Microwave-promoted syntheses of pyridine carboxamides and tert-carboximides from novel 6-acetylpyridine-2-carboxylic acid

Article abstract of DOI:10.1080/00397910902906586

A novel 6-acetylpyridine-2-carboxylic acid (4) was obtained occasionally during the synthesis of asymmetric ethyl 6-acetylpyridine-2-carboxylate (3) from 2,6-dipiclinic acid (1). Compounds 3 and 4 could transform mutually under some specific conditions. T

Full text of DOI:10.1080/00397910902906586

This article was downloaded by: [Moskow State Univ Bibliote]
On: 15 January 2014, At: 03:29
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic
Organic Chemistry
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Microwave-Promoted Syntheses
of Pyridine Carboxamides and
tert-Carboximides from Novel
6-Acetylpyridine-2-carboxylic
Acid
Biyun Su a , Jianshe Zhao b , Qunzheng Zhang a &
Wenlong Qin c
a College of Chemistry and Chemical Engineering,
Xi'an Shiyou University , Xi'an, China
b Department of Chemistry , Northwest University ,
Xi'an, China
c College of Petroleum Engineering, Xi'an Shiyou
University , Xi'an, China
Published online: 12 Nov 2009.
To cite this article: Biyun Su , Jianshe Zhao , Qunzheng Zhang & Wenlong Qin (2009)
Microwave-Promoted Syntheses of Pyridine Carboxamides and tert-Carboximides from
Novel 6-Acetylpyridine-2-carboxylic Acid, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 39:24, 4429-4440,
DOI: 10.1080/00397910902906586
To link to this article: http://dx.doi.org/10.1080/00397910902906586
PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Synthetic Communications1, 39: 4429–4440, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910902906586
Microwave-Promoted Syntheses of Pyridine
Carboxamides and tert-Carboximides from Novel
6-Acetylpyridine-2-carboxylic Acid
Biyun Su,1 Jianshe Zhao,2 Qunzheng Zhang,1 and Wenlong Qin3
1College of Chemistry and Chemical Engineering, Xi’an Shiyou University,
Xi’an, China
2Department of Chemistry, Northwest University, Xi’an, China
3College of Petroleum Engineering, Xi’an Shiyou University, Xi’an, China
Abstract: A novel 6-acetylpyridine-2-carboxylic acid (4) was obtained occasionally
during the synthesis of asymmetric ethyl 6-acetylpyridine-2-carboxylate (3) from
2,6-dipiclinic acid (1). Compounds 3 and 4 could transform mutually under some
specific conditions. Two reactions of distinctive types occurred when they reacted
with the aromatic amines as precursors, due to different functional groups on the
2-position of pyridine in the molecules of 3 and 4: one was Schiff base condensa-
tion and the other was an amidation reaction. From the latter reaction, two series
of new compounds, pyridine carboxamides (5a–d) and pyridine tert-carboximides
(6a–h), resulted. The relevant reaction mechanism is discussed in detail.
Keywords: 6-Acetylpyridine-2-carboxylic acid, amidation reaction, microwave
irradiation, reaction mechanism
Twenty years after the pioneering work of Small et al.[1] and Britovsek
et al.,[2] late-transition-metal catalysts incorporating bis(imino)pyridyl
ligands have received much attention because they are robust and extre-
mely active for polymerization of ethylene to linear, high-density poly-
ethylene. Building on the work of Brookhart and others, chemists have
developed a proprietary family of catalyst analogs.[3] We have previously
Received December 15, 2008.
Address correspondence to Biyun Su, College of Chemistry and Chemical
Engineering, Xi’an Shiyou University, Xi’an, China. E-mail: subiyun@xsyu.
edu.cn
4429

