Synthesis of 2-Aminopyridines via a Base-Promoted Cascade Reaction of N-Propargylic β-Enaminones with Formamides

Article abstract of DOI:10.1021/acs.joc.8b00128

N-Substituted formamides as nucleophiles react with in situ-generated 1,4-oxazepines from N-propargylic β-enaminones followed by spontaneous N-deformylation to deliver densely substituted 2-aminopyridines in good yields (31-88%). The formyl group is found to be a superior traceless activating group of free amines and would ultimately be removed in situ. This reaction proceeds smoothly at room temperature, in the presence of NaOH as sole additive, without protection from the atmosphere and generates H₂O and sodium formate as byproducts.

Full text of DOI:10.1021/acs.joc.8b00128

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Synthesis of 2-Aminopyridines via a Base-Promoted Cascade
Reaction of N-Propargylic #-Enaminones with Formamides
Yunxiang Weng, Changsheng Kuai, Weiwei Lv, and Guolin Cheng
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b00128 • Publication Date (Web): 13 Apr 2018
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Synthesis of 2ꢀAminopyridines via a BaseꢀPromoted Cascade
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Reaction of NꢀPropargylic
β
ꢀEnaminones with Formamides
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Yunxiang Weng, Changsheng Kuai, Weiwei Lv, and Guolin Cheng*
† College of Materials Science & Engineering, Huaqiao University, Xiamen 361021,
China
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ABSTRACT: Nꢀsubstituted formamides as nucleophiles react with in situ generated
1,4ꢀoxazepines from Nꢀpropargylic βꢀenaminones, followed by spontaneous
Nꢀdeformylation to deliver densely substituted 2ꢀaminopyridines in good yields
(31ꢀ88%). The formyl group is found to be a superior traceless activating group of
free amines and would ultimately be removed in situ. This reaction proceeds smoothly
at room temperature, in the presence of NaOH as sole additive, without protection
from the atmosphere, and generating H2O and sodium formate as byproducts.
■ INTRODUCTION
The 2ꢀaminopyridine moiety represents an important motif in
pharmaceuticals and natural products (Figure 1),1 as well as ligands in organic
synthesis and functional materials.2 Intense efforts have been devoted to
developing various methods for the synthesis of 2ꢀaminopyridines and their
derivatives. Transitionꢀmetalꢀcatalyzed amination of aryl halides
，
typically
and
including
palladiumꢀcatalyzed
BuchwaldꢀHartwig
amination3,4
copperꢀcatalyzed Ullmannꢀtype amination,5 provide powerful protocols to build
such scores (Scheme 1, a). However, sophisticated ligands are always required,
and aliphatic amines are not well tolerated in those amination reactions.6
Rutheniumꢀ7 and copperꢀ8 catalyzed cyclization have also been developed for
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Figure 1. Selected Biologically Active Compounds Containing 2ꢀAminopyridines
the divergent synthesis of 2ꢀaminopyridines (Scheme 1, b). An important
additional drawback of the above mentioned approaches has to do with the
toxicity of transitionꢀmetals in biological contexts, which seriously limit their
applications in biological and medicinal research. Although the
2ꢀaminopyridines could be synthesized by the traditional Chichibabin reaction
from sodium amide and pyridines,9 the nucleophilic addition,10 and 1,3ꢀdipolar
cycloaddition reaction of pyridine derivatives,11 the functionalized pyridine
cores as starting materials are always required. Consequently, developing
efficient access to 2ꢀaminopyridines from readily available materials under
transitionꢀmetalꢀfree conditions is of great significance.
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During our ongoing studies on synthesis of heterocyclic compounds,12 we have
recently documented that a variety of NꢀH heteroarenes, alcohols, and thiols could be
used as nucleophiles for the capture of 1,4ꢀoxazepine intermediates leading to
12aꢀc
Nꢀsubstituted heteroarenes (Scheme 1, c)
As research continues, herein we
disclose a simple and highly efficient cascade approach to multisubstituted
2ꢀaminopyridines from Nꢀpropargylic βꢀenaminones13 and formamides (Scheme 1, d).
In this scenario, the formyl group would function as a traceless activating group to
facilitate nucleophilic addition of formamides to in situ generated 1,4ꢀoxazepines and
would spontaneously be released to produce 2ꢀaminopyridines. In contrast to previous
work,3ꢀ8 the advantages of our reported reaction includes (i) mild reaction condition
(room temperature, and using NaOH as the only additive). (ii) environmentally
friendly (transitionꢀmetalꢀfree, H2O and sodium formate are the byproducts). (iii)
highly efficiency (cascade reaction in oneꢀpot mode).
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Scheme 1. Reported and Present Synthetic Strategy for the Synthesis of
2ꢀAminopyridines
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At the outset of our studies, free alkyl/aryl amines were used to react with
Nꢀpropargylic βꢀenaminone 1a, however no desired 2ꢀaminopyridine products were
observed, probably because of the considerably lower nucleophilicity of free amines.
Considering that amides could be deprotonated under strongly basic conditions, and
their conjugate bases may serve as nucleophiles. Then, a variety of activating groups,
including ꢀMs, ꢀTs, ꢀCbz, ꢀBoc, and ꢀAc, were screened, still no desired products were
formed (Scheme 2, a). Back and coꢀworkers reported that Nꢀformyl anilines were
more nucleophilic analogues than anilines under basic conditions for the conjugate
addition to acetylenic sulfones.14 When Nꢀformyl aniline was subjected to react with
1a, it was to our delight that the unpredictable Nꢀdeformylation product 3a was
obtained in 45% isolated yield (Scheme 2, b).
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Scheme 2. Screening Activating Groups of Aniline for the Synthesis of
2ꢀ(Phenylamino)pyridines
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■ RESULTS AND DISCUSSION
(Z)ꢀ1,3ꢀdiphenylꢀ3ꢀ(propꢀ2ꢀynꢀ1ꢀylamino)propꢀ2ꢀenꢀ1ꢀone 1a and formanilide 2a
were chosen as the model substrates for the optimization of the reaction conditions,
and the results were summarized in Table 1. NaOH, KOH, and LiOH were found to
be efficient bases for this cascade reaction, among which NaOH gave the best result
(Table 1, entries 1–3). The lower yields were encountered for other stronger bases
(entries 4–6). Subsequently, various solvents were investigated in the presence of 2
equiv of NaOH as the base (entries 7–9). No better result was obtained than that of
DMSO. 70% isolated yield was obtained when the loading of 2a was decreased to 1.5
equiv (entry 10). Further raising the reaction temperature could improve the yields
slightly (entry 13, 14). Therefore, the optimized reaction conditions were found to
entail the use of 1a and 2a in a molar ratio of 1:1.5, NaOH (2 equiv) as the base at
room temperature under air atmosphere (entry 10).
