed Reaction Mechanism
CONCLUSION:
In summary, we have developed a Pd(II) catalyzed CꢀH sulfonylation of azobenzenes with arylsulfonyl
chlorides. Sulfonylazobenzene series compounds were obtained smoothly by this process. This method
features with a simple system, one step operation, high efficiency, atomic economy, environmental
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friendliness and ligand, additives and base free conditions. Further investigations to expand the substrate
scope and application such chemistry in organic synthesis are underway.
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EXPERIMENT SECTION
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General Information
Unless otherwise noted, all reagents were purchased from commercial suppliers and used without purification.
Dichloroethane was distilled from calcium hydride. Melting points were measured on a microscopic apparatus and were
uncorrected. 1H NMR spectra were recorded on a 400 MHz spectrometer in deuterated chloroform. The chemical shifts δ
are reported in ppm relative to tetramethylsilane. The multiplicity of signals was designated by the following
abbreviations: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet). Coupling constants, J, were reported in Hertz
(Hz). 13C NMR spectra were recorded at 100 MHz spectrometer. The chemical shifts δ were reported relative to residual
CHCl3 (δc= 77.00 ppm). High resolution mass spectra (HRꢀMS) were obtained on a QꢀTOF spectrometer with micromass
MS software using electrospray ionization (ESI). Xꢀray analysis was obtained with a Xꢀray single crystal diffractometer.
Typical procedure for the synthesis of azobenzenes
The mixture of CuBr (4.2 mg, 0.03 mmol), pyridine (8.7 mg, 0.09 mmol) and arylamine (1 mmol) in toluene (4 mL)
was stirred at 60 °C under air (1 atm) for 20 h. Then cooling down to room temperature and concentrating in vacuum, the
residue was purified by flash chromatography on a short silica gel (eluent: petroleum ether) to afford the desired
products.[14]
Typical procedure for the synthesis of sulfonylazobenzenes:
(E)-1-Phenyl-2-(2-tosylphenyl)diazene (3a): In the oil bath, to a 50 mL reaction tube were successively
added azobenzene (1a) (36.4 mg, 0.2 mmol), pꢀtolylsulfonyl chloride (2a) (114.3 mg, 0.6 mmol),
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Pd(OAc)2 (2.25 mg, 0.01 mmol), K2S2O8 (59.5 mg, 0.22 mmol), and DCE (2 mL). The mixture was stirred
on a heating block at 120 °C for 36 h. (Note: The reaction was sluggish at temperatures below 120 °C.) After
cooling to ambient temperature, the resulting mixture was filtered through a pad of tripolite and washed with
50 mL of ethyl acetate. The filtrate was concentrated in vacuum and the resulting residue was purified by
preparative thin layer chromatography (silica gel: ethyl acetate / petroleum ether = 1 : 7, v/v) to afford the
target product 3a as a red solid (60.4 mg, 90%).
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(E)-1-Phenyl-2-(2-tosylphenyl)diazene (3a): red solid (60.4mg, 90%); m.p. 162.8ꢀ163.5 ˚C; 1H NMR (400 MHz,
CDCl3) δ 8.39 (d, J = 8.4 Hz, 1H), 7.86–7.82 (m, 4H), 7.68–7.60 (m, 2H), 7.52–7.59 (m, 4H), 7.16 (d, J = 8 Hz, 2H), 2.31
(s, 3H).13C NMR (100 MHz, CDCl3) δ ppm 115.6, 149.0, 143.9, 139.3, 138.8, 134.4, 132.0, 130.6, 129.30 129.1, 128.2,
123.8, 116.9, 21.54; HRꢀMS (ESI) ([M+H]+) Calcd. for C19H17N2O2S: 337.1005, found: 337.1006.