4430
B. Su et al.
Scheme 1. Synthesis of the precursor 6-acetylpyridine-2-carboxylic acid (4).
reported a series of mono(imino)pyridyl compounds[4] coming from the
precursor ethyl 6-acetylpyridine-2-carboxylate (3) and a series of aro-
matic amines. When incorporated with late transition metals, these
mono(imino)pyridyl compounds have indicated considerable activity
for ethylene polymerization and oligomerization.[5] In this article, we
reported the synthesis of a new compound, 6-acetylpyridine-2-carboxylic
acid (4), which was obtained occasionally during the synthesis of 3 from
2,6-dipiclinic acid (1) (Scheme 1). As is known, the microwave techniques
for organic synthesis have been widely used in a variety of organic reac-
tions since the first article on microwave-assisted synthesis was published
by Gedye and Giguere in Tetrahedron Letters in 1986.[6,7] Use of micro-
wave technology can enhance selectivity and reactivity, increase the che-
mical yields, and shorten the reaction time, so we attempted to employ
this efficient method to synthesize carboxamides. When 4 reacted with
aromatic amines as precursor under microwave irradiation without sol-
vent, two exceptional series of new compounds, pyridine carboxamides
(5a–d) (Scheme 2) and pyridine tert-carboximides (6a–h) (Scheme 3),
resulted. Compared with the conventional solvent synthesis method,[8]
microwave-assisted condensation[9–12] seemed to improve reaction rate,
simplify workup procedure, and form cleaner products in preparing these
pyridine carboxamides and pyridine tert-carboximides.
Scheme 2. Synthesis of pyridine carboxamides (5a–d).

Pyridine Carboxamides and tert-Carboximides
4431
Scheme 3. Synthesis of pyridine tert-carboximides (6a–h).
RESULTS AND DISCUSSION
Mutual Transformation Between 3 and 4
The transformation from 3 to 4 involved acid hydrolysis of ester. The
ester group in 2-position of the pyridine ring in 3 was not stable in acid
aqueous solution; it could slowly hydrolyze into carboxyl group at a
relatively higher temperature (more than 35ꢀC). Compared with the ester
group, other functional groups (the pyridine ring, and the acetyl group)
were more stable at these conditions. The existence of the carboxyl group
made 4 possess the general properties of carboxylic acid, such as rela-
tively stronger polarity and less solubility in water, which made 4 and
3 separate more easily.
Not only 3 could change to 4 in a specific condition, 4 could also
transform to 3 in another condition. The occurrence of latter transforma-
tion was very interesting: as highly pure 4 was dissolved in ethyl acetate
and injected into gas chromatography–mass spectrometry (GC-MS), 3
and 4 were both detected at different peak times. This unexpected result
implied part of 4 changed to 3 under the definite experimental condition
of GC-MS. The possible reaction might be as follows: ethyl acetate
reacted with part of 4 as a reactant to form 3 and acetic acid at high
temperature in GC-MS, which involved the acid decomposition of ethyl
acetate.
Reaction Mechanisms of Aromatic Amines with 4
Theoretically, there are two unique reactive sites in the asymmetric pre-
cursor 6-acetylpyridine-2-carboxylic acid (4), which are the carboxyl
group in 2-position of the pyridine ring and the acetyl group in
6-position. When reacting with 4, the aromatic amine would choose
to attack the carboxyl group to engender amidation products but not
react with acetyl group to give Schiff base products because of the

4432
B. Su et al.
comparatively stronger activity of carboxyl group. Unlike the reaction of
the aromatic amine with 4, the aromatic amine would first attack the
acetyl group of ethyl 6-acetylpyridine-2-carboxylate (3) to create Schiff
base product mono(imino)pyridine but not react with the ester group
to afford amidation product.[4] These results showed that the reactivity
of different groups in the pyridine ring with aromatic amine complied
with the sequence of carboxyl group, acetyl group, and ester group.
The reactions of aromatic amine with 3 and 4 are illustrated in Scheme 4.
Our interest here is how aromatic amines with different structures
influence the reaction and the product. According to the experiments,
when aromatic amines with different substitute kinds and sites in the aryl
ring reacted with a same precursor 4 under microwave irradiation
without solvent, two kinds of new compounds, pyridine carboxamides
and pyridine tert-carboximides, were produced (see Scheme 4). All
of 2,6-dimethylaniline, 2,4,6-trimethylaniline, 2,6-diethylaniline and
2,5-difluoroaniline reacted with 4 according to a 1:1 molar ratio to afford
pyridine carboxamides, whereas all of aniline, 4-methylaniline, 2-chloroa-
niline, 3-chloroaniline, 4-chloroaniline, 2-nitroaniline, 3-nitroaniline, and
4-nitroaniline reacted with 4 in a 2:1 molar ratio to engender pyridine
tert-carboximides. These significant results suggest that the kind of pro-
duct is only related to the number of substituents on the phenyl ring, not
the kinds (electron-withdrawing or electron-donating group) or the sites
(ortho, meta, or para position) of the substituent on the phenyl ring. Aro-
matic amines with a disubstituted or polysubstituted aryl ring are apt to
afford pyridine carboxamides, whereas those with a nonsubstituted or
monosubstituted aryl ring are inclined to give pyridine tert-carboximides.
The possible reasons are demonstrated in detail as follows: for those
aromatic amines with disubstituted or polysubstituted aryl ring, after
Scheme 4. Different reactions of aromatic amine with 3 and 4.

