4
3J 7.8, J 1.7, 1 H), 7.44–7.42 (m, 1H), 4.23 (s, 2 H), 3.35 (app
1-Morpholino-2-phenyl-3-(2-pyridyl)propane-1,3-dione (11d).
sextet (2 overlapping quartets), 3J 7.1, 4 H), 1.34 (t, 3J 7.1, 6 H);
δC (CDCl , 100 MHz) 196.0 (C᎐O), 167.1 (C-1), 152.9 (C),
Yield 59% (reaction for 23 h); δH (200 MHz, CDCl3) 3.25–3.69
(m, 8H), 6.22 (s, 1H, CH), 7.19–7.43 (m, 6H, C5-H, phenyl-H),
7.76 (td, 1H, C4-H) , 8.00 (dd, 1H, C3-H), 8.57 (dd, 1H, C6-H);
δC (200 MHz, CDCl3) 42.3, 46.7, 56.2 (CH), 66.1, 66.5, 122.4
(C3), 127.2 (C5), 127.7, 128.4, 129.6, 133.2, 137.0 (C4), 148.6
(C ), 152.4 (C ), 168.0 (C᎐O), 194.4 (C᎐O). HRMS m/z
᎐
3
148.9 (CH), 136.9 (CH), 127.2 (CH), 122.0 (CH), 47.2 (C-2),
42.3 (NCH2), 40.4 (NCH2), 14.4 (CH3), 13.2 (CH3); data for
enol form: δH 8.57 (br d, 3J 4.7, 1 H), 7.91 (d, 3J 7.8, 1 H), 7.74
(dt, 3J 7.8, 4J 1.8, 1 H), 7.29–7.26 (m, 1H), 6.47 (s, 1 H), 3.44 (q,
᎐
᎐
6
2
3J 7.0, 4 H), 1.24 (t, J 7.0, 6 H); δC (400 MHz, CDCl3) 171.5
310.1308; calcd for C18H18N2O3 310.13119.
3
(C-3), 168.6 (C-1), 152.4 (C), 149.0 (CH), 136.8 (CH), 124.7
(CH), 120.8 (CH), 86.3 (C-2), 42.8 (NCH2), 40.1 (NCH2), 14.2
(CH3), 12.9 (CH3); MS m/z 220 (Mϩ, 10), 202 (16), 148 (21), 121
(24), 106 (53), 93 (19), 79 (15), 78 (50), 72 (100), 58 (14); HRMS
m/z 220.1208; calcd for C12H16N2O2 220.1206.
2-Phenyl-3-(2-pyridyl)-1-pyrrolidinopropane-1,3-dione (10d).
Yield 85% (reaction for 5 min); δH (200 MHz, CDCl3) 1.74–1.95
(m, 4H), 3.25–3.52 (m, 4H), 6.10 (s, 1H, CH), 7.21–7.41 (m, 6H,
C5-H, phenyl-H), 7.73 (td, 1H, C4-H), 8.03 (dd, 1H, C3-H), 8.59
(dd, 1H, C6-H); δC (200 MHz, CDCl3) 24.3, 25.9, 45.9, 46.9, 58.5
(CH), 122.5 (C3), 127.1 (C5), 127.5, 128.4, 130.0, 133.3, 137.0
(C ), 148.7 (C ), 152.7 (C ), 167.5 (C᎐O), 194.7 (C᎐O). HRMS
The analogous product with piperidine existed as a ca. 1:1
mixture of the keto and enol forms of 9a. Data for keto form:
δH (400 MHz, CDCl3) 8.60 (app d, 3J 4.6, 1 H), 8.00 (d, 3J 7.9, 1
H), 7.78 (br t, 3J 7.8, 1 H), 7.43–7.40 (m, 1H), 4.26 (s, 2 H); data
᎐
᎐
4
6
2
m/z 294.1358; calcd for C18H18N2O2 294.136279.
3
3
for enol form: δH 8.54 (br d, J 4.6, 1 H), 7.88 (d, J 7.9, 1 H),
3
7.72 (br t, J 7.8, 1 H), 7.27–7.24 (m, 1H), 6.54; data assigned
General procedure for the hydrolysis of mesoionic compounds 5
to 2-acylpyridines 12
to either keto or enol form: δH 3.56–3.52 (m, 6 H), 3.36–3.34
(m, 2 H), 1.76–1.51 (m, 12 H); HRMS m/z 232.1206; calcd for
C13H16N2O2 232.1216.