(E)-1-(2-((4-Methoxyphenyl) sulfonyl)phenyl)-2-phenyldiazene (3b): red solid (55.6 mg, 79%); m.p. 158.6ꢀ159.4
1
˚C; H NMR (400 MHz, CDCl3) δ 8.37 (dd, J = 1.7 Hz, J = 3.2 Hz 1H), 7.90 (d, J = 8.8 Hz, 2H), 7.86–7. 84 (m, 2H),
7.65–7.60 (m, 2H), 7.59–7.57 (m, 1H), 7.54–7.52 (m, 3H), 6.82 (d, J = 9.0 Hz, 2H), 3.74 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ ppm 163.2, 152.7, 148.9, 139.1, 134.3, 132.0, 130.6, 130.5, 129.2, 123.7, 116.9, 113.9, 55.6; HRꢀMS (ESI)
([M+H]+) Calcd. for C19H17N2O3S: 353.0954, found: 353.0958.
(E)-1-Phenyl-2-(2-((4-(tert-butyl)phenyl)sulfonyl)phenyl)-2-phenyldiazene(3c): red solid (61.8 mg,82%); m.p.
147.6ꢀ148.2 ˚C; 1H NMR (400 MHz, CDCl3) δ 8.41 (dd, J = 3.3 Hz, J = 5.0 Hz, 1H), 7.87 (d, J = 8.5 Hz, 2H), 7.79ꢀ7.77
(m, 2H), 7.69–7.60 (m, 2H), 7.57–7.51 (m, 4H), 7.36 (d, J = 8.6 Hz, 2H), 1.22 (s, 9H); 13C NMR (100 MHz, CDCl3) δ
ppm 156.8, 152.6, 149.1, 139.3, 138.7, 134.4, 132.0, 130.5, 129.2, 129.1, 127.9, 125.7, 123.8, 116.9, 35.1, 31.0; HRꢀMS
(ESI) ([M+H]+) Calcd. for C22H23N2O2S: 379.1475, found: 379.1475.
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(E)-1-Phenyl-2-(2-((4-trifluoromethyl)phenylsulfonyl)phenyl)diazene(3d): red solid (70.3 mg, 90%); m.p.
131.8ꢀ132.4 ˚C; 1H NMR (400 MHz, CDCl3) δ 8.44 (dd, J = 3.4 Hz, J = 4.4 Hz,1H), 8.09 (d, J = 8.2 Hz, 2H), 7.75–7.71
(m, 3H), 7.70–7.68 (m, 1H), 7.64–7.62 (m, 3H), 7.54–7.53 (m, 3H); 13C NMR (100 MHz, CDCl3) δ ppm 152.6, 148.9,
145.8, 137.6, 135.1, 132.3, 130.8, 129.5, 129.2, 128.6, 125.8 (dd, J1 = 7.3 Hz, J2 = 3.7 Hz), 123.6, 117.1, 26.8; HRꢀMS
(ESI) ([M+H]+) Calcd. for C19H14F3N2O2S: 391.0723, found: 391.0725.
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(E)-1-(2-((4-Fluorophenyl)sulfonyl)phenyl)-2-phenyldiazene(3e): red solid (60.3 mg, 89%); m.p. 191.3ꢀ192.4 ˚C; 1H
NMR (400 MHz, CDCl3) δ 8.47 (dd, J = 1.9 Hz, J = 3.1 Hz, 1H), 8.28 (dd, J = 0.3 Hz, J = 4.8 Hz, 2H), 7.89–7.87 (m,
2H), 7.74–7.69 (m, 2H), 7.66 (dd, J = 3.1 Hz, J = 4.4 Hz, 1H), 7.61–7.60 (m, 3H), 7.10 (t, J = 7.8 Hz, 2H); 13C NMR
(100 MHz, CDCl3) δ ppm 166.5, 164.0, 152.6, 148.9, 138.3 (d, JCꢀF = 9.2 Hz), 138.2, 134.7, 132.2, 131.1 (d, JCꢀF = 9.5
Hz), 130.7, 129.3, 129.2, 123.6, 117.0, 116.0 (d, JCꢀF = 22.5 Hz); HRꢀMS (ESI) ([M+H]+) Calcd. for C18H14FN2O2S:
341.0755, found: 341.0757.