Pyridine Carboxamides and tert-Carboximides
4433
the reaction stage (during which the lone pair electrons in the N atom of
aromatic amine accessed the carboxyl group of 4 and attacked the carbon
atom to afford carboxamide), the strong steric effect of amino in carbox-
amide prevented itself from approaching another molecule 4 to result in
tert-carboximide. In case of those aromatic amines with nonsubstituted
or monosubstituted aryl ring reacting with 4, after the same reaction
stage as aromatic amines with disubstituted or polysubstituted aryl ring,
the smaller steric effect of amino in the obtained carboxamide allowed
itself to approach another molecule 4 and attacked the C atom of
carboxyl to give tert-carboximide.
In summary, a novel 6-acetylpyridine-2-carboxylic acid (4) was
obtained occasionally during the synthesis of ethyl 6-acetylpyridine-2-
carboxylate (3). Under microwave irradiation, the reactivity difference
between the functional groups on the pyridine ring made the reactions
of 3 and 4 with aromatic amines differ greatly, in which one was Schiff
base condensation and the other was an amidation reaction. From the
amidation reaction between 4 and aromatic amines, two kinds of new
compounds, pyridine carboxamides and pyridine tert-carboximides, were
prepared. The experiments indicated that the kind of product was related
only to the number of substituents on the aryl ring, not the kinds
(electron-withdrawing or electron-donating group) or the sites (ortho,
meta, or para position) of substituent on the aryl ring. Aromatic amines
with a disubstituted or polysubstituted aryl ring were apt to afford
pyridine carboxamides (5a–d), whereas those with a nonsubstituted or
monosubstituted aryl ring were inclined to give pyridine tert-carboxi-
mides (6a–h).
EXPERIMENTAL
C, H, and N analyses were performed on a HP-MOD 1106 microanalyzer.
Infrared (IR) spectra were carried out with a Perkin-Elemer Fourier
1
transform (FT)–IR 2000 spectrometer. H NMR spectra were recorded
on an Inova-400 NMR spectrometer, using tetramethylsilane (TMS) as
internal standard. Mass spectra were determined with a Kratos AEI
MS-50 instrument using the electron impact (EI) method. The
microwave-assisted condensations were performed in a domestic oven,
Midea PJ 21B-A 800 w (21 L). Melting points were determined with a
melting-point apparatus and were uncorrected. 2,6-Dipiclinic acid,
2,6-dimethylaniline, 2,4,6-trimethylaniline, 2,6-diethylaniline, 2,5-difluor-
oaniline, aniline, 4-methylaniline, 2-chloroaniline, 3-chloroaniline,
4-chloroaniline, 2-nitroaniline, 3-nitroaniline, and 4-nitroaniline were
purchased from Albemarle Co. (USA).

