Ketenes from N-(2-Pyridyl)amides

Article abstract of DOI:10.1071/CH14714

Methoxycarbonylketene 4a, methoxycarbonyl(methyl)ketene 4b, chloroketene 4c, cyanoketene 4d, diphenylketene 4e, and 2-pyridylketene 4f have been generated by flash vacuum thermolysis of the corresponding 2-pyridylacetamide derivatives 3a-f and isolated in Ar matrices for FT-IR spectroscopic characterisation. The N-(2-pyridyl)-2-pyridylacetamide 3f yielded 2-pyridyl isocyanate in addition to 2-pyridylketene.

Full text of DOI:10.1071/CH14714

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem. 2015, 68, 687–692
Full Paper
http://dx.doi.org/10.1071/CH14714
Ketenes from N-(2-Pyridyl)amides
A
A
A B
,
Carsten Plug, Hussein Kanaani, and Curt Wentrup
¨
A
School of Chemistry and Molecular Biosciences, The University of Queensland,
Brisbane, Qld 4072, Australia.
B
Corresponding author. Email: wentrup@uq.edu.au
Methoxycarbonylketene 4a, methoxycarbonyl(methyl)ketene 4b, chloroketene 4c, cyanoketene 4d, diphenylketene 4e,
and 2-pyridylketene 4f have been generated by flash vacuum thermolysis of the corresponding 2-pyridylacetamide
derivatives 3a–f and isolated in Ar matrices for FT-IR spectroscopic characterisation. The N-(2-pyridyl)-2-pyridylacetamide
3f yielded 2-pyridyl isocyanate in addition to 2-pyridylketene.
Manuscript received: 15 December 2014.
Manuscript accepted: 15 January 2015.
Published online: 12 February 2015.
O
Introduction
O
ꢄ
DCC
R
While there are many methods for the synthesis of ketenes,[1] we
were interested in developing a procedure that would help us
identify ketenes formed in either thermal or photochemical
reactions and isolated in low temperature noble gas matrices.
For this purpose, an efficient method amenable to flash vacuum
thermolysis (FVT) with Ar matrix isolation of the products
and capable of being applied to a wide variety of ketenes
was desirable. In a preliminary publication we reported the
formation of methoxycarbonylketene 4a by FVT of the 2-
pyridylacetamide derivative 3a.[2] We have now examined the
scope of this reaction by generating the ketenes 4a–f and are
pleased to report the details herein.
R
HO
N
N
N
NHRꢂ
ꢃH2O
Rꢂ
Rꢂ
Rꢁ
1
2
3
a: Rꢂ ꢀ Me
b: Rꢂ ꢀ H
R
FVT
ꢄ
C
O
Rꢂ
N
H
N
NHRꢂ
N
Rꢁ
1
4
O
R
Rꢁ
3
a: R ꢀ COOMe, R
b: R ꢀ COOMe, R
c: R ꢀ Cl, R ꢀ R
d: R ꢀ CN, R ꢀ R
e: R ꢀ Ph, R ꢀ Ph, R
f: R ꢀ 2-pyridyl, R
ꢁ
ꢀ H, R
ꢀ R ꢀ Me, 85 %
ꢀ H, 80 %
ꢂ ꢀ H, 65 %
ꢂ ꢀ Me, 83 %
ꢁ
ꢂ
ꢁ
ꢂ
Results and Discussion
ꢁ
The requisite N-(2-pyridyl)acetamides 3 were prepared by con-
densation of N-methyl-N-(2-pyridyl)amine 1a or 2-pyridylamine
1b with acetic or malonic acid derivatives 2 by using dicyclo-
hexylcarbodiimide (DCC) as a dehydrating agent (Scheme 1).
Ketenes 4 were generated by FVT of 3 in high vacuum and
condensed with Ar at 10–15 K to form a matrix. The reaction is a
retro-ene type cycloelimination. The IR spectrum of methoxy-
carbonylketene 4a obtained in this manner at 4808C is shown
in Fig. 1.