To
6
mg of 2,3-dihydro-3-oxo-2-R-1H-4λ5-pyrrolo[1,2-a]-
pyridin-4-ylium-1-olate were added 10 drops of 1% aqueous
NaOH solution. The mixture was stirred overnight at room
temperature under N2, neutralised, and extracted with ether.
The organic layer was dried over MgSO4, filtrated and evapor-
ated. If necessary, the crude product was purified by column
chromatography (silica gel 60 mesh; AcOCH3). Structures and
N,N-Dimethyl-2-methyl-3-oxo-3-(2-pyridyl)propionamide
(7b). Yield 55%; δH (400 MHz, CDCl3) 1.44 (d, 3H, J 7, CH3),
2.95 (s, 3H, CH3), 3.22 (s, 3H, CH3), 5.01 (q, 1H, J 7), 7.45 (t,
1H, J 6, Ar-H5), 7.84 (t, 1H, J 8, Ar-H4), 8.08 (d, 1H, J 8, Ar-H3),
8.62 (d, 1H, J, Ar-H6); δC (400 MHz, CDCl3) 12.8 (CH3), 35.6
(CH3), 37.9 (CH3), 44.7 (CH), 122.5 (C3), 127.2 (C5), 137.2 (C4),
1
purities were confirmed by GC-MS, H and 13C NMR, and
comparison with literature data.16 Yields (not optimised): 12a
99%, 12b 63%, 12c 84%, 12d 95%.
148.7 (C ),152.4 (C ), 172.2 (C᎐O), 197.6 (C᎐O). HRMS m/z
᎐
᎐
6
2
206.1053; calcd for C11H14N2O2 206.10498.
Matrix IR spectra and calculated IR spectra of 5a and 4a (13a)
N,N-Dimethyl-2-ethyl-3-oxo-3-(2-pyridyl)propionamide (7c).
Yield 89% (reaction for 24 h); δH (200 MHz, CDCl3) 1.01 (t, 3H,
J 7, CH3), 2.02 (m, 2H, CH2), 2.95 (s, 3H, CH3), 3.26 (s, 3H,
CH3), 4.96 (t, 1H, J 7), 7.46 (td, 1H, C5-H), 7.83 (td, 1H, C4-H),
8.06 (dd, 1H, C3-H), 8.63 (dd, 1H, C6-H); δC (200 MHz, CDCl3)
12.2 (CH3), 21.8 (CH2), 35.5 (CH3), 37.8 (CH3), 51.9 (CH),
122.2 (C3), 127.1 (C5), 136.9 (C4), 148.6 (C6), 152.4 (C2), 170.9
Mesoion 5a was isolated in an Ar matrix by subliming it at
100 ЊC in a stream of Ar. The resulting IR spectrum is shown in
Fig. 1b: 1794/1783, 1676, 1610, 1585, 1480, 1450, 1340, 1243,
1183, 1103, 1054, 779, 738, 687, 559, 491 cmϪ1. The weak signal
at 2142 cmϪ1 is ascribed to ketene 4a. The same spectrum, with
a slightly stronger ketene signal, is obtained by FVT of 3a at
650 ЊC with matrix isolation of the product at 15 K. Calcu-
lated7 IR frequencies for 5a at the B3LYP/6-31G* level are
scaled by a factor 0.9613, and bands with intensities below 7 km
molϪ1 are ignored. The spectra were calculated for a relative
permittivity ε = 1 (gas phase) and for ε = 40, simulating a highly
(C᎐O), 196.9 (C᎐O). HRMS m/z 220.1202; calcd for C H -
᎐
᎐
12 16
N2O2 220.12063.