(E)-1-(2-((4-Chlorophenyl)sulfonyl)phenyl)-2-phenyldiazene(3f): red solid (51.9 mg, 73%); m.p. 171.0ꢀ172.0 ˚C; 1H
NMR (400 MHz, CDCl3) δ 8.41 (d, J = 7.6 Hz, 1H), 7.91 (d, J = 9.6 Hz, 2H), 7.82–7.79(m, 2H), 7.72–7.65 (m, 2H),
7.63–7.54 (m, 4H), 7.35 (d, J = 8.6 Hz, J = 4.4 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ ppm 152.6, 148.9, 140.7, 139.6,
138.2, 134.8, 132.2, 130.7, 129.7, 129.4, 129.2, 129.0, 123.7, 117.0; HRꢀMS (ESI) ([M+H]+) Calcd. for C18H14ClN2O2S:
357.0459, found: 357.0462.
(E)-1-(2-((4-Bromophenyl)sulfonyl)phenyl)-2-phenyldiazene(3g): red solid (45.5 mg, 57%); m.p. 190.7ꢀ191.5 ˚C;
1H NMR (400 MHz, CDCl3) δ 8.47 (d, J = 7.7 Hz, 1H), 7.90 – 7.85(m, 4H), 7.80–7.70(m, 2H), 7.68–7.60(m, 4H), 7.57 (d,
J = 8.5 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ ppm 152.6, 148.9, 141.3, 138.1, 134.8, 132.2, 132.0, 130.7, 129.8, 129.4,
129.2, 128.2, 123.7, 117.0; HRꢀMS (ESI) ([M+H]+) Calcd. for C18H14BrN2O2S: 400.9954, found: 400.9955.
(E)-1-Phenyl-2-(2-(phenylsulfonyl)phenyl)diazene (3h)[2]: red solid ( 59.3 mg, 92%); m.p. 160–161 ˚C; 1H NMR
(400 MHz, CDCl3) δ 8.43 (d, J = 7.5 Hz, 1H), 7.96 (d, J = 8 Hz, 2H), 7.80–7.78 (m, 2H), 7.71–7.63 (m, 2H), 7.61–7.51
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(m, 4H), 7.46 (d, J = 5.1 Hz, 1H), 7.38 (t, J = 8.8 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ ppm 152.6, 149.0, 142.3, 138.5,
134.58, 133.0, 132.1, 130.6, 129.4 129.3, 128.7, 128.0, 127.6, 123.7, 116.9; HRꢀMS (ESI) ([M+H]+) Calcd. for
C18H14N2O2S: 323.0849, found: 323.0855.
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(E)-1-(2-((2-Chlorophenyl)sulfonyl)phenyl)-2-2pheny)diazene(3i): red solid (47.7 mg, 67%); m.p. 146.7ꢀ148.2˚C;
1H NMR (400 MHz, CDCl3) δ 8.52 (dd, J = 1.7 Hz, J = 3.9 Hz, 1H), 8.38 (dd, J = 1.0 Hz, J = 6.3 Hz, 1H), 7.74ꢀ7.66 (m,
2H), 7.62ꢀ7.56 (m, 3H), 7.48ꢀ7.42(m, 3H), 7.40 (t, J = 5.5 Hz, 1H), 7.35ꢀ7.31 (m, 2H); 13C NMR (100 MHz, CDCl3) δ
ppm 152.3, 148.7, 139.9, 138.0, 134.7, 134.2, 132.1, 132.1, 131.5, 131.4, 130.7, 130.5, 128.9, 126.7, 123.7, 116.5;
HRꢀMS (ESI) ([M+H]+) Calcd. for C18H14ClN2O2S: 357.0459, found: 357.0462.