ꢁ
ꢂ
ꢀ H, 75 %
ꢀ H, 70 %
ꢁ
ꢀ R
ꢂ
Scheme 1. Synthesis of N-(2-pyridyl)amides 3 and ketenes 4. Yields of 3
given in percent.
and incomplete pyrolysis of the pyrazole derivative 6 made
this a less useful precursor.
The identity of compound 4a was confirmed by comparison
with the spectra obtained by FVT of two other precursors,
viz. dimethyl malonate 5 and 3,5-dimethyl-N-(methoxycarbo-
nylacetyl)pyrazole 6 (Eqn 1). As described previously,[2] the
same ketene was obtained by all three methods, but the
pyridylamide route from 3a afforded the cleanest spectrum.
The strong C¼C¼O stretch of 4a is at 2156 cmꢀ1. At 4808C a
small amount of carbon suboxide, C3O2, was the only notice-
able by-product (C, Fig. 1), but this increased at higher
temperatures. Formation of C3O2 was more of a problem in
the FVT of dimethyl malonate 5, and the hygroscopic nature
Me
C
O
FVT
N
(1)
COOMe ,
MeOCO
Me
MeO
N
O
5
COOMe
4a
6
The methyl 2-methylmalonic amide derivative 3b underwent
analogous FVT at 4808C yielding a very clean Ar matrix of
methoxycarbonyl(methyl)ketene 4b with its main IR absorption
Journal compilation Ó CSIRO 2015
www.publish.csiro.au/journals/ajc

688
C. Plu¨g, H. Kanaani, and C. Wentrup
A
A
A
B
B
A
A
B
B
A
B
C
A
A
A
B
A
D
A
E
E
E
E
B
B
E
B
B
B
E
E
B
3500
3000
2500
2000
1500
1000
[cmꢃ1
]
Fig. 1. IR spectra (Ar, 14 K) of methoxycarbonylketene 4a (top) and methoxycarbonyl(methyl)ketene 4b (bottom)
obtained by thermolysis of 3a and 3b, respectively, at 4808C. A: Ketene 4a; B: Amine 1a; C: C3O2 (3065 (w), 2380 (w),
2286 (vs) and 2272 (s) cmꢀ1) D: MeOH; E: Ketene 4b. Ordinate: absorbance in arbitrary units.
K 2143
A A
A
A
830ꢅC
A
C
A
A
A
A
K
K
4000
3000
2000
1500
1000
500
[cmꢃ1
]
Fig. 2. IR spectrum (Ar, 10 K) of chloroketene 4c formed by FVT of 3c at 8308C. K ¼ ketene 4c, A ¼ 2-aminopyridine,
C ¼ CO2. Ordinate: absorbance.
at 2144 cmꢀ1. No C3O2 or other by-products were noticeable in
this case (Fig. 1). In the above experiments N-methyl-N-(2-
pyridyl)amine 1a was used as a starting material and hence also
asa leavinggroup.However, thisisnot necessary;2-pyridylamine
1b is equally good, and this was used in the following
experiments.
Chloroketene 4c was obtained by FVT of 3c above 7908C.
In this case, very little decomposition took place at lower FVT
temperatures. The best yield of ketene was obtained at 8308C.