4434
B. Su et al.
Preparation of the Precursor 6-Acetylpyridine-2-carboxylic Acid (4)
Esterification of 2,6-dipiclinic acid (1) was done with modified procedure,
generating a better yield (84%) than that reported[12] and resulting in
2,6-dicarbethoxypyridine (2), which was purified by a simplified method.
The dry 2 was dissolved in freshly distilled EtOAc and refluxed with dry
EtONa powder for 12 h. Excess concentrated HCl was added, and the
mixture was refluxed for 7–8 h to produce ethyl 6-acetylpyridine-2-car-
boxylate (3). After water was added to dissolve the NaCl formed in the
reaction, the aqueous phase was shaken with CHCl3. After the organic
solvent was evaporated under reduced pressure, the obtained mixture
was allowed to stand for 3 days at 37ꢀC. When a solvent (in which
petroleum ether and EtOAc were mixed in a volume ratio of 8:1) was
added into the mixture, the insoluble solid was filtered and recrystallized
by mixed solvents of ethanol and water to afford pure 6-acetylpyridine-2-
1
carboxylic acid (4) as white powder. Yield: 26.1%, mp 140–142ꢀC. H
NMR (400 MHz, CDCl3): d 8.47 (d, 1H, Py-Hm), 8.35 (d, 1H, Py-Hm),
8.17 (t, 1H, Py-Hp), 2.81 [s, 3H, O¼C(CH3)]. IR (KBr): nC¼O 1758, nC¼O
1694, nO–H 3087, 3023, 2934, 2700, nOHꢁꢁꢁO 958 cmꢂ1. GC-MS Ins: m=z
165 (Mþ), 193(Mþ þ 2C2H2). Anal. calcd. for C8H7NO3: C, 58.18; H,
4.27; N, 8.48. Found: C, 58.62; H, 3.95; N, 8.40.
General Procedure for Syntheses of 5a–d and 6a–h
The microwave-assisted condensations of 6-acetylpyridine-2-carboxylic
acid (4) and aromatic amines were performed in a domestic microwave
oven. Compound 4 (2.0 mmol) and excess of aromatic amine (5.5 mmol)
were put into an open vessel. The mixture was irradiated on a Low or
M-High setting, using thin-layer chromatography (TLC) to monitor the
progress of the reaction. After an optimized reaction time, the mixture
gradually turned pink to red, and the obtained mixture was purified by
recrystallization using the proper solvent under refrigeration to give
desired product. The microwave power, reaction time, yield, melting
point, and solvents used to purify products of 5a–d and 6a–h are reported
in Table 1. Spectral data of these compounds are listed here.
6-Acetyl-N-(2,6-dimethylphenyl)pyridine-2-carboxamide (5a)
1H NMR (400 MHz, CDCl3): d 8.44 (d, 1H, Py-Hm), 8.32 (d, 1H,
Py-Hm), 8.14 (t, 1H, Py-Hp), 7.08 (d, 1H, Ph-Hm), 6.96 (d, 1H, Ph-Hm),
6.70 (t, 1H, Ph-Hp), 2.79 [s, 3H, O¼C (CH3)], 2.23 (d, 6 H, Ph-CH3).

