Chelation-Assisted Copper-Mediated Direct Acetylamination of 2-Arylpyridine C-H Bonds with Cyanate Salts

Article abstract of DOI:10.1021/acs.joc.6b00902

In this study, the coupling of 2-phenylpyridine derivatives and potassium cyanate through C-H bond functionalization in the presence of a copper salt is developed for the first time. By this protocol, various heteroarylated acetanilide derivatives are synthesized in good yields. 2-Phenylpyridines containing electron-donating and -withdrawing groups appear to be well-tolerated by this transformation.

Full text of DOI:10.1021/acs.joc.6b00902

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Note
Chelation-Assisted Copper-Mediated Direct Acetylamination
of 2-Arylpyridine C-H Bonds with Cyanate Salts
Ebrahim Kianmehr, Yousef Amiri Lomedasht, Nasser Faghih, and Khalid Mohammed Khan
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b00902 • Publication Date (Web): 13 Jun 2016
Downloaded from http://pubs.acs.org on June 14, 2016
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Chelation-Assisted Copper-Mediated Direct Acetylamination of 2-Arylpyridine C-H Bonds
with Cyanate Salts
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Ebrahim Kianmehr, * † Yousef Amiri Lomedasht, † Nasser Faghih, † and Khalid Mohammed
Khan‡
†School of Chemistry, College of Science, University of Tehran, Tehran 1417614411, Iran
‡H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological
Sciences, University of Karachi, Karachiꢀ75270, Pakistan
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ABSTRACT: In this study, the coupling of 2ꢀphenylpyridine derivatives and potassium cyanate
through CꢀH bond functionalization in the presence of a copper salt is developed for the first
time. By this protocol, various heteroarylated acetanilide derivatives are synthesized in good
yields. 2ꢀphenylpyridines containing electronꢀdonating and electronꢀwithdrawing groups appear
to be well tolerated by this transformation.
Aryl pyridine derivatives are important building blocks in organic synthesis.1 They have found
widespread application in natural products, herbicides, surfactants, insecticides, pharmaceuticals
and biologically active compounds.2 The C–N bond forming reactions through CꢀH
functionalization have emerged as one of the most important strategy in synthetic chemistry due
to elimination of prefunctionalization step of the coupling partners.3 Buchwald and coꢀworkers
developed tandem directed C−H functionalization and amide arylation for the efficient
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construction of substituted carbazoles as the pioneering study in this area.4 Based on Buchwald’s
study, Inamoto reported a palladiumꢀcatalyzed C−H activation/intramolecular amination reaction
to obtain 3ꢀaryl/alkylindazoles.5 In 2008, the Pd(II)ꢀcatalyzed intramolecular amination of sp2
and sp3 C−H bonds was developed by Yu’s group.6
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Direct CꢀH bond amidation reaction has also been investigated7 and nitrogen sources such as
aroyloxyꢀ or acyloxycarbamates, 1,4,2ꢀdioxazolꢀ5ꢀones, Nꢀhydroxycarbamates, dioxazolones
have been used as amidation reagents. The use of cyanate salts as a coupling partner to form CꢀN
bond have been rarely reported.8 We reported the copperꢀcatalyzed coupling of arylboronic acids
with potassium cyanate as a new approach to the synthesis of aryl carbamates in 2011 as the first
example of the use of potassium cyanate in the ChanꢀLamꢀEvans type coupling reaction.8a
(Scheme 1, eq. 1) The reaction was performed in air, at room temperature and, importantly, no
base, ligand, or additive was required. Since then. the use of cyanate salts in metal catalyzed CꢀN
bond forming reactions has been investigated and improved by others (Scheme 1). In 2012,
Zhang and Ma reported copperꢀcatalyzed coupling of aryl halides with potassium cyanate as
affording the corresponding aryl carbamates.8b (Scheme 1, eq. 3) An efficient protocol for the
synthesis of unsymmetrical ureas that proceeds via palladiumꢀcatalyzed crossꢀcoupling of aryl
chlorides and triflates with sodium cyanate was reported by Buchwald’s group in the same year.
