Synthesis of Polysubstituted Imidazoles and Pyridines via Samarium(III) Triflate-Catalyzed [2+2+1] and [4+2] Annulations of Unactivated Aromatic Alkenes with Azides

Article abstract of DOI:10.1002/adsc.201500584

Samarium(III) triflate-catalyzed [2+2+1] and [4+2] annulations have been identified for the preparation of fully substituted imidazoles and 2,3,5-trisubstituted pyridines from the readily available unactivated aromatic alkenes and azidomethyl aromatics. T

Full text of DOI:10.1002/adsc.201500584

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DOI: 10.1002/adsc.201500584
Synthesis of Polysubstituted Imidazoles and Pyridines via Samar-
ium(III) Triflate-Catalyzed [2+2+1] and [4+2] Annulations of
Unactivated Aromatic Alkenes with Azides
Yingchun Wang,+a,b Jiuling Li,+a Yan He,a Yuyang Xie,a Hengshan Wang,a,*
and Yingming Pana,*
a
Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China),
School of Chemistry and Pharmaceutical Sciences of Guangxi Normal University, Guilin 541004, Peopleꢀs Republic of
China
Fax: (+86)-773-580-3930; phone: (+86)-773-584-6279; e-mail: whengshan@163.com or panym2013@hotmail.com
College of Chemistry and Chemical Engineering, Jishou University, Jishou 416000, Peopleꢀs Republic of China
b
+
These authors contributed equally to this work.
Received: June 16, 2015; Revised: August 7, 2015; Published online: October 14, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201500584.
Abstract: Samarium(III) triflate-catalyzed [2+2+1] induced 1,3 dipolar cycloaddition followed by 1,2-mi-
and [4+2] annulations have been identified for the gration to form an enamine as the key intermediate.
preparation of fully substituted imidazoles and 2,3,5- Density functional theory (DFT) calculations sug-
trisubstituted pyridines from the readily available un- gested that the selectivity of 1,2-H and 1,2-aryl mi-
activated aromatic alkenes and azidomethyl aromat- gration depends on the structure of the alkenes.
ics. These reactions proceeded smoothly with one- or
two-nitrogen synthons to afford a range of two types
of skeletally distinct N-heterocycles in good yields. Keywords: aromatic alkenes; benzyl azides; cascade
Mechanistic studies revealed that the annulation re- reactions; fully substituted imidazoles; 2,3,5-trisubsti-
action proceed via an initial samarium(III) triflate- tuted pyridines
Introduction
partners in heterocycle syntheses, the rare earth
metal-catalyzed intermolecular cascade annulations of
Intermolecular cascade reactions can allow for the unactivated aromatic alkenes and azidomethyl aro-
straightforward and selective construction of compli- matics are rare.
cated molecules in a one-pot manner from relatively
On the other hand, polysubstituted imidazoles and
simple building blocks.[1] Organic azide-alkene cyclo- pyridines are privileged scaffolds in many natural
additions have been proven to be powerful synthetic products and biologically active molecules.[4] Highly
tools for the ready access to diverse azaheterocycles. substituted imidazoles also play important roles in
For example, the uncatalyzed thermal cycloaddition materials chemistry due to their excellent photophysi-
of organic azides with alkenes, especially the intramo- cal properties.[5] However, only a limited number of
lecular azide-alkene cycloaddition reaction, has al- typical methodologies exist for the assembly of highly
lowed many successful syntheses of complex mole- substituted imidazoles and polysubstituted pyridines.[6]
cules.[2] The transition metal-catalyzed annulation of Thus, it is still challenging and highly desirable to de-
alkenes with aryl azides or sulfonyl azides (“C2 +N1” velop novel and efficient synthetic methods for these
addition) represents a general approach for the direct azaheterocycles from simple and readily accessible
synthesis of aziridines, and different transition metal building blocks.
catalysts for this reaction such as Fe, Co, Mn, Cu, Rh
Our group has previously reported the rare earth
and Ru based compounds have been developed.[3] Al- metal-catalyzed [3+2] cycloaddition of organic azides
though extensive efforts have been devoted to the uti- with electron-deficient olefins to produce 1,2,3-tri-
lization of organic azides and alkenes as cyclization azoles or enamines.[7] In this paper, we wish to present
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Yingchun Wang et al.
our findings on the rare earth metal-catalyzed inter- of any metal catalyst in toluene at 1108C for 24 h,
molecular [2+2+1] and [4+2] annulation reactions and TLC analysis indicated no product formation
between unactivated aromatic alkenes and azido- (Table 1, entry 1). When a mixture of 1a and benzyl
methyl aromatics. In the presence of a catalytic azide (1:1.2 mol ratio) was treated with 5 mol%
amount of Sm(OTf)3 and atmospheric pressure Sc(OTf)3 in toluene at 1108C for 24 h, tetrasubstituted
oxygen, the readily available azidomethyl aromatics imidazole 3a was isolated in 30% yield. Doubling the
were successfully applied as two- or one-nitrogen syn- loading amount of benzyl azide enhanced the yield to
thons to prepare 1,2,4,5-tetrasubstituted imidazoles 45%. Interestingly, simply subjecting the reaction
and 2,3,5-trisubstituted pyridines by the reactions with mixture to an atmosphere of oxygen resulted in fur-
stilbenes and aromatic 1,3-dienes, respectively. Pre- ther improvement of the yield to 61% (Table 1,
liminary mechanistic evidence for the bifurcated reac- entry 2). It was noted that other metal catalysts, such
tion pathway will also be presented to highlight key as Cu(OTf)2, In(OTf)3, [Rh(COD)Cl]2, Pd(TFA)2, or
aspects of these transformations.
AuCl3, were not suitable for this transformation
(Table 1, entries 8–12). Sm(OTf)3 was found to be
more effective than other rare earth metal triflates
(Table 1, entry 3 vs. entry 2 and entries 4–7). Among
various solvents examined, toluene and PhCl turned
Results and Discussion
To initiate our investigations, we examined the reac- out to be the best (Table 1, entries 13–17). Additional-
tions of stilbenes with azidomethyl aromatics. Table 1 ly, 5 mol% of the Sm(OTf)3 was sufficient to promote
presents the results of screening for appropriate reac- the reaction effectively. Increasing the catalyst loading
tion conditions for the model reaction between 1a amount to 10 mol% did not facilitate the reaction or
and 2a. We first attempted the reaction in the absence improve the yield (Table 1, entry 3 vs. entry 18). Final-
ly, the optimal conditions were identified as the fol-
lowing: reaction of 1a and 2a in toluene with 5 mol%
Table 1. Optimization of the synthesis of 1,2,4,5-tetrasubsti-
of Sm(OTf)3 and atmospheric pressure oxygen at
1108C for 24 h. Under these conditions, 1,2,4,5-tetra-
substituted imidazole 3a was obtained in 75% yield
(Table 1, entry 3).
tuted imidazoles.[a]
Having identified the optimal conditions for the
synthesis of tetrasubstituted imidazoles, we next ex-
plored the substrate scope of this [2+2+1] annula-
tion reaction. The results are summarized in Table 2.
A variety of benzyl azides substituted with alkyl (3b,
3c), methoxy (3d), halogen (3e, 3f), trifluoromethyl
(3g) and cyano (3h) groups at the ortho, meta, or para
position underwent the [2+2+1] annulation readily,
providing the anticipated tetrasubstituted imidazoles
3 in good yields. In general, benzyl azides possessing
electron-donating groups on the phenyl ring provided
the cyclization products in higher yields than those
bearing electron-withdrawing groups (3b–d vs. 3e–h).