4435

4436

Pyridine Carboxamides and tert-Carboximides
4437
IR (KBr): nN–H 3404, nC¼O 1697, 1654, dN–H 1578 cmꢂ1. MS (EI): m=z
269 (Mþ þ H). Anal. calcd. for C16H16N2O2: C, 71.62; H, 6.01; N,
10.44. Found: C, 72.76; H, 6.62; N, 10.20.
6-Acetyl-N-(2,4,6-trimethylphenyl)pyridine-2-carboxamide (5b)
1H NMR (400 MHz, CDCl3): d 8.44 (d, 1H, Py-Hm), 8.34 (d, 1H,
Py-Hm), 8.13 (t, 1H, Py-Hp), 6.91 (s, 1H, Ph-Hm), 6.82 (s, 1H, Ph-Hm),
2.78 [s, 3H, O¼C(CH3)], 2.36 [s, 3H, Ph-(CH3)o], 2.22 [s, 3H, Ph-(Me)o],
1.99 [s, 3H, Ph-(Me)p]. IR (KBr): nN–H 3284, nC¼O 1643, 1603, dN–H
1579 cmꢂ1. MS (EI): m=z 282 (Mþ). Anal. calcd. for C17H18N2O2: C,
72.32; H, 6.43; N, 9.92. Found: C, 71.82; H, 7.26; N, 9.36.
6-Acetyl-N-(2,6-diethylphenyl)pyridine-2-carboxamide (5c)
1H NMR (400 MHz, CDCl3): d 8.45 (d, 1H, Py-Hm), 8.33 (d, 1H,
Py-Hm), 8.13 (t, 1H, Py-Hp), 6.83 (d, 1H, Ph-Hm), 6.75 (d, 1H, Ph-Hm),
6.70 (d, 1H, Ph-Hp), 3.56 [m, 2H, (CH2)CH3], 3.46 [m, 2H, (CH2)CH3],
2.80 [s, 3H, O¼C(CH3)], 1.23 [t, 3H, CH2(CH3)], 1.19 [t, 3H, CH2(CH3)].
IR (KBr): nN–H 3284, nC¼O 1633, 1590, dN–H 1556 cmꢂ1. MS (EI): m=z
296 (Mþ). Anal. calcd. for C18H20N2O2: C, 72.95; H, 6.80; N, 9.45.
Found: C, 72.51; H, 6.66; N, 9.54.
6-Acetyl-N-(2,5-difluorophenyl)pyridine-2-carboxamide (5d)
1H NMR (400 MHz, CDCl3): d 8.45 (d, 1H, Py-Hm), 8.37 (d, 1H,
Py-Hm), 8.16 (t, 1H, Py-Hp), 6.90 (d, 1H, Ph-Ho), 6.46 (d, 1H, Ph-Hm),
6.37 (d, 1H, Ph-Hp), 2.78 [s, 3H, O¼C(CH3)]. IR (KBr): nN–H 3425, nC¼O
1703, 1643, dN–H 1600 cmꢂ1. MS (EI): m=z 276 (Mþ). Anal. calcd. for
C14H10F2N2O2: C, 60.87; H, 3.65; N, 10.14. Found: C, 60.65; H, 3.25;
N, 10.06.
N-Phenyl-bis(6-acetylpyridine-2-carboximide) (6a)
1H NMR (400 MHz, CDCl3): d 8.48 (d, 2H, Py-Hm), 8.36 (d, 2H,
Py-Hm), 8.10 (t, 2H, Py-Hp), 7.26 (d, 2H, Ph-Ho), 7.07 (t, 1H, Ph-Hm),
6.95 (t, 1H, Ph-Hm), 6.84 (t, 1H, Ph-Hp), 2.75 (s, 6H, Me). IR (KBr):
nC¼O 1708, nC¼O 1600 cmꢂ1. MS (EI): m=z 387 (Mþ). Anal. calcd. for
C22H18N3O4.5: C, 66.66; H, 4.58; N, 10.60. Found: C, 66.80; H, 4.45;
N, 10.23.