8c (Scheme 1, eq. 2) A palladiumꢀcatalyzed crossꢀcoupling reaction of aryl chlorides and triflates
with sodium cyanate in the presence of alcohols as the nucleophiles was reported by the same
group in 2013.8d (Scheme 1, eq. 4) Synthesis of aryl thiocyanates via copperꢀcatalyzed aerobic
oxidative crossꢀcoupling between arylboronic acids and KSCN was reported by Hu in the same
year.8e (Scheme 1, eq. 5). Assembly of N,NꢀdisubstitutedꢀNꢀarylureas via a copperꢀcatalyzed
oneꢀpot threeꢀcomponent reaction of aryl bromides, potassium cyanate, and secondary amines
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was also reported in the same year.8f (Scheme 1, eq. 6) Synthesis of acyl carbamates via four
component Pdꢀcatalyzed carbonylative coupling of aryl halides, potassium cyanate, and alcohols
was reported by Skrydstrup and Lindhardt in 2015.8g (Scheme 1, eq. 7).
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Scheme 1. Synthetic strategies using cyanate salts.
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The use of prefunctionalized substrates such as arylboronic acids, halides and triflates as
coupling partners along with cyanate salts is essential in all the previous reports. To the best of
our knowledge, direct CꢀH functionalization through CꢀN bond formation using a cyanate salt as
the coupling partner has not been reported yet. As a continuation of our interest in the field of Cꢀ
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H functionalization reactions,9 we herein report the first example of a chelationꢀassisted, copperꢀ
mediated, direct and regioselective acetylamination of CꢀH bonds of 2ꢀarylpyridines using a
cyanate salt as a coupling partner. We began our study with the selection of 2ꢀphenylpyridine
(1a) and potassium cyanate as a model (Table 1). Various conditions were screened to optimize
the reaction condition. After preliminary screening of solvents, the results revealed that toluene
was the best choice (Table 1, entries 1ꢀ4), which was then used to optimize the reaction
conditions.
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Table 1. Optimization of the Reaction Conditions.a
Temp
(°C)
Entry
Copper-salt (equiv.)
co-oxidantb
Solvent
Additive
Yield (%)
1
2
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
CuI (2)
air
air
DMF
PhCl
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
TFA
125
0
11
43
23
0
125
125
125
125
125
125
125
125
125
100
140
140
140
140
140
140
3
air
toluene
p-xylene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
4
air
5
air
6
CuBr2 (2)
air
0
7
CuBr (2)
air
0
8
CuO (2)
air
0
9
Cu(OAc)2.H2O (3)
Cu(OAc)2.H2O (1)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
air
38
32
trace
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65
23
78
0c
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air
air
air
Na2S2O8
Ag2CO3
K2S2O8
-
K2S2O8
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18
19
Cu(OAc)2.H2O (2)
Cu(OAc)2.H2O (2)
K2S2O8
K2S2O8
toluene
toluene
AcOH
-
140
140
14
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aThe reaction was performed on a 0.25 mmol scale for 20 hours. b Co-oxidant : 1.5 equiv. c Under an argon atmosphere.
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The control experiment showed that copper acetate is crucial for this reaction and the desired
product 2a was not obtained using other copper salts (Table 1, entries 5ꢀ8). The amount of the
copper acetate was also examined and the best result was obtained with 2.0 equiv. of this salt
(Table 1, entries 3, 9 and 10). Unfortunately, the reaction was not successful with the catalytic
amounts of the copper salt (please see the supporting information).The yield of the reaction was
satisfyingly increased with the increase of the reaction temperature from 100 to 140 °C (Table 1,
entries 3, 11 and 12). To our delight, when the reaction was performed under 1.5 equiv of
potassium persulfate as a coꢀoxidant with the combination of air atmosphere at 140°C, the yield
of 2a was increased to 78% (Table 1, entry 15). It is worth noting that the reaction was
suppressed under an argon atmosphere (Table 1, entry 16).
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Table 2. substrate scopea
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aReaction conditions: 2-phenylpyridines (0.25 mmol), Cu(OAc)2.H2O (2.0 equiv), PivOH (1.0
equiv), K2S2O8 (1.5 equiv) in toluene at 140 °C for 20 h.