The structure of a representative product 3f[8] was un-
ambiguously confirmed by X-ray crystallographic
analysis (Figure 1). In addition, azides bearing 2-
naphthyl (3i) and 3-pyridyl (3j) groups also reacted
smoothly and afforded the corresponding imidazoles
in good yields. Noteworthy, substrates with steric hin-
drance (3k and 3l) could be employed in [2+2+1]
annulations with the stilbene 1a, although in moder-
ate yields. Both electron-neutral and electron-poor
stilbenes were found to be suitable for this transfor-
mation while electron-poor stilbenes afforded the
products in lower yields (3n–q vs. 3m). In the case of
asymmetric stilbene 1q, tetrasubstituted imidazoles 3q
and 3q’ were isolated in 32% and 37% yield, respec-
tively (Scheme 1). Stilbene 1r possessing a strongly
electron-donating group (OCH3) at the meta position
Entry Catalyst
Solvent Yield [%][b] of 3a
toluene
toluene 61
toluene 75
toluene 57
toluene 42
toluene 47
toluene 45
1
none
0
2
3
4
5
6
7
8
9
Sc(OTf)3 (5 mol%)
Sm(OTf)3 (5mol%)
Ce(OTf)3 (5 mol%)
Yb(OTf)3 (5 mol%)
Pr(OTf)3 (5 mol%)
La(OTf)3 (5 mol%)
Cu(OTf)2 (5 mol%)
In(OTf)3 (5 mol%)
toluene
toluene
0
0
10
11
12
13
14[c]
15[c]
16
17
18
[Rh(COD)Cl]2 (5 mol%) toluene
Pd(TFA)2 (5 mol%)
AuCl3 (5 mol%)
Sm(OTf)3 (5 mol%)
Sm(OTf)3 (5 mol%)
Sm(OTf)3 (5 mol%)
Sm(OTf)3 (5 mol%)
Sm(OTf)3 (5 mol%)
Sm(OTf)3 (10 mol%)
0
toluene
toluene
PhCl
0
0
72
0
DCE
CH3CN 0
DMF
DMSO
0
0
toluene 73
[a]
Carried out with 0.5 mmol of stilbene 1a and 1.1 mmol of
benzyl azide 2a in the presence of catalyst and atmos-
pheric-pressure oxygen in solvent (4 mL) at 1108C for
24 h (except for entry 1).
Isolated yield of pure product based on 1a.
The reaction mixture of stilbene 1a (0.5 mmol), benzyl
azide 2a (1.1 mmol), Sm(OTf)3 (0.025 mmol) and solvent
(4 mL) in a 20 mL sealed tube was stirred at 1108C for
24 h.
[b]
[c]
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Synthesis of Polysubstituted Imidazoles and Pyridines
Table 2. Sm(OTf)3-catalyzed [2 + 2 + 1] annulations of symmetric stilbenes 1 with azidomethyl aromatics 2.[a,b]
[a]
Reaction conditions: 0.5 mmol of 1 and 1.1 mmol of azidomethyl aromatics in the presence of Sm(OTf)3
(5 mol%) and atmospheric-pressure oxygen in 4 mL of toluene at 1108C for 24 h.
Isolated yield of pure product based on 1.
[b]
Scheme 1. Sm(OTf)3-catalyzed [2+2+1] annulations of asymmetric stilbenes 1 with benzyl azide 2a.
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Yingchun Wang et al.
ring product has not been reported, which represents
a new application of this versatile class of molecules
under rare earth metal catalysis.
On the basis of the reported mechanistic studies of
azides and alkenes,[7,10] we proposed a plausible path-
way for the stilbene-azide [2+2+1] annulation reac-
tion, as depicted in Scheme 2. Under Sm(OTf)3 acti-
vation, 1,3-dipolar cycloaddition of benzyl azide 2a
with the stilbene 1a occurs first to form the unstable
triazoline intermediate A. Subsequently, A decompos-
es to a zwitterionic species B, which undergoes 1,2 H-
shift with the loss of nitrogen and 1,3 H-shift to give
the enamine D. This rationale was supported by the
isolation of enamines D-1 and D-2 from the reaction
mixtures. Oxidation of D delivers the a,b-unsaturated
imine E, which undergoes a second intermolecular
1,3-dipolar cycloaddition, followed by 1,2 H-shift with
the loss of nitrogen and 1,3 H-shift to form intermedi-
ate I. Ultimately, intermediate I generates the final
tetrasubstituted imidazole 3a via 5-endo-trig cycliza-
tion[11] and oxidation.
Figure 1. X-ray crystal structure of 1,2,4,5-tetrasubstituted
imidazole 3f.
Under the standard reaction conditions, enamine D
did not accumulate even for the [2+2+1] annulation
afforded imidazole 3r in 63% yield along with its reaction of stilbene 1a with sterically hindered benzyl
isomer 3r’ in 15% yield. However, 4-methoxy-4’- azide 2k. When a mixture of 1a (0.5 mmol) and 2k
fluoro-substituted stilbene 1s provided imidazole 3s as (1.1 mmol) was treated with 5 mol% Sm(OTf)3 and
the only isolated product (77% yield).
atmospheric pressure oxygen in toluene at 1108C for
Although the azidomethyl aromatics 2 have been 24 h, only a trace amount of D was detected by
extensively studied for the synthesis of nitrogen-con- 1H NMR and LC-MS analyses. However, when these
taining heterocycles,[9] the incorporation of two mole- substrates were allowed to react at 1108C for 8 h on
cules of azidomethyl aromatics into a five-membered a 5 mmol scale, chromatography resulted in the isola-
Scheme 2. A plausible reaction mechanism for the stilbene-azide [2+2+1] annulation reaction.
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Scheme 4. Synthesis of 2,3,5-trisubstituted 5a and X-ray crys-
tal structure of 5a.
The substrate scope was explored with a diverse set
of azidomethyl aromatics and aromatic 1,3-dienes
(Table 3). Consistent with the results of fully substi-
tuted imidazole synthesis, good functional group com-
Scheme 3. Control experiments.
tion of 65% of the starting material 1a along with patibility was observed, as products with tertiary butyl
15% yield of imidazole 3k and 6% enamine D-2 (5b), methoxy (5c, 5d), phenyl (5f), fluoro (5g, 5h),
(Scheme 3, a).To further support the proposed reac- chloro (5i, 5j), and trifluoromethyl (5k) substituents
tion pathway, additional two control experiments were obtained. Moreover, the substituent at the para
were carried out. It was observed that the presence of (5c) and meta (5d) positions were not detrimental to
2.2 equiv. of TEMPO (2,2,6,6-tetramethyl-1-piperidi- the reaction yield. In analogy to the electronic effects
nyloxy) did not suppress the annulation of stilbene 1a observed for the reactions with stilbenes 1, electron-
with benzyl azide 2k under optimized conditions donating groups (5c, 5d) resulted in higher yields than
(Scheme 3, b), suggesting that a radical mechanism electron-withdrawing groups (5g–k). The azides bear-
was not likely involved. Furthermore, when the enam- ing 2-naphthyl (5e) and 3-pyridyl (5l) also readily un-
ine D-2 was employed to react with benzyl azide 2k derwent cycloadditions with 4a, affording the corre-
under standard reaction conditions, the desired prod- sponding 2,3,5-trisubstituted pyridines in good yields.
uct 3k was obtained in 64% yield (Scheme 3, c), While ortho substituents on the benzyl azide resulted
which further supported that the imidazole product in low yields (5h, 5j), both electron-neutral (5m) and
could be derived from the intermediate enamine D in electron-deficient (5n) 1,4-diphenylbuta-1,3-dienes
the annulation reaction.
were effective annulation reaction partners, and fur-
Encouraged by the successful incorporation of the nished the 2,3,5-trisubstituted pyridines in good
stilbenes 1 as annulation reaction partners, we investi- yields. Especially, a heterocyclic 1,3-diene afforded 5o
gated the reaction of 1,4-diphenylbuta-1,3-dienes 4a in high yield.
with benzyl azide 2a. We envisaged that the 1,4-diphe-
The proposed mechanistic pathway for the 1,3-
nylbuta-1,3-diene 4a would function as a four-carbon diene-azide [4+2] annulation reaction is shown in
synthon for [4+N] annulation with the azide. To our Scheme 5. The key event is the formation of the tri-
delight, under identical conditions as described for azoline intermediate J, generated via 1,3-dipolar cy-
stilbenes 1, the reaction of 4a and 2a proceeded readi- cloaddition of benzyl azide 2a with an olefinic double
ly to produce 2,3,5-triphenylpyridine 5a as the sole bond of 1,3-diene 4a. The decomposition of inter-
product via a formal [4+2] cycloaddition in 77% iso- mediate J leads to 1,2-phenyl migration with the elim-
lated yield (Scheme 4). The structure of 5a[12] was fur- ination of molecular nitrogen and 1,3 H-shift to form
ther confirmed by X-ray crystallography analysis, as enamine M. Oxidation of M provides the aza-triene
described in Scheme 4.
intermediate N, which subsequently undergoes 6p-
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Table 3. Sm(OTf)3-catalyzed [4+2] annulations of aromatic 1,3-dienes 4 with azidomethyl aromatics
2.[a,b]
[a]
Reaction conditions: 0.5 mmol of 4 and 0.6 mmol of azidomethyl aromatics in the presence of
Sm(OTf)3 (5 mol%) and atmospheric-pressure oxygen in 4 mL of toluene at 1108C for 24 h.