On the basis of the optimized conditions, the generality of this reaction was
investigated. As shown in Scheme 3, a variety of substituted formanilides ran
smoothly, affording the corresponding products in moderate to good yields (3a–k,
yields 45–77%). The structure of 3a was confirmed by singleꢀcrystal Xꢀray diffraction
analysis. At first, formanilides with electronꢀdonating groups (Me, OMe) were tested
and smoothly converted into the desired products (3b–e). The oꢀmethylꢀsubstituted
substrates, 3b and 3d, led to lower yields than pꢀmethylꢀsubstituted substrate 3c,
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Table 1. Screening of the Reaction Conditionsa
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entry
base
solvent
temp (oC) yield (%)b
1
NaOH
KOH
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
rt
rt
rt
rt
rt
rt
rt
rt
rt
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50
80
70
2
67
3
LiOH
69
4
KOtBu
NaOtBu
Cs2CO3
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
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14
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50
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NMP
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CH3CN
DMSO
DMSO
DMSO
DMSO
DMSO
0
10 c
11d
12e
13
14
75 (70)
48
68
76 (70)
79 (72)
aReaction conditions: 1a (0.2 mmol), 2a (0.4 mmol ), base (0.4 mmol), and solvent (1
mL) at room temperature under air atmosphere.bYields were determined by GC
c
analysis with dodecane as internal standard. Isolated yields in parentheses. 1.5 equiv
of 2a was used. d1.2 equiv of 2a was used. e1.5 equiv of NaOH was used. DMSO =
dimethylsulfoxide, DMF = N,Nꢀdimethylformamide, NMP = Nꢀmethylꢀ2ꢀpyrrolidone.
implying that the steric hindrance of the amides had an obvious effect on the reaction.
Formanilides bearing halogen groups (F, Cl, Br, I) at metaꢀ or paraꢀ position of the
aryl ring afforded the desired products in moderate yields (3f–k, yields 45–72%), thus
the corresponding products are suitable for further functionalization. Remarkably,
1ꢀnaphthalenyl amides 3l, and heterocyclic aromatic amides (3m, 3n) could be
compatible with this procedure, providing the desired products in 51%, 31%, and 66%
yields, respectively. In addition, various aliphatic formamides, including terminal
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alkene and alkyne, furnished the corresponding 2ꢀaminopyridines in moderate yields
(3o–s, yields 45–63%).
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Scheme 3. Scope of Formamidesa
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aReaction conditions: 1a (0.2 mmol), 2 (0.3 mmol), and NaOH (2 equiv) in DMSO (1
mL) at room temperature under air atmosphere. Yields based on 1a.
Furthermore, the scope of Nꢀpropargylic βꢀenaminones was also explored (Scheme
4). The steric hindrance of the Nꢀpropargylic βꢀenaminones also had an obvious effect
on the reaction (4a, yield 56%). In general, enaminone components bearing
electronꢀdonating substituents (4b−e and 4o, yields 42−73%) tended to give slightly
lower yields than those bearing electronꢀwithdrawing substituents (4f−k, 4n, yields
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72−88%). Remarkably, when R1 was 2ꢀthienyl and 2ꢀfuryl, the desired products 4l and
4m were obtained in 60% and 44% yields, respectively.
Scheme 4. Scope of NꢀPropargylic βꢀEnaminonesa
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aReaction conditions: 1 (0.2 mmol), 2a (0.3 mmol), and NaOH (2 equiv) in DMSO (1
mL) at room temperature under air atmosphere. Yields based on 1.
When 1a was treated with methanamide under the standard reaction conditions,
interestingly, Nꢀ(3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀyl) formamide 5t was obtained
instead of the decarboxylative product 3t. Then 5t was treated with 1 equivalent of
o
NaOH at 100 C for 12 h, 3t and sodium formate were obtained in 95% and 61%
yields, respectively. Those results indicated that the intermediates 5 could proceed
through a baseꢀpromoted decarbonylation to produce sodium formate (eq 1). Our
previous work12aꢀc had indicated that the active intermediate 1,4ꢀoxazepines were
generated from baseꢀpromoted 7ꢀexoꢀdig cyclization of Nꢀpropargylic
βꢀenaminones,
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which could be used as pyridylation reagents of various Nꢀheteroarenes, alcohols and
thiols. Then the intermediate 1,4ꢀoxazepine 6a was treated with formamide 2e under
the standard reaction, the 3e was obtained in 71% yield (eq 2). To further clarify the
reaction mechanism, the reaction of 1a with Nꢀ(4ꢀmethoxyphenyl) formamide 2e was
quenched with water after stirring at room temperature for 0.5 h, the formamide
intermediate 5e was isolated in 56% yield, which could be further transformed to 3e at
standard conditions for 2 h (eq 3).
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Based on the above results and our previous researches,12a a possible mechanism is
proposed (Scheme 5). Initially, the active intermediate 1,4ꢀoxazepine 6 was formed by
baseꢀpromoted cyclization from 1. Subsequent 6 was isomerized to provide epoxide
intermediate A undergoing 6πꢀelectrocyclization. Then nucleophilic addition of
formamide to epoxide A generated 2,3ꢀdihydropyridine intermediates B, which
subsequently aromatized to intermediate 5. Finally, Nꢀdeformylation occurred leading
to the final 2ꢀaminopyridine products 3 and 4.
Scheme 5. Plausible Mechanism for the Synthesis of 2ꢀAminopyridines
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■ CONCLUSION
In summary, we have developed a concise and efficient protocol for the synthesis of
a variety of 2ꢀaminopyridine derivatives from Nꢀpropargylic βꢀenaminones at room
temperature. In this reaction, the formyl group was used as a traceless activating
group of amines, which would ultimately be released without any other process
followed.
■ EXPERIMENTAL SECTION
General Information. All reagents were used directly without further purification.
All melting points were determined on a Beijing Science Instrument Dianguang
1
13
Instrument Factory XT4B melting point apparatus and were uncorrected. H and C
NMR spectra were measured on a 400 MHz Bruker spectrometer (1H 400 MHz, C
13
100 MHz), using CDCl3 as the solvent with tetramethylsilane (TMS) as the internal
standard at room temperature. HRMSꢀAPCI spectra were obtained on Agilent 6450
QꢀTOF spectrometer. IR data were recorded on a Nicolet iS10 spectrometer. The
1
13
products listed below were determined by H, C NMR. PE is petroleum ether (60–
o
90 C). The 2ꢀmethylꢀ5,7ꢀdiphenylꢀ1,4ꢀoxazepine 6a was prepared according to the
litertures.12aꢀb
Preparation of Nꢀpropargylic βꢀenaminones 1.13c A mixture of propargylamine
(1.1 g, 20 mmol), propynones (20 mmol), and CH3OH (50 mL) was stirred at room
temperature under air overnight. After propynones was exhausted completely
(monitored by TLC), the solvent was evaporated and the residue was purified by
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chromatography (silica gel, 5% EtOAc in PE ) to give 1.
Preparation of formamides 2.15 A mixture of amide or aniline (10 mmol),
methanamide (10 mmol) and Lꢀproline (115 mg, 1 mmol) was stirred in sealed tubes
at indicated temperature for indicated reaction time (See reference 15). After being
cooled to room temperature, 20 ml of water was added and extracted with DCM (20
mL x 3). After removal of solvent, the crude reaction mixture was purified by
recrystallization or chromatography.
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Preparation of 3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine 3t and sodium formate.
A mixture of Nꢀ(3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀyl)formamide 5t (144 mg, 0.5 mmol)
o
and NaOH (20 mg, 0.5 mmol) in DMSO (1 mL) was stirred at 100 C for 12 h. Then
DCM (10 mL) was poured into the reaction mixture and the resulting solution was
o
stirred for additional 5 min. Subsequently, the mixture was allowed to cool to 0 C
overnight, the resulting white solid was filtered off, washed with DCM and dried in
vacuo to give sodium formate (21 mg, 61%). The organic residue was concentrated
and purified by chromatography (silica gel, 5% EtOAc in PE ) to give 3t (123 mg,
95%).
Sodium formate. 1H NMR (400 MHz, D2O) δ 8.3 (s, 1H); 13C NMR (100 MHz, D2O)
δ 171.1.