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Finally, the results showed that pivalic acid was the best additive to obtain the desired products
(Table 1, entries 15, 17 and 18). The best yield was achieved under the following optimal
conditions: 2.0 equiv. of Cu(OAc)2.H2O, 1.5 equiv. of K2S2O8 and 1.0 equiv. of PivOH in
toluene (2.0 ml) under an air atmosphere at 140 °C for 20 h (Table 1, entry 15). The yield of the
reaction was not improved by increasing the reaction time beyond 20 h. Having identified the
optimized reaction conditions, we next examined the scope of this reaction (Table 2). It could be
seen that electronꢀdonating substituents on the aryl ring of 2ꢀphenylpyridines were more
compatible with this protocol and gave a higher yield relative to the substrates containing
electronꢀwithdrawing substituents such as 2d and 2o. It can also be observed from Table 2 that
the alkyl group at the para position of the phenyl ring provided the desired product in higher
yield, whereas metaꢀalkyl groups somehow decreased the reactivity of the reaction (Table 2, 2b,
2c, 2e and 2i). Gratifyingly, we have been able to isolate the reaction intermediate, during the
investigation of the reaction scope, to gain further insight into the reaction mechanism. When the
reaction of 2ꢀ(4ꢀmethylphenyl)ꢀ4ꢀphenylpyridine was suppressed after 10 hours, 2ꢀ(2ꢀisocyanatoꢀ
4ꢀmethylphenyl)ꢀ4ꢀphenylpyridine (3) was isolated from the reaction mixture. (Scheme 2,
equation 1). Surprisingly, when the reaction of 2ꢀ(3ꢀmethoxyphenyl)pyridine was investigated
under the optimized conditions the reaction did not lead to the desired acetylamination product
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and 2ꢀ(2ꢀisocyanatoꢀ5ꢀmethoxyphenyl)ꢀ4ꢀphenylpyridine (4) was isolated as the major product
.
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Scheme 2. Exploring the mechanistic study.
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On the basis of the above results and the previous reports, a plausible mechanism for the reaction
is proposed in Scheme 3.10 Initially, copper acetate is coordinated to 2ꢀphenylpyridine to give
intermediate A. Subsequent ligand exchange between acetate and the isocyanate anion gives
intermediate B. A single electron transfer (SET) from the aryl ring to the coordinated Cu(II)
leads to the formation of a radical cation intermediate C in the next step. Subsequent trapping of
the radical cation part of the substrate with the nearby isocyanate in the presence of the oxidants
accounts for the ortho regioselection and gives the cationic species D. Deprotonation of the
intermediate D affords the isocyanate derivative E which in the presence of copper acetate and
pivalic acid leads to the formation of F. Decarboxylation of F under the reaction conditions gives
the product G.11
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Scheme 3. Plausible reaction mechanism
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N
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8
9
N
N
CuII
OAc
CuII
OAc
Cu(OAc)2
KOCN
-KOAc
OAc
NCO
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A
B
SET
N
CuI-
OAc
NCO
oxidant
-Cu(OAc)
C
N H3C
O
O
N
N
HOAc
H
N
H
NCO
-HOAc
NCO
O
D
E
F
-CO2
N
H
N
O
CH3
G
In summary, we have developed a oneꢀpot, efficient and practical copperꢀmediated direct
acetylamination of CꢀH bonds of 2ꢀphenylpyridine derivatives by potassium cyanate for the first
time to access a variety of new heteroarylated acetanilide compounds. K2S2O8 and pivalic acid,
which serve as coꢀoxidant and additive respectively, were of crucial importance and the reaction
led to considerably lower yields in the absence of each. The regioselectivity of the reaction was
also very high and all the products were formed in the ortho position of the phenyl ring.
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EXPERIMENTAL SECTION
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General Information. Solvents, Cu(OAc)2.H2O, K2S2O8, , KOCN, PivOH and toluene were
purchased from the market. 2ꢀArylpyridine derivatives were synthesized via SuzukiꢀMiyaura
coupling of the corresponding aryl boronic acids with 2ꢀbromopyridine and 2ꢀchloropyrimidine,
respectively.12 Other reagents were purchased from commercial distributors and used without
further purification. Analytical thin layer chromatography (TLC) was performed on precoated
silica gel 60 F254 plates. The products were purified by preparative column chromatography on
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silica gel (0.063ꢀ0.200 mm). H and CꢀNMR Spectra: were recorded on 500, 400 or 300 MHz
spectrometers in CDCl3; δ in ppm, J in Hz. High resolution mass spectra were recorded with a
QꢀTOF mass spectrometer, equipped with an ESI source.