Isolated yield of pure product based on 4.
[b]
electrocyclization to yield a transient dihydropyridine uct was not generated at all (Scheme 6). Evidently,
O.[13] Rapid aerobic oxidation generates the final the products of 7a and 7a’ were obtained via
2,3,5-trisubstituted pyridine 5a.
Sm(OTf)3-mediated 1,3-dipolar cycloaddition to form
We also investigated the possibility of extending triazolines, followed by oxygen oxidation. A range of
the substrate scope to aromatic terminal alkenes. Our reaction conditions (catalysts, solvents, temperatures)
anticipation was that the aromatic terminal alkenes for the above transformation were screened, but we
would undergo regioselective 1,3-dipolar cycloaddi- only obtained mixtures of several other products
tion with azidomethyl aromatics to yield imidazoles (data not shown). Intriguingly, the reaction of 1,1-di-
via a cascade process. However, under the same reac- phenylethylene 6b with the benzyl azide 2a exclusive-
tion conditions, the reaction of styrene 6a with benzyl ly provided the [2+2+1] annulation product, tetra-
azide 2a gave the [3+2] cycloaddition products 7a substituted imidazole 3a in 72% yield, whereas the
and 7a’ in 43% and 25% isolated yields, respectively, [3+2] adduct was not detected (Scheme 7). Scheme 8
along with homo-coupling side product 1,4-diphenyl- presents a mechanistic rationale for the [2+2+1] an-
buta-1,3-dienes (9%). The expected imidazole prod- nulation of 6b and 2a to form 3a. This reaction pro-
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Scheme 5. A plausible reaction mechanism for the 1,3-diene-azide [4+2] annulation reaction.
Scheme 7. Sm(OTf)3-catalyzed [2+2+1] annulation of 1,1-
diphenylethylene 6b with benzyl azide 2a.
ceeds via an initial Sm(OTf)3-induced 1,3 dipolar cy-
Scheme 6. Sm(OTf)3-catalyzed [3+2] cycloaddition of sty- cloaddition followed by a series of rearrangements,
rene 6a with benzyl azide 2a.
cyclizations, and oxidations to furnish the final com-
pound 3a.
Scheme 8. Proposed mechanistic pathway for the formation of imidazole 3a from 6b and 2a.
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Figure 2. Comparison of the transition state energy between the 1,2-H migration and the 1,2-aryl migration mechanism.
The above experimental results revealed that the tion reaction is less favorable than the 1,2-aryl migra-
zwitterionic intermediates could undergo the 1,2-H or tion, consistent with the experimental results.
1,2-aryl migration with the elimination of N2, which is
dependent on the structure of the alkene. Density
functional theory (DFT) calculations [B3LYP with Conclusions
the 6-31+G (d, p) basis set] were performed on 1,2-
H and 1,2-aryl migration (Figure 2). Evidently, in the We have developed a new cascade process for the
stilbene-azide [2+2+1] annulation reaction, the acti- Sm(OTf)3-catalyzed [2+2+1] and [4+2] annulations
vation energy difference between 1,2-H and 1,2-aryl of unactivated aromatic alkenes with azidomethyl ar-
migrations is ca. 5 kcalmolÀ1, suggesting that 1,2-H omatics to prepare fully substituted imidazoles and
migration is 4.6”103-fold faster than 1,2-aryl migra- 2,3,5-trisubstituted pyridines in good yields. This sub-
tion according to the Arrhenius equation. And the strate-controlled bifurcated cascade process not only
thermodynamic energy from B to C was found to be provides an approach to access a range of skeletally
3 kcalmolÀ1 lower than that from B to C’. These re- distinct N-heterocycles but also represents a new
sults are in good agreement with the experimental ob- strategy to develop cascade reactions from organic
servations. In addition, the molecular orbital surfaces azides. Notably, the incorporation of two molecules of
and energy levels of corresponding reaction state azidomethyl aromatics into a five-membered ring
were also calculated (see Figure S1 in the Supporting product is a new application for this versatile class of
Information). The transition state energy of 1,2-H mi- molecules under rare earth metal catalysis conditions.
gration is about 0.64 eV higher than that of 1,2-aryl
migration (2.27 eV vs. 1.63 eV), indicating that the
transition state of 1,2-H migration is more favorable
than that of 1,2-aryl migration. Similar computations
Experimental Section
and analyses were also performed for the 1,3-diene-
azide [4+2] annulation reaction, and the results in
Figure 2 and Figure S2 (in the Supporting Informa-
tion) indicate that the 1,3-diene-azide [4+2] annula- carbon nuclear magnetic resonance spectra (13C NMR) were
General Experimental Details
Proton nuclear magnetic resonance spectra (1H NMR) and
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Synthesis of Polysubstituted Imidazoles and Pyridines
recorded at 500 MHz and 125 MHz, respectively, using
CDCl3 as a reference standard (d=7.26 ppm) for H NMR
55.3, 55.2, 47.7; HRMS (ESI-ion trap): m/z=447.2070, calcd.
for C30H27N2O2 [M+H]+: 447.2073.
1
and (d=77.04 ppm) for 13C NMR. HR-MS (ion trap) were
recorded using APCI or ESI. Melting points were uncorrect-
ed. Precoated silica gel plates F-254 were used for analytical
thin-layer chromatography. Column chromatography was
performed on silica gel (300–400 mesh). Starting azidometh-
yl aromatics were readily prepared according to literature
procedures. Unless otherwise noted, all reagents were ob-
tained commercially and used without further purification.
1-(2-Fluorobenzyl)-2-(2-fluorophenyl)-4,5-diphenyl-1H-
imidazole (3e): white solid; mp 169–1718C; 1H NMR
(500 MHz, CDCl3): d=7.63–7.58 (m, 2H), 7.56–7.54 (m,
2H), 7.39–7.33 (m, 3H), 7.23–7.19 (m, 4H), 7.17–7.13 (m,
1H), 7.12–7.08 (m, 2H), 6.92–6.85 (m, 2H), 6.72 (dd, J=8.7,
5.2 Hz, 2H), 5.04 (s, 2H); 13C NMR (125 MHz, CDCl3): d=
1
1
163.2 (d, JC,F =247.8 Hz), 162.0 (d, JC,F =245.0 Hz), 147.1,
138.2, 134.2, 133.0 (d, 4JC,F =3.1 Hz), 132.9, 131.0, 131.0,
3
130.9, 130.8, 130.0, 129.0, 128.8, 128.2, 127.7 (d, JC,F
=
8.1 Hz), 127.6, 127.1 (d, 4JC,F =3.3 Hz), 127.0, 126.8, 126.6,
115.8 (d, 2JC,F =21.8 Hz), 115.6 (d, 2JC,F =21.8 Hz), 47.63;
HR-MS (ESI-ion trap): m/z=423.1667, calcd. for C23H18N:
423.1673 [M+H]+.