The Ar matrix IR spectrum is shown in Fig. 2, where the main
C¼C¼O absorption is seen at 2143 cmꢀ1. The spectrum is in
good agreement with the spectrum obtained by photolysis of
chloroacetyl chloride in a Xe matrix.[3]
main absorptions in the cumulene region, viz. 2-pyridylketene
(2132 cmꢀ1) and 2-pyridyl isocyanate (2257 cmꢀ1) (Fig. 5). We
have investigated these two compounds before and therefore
were able to identify them securely in the IR spectrum.[6,8,9] An
expansion of the ketene region reveals the presence of the
two s-Z and s-E conformers of 2-pyridylketene at 2132 and
2123 cmꢀ1 respectively (Fig. S1, Supplementary Material) in
exact agreement with the previously reported data for this ketene
obtained by the Wolff rearrangement of 2-(diazoacetyl)
pyridine.[9]
Isocyanates exhibit very strong and often complex absorp-
tions in the 2200 cmꢀ1 region. This is shown for isocyanate 7 in
Fig. 6, where excellent agreement with the spectrum obtained by
matrix photolysis of 2-picolinyl azide[8] is seen. The formation
of both 4f and 7 in this reaction is obviously due to the presence
of two pyridine rings. Thus, two different retro-ene type reac-
tions are possible, as illustrated in Scheme 2. By slow warming
of an Ar matrix it is possible to evaporate the Ar and still
maintain a solid film for IR observation. This causes broadening
of the peaks and shifts towards smaller wavenumbers (Fig. S2,
Supplementary Material). When such a warming experiment
was performed on the matrix corresponding to the IR spectrum
shown in Fig. 4, the ketene was seen to start disappearing
at a temperature of 135 K, whereas the isocyanate remained
stable till room temperature. The NCO stretching vibrations in
Cyanoketene 4d was obtained by FVT of 3d at 7758C
(Fig. 3). The CN group appears as a relatively weak absorption
at 2239 cmꢀ1, and the very strong ketene stretch at 2163 cmꢀ1 [4]
.
Diphenylketene 4e was obtained by FVT of the diphenyla-
cetamide derivative 3e at 6008C. The Ar matrix IR spectrum
(Fig. 4) shows the very strong C¼C¼O absorption at
2106 cmꢀ1. Peaks due to 2-aminopyridine are also noticeable.
The identity of the ketene was ascertained by comparison with
the IR spectrum of 4e prepared by other methods.[5,6] Diphe-
nylketene was the first ketene ever to be characterised.[7]
2-Pyridylketene 4f and 2-pyridyl isocyanate 7 were obtained
by FVT of 3f at 6408C and yielded an IR spectrum featuring two

Ketenes from N-(2-Pyridyl)amides
689
H
(2132)
K
N
1.00
N
I
N C O
C
C
O
K (2163)
C
C O
1.00
H
NC
K
A
K
I
N
NH2
K
NH2
N
I
A
A
0.50
A
A
A
A
K
K
A
I
A
0.50
K
A
A
A
A
K
A
C
A
C
A
A
A
A
0
4000
3000
2000
1500
1000
500
A
A
[cmꢃ1
]
A
K
A
Fig. 5. IR spectrum of 2-pyridylketene 4f and 2-pyridyl isocyanate 7
(Ar, 10 K) obtained by FVT of 3f at 6408C. K ¼ ketene 4f, I ¼ isocyanate 7.
A ¼ 2-aminopyridine, C ¼ CO2. Ordinate: absorbance in arbitrary units.
A
K
A
0
N
C
O
4000
3000
2000
[cmꢃ1
1500
1000
500
]
2245
N
A
1.00
Fig. 3. IR spectrum (Ar, 10 K) of cyanoketene 4d formed by FVT of 3d
at 7758C. K ¼ ketene 4d, A ¼ 2-aminopyridine, C ¼ CO2. Ordinate: absor-
bance in arbitrary units.
2236
K (2106)
C
C
K
O
1.00
A
2257
2213
N
C O
N
A
0.50
B
NH2
N
A
2400
2100
[cmꢃ1
]
K
A
K
A
Fig. 6. IR spectrum of 2-pyridyl isocyanate 7 obtained by FVT of 3f (A)
and by Curtius rearrangement of 2-picolinoyl azide[9] (B). Ordinate: absor-
bance in arbitrary units.
K
A
A A
A
0
4000
3000
2000
1500
[cmꢃ1
1000
400
isocyanates are stronger than the C¼C¼O vibrations in ketenes;
i.e. the amount of isocyanate 7 formed is much lower than that of
ketene 4f. When the FVT of 3f was carried out at 6208C instead
of 6408C, the intensity of the isocyanate peak at 2245 cmꢀ1 was
]
Fig. 4. IR spectrum (Ar, 20 K) of diphenylketene 4e formed by FVT of 3e
at 6008C. K ¼ ketene 4e, A ¼ 2-aminopyridine. Ordinate: absorbance in
arbitrary units.
only ,40 % of that of the ketene at 2133 cmꢀ1
.