General Procedure.
A 10 mL microwave vial was charged with 2ꢀphenylpyridines (1.0 equiv), Cu(OAc)2.H2O (2
equiv), K2S2O8 (1.5 equiv), PivOH (1.0 equiv) and toluene (2 ml). The vial was then sealed and
immersed in an oil bath, which was preheated at 140 °C, for 20 h. After this time the reaction
mixture was cooled to room temperature and then diluted with DCM and filtered. The residue was
then purified by using column chromatography (nꢀhexane/EtOAc, 1/1) to yield the desired
products.
N-(2-(pyridin-2-yl)phenyl)acetamide (2a).8a,b The general procedure was followed using 2ꢀ
phenylpyridine (0.25 mmol, 39 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg, 0.50 mmol),
Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2 mL).
Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final product
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2a (41 mg, 78% yield) as a brown oil; HNMR (500 MHz, , CDCl3) δ 11.99 (s, 1H), 8.66 (s,
1H), 8.49 (d, J = 8.2 Hz, 1H), 7.88 (t, J = 7 Hz, 1H), 7.75 (d, J = 8 Hz, 1H), 7.64 (d, J = 8 Hz,
1H), 7.43 (t, J = 8 Hz, 1H), 7.32 (t, J = 6.3 Hz, 1H), 7.19 (t, J = 7.5 Hz, 1H), 2.186 (s, 3H)
13CNMR (125 MHz, CDCl3) δ 168.6, 158.2, 147.2, 137.9 137.5, 130.1, 128.9, 125.7, 123.6,
123.3, 122.1, 122.0, 25.1; IR(Film) 3178, 3059, 1686, 1589, 1529, 1435, 1311, 756 cmꢀ1 ;
HRMS (EI) m/z calculated for C13H12ON2 (M+): 212.0950 found: 212.0950.
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N-(5-methyl-2-(pyridin-2-yl)phenyl)acetamide (2b). The general procedure was followed
using 2ꢀ(pꢀtolyl)pyridine (0.25 mmol, 42 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg,
0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2
mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final
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product 2b (47 mg, 83% yield) as a white solid; mp: 81 °C; HNMR (400 MHz, , CDCl3) δ
12.03 (s, 1H), 8.60 (d, J = 4.4Hz, 1H), 8.29 (s, 1H), 7.83 (t, J = 7.8Hz, 1H), 7.70 (d, J = 8Hz,
1H), 7.50 (d, J = 8 Hz, 1H), 7.26 (t, J = 3.4 Hz, 1H), 6.97 (d, J = 8 Hz, 1H), 2.36 (s, 3H), 2.15
(s, 3H) ; CNMR (100 MHz, CDCl3) δ 168.7, 146.8, 140.7, 138.2, 137.2, 128.7, 124.6, 123.1,
122.8, 121.7, 25.1, 21.6; IR(Film) 3055, 1680, 1585, 1539, 1471, 1419, 783; HRMS (EI) m/z
calculated for C14H14ON2 (M+): 226.1106. found: 226.1112.
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N-(4-methyl-2-(pyridin-2-yl)phenyl)acetamide (2c). The general procedure was followed
using 2ꢀ(mꢀtolyl)pyridine (0.25 mmol, 42 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg,
0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2
mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final
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product 2c (42 mg, 74% yield) as a pale yellow oil; HNMR (400 MHz, , CDCl3) δ 11.74 (s,
1H), 8.61 (d, J = 4.4 Hz, 1H), 8.30 (d, J = 8.4 Hz, 1H), 7.84 (t, J = 8 Hz, 1H), 7.71 (d, J = 8 Hz,
1H), 7.39 (s, 1H), 7.27 (t, J = 6.2 Hz, 1H), 7.20 (d, J = 8.4Hz, 1H), 2.35 (s, 1H), 2.12 (s, 1H);
13CNMR (100 MHz, CDCl3) δ 168.5, 158.2, 147.2, 138.0, 134.8, 133.1, 130.8, 129.4, 125.9,
123.3, 122.3, 121.9, 25.1, 21.0; IR(Film) 3244, 2972, 1720, 1684, 1593, 1522, 1413, 791;
HRMS (EI) m/z calculated for C14H14ON2 (M+): 226.1106. found: 226.1109.