General Experimental Procedure for the Synthesis of
1,2,4,5-Tetrasubstituted Imidazoles 3
1-(4-Bromobenzyl)-2-(4-bromophenyl)-4,5-diphenyl-1H-
imidazole (3f): white solid; mp 183–1858C; 1H NMR
(500 MHz, CDCl3): d=7.56–7.48 (m, 6H), 7.39–7.33 (m,
5H), 7.23–7.20 (m, 4H), 7.16 (t, J=7.2 Hz, 1H), 6.66 (d, J=
8.2 Hz, 2H), 5.03 (s, 2H); 13C NMR (125 MHz, CDCl3): d=
146.9, 138.5, 136.3, 134.1, 131.9, 131.9, 131.0, 130.6, 130.4,
130.3, 129.6, 129.0, 129.0, 128.2, 127.6, 126.8, 126.7, 123.5,
121.5, 47.9; HR-MS (ESI-ion trap): m/z=545.0046,
543.0066, calcd. for C28H21Br2N2: 545.0051, 543.0071 [M+
H]+.
4,5-Diphenyl-1-[3-(trifluoromethyl)benzyl]-2-[3-(trifluoro-
methyl)phenyl]-1H-imidazole (3g): light yellow solid; mp
128–1308C; 1H NMR (500 MHz, CDCl3): d=7.89 (s, 1H),
7.80 (d, J=7.8 Hz, 1H), 7.66 (d, J=7.8 Hz, 1H), 7.59–7.53
(m, 3H), 7.45 (d, J=7.7 Hz, 1H), 7.41–7.32 (m, 4H), 7.27–
7.22 (m, 4H), 7.19–7.16 (m, 1H), 6.97 (d, J=6.0 Hz, 2H),
5.15 (s, 2H); 13C NMR (125 MHz, CDCl3): d=146.5, 138.7,
137.9, 133.9, 132.1, 131.6, 131.2 (q, JCF =32.5 Hz), 131.0,
130.8 (q, JCF =32.5 Hz), 130.5, 130.4, 129.4, 129.3, 129.3,
129.2, 129.1, 128.2, 126.8, 126.7, 126.0 (q, J=3.9 Hz), 125.8
Under an oxygen atmosphere,
a mixture of stilbene
1 (1.0 equiv., 0.5 mmol), azidomethyl aromatics 2 (2.2 equiv.,
1.1 mmol), Sm(OTf)3 (0.05 equiv., 0.025 mmol), and 4 mL of
toluene was refluxed at 1108C for 24 h. The progress of the
reaction was monitored by thin-layer chromatography. After
cooling down the reaction mixture, the solvent was evapo-
rated under reduced pressure. The residue was purified by
flash column chromatography (petroleum ether/ethyl ace-
tate) to afford 1,2,4,5-tetrasubstituted imidazoles 3.
1-Benzyl-2,4,5-triphenyl-1H-imidazole (3a): white solid;
mp 167–1698C (lit.[14] 165–1678C); 1H NMR (500 MHz,
CDCl3): d=7.69–7.63 (m, 2H), 7.62–7.55 (m, 2H), 7.42–7.38
(m, 3H), 7.37–7.30 (m, 3H), 7.24–7.18 (m, 7H), 7.17–7.13
(m, 1H), 6.82–6.80 (m, 2H), 5.12 (s, 2H); 13C NMR
(125 MHz, CDCl3): d=148.1, 138.2, 137.6, 134.5, 131.1,
131.2, 130.1, 129.1, 128.9, 128.8, 128.7, 128.6, 128.6, 128.1,
127.4, 126.8, 126.4, 126.1, 48.3; HR-MS (ESI): m/z=
387.1857, calcd. for C28H23N2 387.1861 [M+H+].
1-(4-Methylbenzyl)-4,5-diphenyl-2-p-tolyl-1H-imidazole
(3b): white solid; mp 135–1378C (lit.[15] 132–1358C);
1H NMR (500 MHz, CDCl3): d=7.58–7.54 (m, 4H), 7.36–
7.29 (m, 3H), 7.24–7.18 (m, 6H), 7.15–7.12 (m, 1H), 7.01 (d,
J=7.9 Hz, 2H), 6.70 (d, J=8.0 Hz, 2H), 5.06 (s, 2H), 2.37
(s, 3H), 2.29 (s, 3H); 13C NMR (125 MHz, CDCl3): d=
148.2, 138.8, 137.9, 136.9, 134.7, 134.6, 131.2, 131.1, 130.9,
129.9, 129.3, 129.3, 128.9, 128.8, 128.6, 128.1, 126.9, 126.3,
125.9, 48.0, 21.4, 21.1; HR-MS (ESI-ion trap): m/z=
415.2181, calcd. for C30H27N2: 415.2174 [M+H]+.
(q, J=3.6 Hz), 123.7 (q, JC,F =271.0 Hz), 123.6 (q, JC,F
=
271.0 Hz), 124.6 (q, J=3.8 Hz), 123.2 (q, J=3.8 Hz), 48.07;
HR-MS (ESI-ion trap): m/z=523.1600, calcd. for
C30H21F6N2: 523.1609 [M + H]+.
4-[1-(4-Cyanobenzyl)-4,5-diphenyl-1H-imidazol-2-yl]ben-
1
zonitrile (3h): light yellow solid; mp 176–1778C; H NMR
(500 MHz, CDCl3): d=7.79–7.77 (m, 2H), 7.74–7.70 (m,
2H), 7.57–7.54 (m, 4H), 7.44–7.40 (m, 1H), 7.40–7.36 (m,
2H), 7.26–7.18 (m, 5H), 6.95–6.91 (m, 2H), 5.21 (s, 2H);
13C NMR (125 MHz, CDCl3): d=145.8, 142.0, 139.4, 134.8,
133.5, 132.7, 132.6, 131.1, 130.8, 130.0, 129.3, 129.2, 129.2,
128.3, 127.1, 126.8, 126.6, 118.3, 118.1, 112.7, 112.0, 48.3;
HR-MS (ESI-ion trap): m/z=437.1759, calcd. for C30H21N4:
437.1766 [M+H]+.
2-(Naphthalen-2-yl)-1-(naphthalen-2-ylmethyl)-4,5-di-
phenyl-1H-imidazole (3i): light yellow solid; mp 149–1518C;
1H NMR (500 MHz, CDCl3): d=8.17 (s, 1H), 7.90–7.80 (m,
4H), 7.77–7.66 (m, 5H), 7.52–7.44 (m, 4H), 7.38–7.26 (m,
8H), 7.20 (t, J=7.1 Hz, 1H), 7.03 (d, J=8.4 Hz, 1H), 5.36
(s, 2H); 13C NMR (125 MHz, CDCl3): d=148.1, 138.5, 135.2,
134.5, 133.3, 133.3, 133.1, 132.7, 131.1, 131.0, 130.9, 130.5,
128.9, 128.8, 128.7, 128.5, 128.4, 128.4, 128.2, 128.2, 127.9,
127.7, 126.9, 126.7, 126.5, 126.4, 126.1, 125.0, 123.9, 48.7;
HR-MS (ESI-ion trap): m/z=487.2172, calcd. for C36H27N2:
487.2174 [M + H]+.
1-(4-tert-bButylbenzyl)-2-(4-tert-butylphenyl)-4,5-diphen-
yl-1H-imidazole (3c): white solid; mp 167–1698C; H NMR
1
(500 MHz, CDCl3): d=7.64–7.59 (m, 4H), 7.46–7.42 (m,
2H), 7.36–7.33 (m, 1H), 7.32–7.28 (m, 2H), 7.21 (dd, J=7.8,
5.9 Hz, 6H), 7.15–7.12 (m, 1H), 6.74 (d, J=8.3 Hz, 2H),
5.09 (s, 2H), 1.35 (s, 9H), 1.29 (s, 9H); 13C NMR (125 MHz,
CDCl3): d=151.9, 150.3, 148.2, 137.9, 134.7, 131.3, 131.2,
130.9, 129.9, 128.8, 128.7, 128.5, 128.1, 128.0, 126.8, 126.2,
125.9, 125.5, 125.4, 48.1, 34.7, 34.5, 31.5, 31.3; HR-MS (ESI-
ion trap): m/z=499.3112, calcd. for C36H39N2: 499.3113 [M+
H]+.