Preparation of Nꢀ(4ꢀmethoxyphenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine
3e. A mixture of 2ꢀmethylꢀ5,7ꢀdiphenylꢀ1,4ꢀoxazepine 6a (52 mg, 0.2 mmol),
Nꢀ(4ꢀmethoxyphenyl)formamide 2e (45 mg, 0.3 mmol), NaOH (16 mg, 0.4 mmol) in
DMSO (1 mL) was stirred at room temperature for 2 h. Then the reaction was
quenched with H2O (4 mL) and extracted with EtOAc (5 mL x 3). The combined
EtOAc extracts were dried over Na2SO4 and concentrated. Then solvent was
evaporated and the residue was purified by chromatography (silica gel, 5% EtOAc in
PE ) to give 3e (52 mg, 71%).
Preparation of multisubstituted 2ꢀaminopyridines 3, 4. A mixture of
Nꢀpropargylic βꢀenaminones 1 (0.2 mmol), formamides 2 (0.3 mmol), NaOH (16 mg,
0.4 mmol) in DMSO (1 mL) was stirred at room temperature. After Nꢀpropargylic
βꢀenaminones 1 was exhausted completely (monitored by TLC), the reaction was
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quenched with H2O (4 mL) and extracted with EtOAc (5 mL x 3). The combined
EtOAc extracts were dried over Na2SO4 and concentrated. Then solvent was
evaporated and the residue was purified by chromatography (silica gel, 5% EtOAc in
PE ).
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3ꢀMethylꢀN,4,6ꢀtriphenylpyridinꢀ2ꢀamine (3a). Reaction time: 1 h; 47 mg (70%);
white solid; m.p. 151–154 °C; IR (KBr): ν 1603, 1529, 1492, 1368, 751, 689, 491
cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 7.2 Hz, 2H), 7.73 (d, J = 7.7 Hz, 2H),
7.49–7.40 (m, 5H), 7.39–7.34 (m, 5H), 7.21 (s, 1H), 7.03 (t, J = 7.4 Hz, 1H), 6.39 (s,
13
1H), 2.19 (s, 3H); C NMR (100 MHz, CDCl3) δ 153.8, 152.1, 151.1, 141.2, 140.5,
139.5, 128.9, 128.8, 128.6, 128.4, 128.4, 127.7, 126.6, 121.7, 119.4, 114.0, 113.4,
13.9; HRMS m/z (APCI) calcd for C24H21N2 (M + H)+ 337.1699, found 337.1705.
3ꢀMethylꢀ4,6ꢀdiphenylꢀNꢀ(oꢀtolyl)pyridinꢀ2ꢀamine (3b). Reaction time: 2 h; 43 mg
(61%); pale green solid; m.p. 157–160 °C; IR (KBr): ν 1597, 1530, 1482, 1455, 1368,
759 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.24 (d, J = 8.1 Hz, 1H), 8.01 (d, J = 7.2 Hz,
2H), 7.50–7.25 (m, 9H), 7.24–7.21 (m, 2H), 7.00 (t, J = 7.4 Hz, 1H), 6.21 (s, 1H),
2.36 (s, 3H), 2.19 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 154.2, 152.1, 151.1, 140.5,
139.5 (2C), 130.3, 128.9, 128.5, 128.4, 127.7, 127.2, 126.6, 122.1, 120.5, 114.4, 113.3,
18.2, 13.9; HRMS m/z (APCI) calcd for C25H23N2 (M + H)+ 351.1856, found
351.1866. (Note that three carbon peaks overlap with other peaks)
3ꢀMethylꢀ4,6ꢀdiphenylꢀNꢀ(pꢀtolyl)pyridinꢀ2ꢀamine (3c). Reaction time: 2 h; 54 mg
(77%); white solid; m.p. 143–146 °C; IR (KBr): ν 1608, 1529, 1401, 1370, 772, 698
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cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.08–7.99 (m, 2H), 7.61 (d, J = 8.4 Hz, 2H),
7.47–7.30 (m, 8H), 7.20–7.13 (m, 3H), 6.29 (s, 1H), 2.34 (s, 3H), 2.14 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 154.1, 152.0, 150.9, 140.6, 139.7, 138.6, 131.2, 129.4,
128.9, 128.6, 128.4, 127.7, 126.7, 119.8, 113.8, 113.1, 20.9, 13.9; HRMS m/z (APCI)
calcd for C25H23N2 (M + H)+ 351.1856, found 351.1864. (Note that two carbon peaks
overlap on each other)
Nꢀ(2,4ꢀDimethylphenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3d). Reaction time:
2 h; 45 mg (62%); white solid; m.p. 148–152 °C; IR (KBr): ν 1609, 1530, 1493, 1398,
1373, 772, 698 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 8.1 Hz, 1H), 7.99 (d,
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J = 7.5 Hz, 2H), 7.49–7.29 (m, 8H), 7.18 (s, 1H), 7.08 (d, J = 8.3 Hz, 1H), 7.05 (s,
1H), 6.11 (s, 1H), 2.33 (s, 3H), 2.32 (s, 3H), 2.16 (s, 3H); 13C NMR (100 MHz, CDCl3)
δ 154.4, 152.0, 150.9, 140.5, 139.5, 136.8, 131.7, 131.0, 128.8, 128.4, 128.3, 128.3,
127.7, 127.6, 126.9, 126.5, 121.2, 113.9, 112.9, 20.8, 18.1, 13.9; HRMS m/z (APCI)
calcd for C26H25N2 (M + H)+ 365.2012, found 365.2019.
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Nꢀ(4ꢀMethoxyphenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3e). Reaction time: 2 h;
38 mg (52%); white solid; m.p. 162–165 °C; IR (KBr): ν 1530, 1506, 1241, 1036, 824,
772, 701 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.07–7.96 (m, 2H), 7.66–7.58 (m, 2H),
7.50–7.25 (m, 8H), 7.16 (s, 1H), 6.99–6.84 (m, 2H), 6.23 (s, 1H), 3.82 (s, 3H), 2.15 (s,
13
3H); C NMR (100 MHz, CDCl3) δ 154.9, 154.2, 151.9, 150.8, 140.5, 139.6, 134.4,
128.8, 128.5, 128.3, 127.6, 126.5, 121.7, 114.0, 113.3, 112.8, 55.6, 13.8; HRMS m/z
(APCI) calcd for C25H23N2O (M + H)+ 367.1805, found 367.1811. (Note that two
carbon peaks overlap on each other)
Nꢀ(3ꢀFluoroꢀ4ꢀmethylphenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3f). Reaction
time: 2 h; 48 mg (65%); yellow solid; m.p. 101–104 °C; IR (KBr): ν 1607, 1509, 1372,
1262, 1103, 1027, 803, 698 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 7.5 Hz,
2H), 7.74 (dd, J = 12.4, 1.8 Hz, 1H), 7.49–7.31 (m, 8H), 7.17–7.22 (m, 2H), 7.10 (t, J
= 8.4 Hz, 1H), 6.36 (s, 1H), 2.25 (s, 3H), 2.16 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
161.30 (d, J = 242.0 Hz), 153.5, 152.1, 151.1, 140.4, 140.3, 139.4, 131.0 (d, J = 6.7
Hz), 128.8, 128.6, 128.5, 128.4, 127.7, 126.6, 117.4 (d, J = 17.7 Hz), 114.5 (d, J = 2.7
Hz), 113.9, 113.5, 106.5 (d, J = 27.5 Hz), 14.0 (d, J = 2.8 Hz), 13.8; HRMS m/z
(APCI) calcd for C25H22FN2 (M + H)+ 369.1762, found 369.1766.