N-(5-acetyl-2-(pyridin-2-yl)phenyl)acetamide (2d). The general procedure was followed using
1ꢀ(4ꢀ(pyridineꢀ2ꢀyl)phenyl)ethanꢀ1ꢀone (0.25 mmol, 49 mg), K2S2O8 (102 mg, 0.38 mmol),
KOCN (40 mg, 0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol),
and toluene (2 mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1)
gave the final product 2d (31 mg, 49% yield) as a yellow oil; mp: 99 °C; 1HNMR (300 MHz, ,
CDCl3) δ 12.19 (s, 1H), 9.15 (s, 1H), 8.66 (d, J = 4.2 Hz, 1H), 7.87 (td, J = 6.5 Hz & J = 1.8 Hz,
1H), 7.79ꢀ7.70 (m, 3H), 7.34 (td, J = 6.2Hz & J = 1 Hz, 1H), 2.64 (s, 3H), 2.19 (s, 3H);
13CNMR (100 MHz, CDCl3) δ; 197.7, 169.1, 156.4, 146.6, 139.1, 138.3, 137.6, 131.9, 129.3,
124.2, 123.6, 123.1 HRMS (EI) m/z calculated for C15H14O2N2 (M+): 254.1055. found:
254.1060.
N-(5-methyl-2-(4-phenylpyridin-2-yl)phenyl)acetamide(2e). The general procedure was
followed using 4ꢀphenylꢀ2ꢀ(pꢀtolyl)pyridine (0.25 mmol, 61 mg), K2S2O8 (102 mg, 0.38 mmol),
KOCN (40 mg, 0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol),
and toluene (2 mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1)
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gave the final product 2e (61 mg, 81% yield) as a yellow oil; HNMR (400 MHz, , CDCl3) δ
11.35 (s, 1H), 8.69 (s, 1H), 7.95 (s, 1H), 7.71 (d, J = 6 Hz, 2H), 7.63 (s, 1H), 7.55 (m, 5H), 7.09
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(d, J = 8.1 Hz, 1H), 2.42 (s, 3H), 2.16 (s, 3H); CNMR (100 MHz, CDCl3) δ 169.3, 141.9,
136.5, 130.9, 130.4, 130.1, 129.5, 129.4, 129.0, 128.8, 128.6, 128.1, 127.4, 126.1, 120.5, 23.7,
21.6; IR(Film) 2927, 2864, 1720, 1591, 1539, 1470, 1417, 1379, 1238, 761, 700; HRMS (EI)
m/z calculated for C20H18ON2 (M+): 302.1419. found: 302.1416.
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N-(5-chloro-2-(4-phenylpyridin-2-yl)phenyl)acetamide (2f). The general procedure was
followed using 2ꢀ(4ꢀchlorophenyl)ꢀ4ꢀphenylpyridine (0.25 mmol, 66 mg), K2S2O8 (102 mg, 0.38
mmol), KOCN (40 mg, 0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25
mmol), and toluene (2 mL). Purification by column chromatography (silica gel, nꢀhexane/
EtOAc 1:1) gave the final product 2f (38 mg, 47% yield) as a white solid; mp: 136 °C; 1HNMR
(300 MHz, , CDCl3) δ 11.69 (s, 1H), 8.67 (d, J = 5.4 Hz, 1H), 8.38 (s, 1H), 7.91 (s 1H), 7.70ꢀ
7.67 (m, 2H), 7.60 (d, J = 8.4 Hz, 2H), 7.55ꢀ7.51 (m, 3H), 7.20 (d, J = 8.4 Hz, 1H), 2.16 (s, 3H);
13CNMR (75 MHz, CDCl3) δ 169.3, 145.1, 137.8, 130.6, 130.4, 129.5, 127.4, 125.2, 122.6,
121.1, 24.5; HRMS (EI) m/z calculated for C19H15ON2Cl (M+): 322.0873. found: 322.0876.