1-(4-Methoxybenzyl)-2-(4-methoxyphenyl)-4,5-diphenyl-
1H-imidazole (3d): white solid; mp 145–1468C (lit.[15] 152–
1
1548C); H NMR (500 MHz, CDCl3): d=7.59–7.54 (m, 4H),
7.35–7.32 (m, 2H), 7.23–7.17 (m, 5H), 7.15–7.11 (m, 1H),
6.94–6.90 (m, 2H), 6.74–6.89 (m, 4H), 5.02 (s, 2H), 3.82 (s,
3H), 3.75 (s, 3H); 13C NMR (125 MHz, CDCl3): d=160.1,
158.8, 147.9, 131.2, 131.1, 130.5, 129.8, 129.7, 129.6, 129.4,
128.8, 128.6, 128.4, 128.1, 127.3, 126.8, 126.3, 114.0, 113.9,
2-Chloro-5-{[2-(6-chloropyridin-3-yl)-4,5-diphenyl-1H-imi-
dazol-1-yl]methyl}pyridine (3j): light yellow solid; mp 181–
Adv. Synth. Catal. 2015, 357, 3229 – 3241
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Yingchun Wang et al.
1
1828C; H NMR (500 MHz, CDCl3): d=8.71–8.55 (m, 1H),
7.58–7.56 (m, 2H), 7.53 (d, J=8.5 Hz, 2H), 7.50–7.48 (m,
3H), 7.20–7.14 (m, 3H), 6.73 (d, J=7.3 Hz, 2H), 5.21 (s,
2H); 13C NMR (125 MHz, DMSO): d=149.2, 139.1, 137.1,
136.5, 135.4, 133.4, 133.2, 132.8, 132.1, 130.8, 130.5, 129.2,
129.2, 129.1, 128.1, 127.2, 126.2, 119.4, 118.9, 112.3, 109.3,
48.6; HR-MS (APCI-ion trap): m/z=437.1747, calcd. for
C30H21N4: 437.1766.
1-Benzyl-4-(4-bromophenyl)-2,5-diphenyl-1H-imidazole
(3q): white solid; mp 154–1568C; 1H NMR (500 MHz,
CDCl3): d=7.66–7.64 (m, 2H), 7.46–7.42 (m, 2H), 7.42–7.35
(m, 4H), 7.35–7.30 (m, 4H), 7.22–7.16 (m, 5H), 6.79–6.78
(m, 2H), 5.10 (s, 2H); 13C NMR (125 MHz, CDCl3): d=
148.2, 137.3, 136.9, 133.2, 132.0, 131.2, 131.0, 130.6, 130.4,
129.2, 129.1, 129.0, 128.9, 128.7, 128.6, 128.4, 127.5, 126.0,
120.4, 48.4; HR-MS (ESI-ion trap): m/z=465.0956,
467.0934, calcd. for C28H22BrN2; 465.0966, 467.0946 [M+
H]+.
1-Benzyl-5-(4-bromophenyl)-2,4-diphenyl-1H-imidazole
(3q’): white solid; mp 135–1378C; 1H NMR (500 MHz,
CDCl3): d=7.67–7.65 (m, 2H), 7.57–7.55 (m, 2H), 7.46–7.39
(m, 5H), 7.25–7.20 (m, 5H), 7.19–7.16 (m, 1H), 7.08–7.04
(m, 2H), 6.81–6.80 (dd, J=7.3, 2.2 Hz, 2H), 5.10 (s, 2H);
13C NMR (125 MHz, CDCl3): d=148.4, 137.2, 132.7, 132.1,
132.0, 129.9, 129.2, 129.1, 129.0, 128.7, 128.7, 128.6, 128.2,
127.6, 127.3, 127.0, 126.7, 125.9, 123.1, 48.4; HR-MS (ESI-
ion trap): m/z=465.0951, 467.0930, calcd. for C28H22BrN2:
465.0966, 467.0946 [M+H]+.
1-Benzyl-5-(3-chlorophenyl)-4-(3-methoxyphenyl)-2-
phenyl-1H-imidazole (3r): light yellow oil; 1H NMR
(500 MHz, CDCl3): d=7.75 (d, J=1.8 Hz, 1H), 7.66 (dd, J=
6.6, 2.9 Hz, 2H), 7.42–7.38 (m, 3H), 7.36 (d, J=6.8 Hz, 1H),
7.26–7.19 (m, 4H), 7.13–7.08 (m, 2H), 6.92 (dd, J=8.3,
2.6 Hz, 1H), 6.83 (t, J=7.0 Hz, 3H), 6.68–6.65 (m, 1H), 5.11
(s, 2H), 3.57 (s, 3H); 13C NMR (125 MHz, CDCl3): d=
159.8, 148.2, 137.6, 134.2, 131.7, 130.6, 130.0, 129.4, 129.3,
129.1, 129.0, 128.7, 128.6, 127.5, 126.8, 126.4, 126.1, 126.0,
125.8, 124.7, 123.4, 115.6, 115.4, 55.1, 48.4; HR-MS (ESI-ion
trap): m/z=451.1562, calcd. for C29H24ClN2O: 451.1577
[M+H]+.
7.97 (dd, J=8.3, 2.5 Hz, 1H), 7.76 (d, J=2.1 Hz, 1H), 7.51
(dd, J=8.3, 1.3 Hz, 2H), 7.44–7.37 (m, 4H), 7.24–7.16 (m,
6H), 7.00 (dd, J=8.3, 2.6 Hz, 1H), 5.11 (s, 2H); 13C NMR
(125 MHz, CDCl3): d=152.1, 151.2, 148.9, 147.5, 143.7,
139.5, 139.1, 136.4, 133.5, 131.1, 130.8, 130.0, 129.5, 129.4,
128.3, 127.1, 126.8, 125.8, 124.6, 124.4, 45.6; HR-MS (ESI-
ion trap): m/z=457.0993, calcd. for C26H19Cl2N4: 457.0987
[M+H]+.
2-Mesityl-4,5-diphenyl-1-(2,4,6-trimethylbenzyl)-1H-imi-
dazole (3k): white solid; mp 175–1768C; 1H NMR
(500 MHz, CDCl3): d=7.51 (d, J=7.4 Hz, 2H), 7.41–7.36
(m, 3H), 7.32 (dd, J=6.5, 3.0 Hz, 2H), 7.18 (t, J=7.5 Hz,
2H), 7.11 (t, J=7.2 Hz, 1H), 6.75 (s, 2H), 6.48 (s, 2H), 4.85
(s, 2H), 2.27 (s, 3H), 2.14 (s, 3H), 1.94 (s, 6H), 1.75 (s, 6H);
13C NMR (125 MHz, CDCl3): d=147.2, 138.8, 138.5, 137.4,
137.0, 131.6, 130.9, 129.8, 129.4, 128.9, 128.6, 128.3, 128.0,
127.9, 126.8, 126.6, 126.0, 124.5, 124.0, 43.9, 21.2, 20.7, 20.0,
19.6 ; HR-MS (ESI-ion trap): m/z=471.2804, calcd. for
C34H35N2: 471.2800 [M+H]+.
1-(2,6-Dichlorobenzyl)-2-(2,6-dichlorophenyl)-4,5-diphen-
yl-1H-imidazole (3l): light yellow solid; mp 179–1818C;
1H NMR (500 MHz, CDCl3): d=7.55–7.53 (m, 2H), 7.48–
7.43 (m, 5H), 7.22–7.17 (m, 5H), 7.15–7.12 (m, 1H), 7.01–
6.95 (m, 3H), 5.25 (s, 2H); 13C NMR (125 MHz, CDCl3):
d=141.8, 137.4, 137.3, 136.5, 134.5, 131.6, 131.1, 130.9, 130.7,
130.6, 130.2, 129.3, 128.9, 128.7, 128.4, 128.0, 127.9, 126.9,
126.3, 44.8; HR-MS (ESI-ion trap): m/z=525.0278, calcd.
for C28H19N2Cl4; 525.0273 [M+H]+.