690
C. Plu¨g, H. Kanaani, and C. Wentrup
H
may be present. It is anticipated that pulsed pyrolysis[10] with
supersonic free-jet cooling of the initial pyrolysis products
would be the method of choice for the matrix isolation and
detection of the unstable iminopyridine tautomers.
FVT
ꢄ
O
C
H
O
N
H
N
H
N
NH
N
H
4f
N
1b
Conclusion
FVT of N-(2-pyridyl)amides is a versatile method for the syn-
thesis of a variety of ketenes, inter alia alkoxycarbonylketenes,
chloroketene, cyanoketene, 2-pyridylketene, and arylketenes. It
is emphasised that, apart from diphenylketene, these ketenes
are highly reactive species that cannot be isolated under con-
ventional reaction conditions. This method is expected to be
applicable in the investigation of many other reactive ketenes.
3f
HN
O
ꢄ
FVT
H
C
H2C
N
N
N
N
N
8a
8b
7
O
3f
N
Experimental
H3C
The apparatus and methods used for FVT and matrix isolation
have been described in detail.[10] An apparatus analogous to the
one illustrated in fig. 7 in ref. [10] was used with an APD HC-2
liquid helium cryostat capable of reaching an ultimate temper-
ature of 7 K. Vacuum was maintained at 10ꢀ7–10ꢀ5 hPa with a
Balzers Pfeiffer turbomolecular pump. Starting materials were
sublimed into the pyrolysis tube at a temperature of ,758C,
pyrolyses were carried out at the temperatures given in the text,
and pyrolysis products were condensed on a CsI target at
,10 K together with Ar in a ratio of roughly 1 : 1000. Gas
chromatography–mass spectrometry (GC-MS) was performed
on a Hewlett–Packard GC 5890–MS5970 instrument with
helium carrier gas, injector port 2008C, initial temperature
1008C, increasing at 168C per min on a 30-m ALLTECH cap-
illary column. Mass spectra were recorded in electron ionisation
(EI) mode at 70 eV unless noted otherwise (ESI ¼ electrospray).
IR spectra were recorded with 2 cmꢀ1 resolution for measure-
ments in KBr, neat, or in solution, and with 1 cmꢀ1 resolution for
matrix-isolation experiments.
Scheme 2. Formation of 2-pyridylketene 4f and 2-pyridyl isocyanate 7.
Me
Me
N
H
N
N
N
NH
Me
N
H
N
H
N
Me
s-E1a 0
s-Z1a 2
E9a 61
Z9a 67
Chart 1. Relative energies of 2-(methylamino)pyridines 1a and 2-
(methylimino)-1H-pyridines 9a in kJ molꢀ1 calculated at the B3LYP/6–
311þG**//B3LYP/6–31G* level.
In all the FVT reactions reported here, 2-pyridylamine 1b,
N-methyl-N-(2-pyridyl)amine 1a, and 2-picoline 8b were
obtained rather than the corresponding 2-methylene-1H-
pyridines 8a (see Scheme 2) or 2-imino-1H-pyridines 9 (see
Chart 1), which are expected as the initial products of a retro-ene
type reaction.