N,N-Dimethyl-2-phenyl-3-oxo-3-(2-pyridyl)propionamide
(7d). Yield 81%; δH (200 MHz, CDCl3) 2.93 (s, 3H, CH3), 3.13
(s, 3H, CH3), 6.08 (s, 1H, CH), 7.25–7.48 (m, 6H, C5-H, phenyl-
H), 7.80 (td, 1H, C4-H), 8.08 (dd, 1H, C3-H), 8.64 (dd, 1H,
C6-H); δC (200 MHz, CDCl3) 35.6 (CH3), 37.85 (CH3), 56.9
(CH), 122.5 (C3), 127.1 (C5), 127.6, 128.5, 129.9, 133.4, 137.0
polar environment.9 The higher frequency C᎐O stretching
᎐
vibration at 1814/1794 cmϪ1 (for ε = 1 and 40, respectively)
corresponds to the ylidic “lactam” carbonyl, C3. The lower
frequency carbonyl vibration at 1693/1681 cmϪ1 corresponds to
the C1 ketone. Calculated IR spectrum of 5a (wavenumber/
cmϪ1 for ε = 1, wavenumber for ε = 40, (intensity/km molϪ1 for
ε = 1, intensity for ε = 40) given): 1814, 1794 (394, 497); 1693,
1681 (517, 914); 1597, 1595 (99, 208); 1576, 1571 (38, 72); 1458,
1460 (13, 20); 1337, 1339 (25, 51); 1214, 1219 (98, 221); 1154,
1156 (25, 31); 1085, 1087 (17, 37); 1019, 1025 (54, 113); 1004,
1006 (12, 18); 768, 776 (22, 27); 746, 750 (11, 7); 712, 702 (81,
104); 659, 672 (27, 51); 539, 544 (27, 34); 463, 472 (42, 60).
Broad band irradiation with the Hg/Xe lamp caused an
increase in the intensity of the ketene band at 2142 cmϪ1 with
concomitant decrease in the bands due to 5a. A drastic increase
in the ketene band resulted after 25 min of irradiation, and
only little further increase resulted after a further 35 min. IR
spectrum of the resulting ketene (Fig. 2b): 2143s, 2122w–m,
1663w–m, 1592w, 1585w, 1443w, 1380m, 1224w, 1069w, 1002w,
992w, 875w, 746w, 702 w, 694w, 560 w. The bands at 3730 and
1610 cmϪ1 are due to water. Calculated7 IR frequencies at the
B3LYP/6-31G* level are scaled by a factor 0.9613, and bands
with intensities below 6 km molϪ1 are ignored. Calculated IR
spectrum of 13a (gas phase; wavenumber/cmϪ1 (intensity/km
molϪ1) given): 3109 (47), 3092 (19), 3075 (11), 2147 (1169), 1669
(167), 1577 (17), 1566 (20), 1423 (28), 1370 (464), 1201 (34),
(C ), 148.7 (C ),152.7 (C ), 169.4 (C᎐O), 194.8 (C᎐O). HRMS
᎐
᎐
4
6
2
m/z 268.1212; calcd for C16H16N2O2 268.12063.
N,N-Diethyl-2-phenyl-3-oxo-3-(2-pyridyl)propionamide (8d).
Yield 19% (reaction for 3 d); δH (400 MHz, CDCl3) 1.04 (t, 3H,
J 7, CH3), 1.23 (t, 3H, J 7, CH3), 3.30–3.35 (m, 4H, CH2), 6.24
(s, 1H, CH), 7.33–7.39 (m, 5H, phenyl-H), 7.44 (t, 1H, C5-H),
7.81 (td, 1H, C4-H), 8.07 (dd, 1H, C3-H), 8.62 (dd, 1H, C6-H);
δC (400 MHz, CDCl3) 12.6 (CH3), 13.6 (CH3), 40.2 (CH2), 42.8
(CH2), 57.3 (CH), 122.5 (C3), 126.9 (C5), 127.6, 128.6, 129.78,
134.1, 137.0 (C ), 148.4 (C ),153.1 (C ), 168.4 (C᎐O), 194.9
᎐
4
6
2
(C᎐O). HRMS m/z 296.1523; calcd for C H N O 296.15193.
᎐
18 20
2
2
2-Methyl-1-morpholino-3-(2-pyridyl)propane-1,3-dione (11b).
Yield = 100% (reaction for 17 h); δH (200 MHz, CDCl3) 1.351
(d, 3H, J 7, CH3), 3.46–3.76 (m, 8H), 4.89 (q, 1H, J 7, CH), 7.40
(t, 1H, C5-H), 7.79 (td, 1H, C4-H), 7.97 (dd, 1H, C3-H), 8.55
(dd, 1H,C6-H); δC (200 MHz, CDCl3) 12.8 (CH3), 42.0, 43.8
(CH), 46.6, 66.3, 66.5, 122.1 (C3), 127.1 (C5), 136.9 (C4), 148.5
(C ), 151.9 (C ), 170.6 (C᎐O), 197.0 (C᎐O). HRMS m/z
᎐
᎐
6
2
248.1150; calcd for C13H16N2O3 248.11554.
J. Chem. Soc., Perkin Trans. 1, 2000, 401–406
405