(E)-2-((2-Phenyldiazenyl)phenyl)sulfonyl)benzonitrile (3j): red liquid ( 49.3 mg, 71%); 1H NMR (400 MHz, CDCl3)
δ 8.63 (dd, J = 0.6 Hz, J = 2.1 Hz, 1H), 8.40–8.37 (m, 1H), 7.79–7.73 (m, 3H), 7.69 (dd, J = 2.3 Hz, J = 3.9 Hz, 1H), 7.64
(dd, J = 3.2 Hz, J = 4.7 Hz, 2H), 7.62–7.56 (m, 3H), 7.49 (d, J = 7.2 Hz, 2H). 13C NMR (100 MHz, CDCl3) δ ppm 151.3,
147.7, 143.2, 137.8, 135.3, 134.4, 132.7, 132.1, 131.4, 131.3, 129.7, 129.5, 129.1, 128.1, 122.6, 115.8, 114.2; HRꢀMS
(ESI) ([M+H]+) Calcd. for C19H14N3O2S: 348.0801, found: 348.0804.
(E)-1-(2-((3-Chloro-2-methylphenyl)sulfonyl)phenyl)-2-phenyldiazene(3k): red solid (33.2 mg, 45%); m.p.
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142.5ꢀ143.2 ˚C; H NMR (400 MHz, CDCl3) δ 8.53 (d, J = 7.3 Hz, 1H), 8.28 (d, J = 7.2 Hz, 1H), 7.82–7. 74 (m, 2H),
7.69–7.67 (m, 3H), 7.54 (d, J = 7.84 Hz, 4H), 7.22 (t, J = 10.5 Hz, 1H), 2.47 (s, 3H); 13C NMR (100 MHz, CDCl3) δ ppm
152.3, 148.8, 142.6, 138.3, 136.4, 135.0, 134.7, 134.0, 132.1, 130.6, 129.5, 128.9, 128.7, 126.3, 123.8, 116.9, 16.6;
HRꢀMS (ESI) ([M+H]+) Calcd. for C19H16ClN2O2S: 371.0616, found: 371.0617.
(E)-1-Phenyl-2-(2-(m-tolylsulfonyl)phenyl)diazene(3l): red solid (53.8 mg, 80%); m.p. 133.5ꢀ134.4 ˚C; 1H NMR
(400 MHz, CDCl3) δ 8.49 (dd, J = 1.8 Hz, J = 3.3 Hz, 1H), 7.88 (d, J = 1.9 Hz, 3H), 7.76–7.68(m, 3H), 7.65–7.58 (m,
4H), 7.31 (d, J = 8.6 Hz, 2H). 2.28 (s, 3H); 13C NMR (100 MHz, CDCl3) δ ppm 152.6, 148.9, 142.0, 138.8, 138.7, 134.5,
133.8, 130.1, 129.29, 129.26, 129.1, 128.6, 128.6, 125.2, 123.8, 116.8, 21.1; HRꢀMS (ESI) ([M+H]+) Calcd. for
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C19H17N2O2S: 337.1011, found: 337.1008.
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(E)-1-(2-(Naphthalene-1-ylselfonyl)phenyl)-2-phenyldiazene(3m): red solid （64.8 mg, 87%）; m.p. 151.2ꢀ151.9 ˚C;
1H NMR (400 MHz, CDCl3) δ 8.62 (s, 1H), 8.49 (d, J = 7.2 Hz, 1H), 7.82 (t, J = 9.6 Hz, 3H), 7.75 (d, J = 7.5 Hz, 3H),
7.31 (t, J = 5.3 Hz, 2H), 7.57–7.48 (m, 6H); 13C NMR (100 MHz, CDCl3) δ ppm 152.7, 148.9, 138.9, 138.5, 134.9, 134.6,
132.0, 131.9, 130.6, 130.2, 129.4, 129.1, 129.1, 128.9, 127.8, 127.4, 123.7, 123.0, 116.9; HRꢀMS (ESI) ([M+H]+) Calcd.
for C22H17N2O2S: 373.1005, found: 373.1005.