Methyl 2-[N-methyl-N-(2-pyridyl)aminocarbonyl]
acetate 3a
This is ascribed to facile tautomerisation, taking place
already in the FVT reactions, possibly during collisions with
the hot quartz wall of the pyrolysis tube. It is a common
observation that very facile tautomerisation of OH and NH
functions can take place under FVT conditions.[10] The aromatic
2-amino-, 2-(methylamino)-, and 2-methylpyridines have sig-
nificantly lower energies than the corresponding 2-(1H)-imine
and 2-(1H)-methylene derivatives.[11] Our own calculations at
the B3LYP/6–311þG**//B3LYP/6–31G* level yield the fol-
lowing relative energies in the gas-phase for 2-(pyridylamino)
pyridine 1a: s-E1a (0), s-Z1a (2), E-2-(methylimino)-1H-
pyridine E9a (61), and Z-2-(methylimino)-1H-pyridine Z9a
(67 kJ molꢀ1) (Chart 1). The presence of two NH stretching
bands at 3504 and 3480 cmꢀ1 in the matrix IR spectrum of 1a
formed in the FVT reaction (Fig. 1) indicates the presence of
the two rotameric forms, s-Z1a and s-E1a respectively. These
A mixture of monomethyl malonate 2a and 2-(methylamino)
pyridine 1a (5 mmol each) in 5 mL of dry (CaH2) CH2Cl2 was
treated with DCC (5 mmol) in 5 mL of CH2Cl2 with stirring
under N2. After the initial exothermic reaction had subsided, the
mixture was allowed to stand for 1 h at room temperature, fil-
tered, the precipitate washed with ether (50 mL), and the com-
bined yellowish filtrates evaporated. The resulting yellow oil
was purified by chromatography on a short column (SiO2, ether)
to yield 870 mg (83 %) of 3a as a colourless oil, turning yellow
after exposure to air. nmax (Ar, 14 K)/cmꢀ1 1777 (m), 1771 (m),
1762 (m), 1757 (m), 1754 (m), 1745 (m), 1688 (s), 1624 (m),
1608 (m), 1593 (m), 1484 (m), 1437 (s). dH (CDCl3) 8.47 (1H,
ddd, J 4.9, 2.0, 0.9, H-6), 7.81 (1H, ddd, J 7.0, 2.0, 0.9, H-4), 7.31
(1H, ddd, J 7.0, 1.0, 0.9, H-3), 7.25 (1H, ddd, J 7.0, 4.9, 1.0, 5-H),
3.70 (3H, s, OMe), 3.53 (2H, s, CH2), 3.42 (3H, s, NMe). dC
(CDCl3) 167.9 (C¼O), 166.0 (C¼O), 155.2 (py-C-2)),
148.5, 138.4, 121.8, 119.1, 52.0 (COOMe), 42.4 CH2), 35.2
(NMe). m/z 208 (15 %), 177 (15), 149 (43), 135 (15), 108 (100),
107 (75), 80 (48), 79 (71), 78 (40), 59 (14). HRMS m/z 208.0843;
calcd for C10H12N2O3: 208.0848.
absorptions have calculated intensities of 20 and 34 kJ molꢀ1
,
respectively, at the B3LYP/6–31G* level. Experimentally, the
two bands have nearly equal intensities, which means that the
s-Z conformer is in fact the major constituent, and this can be
ascribed to lone pair–lone pair repulsion in the E isomer. The
strongest bands in the 2-(methylimino)-1H-pyridine 9a are
calculated at 1667 (s-E) and 1659 (s-Z) cmꢀ1 (intensities 506
and 377 kJ molꢀ1, respectively) at the B3LYP/6–31G* level.
Weak bands at 1661 cmꢀ1 are present in some of the experi-
mental IR spectra (see Fig. S4, Supplementary Material),
thereby suggesting that minor amounts of the imine tautomers
Methyl 2-[N-methyl-N-(2-pyridyl)aminocarbonyl]
propanoate 3b
This compound was prepared in the same manner as described
for 3a and obtained as a colourless oil: 912 mg (85 %). nmax
(Ar, 14 K)/cmꢀ1 1766 (sh, m), 1764 (m), 1762 (m), 1757 (m),

Ketenes from N-(2-Pyridyl)amides
691
1754 (m), 1749 (m), 1697 (s), 1692 (s), 1687 (s), 1683 (m), 1593
(s), 1481 (m) and 1437 (s). dH (CDCl3) 8.49 (1H, ddd, J 4.9, 2.0,
0.9, H-6), 7.79 (1H, dd, J 7.0, 2.0, H-4), 7.28 (1H, ddd, J 7.0,
1.0, 0.9, 3-H), 7.24 (1H, ddd, J 7.0, 4.9, 1.0, H-5), 3.71 (1H, q, J
7.0, CH), 3.67 (3H, s, OMe), 3.53 (2H), 3.41 (3H, s, NMe), 1.39
(3H, d, J 7.0, CMe). dC (CDCl3) 171.3, 170.1, 155.7, 148.9,
138.5, 122.1, 120.0, 52.3, 44.7, 35.7, 14.3 (C-CH3). m/z 222
(M.þ, 7 %), 191 (11), 163 (43), 135 (10), 108 (100), 107 (44), 80
(35), 79 (43), 78 (33), 59 (20). m/z (ESI) 223 ([M þ H].þ, 100 %),
222 (35), 163 (40), 109 (30), 108 (45), 107 (30). HRMS m/z
222.1004; calcd for C11H14N2O3: 222.1004. Anal. Calc. for
C11H14N2O3: C 59.45, H 6.35, N 12.60. Found: C 59.33, H 6.39,
N 12.55 %.