4438
B. Su et al.
N-(4-Methylphenyl)-bis(6-acetylpyridine-2-carboximide) (6b)
1H NMR (400 MHz, CDCl3): d 8.46 (d, 2H, Py-Hm), 8.34 (d, 2H,
Py-Hm), 8.10 (t, 2H, Py-Hp), 7.15 (d, 2H, Ph-Ho), 7.11 (d, 1H, Ph-Hm),
7.05 (d, 1H, Ph-Hm), 2.76 (s, 6H, CH3), 2.23 [s, 3H, Ph-(Me)p]. IR (KBr):
nC¼O 1712, nC¼O 1580 cmꢂ1. MS (EI): m=z 400 (Mþ-H). Anal. calcd.
for C23H19N3O4: C, 68.82; H, 4.77; N, 10.47. Found: C, 69.26; H, 5.13;
N, 10.73.
N-(2-Chlorophenyl)-bis(6-acetylpyridine-2-carboximide) (6c)
1H NMR (400 MHz, CDCl3): d 8.45 (d, 2H, Py-Hm), 8.34 (d, 2H,
Py-Hm), 8.16 (t, 2H, Py-Hp), 7.23 (d, 1H, Ph-Ho), 7.07 (t, 1H, Ph-Hm),
6.77 (t, 1H, Ph-Hm), 6.69 (t, 1H, Ph-Hp), 2.80 (s, 6H, CH3). IR (KBr):
nC¼O 1758, nC¼O 1707 cmꢂ1. MS (EI): m=z 421 (Mþ). Anal. calcd. for
C22H18ClN3O5: C, 60.07; H, 4.12; N, 9.55. Found: C, 59.97; H, 3.80;
N, 9.47.
N-(3-Chlorophenyl)-bis(6-acetylpyridine-2-carboximide) (6d)
1H NMR (400 MHz, CDCl3): d 8.45 (d, 2H, Py-Hm), 8.32 (d, 2H,
Py-Hm), 8.14 (t, 2H, Py-Hp), 7.24 (s, 1H, Ph-Ho), 7.18 (t, 1H, Ph-Ho),
6.91 (t, 1H, Ph-Hm), 6.67 (d, 1H, Ph-Hp), 2.76 (s, 6H, CH3). IR
(KBr): nC¼O 1730, nC¼O 1588 cmꢂ1. MS (EI): m=z 420 (Mþ-H). Anal.
calcd. for C22H16ClN3O4: C, 62.64; H, 3.82; N, 9.96. Found: C, 63.02;
H, 3.47; N, 10.03.
N-(4-Chlorophenyl)-bis(6-acetylpyridine-2-carboximide) (6e)
1H NMR (400 MHz, CDCl3): d 8.46 (d, 2H, Py-Hm), 8.33 (d, 2H,
Py-Hm), 8.15 (t, 2H, Py-Hp), 7.26 (s, 1H, Ph-Ho), 7.21 (t, 1H, Ph-Ho),
7.08 (t, 1H, Ph-Hm), 6.72 (t, 1H, Ph-Hm), 2.70 (s, 6H, CH3). IR
(KBr): nC¼O 1720, nC¼O 1631 cmꢂ1. MS (EI): m=z 420 (Mþ-H). Anal.
calcd. for C22H16ClN3O4: C, 62.64; H, 3.82; N, 9.96. Found: C, 63.10;
H, 3.87; N, 9.91.
N-(2-Nitrophenyl)-bis(6-acetylpyridine-2-carboximide) (6f)
1H NMR (400 MHz, CDCl3): d 8.25 (d, 2H, Py-Hm), 8.10 (d, 2H,
Py-Hm), 7.89 (t, 2H, Py-Hp), 7.32 (d, 1H, Ph-Ho), 7.14 (t, 1H, Ph-Hm),