1-Benzyl-2-phenyl-4,5-di-p-tolyl-1H-imidazole (3m): white
solid; mp 74–768C; H NMR (500 MHz, CDCl3): d=7.66–
1
7.62 (m, 2H), 7.49–7.46 (m, 2H), 7.39–7.35 (m, 3H), 7.21–
7.18 (m, 3H), 7.12–7.09 (m, 4H), 7.03 (d, J=8.0 Hz, 2H),
6.83–6.81 (m, 2H), 5.09 (s, 2H), 2.36 (s, 3H), 2.28 (s, 3H);
13C NMR (125 MHz, CDCl3): d=147.8, 138.4, 138. 1, 137.8,
135.8, 131.8, 131.2, 131.0, 130.2, 129.7, 129.5, 129.1, 128.8,
128.5, 128.4, 128.1, 127.3, 126.7, 126.0, 48.2, 21.3, 21.1; HR-
MS (ESI-ion trap): m/z=415.2181, calcd. for C30H27N2:
415.2174 [M+H]+.
1-Benzyl-4,5-bis(4-chlorophenyl)-2-phenyl-1H-imidazole
(3n): white solid; mp 123–1248C; 1H NMR (500 MHz,
CDCl3): d=7.65–7.63 (m, 2H), 7.47 (d, J=8.6 Hz, 2H),
7.42–7.39 (m, 3H), 7.29 (d, J=8.4 Hz, 2H), 7.23–7.17 (m,
5H), 7.10 (d, J=8.4 Hz, 2H), 6.84–6.76 (m, 2H), 5.09 (s,
2H); 13C NMR (125 MHz, CDCl3): d=148.6, 137.5, 137.2,
135.0, 132.7, 132.3, 132.3, 130.5, 129.2, 129.2, 129.2, 129.0,
128.9, 128.7, 128.7, 128.4, 128.1, 127.6, 125.9, 48.4; HR-MS
(ESI-ion trap): m/z=455.1084, calcd. for C28H21Cl2N2:
455.1082 [M+H]+.
1-Benzyl-4-(3-chlorophenyl)-5-(3-methoxyphenyl)-2-
phenyl-1H-imidazole (3r’): light yellow oil; 1H NMR
(500 MHz, CDCl3): d=7.68 (dd, J=6.1, 2.7 Hz, 2H), 7.44–
7.40 (m, 3H), 7.34–7.32 (m, 1H), 7.24–7.21 (m, 4H), 7.19–
7.14 (m, 2H), 7.13–7.12 (m, 2H), 7.09 (d, J=7.7 Hz, 1H),
6.82–6.77 (m, 2H), 6.76–6.71 (m, 1H), 5.11 (s, 2H), 3.68 (s,
3H); 13C NMR (125 MHz, CDCl3): d=159.5, 148.3, 137.1,
134.6, 131.5, 131.1, 130.0, 129.9, 129.5, 129.3, 129.2, 129.1,
128.9, 128.8, 128.7, 128.6, 128.5, 128.0, 127.6, 126.0, 119.4,
113.4, 111.6, 55.1, 48.6; HR-MS (ESI-ion trap): m/z=
451.1582, calcd. for C29H24ClN2O: 451.1577 [M+H]+.
1-Benzyl-5-(4-fluorophenyl)-4-(4-methoxyphenyl)-2-
phenyl-1H-imidazole (3s): light yellow oil; 1H NMR
(500 MHz, CDCl3): d=7.77 (d, J=8.7 Hz, 1H), 7.60–7.57
(m, 2H), 7.43 (d, J=8.8 Hz, 1H), 7.38–7.25 (m, 5H), 7.21–
7.09 (m, 7H), 6.94–6.89 (m, 1H), 6.87 (dd, J=8.7, 2.3 Hz,
1H), 6.78 (d, J=2.2 Hz, 1H), 5.30 (s, 2H), 3.83 (s, 3H);
1-Benzyl-4,5-bis(4-bromophenyl)-2-phenyl-1H-imidazole
(3o): white solid; mp 132–1338C (lit.[15] 128–1318C);
1H NMR (500 MHz, CDCl3): d=7.65–7.61 (m, 2H), 7.45 (d,
J=8.4 Hz, 2H), 7.42–7.40 (m, 5H), 7.34 (d, J=8.6 Hz, 2H),
7.24–7.21 (m, 3H), 7.04 (d, J=8.4 Hz, 2H), 6.82–6.76 (m,
2H), 5.09 (s, 2H); 13C NMR (125 MHz, CDCl3): d=148.66,
137.5, 137.1, 133.1, 132.5, 132.2, 131.3, 130.5, 129.7, 129.2,
129.0, 128.9, 128.8, 128.7, 128.4, 127.6, 125.9, 123.3, 120.5,
48.5; HR-MS (ESI-ion trap): m/z=545.0056, 543.0078,
calcd. for C28H21Br2N2, 545.0051, 543.0071 [M+H]+.
4,4’-(1-Benzyl-2-phenyl-1H-imidazole-4,5-diyl)dibenzoni-
1
13C NMR (125 MHz, CDCl3): d=161.4 (d, JC,F =242.5 Hz),
4
156.6, 137.9, 137.1, 131.6 (d, JC,F =2.5 Hz), 128.9, 128.6 (d,
3JC,F =7.8 Hz), 127.8, 127.4, 126.9, 126.2, 124.5, 124.4, 120.8,
2
120.5, 116.5, 115.4 (d, JC,F =21.2 Hz), 114.1, 109.9, 55.7, 50.1;
1
trile (3p): yellow solid; mp 205–2078C; H NMR (500 MHz,
HR-MS (ESI-ion trap): m/z=435.1865, calcd. for
DMSO): d=7.89 (d, J=8.5 Hz, 2H), 7.72–7.67 (m, 4H),
C29H24FN2O: 435.1873 [M+H]+.
3238
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FULL PAPERS
Synthesis of Polysubstituted Imidazoles and Pyridines
(E)-N-(4-tert-Butylbenzyl)-1,2-diphenylethenamine (D-1):
yellow oil; 1H NMR (500 MHz, CDCl3): d=7.70–7.67 (m,
2H), 7.57 (d, J=7.4 Hz, 2H), 7.44–7.39 (m, 4H), 7.30 (d, J=
6.8 Hz, 2H), 7.20–7.18 (m, 4H), 6.69 (d, J=8.3 Hz, 2H),
5.08 (s, 2H), 1.26 (s, 9H); 13C NMR (125 MHz, CDCl3): d=
131.2, 130.9, 130.1, 129.3, 128.8, 128.6, 128.5, 128.3, 128.1,
127.3, 126.9, 126.0, 125.6, 125.4, 48.2, 31.4, 31.3.
(E)-1,2-Diphenyl-N-(2,4,6-trimethylbenzyl)ethenamine
(D-2): light yellow solid; mp 103–1058C; 1H NMR
(500 MHz, CDCl3): d=7.57–7.46 (m, 6H), 7.44 (dd, J=7.7,
1.7 Hz, 2H), 7.20 (t, J=7.5 Hz, 2H), 7.13 (t, J=7.3 Hz, 1H),
7.01 (s, 1H), 6.90 (s, 2H), 4.79 (s, 2H), 2.30 (s, 3H), 2.21 (s,
6H); 13C NMR (125 MHz, CDCl3): d=138.5, 138.2, 137.6,
135.5, 134.7, 131.2, 130.9, 129.5, 129.1, 128.8, 128.1, 127.9,
126.6, 126.2, 44.1, 21.0, 19.5; HR-MS (APCI-ion trap): m/z=
328.2069, calcd. for C24H26N: 328.2065 [M+H]+.
146.6, 141.5, 140.0, 137.4, 136.9, 136.1, 135.2, 129.5, 129.2,
128.4, 128.2, 127.4, 127.1, 107.9, 106.6, 101.2, 55.3; HR-MS
(ESI-ion trap): m/z=368,1665, calcd. for C25H22NO2:
368.1651 [M+H]+.
2-(Naphthalen-2-yl)-3,5-diphenylpyridine (5e): yellow
1
solid; mp 183–1858C; H NMR (500 MHz, CDCl3): d=9.05–
8.96 (m, 1H), 8.04 (s, 1H), 7.99 (d, J=2.2 Hz, 1H), 7.80–
7.76 (m, 2H), 7.72–7.69 (m, 3H), 7.53 (t, J=7.5 Hz, 2H),
7.47–7.42 (m, 4H), 7.33–7.29 (m, 5H); 13C NMR (125 MHz,
CDCl3): d=155.6, 146.8, 139.9, 137.4, 137.3, 137.1, 136.2,
135.1, 133.2, 132.9, 129.6, 129.6, 129.2, 128.5, 128.5, 128.2,
127.6, 127.5, 127.4, 127.3, 127.2, 126.3, 125.9; HR-MS (ESI-
ion trap): m/z=358.1582, calcd. for C27H20N: 358.1596 [M+
H]+.