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N-(3-(pyridin-2-yl)biphenyl-4-yl)acetamide (2g). The general procedure was followed using 2ꢀ
(biphenylꢀ3ꢀyl)pyridine (0.25 mmol, 58 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg, 0.50
mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2 mL).
Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final product
2g (42 mg, 58% yield) as a yellow solid; mp: 144 °C; 1HNMR (400 MHz, , CDCl3) δ 11.86 (s,
1H), 8.66 (dd, J = 4.8Hz & J = 0.8 Hz, 1H), 8.50 (d, J = 8.8 Hz, 1H), 7.88 (td, J = 7.8 Hz & J =
1.6 Hz, 1H), 7.82ꢀ7.79 (m, 2H), 7.64 (dd, J = 8.8 Hz & J = 2.2 Hz, 1H) 7.60ꢀ7.58 (m, 2H), 7.43
(t, J = 7.2 Hz, 2H), 7.35ꢀ7.31 (m, 2H), 2.17 (s, 3H); 13CNMR (100 MHz, CDCl3) δ 168.7, 157.8,
146.9, 140.3, 138.4, 136.7, 128.7, 127.7, 127.2, 126.8, 126.1, 123.6, 122.9, 122.2, 25.1; IR(Film)
3236, 3051, 1681, 1587, 1506, 1442, 1392, 1294, 765, 596; HRMS (EI) m/z calculated for
C19H16ON2 (M+): 288.1263. found: 288.1271.
N-(5-chloro-2-(pyridin-2-yl)phenyl)acetamide(2h). The general procedure was followed using
2ꢀ(4ꢀchlorophenyl)pyridine (0.25 mmol, 47 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg,
0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2
mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final
product 2h (33 mg, 53% yield) as a white solid; mp: 127 °C; 1HNMR (300 MHz, , CDCl3) δ
11.75 (s, 1H), 8.65 (d, J = 4.2 Hz, 1H), 8.39 (s, 1H), 7.96 (t, J = 7.5 Hz, 1H), 7.74 (d, J = 8.1 Hz,
1H), 7.53 (d, J = 8.4 Hz, 1H), 7.40 (t, J = 6 Hz, 1H), 7.17 (dd, J = 8.4 Hz & J = 2.4 Hz, 1H), 2.14
(s, 3H);13CNMR (75 MHz, CDCl3) δ 168.9, 145.9, 139.6, 138.2, 136.6, 130.0, 124.4, 124.0,
123.3, 122.7, 24.8; IR(Film) 3417, 2925, 1685, 1587, 1523, 1469, 1367, 1278, 783, 665; HRMS
(EI) m/z calculated for C13H11ON2Cl (M+): 246.0560. found: 246.0547.
N-(4-ethyl-2-(pyridin-2-yl)phenyl)acetamide(2i). The general procedure was followed using 2ꢀ
(3ethylphenyl)pyridine (0.25 mmol, 46 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg, 0.50
mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2 mL).
Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final product
2i (46 mg, 76% yield) as a yellow oil; 1HNMR (300 MHz, , CDCl3) δ 11.76 (s,1H), 8.61 (d, J =
4.2 Hz, 1H), 8.33 (d, J = 8.4 Hz, 1H), 7.83 (td, J = 7.8 Hz, J = 1.8 Hz, 1H), 7.71 (d, J = 8.1 Hz,
1H), 7.41 (d, J = 1.8 Hz, 1H), 7.27 (td, J = 3.7 Hz, J = 1.2 Hz, 1H), 7.21 (d, J = 1.8 Hz, 1H), 2.67
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(q, J = 6.0 Hz , 2H), 2.12 (s,3H), 1.23 (t, J = 7.8 Hz,3H); CNMR (75 MHz, CDCl3) δ 168.5,
158.3, 147.2, 139.5, 138.0, 135.0, 129.6, 128.3, 125.9, 123.3, 122.4, 121.9, 28.4, 25.0, 15.7;
IR(Film) 3170, 2966, 1683, 1591, 1523, 1473, 1413, 1301, 790, 596; HRMS (EI) m/z calculated
for C15H16ON2 (M+): 240.1263. found: 240.1253.