Pyridine Carboxamides and tert-Carboximides
4439
7.13 (t, 1H, Ph-Hm), 7.09 (t, 1H, Ph-Hp), 2.35 (s, 6H, CH3). IR (KBr):
nC¼O 1700, nC¼O 1642 cmꢂ1. MS (EI): m=z 432 (Mþ). Anal. calcd.
for C22H16N4O6: C, 61.11; H, 3.73; N, 12.96. Found: C, 61.26; H, 4.12;
N, 13.30.
N-(3-Nitrophenyl)-bis(6-acetylpyridine-2-carboximide) (6g)
1H NMR (400MHz, CDCl3): d 8.20 (d, 2H, Py-Hm), 8.11 (d, 2H, Py-Hm),
7.89 (t, 2H, Py-Hp), 7.34 (s, 1H, Ph-Ho), 7.20 (t, 1H, Ph-Ho), 7.18 (t, 1H,
Ph-Hm), 7.08 (d, 1H, Ph-Hp), 2.38 (s, 6H, CH3). IR (KBr): nC¼O 1696,
nC¼O 1579cmꢂ1. MS (EI): m=z 432 (Mþ). Anal. calcd. for C22H16N4O6:
C, 61.11; H, 3.73; N, 12.96. Found: C, 61.45; H, 3.96; N, 13.43.
N-(4-Nitrophenyl)-bis(6-acetylpyridine-2-carboximide) (6h)
1H NMR (400 MHz, CDCl3): d 8.17 (d, 2H, Py-Hm), 8.02 (d, 2H,
Py-Hm), 7.91 (t, 2H, Py-Hp), 7.35 (s, 1H, Ph-Ho), 7.34 (t, 1H, Ph-Ho),
7.32 (t, 1H, Ph-Hm), 7.10 (d, 1H, Ph-Hm), 2.33 (s, 6H, CH3). IR
(KBr): nC¼O 1712, nC¼O 1653 cmꢂ1. MS (EI): m=z 431 (Mþ-H). Anal.
calcd. for C22H16N4O6: C, 61.11; H, 3.73; N, 12.96. Found: C, 61.05;
H, 4.06; N, 13.27.
ACKNOWLEDGMENTS
We are grateful to the Natural Science Basic Research Plan in Shaanxi
Province (No. 2009JQ2006), the Scientific Research Plan Projects of
Shaanxi Education Department (No. 09JK696), the Natural Science
Foundation of Shaanxi Province (No. 2006B17), and the Science and
Technology Research Project Foundation of Xi’an Shiyou University
(No. Ys29030511) for financial support.
REFERENCES
1. Small, B. L.; Brookhart, M.; Bennett, A. M. A. Highly active iron and cobalt
catalysts for the polymerization of ethylene. J. Am. Chem. Soc. 1998, 120,
4049–4050.
2. Britovsek, G. J. P.; Bruce, M.; Gibson, V. C.; Kimberley, B. S.; Maddox, P.
J.; Mastroianni, S.; McTavish, S. J.; Redshaw, C.; Solan, G. A.; Stro¨mberg,
S.; White, A. J. P.; Williams, D. J. Iron and cobalt ethylene polymerization
catalysts bearing 2,6-bis(imino)pyridyl ligands: Synthesis, structures, and
polymerization studies. J. Am. Chem. Soc. 1999, 121, 8728–8740.

4440
B. Su et al.
3. Kaul, F. A. R.; Puchta, G. T.; Schneider, H.; Bielert, F.; Mihalios, D.;
Herrmann, W. A. Immobilization of bis(imino)pyridyl iron(II) complexes
on silica. Organometallics 2002, 21, 74–82.
4. Su, B. Y.; Zhao, J. S.; Zhao, P. Two novel microwave promoted reactions
between ethyl 6-acetylpyridine-2-carboxylate and aromatic amine=aliphatic
amine. Synth. Commun. 2006, 36 (15), 2214–2220.
5. Su, B. Y.; Zhao, J. S. Preparation, structure, and ethylene polymerization=
oligomerization behavior of 2-carbethoxy-6-iminopyridine-based transition
metal complexes. Polyhedron 2006, 25, 3289–3298.
6. Gedye, R.; Smith, F.; Westaway, K.; Humera, A.; Baldisera, L.; Laberge, L.;
Roussell, J. The use of microwave ovens for rapid organic synthesis. Tetrahe-
dron Lett. 1986, 27 (3), 279–282.
7. Giguere, R. J.; Bray, T. L.; Duncan, S. M.; Majetich, G. Application of
commercial microwave ovens to organic synthesis. Tetrahedron Lett. 1986,
27 (41), 4945–4948.
8. Hamuro, Y.; Geib, S. J.; Hamilton, A. D. Novel folding patterns in a family
of oligoanthranilamides: Non-peptide oligomers that form extended helical
secondary structures. J. Am. Chem. Soc. 1997, 119, 10587–10593.
9. Varma, R. S. Solvent-free organic syntheses: Using supported reagents and
microwave irradiation. Green Chem. 1999, 1, 43–46.
10. Loupy, A. Solvent-free reactions. Topics Curr. Chem. 1999, 206, 153–208.
11. Bose, D. S.; Jayalakshmi, B. Reagents for organic synthesis: Use of organos-
tannyl oxides as catalytic neutral agents in the preparation of nitriles from
primary amides under microwave irradiation. J. Org. Chem. 1999, 64,
1713–1714.
12. Sauer, D. R.; Kalvin, D.; Phelan, K. M. Microwave-assisted synthesis utiliz-
ing supported reagents: A rapid and efficient acylation procedure. Org. Lett.
2003, 5 (24), 4721–4724.