Nꢀ(4ꢀFluorophenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3g). Reaction time: 2 h;
47 mg (66%); white solid; m.p. 141–145 °C; IR (KBr): ν 1610, 1503, 1398, 1371,
1202, 771 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.04–7.97 (m, 2H), 7.69–7.63 (m, 2H),
7.50–7.33 (m, 8H), 7.20 (s, 1H), 7.11–7.01 (m, 2H), 6.30 (s, 1H), 2.17 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 158.1 (d, J = 240.3 Hz), 153.9, 152.0, 151.1, 140.4, 139.5,
137.1 (d, J = 2.6 Hz), 128.8, 128.6, 128.5, 128.4, 127.8, 126.6, 121.4 (d, J = 7.6 Hz),
115.3 (d, J = 22.2 Hz), 113.6, 113.4, 13.8; HRMS m/z (APCI) calcd for C24H20FN2
(M + H)+ 355.1605, found 355.1612.
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Nꢀ(3ꢀChlorophenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3h). Reaction time: 2 h;
53 mg (72%); yellow solid; m.p. 100–105 °C; IR (KBr): ν 1601, 1532, 1480, 1396,
1371, 768, 700 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.05 (d, J = 8.1 Hz, 2H), 7.99 (s,
1H), 7.52–7.32 (m, 9H), 7.27–7.21 (m, 2H), 6.98 (d, J = 7.9 Hz, 1H), 6.39 (s, 1H),
2.17 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 153.3, 152.1, 151.3, 142.3, 140.2, 139.24,
134.4, 129.6, 128.8, 128.6, 128.6, 128.4, 127.8, 126.6, 121.4, 119.3, 117.1, 114.2,
113.9, 13.8; HRMS m/z (APCI) calcd for C24H20ClN2 (M + H)+ 371.1310, found
371.1301.
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Nꢀ(4ꢀChlorophenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3i). Reaction time: 2 h;
37 mg (50%); white solid; m.p. 153–156 °C; IR (KBr): ν 1605, 1527, 1489, 1397,
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1030 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.06–7.97(m, 2H), 7.72–7.64 (m, 2H),
7.49–7.28 (m, 10H), 7.22 (s, 1H), 6.35 (s, 1H), 2.17 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 153.5, 152.1, 151.2, 140.3, 139.8, 139.4, 128.8, 128.7, 128.6, 128.6, 128.4,
127.8, 126.6, 126.3, 120.7, 114.0, 113.7, 13.9; HRMS m/z (APCI) calcd for
C24H20ClN2 (M + H)+ 371.1310, found 371.1278.
Nꢀ(4ꢀBromophenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3j). Reaction time: 2 h;
51 mg (61%); white solid; m.p. 173–175 °C; IR (KBr): ν 1604, 1524, 1486, 1393,
1369, 1029, 799 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.01 (d, J = 8.1 Hz, 2H), 7.63 (d,
J = 8.5 Hz, 2H), 7.52–7.29 (m, 10H), 7.22 (s, 1H), 6.35 (s, 1H), 2.17 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 153.4, 152.0, 151.2, 140.2 (2C), 139.3, 131.6, 128.8,
128.6, 128.5, 128.4, 127.8, 126.5, 121.0, 114.0, 113.7, 113.7, 13.8; HRMS m/z
(APCI) calcd for C24H20BrN2 (M + H)+ 415.0804, found 415.0784. (Note that two
carbon peaks overlap on each other)
Nꢀ(4ꢀIodophenyl)ꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3k). Reaction time: 5 h; 42
mg (45%); white solid; m.p. 194–196 °C; IR (KBr): ν 1603, 1520, 1484, 1392, 1369,
698 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.06–7.96 (m, 2H), 7.68–7.60 (m, 2H), 7.54–
13
7.52 (m, 2H), 7.49–7.33 (m, 8H), 7.23 (s, 1H), 6.36 (s, 1H), 2.17 (s, 3H); C NMR
(100 MHz, CDCl3) δ 153.3, 152.1, 151.2, 140.9, 140.2, 139.3, 137.5, 128.8, 128.6,
128.5, 128.4, 127.8, 126.5, 121.3, 114.1, 113.8, 83.7, 13.8; HRMS m/z (APCI) calcd
for C24H20IN2 (M + H)+ 463.0666, found 463.0667.
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3ꢀMethylꢀNꢀ(naphthalenꢀ1ꢀyl)ꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3l). Reaction time: 5 h;
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39 mg (51%); pale purple solid; m.p. 177–180 °C; IR (KBr): ν 1599, 1537, 1498,
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1414, 1372, 769, 701 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.11 (d, J = 7.5 Hz, 1H),
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8.08–8.03 (m, 1H), 7.94 (d, J = 7.9 Hz, 2H), 7.91–7.86 (m, 1H), 7.61 (d, J = 8.1 Hz,
1H), 7.56–7.45 (m, 5H), 7.45–7.28 (m, 6H), 7.26 (s, 1H), 6.81 (s, 1H), 2.26 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 154.6, 152.3, 151.4, 140.4, 139.4, 136.6, 134.4, 128.9,
128.7, 128.5, 128.4, 127.8, 127.2, 126.6, 125.9, 125.7, 125.6, 122.9, 121.2, 117.2,
115.0, 113.9, 14.3; HRMS m/z (APCI) calcd for C28H23N2 (M + H)+ 387.1856, found
387.1858. (Note that two carbon peaks overlap on each other)
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3ꢀMethylꢀ4,6ꢀdiphenylꢀNꢀ(pyridinꢀ3ꢀyl)pyridinꢀ2ꢀamine (3m). Reaction time: 2 h; 21
mg (31%); brown solid; m.p. 161–165 °C; IR (KBr): ν 1601, 1525, 1484, 1372, 1261,
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1094, 1025, 803, 696 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.83 (d, J = 2.3 Hz, 1H),
8.42–8.32 (m, 1H), 8.27 (d, J = 3.8 Hz, 1H), 8.07–7.95 (m, 2H), 7.53–7.34 (m, 8H),
7.34–7.28 (m, 1H), 7.26 (s, 1H), 6.43 (s, 1H), 2.23 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 153.3, 152.2, 151.4, 142.6, 141.2, 140.1, 139.2, 137.8, 128.8, 128.6, 128.6,
128.4, 127.9, 126.6, 126.3, 123.4, 114.2, 13.8; HRMS m/z (APCI) calcd for C23H20N3
(M + H)+ 338.1652, found 338.1657. (Note that two carbon peaks overlap on each
other)
9ꢀEthylꢀNꢀ(3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀyl)ꢀ9Hꢀcarbazolꢀ3ꢀamine (3n). Reaction
time: 2 h; 60 mg (66%); brown solid; m.p. 68–72 °C; IR (KBr): ν 1596, 1528, 1489,
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1370, 1090, 1025, 802, 698 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.71 (s, 1H), 8.20–
8.09 (m, 3H), 7.73–7.67 (m, 1H), 7.54–7.33 (m, 11H), 7.28–7.22 (m, 2H), 6.53 (s,
13
1H), 4.40 (q, J = 7.2 Hz, 2H), 2.25 (s, 3H), 1.48 (t, J = 7.2 Hz, 3H); C NMR (100
MHz, CDCl3) δ 154.6, 151.8, 150.8, 140.7, 140.4, 139.6, 136.2, 133.2, 128.9, 128.5,
128.3, 127.6, 126.5, 125.5, 123.1, 123.1, 120.4, 120.1, 118.4, 113.3, 112.5, 112.5,
108.7, 108.3, 37.6, 13.9; HRMS m/z (APCI) calcd for C32H28N3 (M + H)+ 454.2278,
found 454.2280. (Note that two carbon peaks overlap with other peaks)
N,3ꢀDimethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3o). Reaction time: 2 h; 26 mg (47%);
white solid; m.p. 101–105 °C; IR (KBr): ν 1590, 1557, 1509, 1365, 776, 703 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 8.08 (d, J = 7.6 Hz, 2H), 7.47–7.30 (m, 8H), 7.02 (s, 1H),
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4.35 (brs, 1H), 3.19 (s, 3H), 2.01 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 157.5, 151.9,
149.6, 140.74, 140.0, 128.8, 128.4, 128.2, 128.1, 127.4, 126.5, 112.5, 110.8, 29.0,
13.3; HRMS m/z (APCI) calcd for C19H19N2 (M + H)+ 275.1543, found 275.1549.
NꢀAllylꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3p). Reaction time: 2 h; 28 mg
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(47%); colourless oil; IR (KBr): ν 1592, 1560, 1510, 1373, 773, 699 cmꢀ1; H NMR
(400 MHz, CDCl3) δ 8.09–8.00 (m, 2H), 7.48–7.29 (m, 8H), 7.03 (s, 1H), 6.20–6.07
(m, 1H), 5.38–5.26 (m, 1H), 5.21–5.13 (m, 1H), 4.44–4.35 (m, 1H), 4.35–4.28 (m,
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2H), 2.04 (s, 3H); C NMR (100 MHz, CDCl3) δ 156.5, 151.8, 149.9, 140.7, 139.9,
136.5, 128.8, 128.4, 128.2, 128.1, 127.44, 126.5, 115.6, 112.4, 111.1, 44.5, 13.3;
HRMS m/z (APCI) calcd for C21H21N2 (M + H)+ 301.1699, found 301.1705.
3ꢀMethylꢀ4,6ꢀdiphenylꢀNꢀ(propꢀ2ꢀynꢀ1ꢀyl)pyridinꢀ2ꢀamine (3q). Reaction time: 2 h;
32 mg (54%); brown solid; m.p. 88–91 °C; IR (KBr): ν 3281, 1594, 1560, 1506, 1070,
1027, 697 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.07 (d, J = 7.4 Hz, 2H), 7.48–7.30 (m,
8H), 7.09 (s, 1H), 4.47 (brs, 3H), 2.25 (s, 1H), 2.06 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 155.6, 151.7, 150.2, 140.4, 139.6, 128.8, 128.4, 128.3, 127.5, 126.5, 112.9,
111.9, 82.2, 70.5, 31.7, 13.3; HRMS m/z (APCI) calcd for C21H19N2 (M + H)+
299.1543, found 299.1537. (Note that two carbon peaks overlap on each other)
NꢀBenzylꢀ3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3r). 44 mg (63%); Reaction time: 1
h; white solid; m.p. 79–81 °C; IR (KBr): ν 1592, 1559, 1511, 772, 699 cmꢀ1; 1H NMR
(400 MHz, CDCl3) δ 8.11–7.98 (m, 2H), 7.54–7.25 (m, 13H), 7.06 (s, 1H), 4.88 (d, J
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= 5.2 Hz, 2H), 4.63 (t, J = 4.7 Hz, 1H), 2.04 (s, 3H); C NMR (100 MHz, CDCl3) δ
156.5, 151.8, 149.9, 140.7, 140.6, 139.9, 128.8, 128.5, 128.4, 128.2, 128.1, 128.0,
127.5, 127.0, 126.5, 112.4, 111.2, 46.1, 13.4; HRMS m/z (APCI) calcd for C25H23N2
(M + H)+ 351.1856, found 351.1859.
3ꢀMethylꢀNꢀphenethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3s). 33 mg (45%); Reaction
time: 2 h; white solid; m.p. 93–97 °C; IR (KBr): ν 1593, 1511, 1028, 774, 697 cmꢀ1;
1H NMR (400 MHz, CDCl3) δ 8.12–8.06 (m, 2H), 7.47–7.24 (m, 13H), 7.04 (s, 1H),
4.40 (t, J = 5.3 Hz, 1H), 3.97–3.86 (m, 2H), 3.06 (t, J = 7.0 Hz, 2H), 1.93 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 156.7, 151.8, 149.8, 140.7, 140.1, 140.0, 129.0, 128.8,
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128.5, 128.4, 128.2, 128.1, 127.4, 126.5, 126.2, 112.5, 110.9, 43.3, 36.0, 13.2; HRMS
m/z (APCI) calcd for C26H25N2 (M + H)+ 365.2012, found 365.2017.
3ꢀMethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀamine (3t). This reaction was carried out in 0.5
mmol scale in the presence of 1 equivalent of NaOH; reaction time: 12 h; white solid;
123 mg (95%); m.p. 107–109 °C; IR (KBr): ν 3296, 3174, 1627, 1591, 767, 702 cmꢀ1;
1H NMR (400 MHz, CDCl3) δ 7.97–7.90 (m, 2H), 7.45–7.36 (m, 5H), 7.35–7.30 (m,
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3H), 7.05 (s, 1H), 4.64 (s, 2H), 2.04 (s, 3H); C NMR (100 MHz, CDCl3) δ 157.5,
152.8, 150.8, 140.2, 139.6, 128.7, 128.4, 128.2, 127.5, 126.6, 113.0, 112.5, 13.7;
HRMS m/z (APCI) calcd for C18H17N2 (M + H)+ 261.1386, found 261.1389. (Note
that two carbon peaks overlap on each other)
3ꢀMethylꢀN,6ꢀdiphenylꢀ4ꢀ(oꢀtolyl)pyridinꢀ2ꢀamine (4a). Reaction time: 2 h; 39 mg
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(56%); colourless oil; IR (KBr): ν 1602, 1526, 1495, 1372, 752, 693 cmꢀ1; H NMR
(400 MHz, CDCl3) δ 8.04 (d, J = 7.6 Hz, 2H), 7.76 (d, J = 8.1 Hz, 2H), 7.46 – 7.24 (m,
8H), 7.17 – 7.11 (m, 2H), 7.03 (t, J = 7.4 Hz, 1H), 6.37 (s, 1H), 2.13 (s, 3H), 2.01 (s,
13
3H); C NMR (100 MHz, CDCl3) δ 153.6, 152.0, 150.8, 141.1, 140.0, 139.5, 135.4,
130.0, 128.8, 128.7, 128.5, 128.4, 127.8, 126.5, 125.8, 121.6, 119.3, 114.5, 113.1,
19.7, 13.4; HRMS m/z (APCI) calcd for C25H23N2 (M + H)+ 351.1856, found
351.1850.