Methoxycarbonyl(methyl)ketene 4b: 2142, 2136, 2130,
1739, 1729, 1721, 1296, 1290, 1194, 1137, 746, 731 cmꢀ1
.
Chloroketene 4c: 2149, 2143, 1290, 1107, 844, 772 cmꢀ1
Cyanoketene 4d: 2239, 2163, 1354, 553 cmꢀ1
Diphenylketene 4e: 2106, 1674, 1597, 1293, 694, 485 cmꢀ1
2-Pyridylketene 4f: 2132, 2123, 1594, 1586, 1474, 1452,
.
.
.
773 cmꢀ1
.
Warm-up of Ketene 4a and Recombination
with Amine 1a
The mixture of ketene 3a and amine 1a formed by FVT of 2a at
4208C was deposited neat on a liquid N2-cooled KBr target
(ꢀ1968C) and observed by IR spectroscopy. After warm-up to
ꢀ1308C, bands due to 3a and 1a were observed to decrease with
concomitant appearance of the bands due to the precursor 2a. IR
of 3a and 1a (neat, ꢀ1308C): 2147 (v), 1696 (s), 1521 (m),
1393 (m), 1355 (m), 1247 (s), 1210 (w), 758 (w) cmꢀ1. IR of 2a
(neat, ꢀ1308C): 1739 (m), 1642 (s), 1585 (s), 1543 (m), 1469
N-(2-Pyridyl)chloroacetamide 3c
2-Aminopyridine (0.47 g, 5 mmol) was added to a solution of
chloroacetic acid (5 mmol) in 10 mL of CH2Cl2. The resulting
mixture was treated with DCC (1.03 g, 5 mmol) in 10 mL of
CH2Cl2 with stirring under N2. This mixture was kept at 408C for
2 h and then at room temperature for 15 min, filtered, and the
precipitate was washed with dry diethyl ether. The pale brown
filtrate was evaporated, and the yellow-brown solid so obtained
was purified by chromatography on SiO2, eluting with diethyl
ether/ethyl acetate, to yield 680 mg (80 %) of white crystals
which turned red-purple on exposure to air, mp 1758C. GC: a
single peak at Rt 7.6 min. m/z 172 (6 %), 170 (18), 135 (90), 94
(100), 78 (90). dH (CDCl3) 8.35 (d, J 4.5, 1H), 8.20 (d, J 8.2, 1H),
7.75 (ddd, J 8.1, 7.9, 1.3, 1H), 7.71 (ddd, J 8.0, 7.8, 1.0, 1H), 4.18
(s, 2H). dC (CDCl3) 164.3, 150.1, 147.7, 138.7, 120.5, 113.8, 42.9.
N-(2-Pyridyl)cyanoacetamide 3d was prepared in the same
way as described for 3c and obtained in 65 % yield (443 mg) of
white needles, mp 1578C. GC: one single peak at Rt 7.5 min. m/z
161 (29 %), 94 (100), 78 (48). dH (DMDO-d6) 8.31 (d, J 8.2, 1H),
8.0 (d, J 8.2, 1H), 7.8 (ddd, J 7.1, 6.9, 1.5, 1H), 7.13 (ddd, J 7.2,
7.0, 1.0, 1H), 3.97 (s, 2H). dC (DMSO-d6) 162.1, 151.3, 148.2,
138.5, 120.0, 115.8, 113.5, 26.8.