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N-(4,5-dimethyl-2-(pyridin-2-yl)acetamide (2j). The general procedure was followed using 2ꢀ
(3,4ꢀdimethylphenyl)pyridine (0.25 mmol, 46 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40
mg, 0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene
(2 mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final
product 2j (41 mg, 68% yield) as a white solid; mp: 111 °C; 1HNMR (300 MHz, , CDCl3) δ
11.62 (s, 1H), 8.61 (d, J = 4.2 Hz, 1H), 8.13 (s, 1H), 7.87 (td, J = 7.8 Hz & J = 1.5Hz, 1H), 7.72
(d, J = 8.1Hz, 1H), 7.35 (s, 1H), 7.29 (t, J = 6.2Hz, 1H), 2.29 (s, 3H), 2.26 (s, 3H), 2.12 (s, 3H);
13CNMR (75 MHz, CDCl3) δ 168.7, 157.5, 146.3, 139.4, 138.7, 134.9, 132.4, 129.9, 124.1,
123.7, 123.4, 121.8, 24.9, 19.9, 19.3; IR(Film) 3236, 2923, 1678, 1585, 1521, 1448, 1396, 1290,
790, 590; HRMS (EI) m/z calculated for C15H16ON2 (M+): 240.1263. found: 240.1266.
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N-(4-chloro-2-(pyridin-2-yl)phenyl)acetamide(2k). The general procedure was followed using
2ꢀ(3ꢀchlorophenyl)pyridine (0.25 mmol, 47 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg,
0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2
mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final
product 2k (28 mg, 45% yield) as a white solid; mp:103 °C; 1HNMR (400 MHz, , CDCl3) 12.10
(s, 1H), 8.59 (d, J = 4.0 Hz, 1H), 8.49 (d, J = 8.0Hz, 1H), 7.77 (td, J = 4.0 Hz & J = 1.6Hz, 1H),
7.62 (d, J = 8.0Hz, 1H), 7.53 (d, J = 2.4 Hz, 1H), 7.25 (m, 2H), 2.12 (s, 3H); 13CNMR (100
MHz, CDCl3) δ 168.5, 156.8, 147.5, 137.9, 136.2, 129.9, 129.5, 128.3, 128.1, 123.0, 122.9,
121.7, 25.1; IR(Film) 3416, 2928, 1689, 1587, 1526, 1473, 1369, 1281, 784, 666; MS(EI) m/z
(relative intensity) 246 (M+ , 52), 231 (100), 203 (92), 168 (39), 140 (15), 79 (23). Anal. Calcd.
for C13H11ClN2O: C, 63.40; H, 4.51; N, 11.38; found: C, 63.35; H, 4.49; N, 11.36.
N-(4-(pyridin-2-yl)biphenyl-3-yl)acetamide (2l). The general procedure was followed using 2ꢀ
(biphenylꢀ4ꢀyl)pyridine (0.25 mmol, 58 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg, 0.50
mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2 mL).
Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final product
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2l (39 mg, 54% yield) as a brown oil; HNMR (400 MHz, , CDCl3) 12.30 (s, 1H), 8.90 (s, 1H),
8.69 (d, J = 4.8 Hz, 1H), 7.89 (td, J = 8.0 Hz & J = 1.6Hz, 1H), 7.82 (d, J = 8.0Hz, 1H), 7.74 (t,
J = 8.4 Hz, 2H), 7.47 (m, 3H), 7.39 (m, 2H), 7.32 (td, J = 5.2 Hz & J = 1.2 Hz, 1H), 2.25 (s,
3H); 13CNMR (100 MHz, CDCl3) δ 168.7, 158.1, 147.5, 142.7, 137.7, 129.1, 128.8, 128.7,
128.3, 127.7, 127.2, 127.1, 122.9, 121.9, 121.8, 120.4, 25.3; IR(Film) 3235, 3047, 1677, 1586,
1505, 1438, 1390, 1291, 764, 595; MS(EI) m/z (relative intensity) 288 (M+ , 41), 273 (100), 245
(71), 217 (23), 178 (39), 78 (18). Anal. Calcd. for C19H16N2O: C, 79.13; H, 5.60; N, 9.72; found:
C, 79.16; H, 5.59; N, 9.70
N-(2-(1H-pyrazol-1-yl)phenyl)acetamide (2m). The general procedure was followed using 1ꢀ
phenylꢀ1Hꢀpyrazole (0.25 mmol, 36 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg, 0.50
mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2 mL).
Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final product
2m (16 mg, 31% yield) as a yellow oil; 1HNMR (500 MHz, , CDCl3) δ 10.23 (s, 1H), 8.44 (d, J
= 8.5 Hz, 1H), 7.79 (d, J = 2 Hz, 1H), 7.64 (d, J = 3 Hz, 1H), 7.34 (m, 2H), 7.13 (t, J = 7.8 Hz,
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1H), 6.49 (t, J = 2.2 Hz, 1H), 2.12 (s, 3H); CNMR (125 MHz, CDCl3) δ 168.5, 141.4, 131.6,
130.2, 128.1, 127.1, 122.9, 122.4, 122.1, 107.2, 25.1; IR(Film) 3441, 2924, 2856, 1691, 1597,
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1515, 1461, 1394, 1047, 752; HRMS (EI) m/z calculated for C11H11ON3 (M+): 201.0902. found:
201.0895
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2-(2-isocyanato-4-methylphenyl)-4-phenylpyridine(3). The general procedure was followed
using 4ꢀphenylꢀ2ꢀ(pꢀtolyl)pyridine (0.25 mmol, 61 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN
(40 mg, 0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and
toluene (2 mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave
the final product 3 (25 mg, 35% yield) as a yellow solid; mp:82 °C; 1HNMR (500 MHz, CDCl3)
δ 8.81 (d, J = 5 Hz, 1H), 8.07 (s, 1H), 7.90 (d, J = 8 Hz, 1H), 7.72 (dd, J = 8 Hz & J = 1 Hz, 2H),
7.63 (s, 1H), 7.55ꢀ 7.48 (m, 5H), 2.45 (s, 3H); 13CNMR (100 MHz, CDCl3) δ 155.7, 150.3,
149.4, 140.8, 139.2, 138.0, 134.4, 133.8, 129.9, 129.3, 129.2, 127.2, 121.4, 121.1, 119.0, 110.9,
20.9; IR(Film) 2466, 1595, 1461, 1383, 831, 767, 694; HRMS (EI) m/z calculated for
C19H14ON2 (M+): 286.1106, found: 286.1115.
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2-(2-isocyanato-5-methoxyphenyl)pyridine(4). The general procedure was followed using 2ꢀ
(3ꢀmethoxyphenyl)pyridine (0.25 mmol, 46 mg), K2S2O8 (102 mg, 0.38 mmol), KOCN (40 mg,
0.50 mmol), Cu(OAc)2.H2O (100 mg, 0.50 mmol), PivOH (25 mg, 0.25 mmol), and toluene (2
mL). Purification by column chromatography (silica gel, nꢀhexane/ EtOAc 1:1) gave the final
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product 4 (17 mg, 31% yield) as a yellow oil; HNMR (400 MHz, , CDCl3) δ 8.84 (s, 1H), 8.06
(t, J = 8 Hz, 1H), 7.99 (d, J = 8 Hz, 1H), 7.72 (d, J = 8.4 Hz, 1H), 7.56 (t, J = 6.2 Hz, 1H), 7.52
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(d, J = 2 Hz, 1H), 7.06 (dd, J = 8.4 Hz & J = 2.2 Hz, 1H), 3.97 (s, 3H); CNMR (100 MHz,
CDCl3) δ 163.1, 153.2, 147.4, 135.9, 124.9, 124.4, 121.7, 119.6, 118.5, 116.9, 115.5, 102.6, 56.1;
IR(Film) 2938, 2839, 2219, 1604, 1562, 1491, 1465, 1305, 1225, 1029, 790; HRMS (EI) m/z
calculated for C13H10O2N2 (M+): 226.0742. found: 226.0768.
ASSOCIATED CONTENT
Supporting Information
1H NMR and 13C NMR spectra for new compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Eꢀmail: kianmehr@khayam.ut.ac.ir
Acknowledgements
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We gratefully acknowledge the financial support from the Research Council of the University of
Tehran. We thank Dr. Karol Gajewski, Canadian Intellectual Property Office, for helpful
comments on this work.
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