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(E)-1-(4-Methyl-2-tosylphenyl)-2-(p-tolyl)diazene(3n): red solid (62.0 mg, 85%); m.p. 178.2ꢀ179.8 ˚C; 1H NMR
(400 MHz, CDCl3) δ 8.20 (s, 1H), 7.85 (d, J = 8.2 Hz, 2H), 7.72 (d, J = 8.2 Hz, 2H), 7.53 (d, J = 8.1 Hz, 1H), 7.45 (d, J =
6.7 Hz, 1H), 7.31 (d, J = 8.1 Hz, 2H), 7.16 (d, J = 8.0 Hz, 2H), 2.51 (s, 3H), 2.45 (s, 3H), 2.32 (s, 3H). 13C NMR (100
MHz, CDCl3) δ ppm 150.9, 147.0, 143.7, 142.5, 141.3, 139.5, 138.5, 134.9, 129.7, 129.6, 129.2, 128.1, 123.7, 116.7, 21.6,
21.5, 21.5; HRꢀMS (ESI) ([M+H]+) Calcd. for C21H21N2O2S: 365.1318, found: 365.1321.
(E)-1-(2-Tosyl-4-trifluoromethoxy)phenyl)-2-(4-(trifluoromethyl)phenyl)diazene(3o): red solid (53.8 mg, 54%);
m.p. 129.7ꢀ 130.5 ˚C; 1H NMR (400 MHz, CDCl3) δ 8.25 (d, J = 2.2 Hz, 1H), 7.88 (d, J = 8.8 Hz, 2H), 7.83 (d, J = 8.2
Hz, 2H), 7.69 (d, J = 8.8 Hz, 1H), 7.52–7.49 (m, 1H), 7.39 (d, J = 8.6 Hz, 2H), 7.22 (d, J = 8.1 Hz, 2H), 2.36 (s, 3H).13
C
NMR (100 MHz, CDCl3) δ ppm 151.8, 150.5, 150.4, 146.6, 144.7, 141.0, 138.4, 129.8 (dd, J = 3.6 Hz), 129.5 (dd, J = 3.8
Hz), 128.2, 127.9, 126.2, 125.4, 121.7, 121.2, 118.8, 21.6; HRꢀMS (ESI) ([M+H]+) Calcd. for C21H15F6N2O4S: 505.0651,
found: 505.0655.
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(E)-1-(4-Fluoro-2-tosylphenyl)-2-(4-fluorophenyl)diazene(3p): red solid (32.0 mg, 43%); m.p. 191.5–192.5 ˚C; H
NMR (400 MHz, CDCl3) δ 8.10 (dd, J = 1.5 Hz, J = 3.6 Hz, 1H), 7.86– .82 (m, 4H), 7.70–7.67 (m, 1H), 7.38–7.34 (m,
1H), 7.24–7.19 (m, 4H), 2.35 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 166.2, 164.5, 163.7, 162.0, 149.1 (d, JCꢀF = 2.8
Hz), 145.9(d, JCꢀF = 3.8 Hz), 144.4, 141.2 (d, JCꢀF = 6.7 Hz), 138.7, 129.4, 128.2, 125.9 (d, JCꢀF = 9.1 Hz), 121.4, 121.1,
119.1(d, JCꢀF = 8.1 Hz), 116.7 (d, JCꢀF =26.1 Hz), 116.2 (d, JCꢀF =22.9 Hz), 21.6; HRꢀMS (ESI) ([M+H]+) Calcd. for
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C19H15F2N2O2S: 373.0817, found: 373.0819.
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(E)-Ethyl 4-((4-ethoxycarbonyl)phenyldiazenyl)3-tosylbenzoate (3q): red solid (62.2 mg, 65%); m.p. 151.6ꢀ152.5
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˚C; H NMR (400 MHz, CDCl3) δ 9.03 (s, 1H), 8.35 (d, J = 7.6 Hz, 1H), 8.22 (d, J = 8.2 Hz, 2H), 7.90–7.84 (m, 4H),
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7.60 (d, J = 8.3 Hz, 2H), 7.18 (d, J = 8.0 Hz, 2H), 4.51–4.43 (m, 4H), 2.34 (s, 3H), 1.49–1.44 (m, 6H). 13C NMR (100
MHz, CDCl3) δ ppm 164.9, 153.8, 150.0, 143.4, 138.3, 137.6, 134.5, 129.6, 128.4, 127.2, 122.6, 121.8, 60.3, 20.5, 13.8;
HRꢀMS (ESI) ([M+H]+) Calcd. for C25H25N2O6S: 481.1428, found: 481.1431.