N-(2-Pyridyl)diphenylacetamide 3e was synthesised in the
same way as described for 3c and obtained as a yellow oil, which
was purified first by column chromatography as above, then by
Kugelrohr distillation at 1408C/10ꢀ3 hPa in 75 % yield (1.09 g).
GC: one single peak at Rt 4.03 min. m/z 288 (44 %), 194 (20),
167 (100), 165 (7), 94 (24), 78 (89). dH (CDCl3) 8.25 (d, J 7.8,
1H), 8.05 (d, J 7.0, 1 H), 7.62 (ddd, J 7.6, 8.0, 1.5, 1H), 7.26–7.18
(m, 5H), 6.95 (ddd, J 7.8, 7.6, 1.5, 1H), 5.0 (s, 1H). dC (CDCl3)
171.0, 151.3, 147.3, 138.6, 128.8, 126.9, 119.8, 114.6, 48.0.
(m), 1276 (m), 1170 (m) and 1020 (w) cmꢀ1
.
Reference Spectra
Reference IR spectra of the following materials in Ar matrices
at ,10 K were recorded. A sample of C3O2 was prepared by
FVT of 2,3-diacetoxysuccinic anhydride at 8008C.[12] C3O2:
3065 (m), 2381 (m), 2287 (vs), 2272 (vs). For other IR spec-
troscopic data for C3O2, see ref. [9].
Matrix IR spectra of 2-(methylamino)pyridine 1a and
2-aminopyridine 1b have been published previously.[9] 2-
(Methylamino)pyridine 1a: 3504 (m), 3480 (m), 2821 (w),
1617 (s), 1611 (s), 1603 (v.), 1524 (s), 1511 (s), 1459 (m), 1421
(s), 1366 (m), 1289 (m), 1156 (m), 981 (w), 771 (s), 734 (m)
cmꢀ1. The IR spectra of 2-(methylamino)pyridine 1a, 2-amino-
pyridine 1b (Fig. S3) and 2-picoline (Fig. S4) are shown in the
Supplementary Material.
Dimethyl malonate 4: 1777 (s), 1771 (s), 1765 (s), 1755 (s)
.
and 1747 (s) cmꢀ1
Methanol was characterised by two absorptions at 3667 and
1034 cmꢀ1
.
CO2 in Ar matrix gives rise to a double band at 2345 and
2341 cmꢀ1
.
Supplementary Material
Ar matrix IR spectra of s-Z- and s-E-2-pyridylketenes 4f at 10 K
and on warm-up, 2-(methylamino)pyridine 1a, 2-aminopyridine
1b and 2-picoline 8b, and 1H and 13C NMR spectra of amides 3
are available on the Journal’s website.
N-(2-Pyridyl)-2-pyridylacetamide 3f
Triethylamine (0.51 g, 5 mmol) was used to neutralise 2-
pyridylacetic acid hydrochloride (0.87 g, 5 mmol) in 5 mL of
dry CH2Cl2. 2-Aminopyridine (0.47 g, 5 mmol) was added, and
the resulting mixture was treated with DCC (1.03 g, 5 mmol) in
10 mL of CH2Cl2 with stirring under N2. The reaction was
performed and the product worked up as described above to
yield 745 mg (70 %) of 3f, mp 968C. GC: a single peak at Rt
10.80 min. m/z 213 (4 %), 121 (12), 94 (16), 93 (100), 78 (12). dH
(CDCl3) 8.69 (d, J 8.5, 1H), 8.29 (d, J 7.2, 1H), 8.20 (d, J 8.4,
1H), 7.69 (m, 2H), 7.22 (m, 2H), 7.0 (ddd, J 6.9, 7.5, 1.0, 1H),
3.92 (s, 2H). dC (CDCl3) 167.8, 154.7, 151.4, 149.5, 147.9,
138.2, 137.3, 124.1, 122.3, 119.6, 114.1, 46.0.
Acknowledgement
This work was supported by the Australian Research Council and The
University of Queensland.
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