3ꢀMethylꢀN,6ꢀdiphenylꢀ4ꢀ(pꢀtolyl)pyridinꢀ2ꢀamine (4b). Reaction time: 4 h; 51 mg
(73%); white solid; m.p. 140–142 °C; IR (KBr): ν 1607, 1533, 1495, 1371, 751, 692
cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 7.4 Hz, 2H), 7.72 (d, J = 8.0 Hz, 2H),
7.47–7.39 (m, 2H), 7.39–7.31 (m, 3H), 7.30–7.23 (m, 4H), 7.20 (s, 1H), 7.01 (t, J =
13
7.3 Hz, 1H), 6.37 (s, 1H), 2.42 (s, 3H), 2.18 (s, 3H); C NMR (100 MHz, CDCl3) δ
153.8, 152.0, 151.0, 141.2, 139.6, 137.5, 129.0, 128.8, 128.7, 128.5, 128.3, 126.6,
121.6, 119.3, 114.0, 113.5, 21.2, 13.9; HRMS m/z (APCI) calcd for C25H23N2 (M +
H)+ 351.1856, found 351.1848. (Note that two carbon peaks overlap on each other)
4ꢀ(4ꢀ(Tertꢀbutyl)phenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4c). Reaction time:
2 h; 47 mg (60%); white solid; m.p. 159–162 °C; IR (KBr): ν 1604, 1527, 1498, 1372,
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747, 689 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 8.1 Hz, 2H), 7.73 (d, J =
8.3 Hz, 2H), 7.48 (d, J = 8.2 Hz, 2H), 7.42 (t, J = 7.6 Hz, 2H), 7.39–7.28 (m, 5H),
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7.23 (s, 1H), 7.02 (t, J = 7.3 Hz, 1H), 6.38 (s, 1H), 2.21 (s, 3H), 1.39 (s, 9H); 13C
NMR (100 MHz, CDCl3) δ 153.8, 152.0, 151.0, 150.7, 141.2, 139.6, 137.4, 128.8,
128.6, 128.5, 128.3, 126.6, 125.2, 121.6, 119.4, 114.1, 113.6, 34.6, 31.4, 14.0; HRMS
m/z (APCI) calcd for C28H29N2 (M + H)+ 393.2325, found 393.2330.
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4ꢀ(3ꢀMethoxyphenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4d). Reaction time: 2 h;
31 mg (42%); yellow solid; m.p. 83–85 °C; IR (KBr): ν 1600, 1525, 1494, 1371, 752,
692 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.08–8.00 (m, 2H), 7.77–7.69 (m, 2H), 7.46–
7.33 (m, 6H), 7.21 (s, 1H), 7.06–6.99 (m, 1H), 6.98–6.92 (m, 2H), 6.91–6.88 (m, 1H),
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6.39 (s, 1H), 3.85 (s, 3H), 2.19 (s, 3H); C NMR (100 MHz, CDCl3) δ 159.5, 153.8,
152.0, 150.9, 141.8, 141.1, 139.5, 129.4, 128.8, 128.5, 128.4, 126.6, 121.7, 121.2,
119.4, 114.5, 113.9, 113.2, 113.1, 55.3, 13.9; HRMS m/z (APCI) calcd for C25H23N2O
(M + H)+ 367.1805, found 367.1802.
4ꢀ(4ꢀMethoxyphenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4e). Reaction time: 5 h;
37 mg (51%); white solid; m.p. 207–209 °C; IR (KBr): ν 1602, 1519, 1369, 1238,
1026, 696 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.09–7.98 (m, 2H), 7.72 (d, J = 8.0 Hz,
2H), 7.47–7.39 (m, 2H), 7.39–7.33 (m, 3H), 7.30 (d, J = 8.6 Hz, 2H), 7.20 (s, 1H),
7.06–6.95 (m, 3H), 6.38 (s, 1H), 3.87 (s, 3H), 2.20 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 159.2, 153.8, 152.0, 150.7, 141.2, 139.6, 132.7, 130.0, 128.8, 128.5, 128.3,
126.6, 121.6, 119.3, 114.1, 113.8, 113.6, 55.3, 13.9; HRMS m/z (APCI) calcd for
C25H23N2O (M + H)+ 367.1805, found 367.1812.
4ꢀ(3ꢀChlorophenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4f). 60 mg (81%);
Reaction time: 2 h; white solid; m.p. 125–128 °C; IR (KBr): ν 1602, 1524, 1496, 1371,
1015, 750, 690 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 8.1 Hz, 2H), 7.72 (d,
J = 8.2 Hz, 2H), 7.46–7.31 (m, 8H), 7.25–7.18 (m, 1H), 7.15 (s, 1H), 7.03 (t, J = 7.3
Hz, 1H), 6.37 (s, 1H), 2.15 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 153.8, 152.2,
149.5, 142.2, 141.0, 139.3, 134.3, 129.6, 128.9, 128.8, 128.5, 127.8, 127.0, 126.6,
121.8, 119.5, 113.8, 113.0, 13.8; HRMS m/z (APCI) calcd for C24H20ClN2 (M + H)+
371.1310, found 371.1299. (Note that two carbon peaks overlap on each other)
4ꢀ(3,4ꢀDichlorophenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4g). Reaction time:
2 h; 62 mg (77%); white solid; m.p. 166–170 °C; IR (KBr): ν 1605, 1531, 1495, 752,
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692 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.02 (d, J = 7.3 Hz, 2H), 7.71 (d, J = 8.0 Hz,
2H), 7.52 (d, J = 8.2 Hz, 1H), 7.48–7.40 (m, 3H), 7.39–7.30 (m, 3H), 7.21–7.15 (m,
13
1H), 7.12 (s, 1H), 7.04 (t, J = 7.3 Hz, 1H), 6.37 (s, 1H), 2.15 (s, 3H); C NMR (100
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MHz, CDCl3) δ 153.9, 152.4, 148.5, 140.9, 140.3, 139.1, 132.6, 132.1, 130.7, 130.4,
128.8, 128.6, 128.6, 128.2, 126.6, 122.0, 119.6, 113.6, 112.7, 13.8; HRMS m/z
(APCI) calcd for C24H19Cl2N2 (M + H)+ 405.0920, found 405.0929.
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4ꢀ(4ꢀChlorophenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4h). Reaction time: 5 h;
57 mg (77%); white solid; m.p. 184–186 °C; IR (KBr): ν 1606, 1533, 1492, 1371, 751,
693 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 8.1 Hz, 2H), 7.72 (d, J = 8.3 Hz,
2H), 7.48–7.40 (m, 4H), 7.39–7.32 (m, 3H), 7.32–7.26 (m, 2H), 7.15 (s, 1H), 7.03 (t,
J = 7.3 Hz, 1H), 6.37 (s, 1H), 2.15 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 153.8,
152.2, 149.8, 141.0, 139.3, 138.8, 133.8, 130.2, 128.8, 128.6, 128.6, 128.5, 126.6,
121.8, 119.5, 113.8, 113.0, 13.8; HRMS m/z (APCI) calcd for C24H20ClN2 (M + H)+
371.1310, found 371.1298.
4ꢀ(3ꢀFluorophenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4i). Reaction time: 5 h;
51 mg (72%); white solid; m.p. 110–114 °C; IR (KBr): ν 1604, 1531, 1493, 1373
cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 8.0 Hz, 2H), 7.72 (d, J = 8.2 Hz, 2H),
7.48–7.31(m, 6H), 7.17 (s, 1H), 7.15–6.98 (m, 4H), 6.38 (s, 1H), 2.17 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 162.6 (d, J = 246.9 Hz), 153.8, 152.2, 149.7, 142.5 (d, J =
7.6 Hz), 141.0, 139.3, 130.0 (d, J = 8.3 Hz), 128.8, 128.6, 128.5, 126.6, 124.6 (d, J =
2.7 Hz), 121.8, 119.5, 115.9 (d, J = 21.7 Hz), 114.6 (d, J = 21.0 Hz), 113.8, 112.9,
13.8; HRMS m/z (APCI) calcd for C24H20FN2 (M + H)+ 355.1605, found 355.1601.