(E)-1-(5-Methoxy-2-tosylphenyl)-2-(3-methoxyphenyl)diazene(3r): red solid (66.5 mg, 84%); m.p. 96.6–97.4 ˚C; 1H
NMR (400 MHz, CDCl3) δ 8.31 (d, J = 8.6 Hz, 1H), 7.83 (d, J = 8.3 Hz, 2H), 7.50– .49 (m, 1H), 7.43 (t, J = 7.9 Hz, 1H),
7.38 (t, J = 3.6 Hz, 1H), 7.16 (d, J = 8.3 Hz, 2H), 7.11–7.07 (m, 3H), 3.91 (s, 3H), 3.87 (s, 3H), 2.31 (s, 3H). 13C NMR
(100 MHz, CDCl3) δ ppm 164.1, 160.3, 153.7, 150.7, 143.6, 140.0, 131.4, 130.9, 129.8, 129.3, 127.8, 118.9, 118.1, 116.2,
106.7, 101.2, 56.0, 55.5, 21.5; HRꢀMS (ESI) ([M+H]+) Calcd. for C21H21N2O4S: 397.1217, found: 397.1218.
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(E)-1-(3,5-Dimethyl-2-(3,5-dimethylenyl)diazene(s): red solid (47.1 mg, 60%); m.p. 141.2ꢀ141.7 ˚C; H NMR (400
MHz, CDCl3) δ 7.84 (d, J = 8.2 Hz, 2H), 7.36 (s, 2H), 7.16 (t, J = 9.8 Hz, 4H), 6.98 (s, 1H), 2.88 (s, 3H), 2.42 (s, 6H),
2.37 (s, 3H), 2.33 (s, 3H); 13C NMR (100 MHz, CDCl3) δ ppm 152.0, 151.0, 143.4, 142.2, 140.5, 139.1, 137.6, 134.1,
132.2, 131.6, 128.1, 125.8, 120.5, 115.1, 21.3, 20.5, 20.3, 20.2; HRꢀMS (ESI) ([M+H]+) Calcd. for C23H25N2O2S:
393.1631, found: 393.1631.
(E)-1-(2-Methyl-6-tosylphenyl)-2-(o-tolyl)diazene (3t): red liquid (40.0 mg, 55%); 1H NMR (400 MHz, CDCl3) δ
8.21 (d, J = 7.8 Hz, 1H), 7.66 (d, J = 8.2 Hz, 2H), 7.51 (d, J = 7.7 Hz, 2H), 7.45–7.38 (m, 2H), 7.33 (t, J = 9.1 Hz, 2H),
7.10 (d, J = 8.2 Hz, 2H), 2.52 (s, 3H), 2.32 (s, 3H), 2.20 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 150.8, 150.3, 143.6,
139.3, 138.9, 137.4, 135.8, 132.1, 131.3, 129.2, 128.7, 127.9, 127.4, 127.3, 126.4, 115.8, 21.5, 19.2, 17.5; HRꢀMS (ESI)
([M+H]+) Calcd. for C21H21N2O2S: 365.1318, found: 365.1325.
(E)-1-(4-Methoxy-2-tosylphenyl)-2-phenyldiazene (3u): red solid (32.7 mg, 45%) m.p. 154.4ꢀ155.2 ˚C; 1H NMR
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(400 MHz, CDCl3) δ 7.92 (d, J = 2.6 Hz, 1H), 7.86 (d, J = 8.1 Hz, 2H), 7.78 (d, J = 7.8 Hz, 2H), 7.71 (d, J = 8.9 Hz, 1H),
7.51–7.49 (m, 3H), 7.16 (d, J = 7.9 Hz, 3H), 3.98 (s, 3H), 2.31 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 161.9,148.3,
146.2, 142.8, 138.5, 137.3, 133.4, 128.9, 128.3, 127.1, 125.0, 116.0, 113.3, 54.7, 20.6; HRꢀMS (ESI) ([M+H]+) Calcd. for
C20H19N2O3S: 367.1111, found: 367.1114.