2-(Biphenyl-3-yl)-3,5-diphenylpyridine (5f): yellow oil;
1H NMR (500 MHz, CDCl3): d=8.98 (s, 1H), 7.98 (s, 1H),
7.70 (t, J=7.2 Hz, 2H), 7.62 (s, 1H), 7.54–7.50 (m, 4H),
7.45–7.42 (m, 1H), 7.41–7.24 (m, 11H); 13C NMR (125 MHz,
CDCl3): d=155.7, 146.8, 141.0, 140.6, 137.4, 137.0, 136.2,
135.1, 130.05, 129.7, 129.6, 129.2, 128.8, 128.6, 128.6, 128.5,
128.4, 128.3, 128.0, 127.4, 127.2, 127.1, 126.7; HR-MS (ESI-
ion trap): m/z=384.1720, calcd. for C29H22N: 384.1752 [M+
H]+.
General Experimental Procedure for the Synthesis of
2,3,5-Trisubstituted Pyridines 5
Under an oxygen atmosphere, a mixture of aromatic 1,3-
diene 4 (1.0 equiv., 0.5 mmol), azidomethyl aromatics 2
(1.2 equiv., 0.6 mmol), Sm(OTf)3 (0.05 equiv., 0.025 mmol),
and 4 mL of toluene was refluxed at 1108C for 24 h. The
progress of the reaction was monitored by thin-layer chro-
matography. After cooling down the reaction mixture, the
solvent was evaporated under reduced pressure. The target
product 5 was purified by column chromatography on silica
gel using a mixture of ethyl acetate and petroleum ether.
2,3,5-Triphenylpyridine (5a): light yellow solid; mp 120–
2-(4-Fluorophenyl)-3,5-diphenylpyridine (5g): light yellow
1
solid; mp 128–1308C; H NMR (500 MHz, CDCl3): d=8.91
(s, 1H), 7.92 (s, 1H), 7.68 (d, J=7.5 Hz, 2H), 7.51 (t, J=
7.5 Hz, 2H), 7.45–7.36 (m, 3H), 7.33–7.32 (m, 3H), 7.25–
7.24 (m, 2H), 6.95 (t, J=8.6 Hz, 2H); 13C NMR (125 MHz,
CDCl3): d=162.6 (d, 1JC,F =246.3 Hz), 154.8, 146.7, 139.7,
4
137.3, 137.1, 135.9, 135.8 (d, JC,F =2.5 Hz), 135.2, 131.7 (d,
1
1218C (lit.[16] 121–1228C); H NMR (500 MHz, CDCl3): d=
3JC,F =7.5 Hz), 129.6, 129.2, 128.6, 128.3, 127.5, 127.1, 114.9
2
8.95 (d, J=2.2 Hz, 1H), 7.94 (d, J=2.2 Hz, 1H), 7.72–7.67
(m, 2H), 7.52 (t, J=7.6 Hz, 2H), 7.46–7.41 (m, 3H), 7.33–
7.25 (m, 8H); 13C NMR (125 MHz, CDCl3): d=155.9, 146.7,
139.9, 139.9, 137.4, 137.0, 136.0, 135.0, 129.9, 129.6, 129.2,
128.4, 128.2, 128.0, 127.9, 127.4, 127.2; HR-MS (ESI-ion
trap): m/z=308.1434, calcd. for C23H18N: 308.1439.
(d, JC,F =21.2 Hz); HR-MS (ESI-ion trap): m/z=326.1310,
calcd. for C23H17NF: 326.1345 [M + H]+.
2-(2-Fluorophenyl)-3,5-diphenylpyridine (5h): yellow oil;
1H NMR (500 MHz, CDCl3): d=8.95 (d, J=2.2 Hz, 1H),
7.97 (d, J=2.2 Hz, 1H), 7.71–7.67 (m, 2H), 7.54–7.42 (m,
5H), 7.29–7.27 (m, 3H), 7.25–7.23 (m, 2H), 7.18–7.15 (m,
1H), 6.94–6.89 (m, 1H); 13C NMR (125 MHz, CDCl3): d=
159.6 (d, 1JC,F =247.5 Hz), 146.3, 139.1, 137.8, 137.2, 136.5,
136.0, 131.8, 131.7, 130.2 (d, 3JC,F =8.1 Hz), 129.9, 129.2,
128.9, 128.4, 128.2, 127.5, 127.2, 124.1 (d, 4JC,F =3.5 Hz),
115.6 (d, 2JC,F =21.2 Hz); HR-MS (APCI-ion trap): m/z=
320.1323, calcd. for C23H17NF: 326.1345 [M+H]+.
2-(4-tert-Butylphenyl)-3,5-diphenylpyridine (5b): light
1
yellow solid; mp 140–1428C; H NMR (500 MHz, CDCl3):
d=8.91 (d, J=1.2 Hz, 1H), 7.91 (d, J=1.2 Hz, 1H), 7.68 (d,
J=7.9 Hz, 2H), 7.50 (t, J=7.6 Hz, 2H), 7.42 (t, J=7.4 Hz,
1H), 7.36–7.27 (m, 9H), 1.29 (s, 9H); 13C NMR (125 MHz,
CDCl3): d=155.8, 150.9, 146.6, 140.1, 137.5, 137.0, 136.8,
135.8, 134.7, 129.6, 129.5, 129.1, 128.4, 128.1, 127.3, 127.1,
124.9, 34.57, 31.28; HR-MS (ESI-ion trap): m/z=364.2043,
calcd. for C27H26N: 364.2065 [M+H]+.
2-(4-Methoxyphenyl)-3,5-diphenylpyridine (5c): white
solid; mp 180–1818C (lit.[17] 179.6–181.08C); 1H NMR
(500 MHz, CDCl3): d=8.93 (d, J=1.9 Hz, 1H), 7.91 (d, J=
2.2 Hz, 1H), 7.69–7.67 (m, 2H), 7.53–7.49 (m, 2H), 7.44–
7.38 (m, 3H), 7.37–7.27 (m, 5H), 6.81 (d, J=8.6 Hz, 2H),
3.79 (s, 3H); 13C NMR (125 MHz, CDCl3): d=159.4, 155.5,
146.6, 140.3, 137.5, 137.0, 135.6, 134.5, 132.3, 131.3, 129.6,
129.2, 128.5, 128.1, 127.3, 127.1, 113.4, 55.2; HR-MS (ESI-
ion trap): m/z=338.1542, calcd. for C24H20N: 338.1545 [M+
H]+.
2-(4-Chlorophenyl)-3,5-diphenylpyridine (5i): light yellow
1
solid; mp 176–1778C; H NMR (500 MHz, CDCl3): d=8.92
(s, 1H), 7.92 (s, 1H), 7.67 (d, J=7.6 Hz, 2H), 7.51 (t, J=
7.5 Hz, 2H), 7.43 (t, J=7.2 Hz, 1H), 7.38–7.29 (m, 5H),
7.29–7.25 (m, 4H); 13C NMR (125 MHz, CDCl3): d=154.5,
146.7, 139.5, 138.2, 137.2, 137.1, 136.0, 135.3, 134.0, 131.3,
129.5, 129.2, 128.6, 128.3, 128.2, 127.6, 127.1; HR-MS (ESI-
ion trap): m/z=342.1039, calcd. for C23H17NCl: 342.1050
[M+H]+.