4ꢀ(4ꢀFluorophenyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4j). Reaction time: 5 h;
52 mg (73%); white solid; m.p. 150–154 °C; IR (KBr): ν 1607, 1533, 1494, 1216, 839,
1
753, 691 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 8.2 Hz, 2H), 7.72 (d, J =
8.2 Hz, 2H), 7.47–7.39 (m, 2H), 7.39–7.27 (m, 5H), 7.20–7.07 (m, 3H), 7.02 (t, J =
13
7.2 Hz, 1H), 6.37 (s, 1H), 2.15 (s, 3H); C NMR (100 MHz, CDCl3) δ 162.4 (d, J =
247.0 Hz), 153.8, 152.1, 150.0, 141.0, 139.4, 136.3 (d, J = 3.2 Hz), 130.5 (d, J = 8.0
Hz), 128.8, 128.5, 128.5, 126.6, 121.8, 119.4, 115.3 (d, J = 21.4 Hz), 113.9, 113.3,
13.8; HRMS m/z (APCI) calcd for C24H20FN2 (M + H)+ 355.1605, found 355.1600.
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3ꢀMethylꢀN,6ꢀdiphenylꢀ4ꢀ(4ꢀ(trifluoromethyl)phenyl)pyridinꢀ2ꢀamine (4k). Reaction
time: 2 h; 71 mg (88%); white solid; m.p. 168–170 °C; IR (KBr): ν 1606, 1533, 1496,
1321, 1172, 1126, 1067 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 7.4 Hz, 2H),
7.77–7.67 (m, 4H), 7.50–7.40 (m, 4H), 7.40–7.32(m, 3H), 7.15 (s, 1H), 7.04 (t, J =
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7.3 Hz, 1H), 6.38 (s, 1H), 2.14 (s, 3H); C NMR (100 MHz, CDCl3) δ 153.8, 152.3,
149.5, 144.0, 140.9, 139.2, 129.9 (d, J = 32.6 Hz), 129.2, 128.8, 128.6, 126.6, 125.4
(d, J = 3.6 Hz), 124.1 (d, J = 272.2 Hz), 121.9, 119.5, 113.7, 112.8, 13.8; HRMS m/z
(APCI) calcd for C25H20F3N2 (M + H)+ 405.1573, found 405.1577. (Note that two
carbon peaks overlap on each other)
3ꢀMethylꢀN,6ꢀdiphenylꢀ4ꢀ(thiophenꢀ2ꢀyl)pyridinꢀ2ꢀamine (4l). Reaction time: 2 h; 41
mg (60%); brown solid; m.p. 115–119 °C; IR (KBr): ν 1604, 1534, 1495, 1386, 743,
698 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.03 (d, J = 8.0 Hz, 2H), 7.69 (d, J = 8.2 Hz,
2H), 7.49–7.29 (m, 7H), 7.14 (d, J = 3.0 Hz, 2H), 7.03 (t, J = 7.3 Hz, 1H), 6.39 (s,
13
1H), 2.33 (s, 3H); C NMR (100 MHz, CDCl3) δ 154.1, 152.3, 143.3, 141.3, 141.0,
139.3, 128.8, 128.5, 128.5, 127.5, 127.3, 126.6, 126.2, 121.8, 119.5, 114.5, 113.8,
14.1; HRMS m/z (APCI) calcd for C22H19N2S (M + H)+ 343.1263, found 343.1262.
4ꢀ(Furanꢀ2ꢀyl)ꢀ3ꢀmethylꢀN,6ꢀdiphenylpyridinꢀ2ꢀamine (4m). Reaction time: 2 h; 29
mg (44%); brown solid; m.p. 108–114 °C; IR (KBr): ν 1601, 1525, 1495, 1412, 747,
694 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.06 (d, J = 7.5 Hz, 2H), 7.64 (d, J = 8.0 Hz,
2H), 7.59 (s, 1H), 7.55 (s, 1H), 7.48–7.41 (m, 2H), 7.41–7.31 (m, 3H), 7.02 (t, J = 7.3
Hz, 1H), 6.70 (d, J = 3.3 Hz, 1H), 6.62 – 6.50 (m, 1H), 6.42 (s, 1H), 2.42 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 154.2, 152.5, 152.1, 142.9, 141.3, 139.4, 138.9, 128.8,
128.5, 128.5, 126.6, 121.7, 119.3, 113.2, 111.5, 111.0, 110.7, 14.3; HRMS m/z (APCI)
calcd for C22H19N2O (M + H)+ 327.1492, found 327.1490.
6ꢀ(4ꢀBromophenyl)ꢀ3ꢀmethylꢀN,4ꢀdiphenylpyridinꢀ2ꢀamine (4n). Reaction time: 2 h;
69 mg (83%); white solid; m.p. 124–128 °C; IR (KBr): ν 1605, 1531, 1495, 1370 cmꢀ1;
1H NMR (400 MHz, CDCl3) δ 7.96 (d, J = 8.5 Hz, 2H), 7.69 (d, J = 7.9 Hz, 2H),
7.51–7.30 (m, 9H), 7.15 (s, 1H), 7.03 (t, J = 7.3 Hz, 1H), 6.37 (s, 1H), 2.17 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 153.8, 151.1, 150.8, 141.0, 140.2, 138.0, 134.3, 128.8,
128.8, 128.7, 128.4, 127.8, 127.8, 121.9, 119.5, 114.3, 113.1, 13.8; HRMS m/z (APCI)
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calcd for C24H20BrN2 (M + H)+ 415.0804, found 415.0805.
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3ꢀMethylꢀN,4ꢀdiphenylꢀ6ꢀ(mꢀtolyl)pyridinꢀ2ꢀamine (4o). Reaction time: 3 h; 44 mg
(63%); white solid; m.p. 134–136°C; IR (KBr): ν 1599, 1517, 1448, 1368, 699 cmꢀ1;
1H NMR (400 MHz, CDCl3) δ 7.89–7.82 (m, 2H), 7.73 (d, J = 8.2 Hz, 2H), 7.50–7.29
(m, 8H), 7.20 (s, 1H), 7.17 (d, J = 7.5 Hz, 1H), 7.02 (t, J = 7.2 Hz, 1H), 6.38 (s, 1H),
2.41 (s, 3H), 2.18 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 153.7, 152.2, 151.0, 141.2,
140.4, 139.4, 138.0, 129.2, 128.8, 128.7, 128.4, 128.3, 127.7, 127.3, 123.7, 121.6,
119.3, 113.9, 113.4, 21.6, 13.9; HRMS m/z (APCI) calcd for C25H23N2 (M + H)+
351.1856, found 351.1858.
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Nꢀ(4ꢀMethoxyphenyl)ꢀNꢀ(3ꢀmethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀyl)formamide
(5e
,
rotameric mixture, ratio of the rotamers = 54/46). This reaction was carried out in 0.3
mmol scale; reaction time: 0.5 h; 66 mg (56%); white solid; m.p. 148–151 °C; IR
1
(KBr): ν 1683, 1510, 1246, 1027 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.98–8.63 (m,
1H), 8.07 (d, J = 6.9 Hz, 1H), 7.95 (d, J = 6.2 Hz, 1H), 7.72–7.61 (m, 1H), 7.51–7.26
(m, 10H), 6.92 (m, 2H), 3.80 (s, 3H), 2.26–1.92 (m, 3H); 13C NMR (100 MHz, CDCl3)
δ 162.8, 161.7, 158.4, 157.8, 154.6, 154.0, 153.9, 153.2, 153.0, 151.8, 139.1, 138.9,
138.3, 137.8, 133.3, 131.6, 129.2, 128.9, 128.7, 128.4, 128.3, 128.1, 127.2, 126.7,
126.3, 125.9, 125.3, 121.1, 120.5, 114.6, 114.2, 55.4, 15.6, 15.0; HRMS m/z (APCI)
calcd for C26H23N2O2 (M + H)+ 395.1754, found 395.1760.