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(E)-1-(4-Methoxyphenyl)-2-(2-tosylphenyl)diazene (3u’): red solid (31.3 mg, 43%) m.p. 138.5ꢀ139.5 ˚C; H NMR
(400 MHz, CDCl3) δ 8.39 (d, J = 7.6 Hz, 1H), 7.85 (d, J = 8.5 Hz, 4H), 7.66 (t, J = 7.4 Hz, 1H), 7.59 (t, J = 8.4 Hz, 2H),
7.17 (d, J = 8.4 Hz, 2H), 7.03 (d, J = 8.8 Hz, 2H), 3.91 (s, 3H), 2.32 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 150.8,
150.3, 143.6, 139.3, 138.9, 137.4, 135.8, 132.1, 131.3, 129.2, 128.7, 127.9, 127.4, 127.3, 126.4, 115.8, 21.5, 19.2, 17.5;
HRꢀMS (ESI) ([M+H]+) Calcd. for C20H19N2O3S: 367.1111, found: 367.1118.
(E)-1-(4-Chlorophenyl)-2-(2-tosylphenyl)diazene (3v): red solid (37.8 mg, 51%) m.p. 170.6ꢀ171.3 ˚C; 1H NMR (400
MHz, CDCl3) δ 8.39 (d, J = 7.2 Hz, 1H), 7.82 (d, J = 8.2 Hz, 2H), 7.77 (d, J = 8.6 Hz, 2H), 7.69ꢀ7.63 (m, 2), 7.60ꢀ7.58
(m, 1H), 7.50 (d, J = 8.6 Hz, 2H), 7.19 (d, J = 8.2 Hz, 2H), 2.34 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 151.4, 149.2,
144.4, 139.8, 139.4, 138.5, 134.7, 131.3, 129.9, 129.8, 129.7, 128.4, 125.4, 117.2, 21.9; HRꢀMS (ESI) ([M+H]+) Calcd.
for C19H16ClN2O2S: 371.0616, found: 371.0615.
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(E)-1-(4-Chloro-2-tosylphenyl)-2phenyldiazene (3v’): red solid (14.8 mg, 20%) m.p. 182.0ꢀ183.1 ˚C; H NMR (400
MHz, CDCl3) δ 8.39 (d, J = 7.2 Hz, 1H), 7.82 (d, J = 8.2 Hz, 2H), 7.77 (d, J = 8.6 Hz, 2H), 7.69ꢀ7.63 (m, 2), 7.60ꢀ7.58
(m, 1H), 7.50 (d, J = 8.6 Hz, 2H), 7.19 (d, J = 8.2 Hz, 2H), 2.34 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 151.4, 149.2,
144.4, 139.8, 139.4, 138.5, 134.7, 131.3, 129.9, 129.8, 129.7, 128.4, 125.4, 117.2, 21.9; HRꢀMS (ESI) ([M+H]+) Calcd.
for C19H16ClN2O2S: 371.0616, found: 371.0618.
(E)-1-(4-Fluorophenyl)-2-(2-tosylphenyl)diazene (3w): red liquid (30.4 mg, 43%) m.p. 169.3ꢀ170.7 ˚C; 1H NMR
(400 MHz, CDCl3) δ 8.39 (d, J = 7.4 Hz, 1H), 7.86ꢀ7.81 (m, 4H), 7.69ꢀ7.61 (m, 2H), 7.57 (d, J = 7.6 Hz, 1H), 7.20 (dd, J1
= 7.6 Hz, J2 =15.7 Hz, 4H), 2.33 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 166.6, 164.1, 149.5 (d, JCꢀF = 2.8), 149.3,
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144.4, 139.5 (d, JCꢀF = 62.7), 134.8, 131.0, 129.8, 129.7, 128.4, 126.3 (d, JCꢀF = 9.1), 117.2, 116.6 (d, JCꢀF = 22.4), 21.9;
HRꢀMS (ESI) ([M+H]+) Calcd. for C19H16FN2O2S: 355.0911, found: 355.0914.