2-(2,6-Dichlorophenyl)-3,5-diphenylpyridine (5j): white
1
solid; mp 90–938C; H NMR (500 MHz, CDCl3): d=8.97 (d,
J=2.2 Hz, 1H), 7.98 (d, J=2.2 Hz, 1H), 7.73–7.70 (m, 2H),
7.53–7.50 (m, 2H), 7.45–7.42 (m, 1H), 7.32–7.29 (m, 3H),
7.28–7.26 (m, 2H), 7.28–7.25 (m, 4H); 13C NMR (125 MHz,
CDCl3): d=155.9, 146.7, 139.9, 139.9, 137.4, 136.9, 136.0,
135.0, 129.9, 129.6, 129.2, 128.4, 128.2, 127.9, 127.8, 127.4,
127.1; HR-MS (APCI-ion trap): m/z=376.0637, calcd. for
C23H16Cl2N: 376.0660 [M+H]+.
2-(3,5-Dimethoxyphenyl)-3,5-diphenylpyridine
(5d):
yellow oil; 1H NMR (500 MHz, CDCl3): d=8.93 (d, J=
2.1 Hz, 1H), 7.93 (d, J=2.1 Hz, 1H), 7.68 (d, J=7.7 Hz,
2H), 7.51 (t, J=6.8 Hz, 2H), 7.45–7.41 (m, 1H), 7.35–7.26
(m, 5H), 6.58 (d, J=2.2 Hz, 2H), 6.39 (d, J=2.2 Hz, 1H),
3.62 (s, 6H); 13C NMR (125 MHz, CDCl3): d=160.2, 155.6,
Adv. Synth. Catal. 2015, 357, 3229 – 3241
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FULL PAPERS
Yingchun Wang et al.
3,5-Diphenyl-2-[4-(trifluoromethyl)phenyl]pyridine (5k):
light yellow solid; mp 163–1658C; 1H NMR (500 MHz,
CDCl3): d=8.97 (d, J=1.3 Hz, 1H), 7.97 (d, J=1.3 Hz, 1H),
7.70 (d, J=7.6 Hz, 2H), 7.57–7.50 (m, 6H), 7.45 (t, J=
7.3 Hz, 1H), 7.38–7.36 (m, 3H), 7.28–7.22 (m, 2H);
13C NMR (125 MHz, CDCl3): d=154.2, 146.9, 143.5, 139.3,
137.1, 137.1, 136.4, 135.7, 130.3, 129.8 (q, JC,F =32.1 Hz),
129.6, 129.2, 128.7, 128.4, 127.8, 127.2, 124.9 (q, J=3.8 Hz),
124.2 (q, JC,F =270.9 Hz); HR-MS (ESI-ion trap): m/z=
376.1308, calcd. for C24H17NF3: 376.1313 [M+H]+.
119.6, 54.2; HR-MS (APCI-ion trap): m/z=236.1173, calcd.
for C15H14N3: 236.1188 [M+H]+.
CAUTION: Sufficient care has to be exercised while han-
dling organic azides because of their explosive nature.
Acknowledgements
We would like to thank the Ministry of Education of China
(IRT1225), National Natural Science Foundation of China
(21362002, 41465009 and 81260472), Guangxi Natural Sci-
ence Foundation of China (2014GXNSFDA118007), State
Key Laboratory Cultivation Base for the Chemistry and Mo-
lecular Engineering of Medicinal Resources, Ministry of Sci-
ence and Technology of China (CMEMR2014A02,
CMEMR2012A and CMEMR2013-C01), and Bagui Scholar
Program of Guangxi for financial support.
6’-Chloro-3,5-diphenyl-2,3’-bipyridine (5l): light yellow
1
solid; mp 175–1768C; H NMR (500 MHz, CDCl3): d=8.94
(d, J=2.2 Hz, 1H), 8.42 (d, J=2.1 Hz, 1H), 7.93 (d, J=
2.2 Hz, 1H), 7.70 (dd, J=8.3, 2.5 Hz, 1H), 7.67–7.64 (m,
2H), 7.49 (t, J=7.5 Hz, 2H), 7.43 (t, J=7.3 Hz, 1H), 7.37–
7.32 (m, 3H), 7.25–7.22 (m, 2H), 7.20 (d, J=8.3 Hz, 1H);
13C NMR (125 MHz, CDCl3): d=151.3, 150.8, 150.6, 147.1,
139.9, 138.9, 137.1, 136.9, 136.5, 135.9, 134.5, 129.5, 129.3,
128.9, 128.5, 128.1, 127.2, 123.4; HRMS (ESI-ion trap):
m/z=343.1005, calcd. for C22H16NCl: 343.1002 [M+H]+.
2-Phenyl-3,5-di-p-tolylpyridine (5m):[18] light yellow solid;
References
1
mp 101–1028C; H NMR (500 MHz, CDCl3): d=8.90 (d, J=
2.2 Hz, 1H), 7.90 (d, J=2.3 Hz, 1H), 7.58–7.56 (m, 2H),
7.43–7.40 (m, 2H), 7.31 (d, J=7.9 Hz, 2H), 7.28–7.26 (m,
3H), 7.15–7.09 (m, 5H), 2.43 (s, 3H), 2.35 (s, 3H); 13C NMR
(125 MHz, CDCl3): d=155.6, 146.3, 140.1, 138.1, 137.1,
137.0, 136.7, 135.9, 134.9, 134.6, 129.9, 129.8, 129.5, 129.1,
127.9, 127.7, 127.0, 21.2, 21.1; HR-MS (APCI-ion trap):
m/z=336.1730, calcd. for C25H22N: 336.1752 [M+H]+.
3,5-Bis(4-bromophenyl)-2-phenylpyridine (5n): yellow
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1
solid; mp 154–1558C; H NMR (500 MHz, CDCl3): d=8.91
(d, J=2.2 Hz, 1H), 7.86 (d, J=2.3 Hz, 1H), 7.68–7.64 (m,
2H), 7.57–7.53 (m, 2H), 7.48–7.44 (m, 2H), 7.42–7.38 (m,
2H), 7.34–7.29 (m, 3H), 7.15–7.09 (m, 2H); 13C NMR
(125 MHz, CDCl3): d=156.2, 146.6, 139.3, 138.6, 136.5,
136.1, 134.9, 134.0, 132.4, 131.7, 131.2, 129.8, 128.7, 128.2,
128.2, 122.8, 121.9; HR-MS (ESI-ion trap): m/z=465.9621,
463.9642, calcd. for C23H16NBr2: 465.9629, 463.9649 [M+
H]+.
2-Phenyl-3,5-di(thiophen-2-yl)pyridine (5o): brown oil;
1H NMR (500 MHz, CDCl3): d=8.94 (d, J=2.2 Hz, 1H),
8.02 (d, J=2.3 Hz, 1H), 7.52–7.48 (m, 2H), 7.46 (dd, J=3.6,
1.1 Hz, 1H), 7.41 (dd, J=5.1, 1.1 Hz, 1H), 7.38–7.35 (m,
3H), 7.32 (dd, J=5.1, 1.2 Hz, 1H), 7.17 (dd, J=5.1, 3.6 Hz,
1H), 6.98 (dd, J=5.1, 3.6 Hz, 1H), 6.89 (dd, J=3.6, 1.2 Hz,
1H); 13C NMR (125 MHz, CDCl3): d=156.2, 145.5, 140.8,
139.8, 139.7, 135.4, 129.5, 129.2, 129.0, 128.4, 128.3, 128.1,
127.7, 127.4, 126.7, 126.3, 124.6; HR-MS (APCI-ion trap):
m/z=320.0546, calcd. for C19H14NS2; 320.0568 [M+H]+.
1-Benzyl-5-phenyl-1H-1,2,3-triazole (7a):[19] white solid;
1
mp 68–708C; H NMR (500 MHz, CDCl3): d=7.73 (s, 1H),
7.44–7.38 (m, 3H), 7.29–7.23 (m, 5H), 7.09–7.05 (m, 2H),
5.54 (s, 2H); 13C NMR (125 MHz, CDCl3): d=138.2, 135.5,
133.2, 129.5, 129.0, 128.9, 128.8, 128.1, 127.2, 126.9, 51.8;
HR-MS (ESI-ion trap): m/z=236.1185, calcd. for C15H14N3:
236.1188 [M+H]+.
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1
130–1328C (lit.[20] 129–1318C); H NMR (500 MHz, CDCl3):
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3240
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FULL PAPERS
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Adv. Synth. Catal. 2015, 357, 3229 – 3241
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
3241