Nꢀ(3ꢀMethylꢀ4,6ꢀdiphenylpyridinꢀ2ꢀyl)formamide (5t). Reaction time: 2 h; 26 mg
(45%); white solid; m.p. 208–212 °C; IR (KBr): ν 1696, 1374, 1262, 1101, 467 cmꢀ1;
1H NMR (400 MHz, CDCl3) δ 9.75 (d, J = 10.2 Hz, 1H), 8.45 (d, J = 9.8 Hz, 1H),
8.01 (d, J = 7.2 Hz, 2H), 7.52–7.37 (m, 7H), 7.37–7.31 (m, 2H), 2.20 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 163.8, 152.7, 152.7, 149.4, 139.3, 138.2, 129.1, 128.7,
128.7, 128.5, 128.2, 126.6, 117.5, 115.3, 13.3; HRMS m/z (APCI) calcd for
C19H17N2O (M + H)+ 289.1335, found 289.1336.
■ ASSOCIATED CONTENT
1
Supporting Information. Copies of H NMR and 13C NMR for all synthesized
compounds. Xꢀray crystallographic data of 3a (CIF). This material is available free of
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■ AUTHOR INFORMATION
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Corresponding Author
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*Eꢀmail: glcheng@hqu.edu.cn
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Notes
The authors declare no competing financial interest.
■ ACKNOWLEDGMENT
This work was supported by NSF of China (21672075), Program for New Century
Excellent Talents in Fujian Province University, and Outstanding Youth Scientific
Research Cultivation Plan of Colleges and Universities of Fujian Province (JA14012).
■ REFERENCES
(1) (a) Girgis, A. S.; Tala, S. R.; Oliferenko, P. V.; Oliferenko, A. A.; Katritzky, A. R.
Eur. J. Med. Chem. 2012, 50, 1. (b) Mantri, M.; de Graaf, O.; van Veldhoven, J.;
Göblyös, A.; von Frijtag Drabbe Künzel, J. K.; MulderꢀKrieger, T.; Link, R.; de Vries,
H.; Beukers, M. W.; Brussee, J.; Ijzerman, A. P. J. Med. Chem. 2008, 51, 4449. (c)
Girgis, A. S.; Mishriky, N.; Farag, A. M.; ElꢀEraky, W. I.; Farag, H. Eur. J. Med.
Chem. 2008, 43, 1818.
(2) (a) Horie, H.; Koyama, I.; Kurahashi, T.; Matsubara, S. Chem. Commun. 2011,
47, 2658. (b) Kempe, R. Eur. J. Inorg. Chem. 2003, 791. (c) Fuhrmann, H.; Brenner,
S.; Arndt, P.; Kempe, R. Inorg. Chem. 1996, 35, 6742.
(3) For selected reviews, see: (a) Torborg, C.; Beller, M. Adv. Synth. Catal. 2009,
351, 3027. (b) Hartwig, J. F. Acc. Chem. Res. 2008, 41, 1534. (c) Schlummer, B.;
Scholz, U. Adv. Synth. Catal. 2004, 346, 1599. (d) Littke, A. F.; Fu, G. C. Angew.
Chem. Int. Ed. 2002, 41, 4176.
(4) For recent selected examples, see:(a) Brusoe, A. T.; Hartwig, J. F. J. Am. Chem.
Soc. 2015, 137, 8460. (b) Park, N. H.; Vinogradova, E. V.; Surry, D. S.; Buchwald, S.
L. Angew. Chem. Int. Ed. 2015, 54, 8259. (c) Green, R. A.; Hartwig, J. F. Org. Lett.
2014, 16, 4388.
(5) (a) Wang, D.; Kuang, D.; Zhang, F.; Liu, Y.; Ning, S. Tetrahedron Lett. 2014, 55,
7121. (b) Monnier, F.; Taillefer, M. Angew. Chem. Int. Ed. 2009, 48, 6954. (c) Liu, Y.;
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8
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Bai, Y.; Zhang, J.; Li, Y.; Jiao, J.; Qi, X. Eur. J. Org. Chem. 2007, 2007, 6084.
(6) (a) Chartoire, A.; Frogneux, X.; Nolan, S. P. Adv. Synth. Catal. 2012, 354, 1897.
(b) Maiti, D.; Fors, B. P.; Henderson, J. L.; Nakamura, Y.; Buchwald, S. L. Chem. Sci.
2011, 2, 57. (c) Grasa, G. A.; Viciu, M. S.; Huang, J.; Nolan, S. P. J. Org. Chem. 2001,
66, 7729.
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55
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57
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60
(7) Kumar, D.; Vemula, S. R.; Cook, G. R. ACS Catal. 2016, 6, 3531.
(8) Wu, Q.; Zhang, Y.; Cui, S. Org. Lett. 2014, 16, 1350.
(9) (a) McGill, C. K.; Rappa, A. Adv. Heterocycl. Chem. 1988, 44, 1. (b) Leffler, M.
T. Org. React. 1942, 1, 91.(c) Chichibabin, A. E.; Zeide, O. A. J. Russ. Phys. Chem.
Soc. 1914, 46, 1216.
(10) Thomas, S.; Roberts, S.; Pasumansky, L.; Gamsey, S.; Singaram, B. Org. Lett.
2003, 5, 3867.
(11) Vamos, M.; Cosford, N. D. P. J. Org. Chem. 2014, 79, 2274.
(12) (a) Cheng, G.; Weng, Y.; Yang, X.; Cui, X. Org. Lett. 2015, 17, 3790. (b) Cheng,
G.; Xue, L.; Weng, Y.; Cui, X. J. Org. Chem. 2017, 82, 9515. (c) Shen, J.; Yang, X.;
Wang, F.; Wang, Y.; Cheng, G.; Cui, X. RSC Adv. 2016, 6, 48905. (d) Cheng, G.; Lv,
W.; Kuai, C.; Wen, S.; Xiao, S. Chem. Commu. 2018, 54, 1726. (e) Yang, X.; Cheng,
G.; Shen, J.; Kuai, C.; Cui, X. Org. Chem. Front. 2015, 2, 366. (f) Cheng, G.; Zeng,
X.; Shen, J.; Wang, X.; Cui, X. Angew. Chem. Int. Ed. 2013, 52, 13265. (g) Cheng, G.;
Cui, X. Org. Lett. 2013, 15, 1480.
(13) For recent studies on Nꢀpropargyl βꢀenaminones, see: (a) Arshadi, S.; Vessally,
E.; Edjlali, L.; GhorbaniꢀKalhor, E.; HosseinzadehꢀKhanmiri, R. RSC Adv. 2017, 7,
13198. (b) Yang, X.; Hu, F.; Wang, Y.; Yang, C.; Zou, X.; Liu, J.; Zhang, Q. Chem.
Commun. 2017, 53, 7497. (c) Goutham, K.; Ashok Kumar, D.; Suresh, S.; Sridhar, B.;
Narender, R.; Karunakar, G. V. J. Org. Chem. 2015, 80, 11162.
(14) (a) Zhu, Y.; Back, T. G. J. Org. Chem. 2014, 79, 11270. (b) Gao, D.; Parvez, M.;
Back, T. G. Chem. Eur. J. 2010, 16, 14281. (c) Gao, D.; Back, T. G. Chem. Eur. J.
2012, 18, 14828.
(15) Rao, S. N.; Mohan, D. C.; Adimurthy, S. Org. Lett. 2013, 15, 1496.
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