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(E)-1-(4-Fluoro-2tosylphenyl)-2-phenyldiazene (3w’): red liquid (18.2 mg, 26%) m.p. 189.7ꢀ190.4 ˚C; 1H NMR (400
MHz, CDCl3) δ 8.12 (dd, J1 = 2.6 Hz, J1 = 8.0 Hz, 1H), 7.85ꢀ7.81 (m, 4H), 7.69 (q, J = 5.0 Hz, 1H), 7.54 (d, J = 1.6 Hz,
3H), 7.37ꢀ7.32 (m, 1H), 7.19 (d, J = 8.1 Hz, 2H), 2.34 (s, 3H). 13C NMR (100 MHz, CDCl3) δ ppm 164.9, 162.4, 145.7,
144.7, 141.7 (d, JCꢀF = 6.6), 139.1, 132.4, 129.8, 129.5, 128.8, 124.1, 121.6 (d, JCꢀF = 22.5), 119.5 (d, JCꢀF = 80.7), 117.1(d,
JCꢀF = 26.0), 21.9; HRꢀMS (ESI) ([M+H]+) Calcd. for C19H16FN2O2S: 355.0911, found: 355.0912.
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(E)-Ethyl-4-((2-tosylphenyl)diazenly)benzoate (3x): red solid (34.2 mg, 42%) m.p. 114.1ꢀ115.2 ˚C; H NMR (400
MHz, CDCl3) δ 8.32 (m, 1H), 8.12 (d, J = 8.6 Hz, 2H), 7.69 (t, J = 6.5 Hz, 4H), 7.62ꢀ7.59 (m, 2H), 7.54ꢀ7.51 (m,
1H),7.10 (d, J = 8.2 Hz, 2H), 4.36 (dd, J = 7.0 Hz, J = 14.2 Hz, 2H), 2.25 (s, 3H), 1.37 (t, J = 7.2 Hz, 3H), . 13C NMR
(100 MHz, CDCl3) δ ppm 166.3, 155.3, 149.2, 144.5, 139.74, 139.68, 134.8, 133.4, 131.6, 130.9, 129.9, 129.7, 128.5,
123.8, 120.7, 117.1, 61.8, 21.9, 14.7; HRꢀMS (ESI) ([M+H]+) Calcd. for C22H21N2O4S: 409.1217, found: 409.1220.
1
(E)-Ethyl-4-((2-tosylphenyl)diazenly)benzoate (3x’): red solid (17.4 mg, 21%) m.p. 153.1ꢀ153.5 ˚C; H NMR (400
MHz, CDCl3) δ 8.95 (d, J = 1.4 Hz, 1H), 8.25 (dd, J1 = 1.6 Hz, J2 = 8.3 Hz, 1H), 7.79 (d, J = 8.2 Hz, 4H), 7.53ꢀ7.48 (m,
4H), 7.11 (d, J = 8.1 Hz, 2H), 4.39 (dd, J = 7.8 Hz, J = 14.2 Hz, 2H), 2.26 (s, 3H), 1.38 (t, J = 7.2 Hz, 3H), . 13C NMR
(100 MHz, CDCl3) δ ppm 165.1, 153.1, 151.9, 144.7, 139.34, 139.26, 135.9, 133.0, 132.6, 131.0, 129.8, 129.6, 128.7,
124.4, 122.7, 117.7, 62.3, 21.9, 14.7; HRꢀMS (ESI) ([M+H]+) Calcd. for C22H21N2O4S: 409.1217, found: 409.1218.
ASSOCIATED CONTENT
Supporting Information
Spectral data for all products and crystallographic data for 3a are available free of charge via the Internet at
http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
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*Eꢀmail: cuixl@zzu.edu.cn.
*Eꢀmail: wyj@zzu.edu.cn.
Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENT
We gratefully acknowledge NSF of China (21102133, 21172200) for financial support.
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