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M. Sax et al. / Tetrahedron 61 (2005) 205–211
–C–H), 1676 (s, amide I), 1559 (s, amide II), 1186 (s)/
1137 cmK1 (s, characteristic dihydropyridone-fingerprint);
1H NMR (DMSO-d6): d 7.49 (s broad, 1H, NH), 7.21 (t, JZ
6.8 Hz, 1H, 6-H), 4.63 (d, JZ7.1 Hz, 1H, 5-H), 3.59–3.49
(m, 1H, 2-H), 2.21 (dd, JZ16.0, 5.1 Hz, 1H, 3-H), 2.04
(dd, JZ16.0, 12.1 Hz, 1H, 3-H), 1.73–1.60 (m, 1H,
–CH2CH(CH3)2), 1.55–1.46 (m, 1H, –CH2CH(CH3)2),
1.29–1.19 (m, 1H, –CH2CH(CH3)2), 0.85 (d, JZ6.7 Hz,
3H, –CH3), 0.84 (d, JZ6.7 Hz, 3H, –CH3); 13C NMR
(DMSO-d6): d 189.5 (C-4), 150.5 (C-6), 95.1 (C-5), 48.9
(C-2), 41.1 (–CH2CH(CH3)2), 40.7 (C-3), 22.5 (–CH2-
CH(CH3)2), 21.5, 21.1 (2C, –CH3); MS (70 eV) m/e
(rel.int.): 153 (M, 44), 138 (MKCH3, 23), 110 (MKC3H7,
11), 96 (MK(2-methylpropyl), 100), 68 (MK(2-Methyl-
propyl)–CO, 100); HRMS (70 eV) m/e calcd for C9H15NO:
153.1154, found 153.1111.
Yellow oil, RfZ0.22 (EtOAc); yield: 14.0 mg (26%);
purityO99% (GC); IR (neat): 3247 (broad, –N–H), 3034
(m, –C]C–H), 2927 (w, –C–H), 1675 (w, amide I), 1560
(s, amide II), 1404 (m), 1281 (s)/1227 (s)/1205 (s)/1167
(s, characteristic dihydropyridone-fingerprint), 740 cmK1
1
(m, out-of-plane); H NMR (DMSO-d6): d 7.89 (d broad,
JZ5.1 Hz, 1H, NH), 7.63 (dd, JZ1.6, 0.8 Hz, 1H, 50-H),
7.25 (dd, JZ7.0, 0.8 Hz, 1H, 6-H), 6.41 (dd, JZ3.1, 1.6 Hz,
1H, 40-H), 6.30 (d, JZ3.1 Hz, 1H, 30-H), 4.78 (dt, JZ7.0,
1.6 Hz, 1H, 2-H), 4.71 (dd, JZ7.0, 0.8 Hz, 1H, 5-H), 2.53–
2.47 (m, 2H, 3-H); 13C NMR (DMSO-d6): d 190.1 (C-4),
153.7 (C-20), 151.9 (C-6), 143.3 (C-50), 111.1 (C-40), 107.4
(C-30), 97.6 (C-5), 49.9 (C-2), 40.5 (C-3); MS (70 eV) m/e
(rel.int.): 163 (M, 39), 135 (MKCO, 93), 106 (Furo[2,
3-c]pyrrole, 100), 94 (Retro-Diels–Alder-fragment, 61), 66
(pyrrole, 74); HRMS (70 eV) m/e calcd for C9H9NO2:
163.0633, found 163.0590.
6.2.7. 2-(4-Nitrophenyl)-2,3-dihydropyridin-4(1H)-one
(6g). Yellow oil, RfZ0.12 (EtOAc); yield: 48.1 mg
(67%); purityO99% (GC); IR (neat): 3274 (broad, –N–H),
3045 (w, –C]C–H), 2926 (w, –C–H), 1680 (s, amide I),
1561 (s, amide II), 1518 (s, –NO2 asym.), 1347 (s, –NO2
sym.), 1235 (m)/1204 (s)/1137 (s, characteristic dihydro-
pyridone fingerprint), 698 cmK1 (m, out-of-plane); 1H
NMR (DMSO-d6): d 8.22 (d, JZ9.0 Hz, 2H, 30-H), 8.02
(d broad, JZ5.9 Hz, 1H, NH), 7.67 (d, JZ8.2 Hz, 2H,
20-H), 7.44 (t, JZ6.9 Hz, 1H, 6-H), 4.95–4.88 (m, 1H, 2-H),
4.78 (d, JZ6.7 Hz, 1H, 5-H), 2.53 (dd, JZ16.1, 6.4 Hz, 1H,
3-H), 2.46 (dd, JZ16.1, 10.6 Hz, 1H, 3-H); 13C NMR
(DMSO-d6): d 189.9 (C-4), 152.8 (C-6), 149.3 (C-40), 147.6
(C-10), 128.6 (2C, C-20), 124.4 (2C, C-30), 98.1 (C-5), 56.1
(C-2), 43.9 (C-3); MS (70 eV) m/e (rel.int.): 218 (M, 100),
190 (MKCO, 55), 172 (MKNO2, 7), 149 (MKNHCH]
CHC(]O), 4-nitrostyreneZRetro-Diels–Alder-fragment,
17), 119 (Retro-Diels–Alder-fragment-NO, 23), 96
(MK(4-nitrophenyl), 11), 91 (C7H7, 38); HRMS (70 eV)
m/e calcd for C11H10N2O3: 218.0691, found 218.0667.
6.2.10. 2-(Thiophen-2-yl)-2,3-dihydropyridin-4(1H)-one
(6k). Yellow oil, RfZ0.24 (EtOAc); yield: 14.6 mg (30%);
purityO99% (GC); IR (neat): 3235 (broad, –N–H), 3025
(w, –C]C–H), 2924 (w, –C–H), 2852 (w, –C–H), 1684 (m,
amide I), 1558 (s, amide II), 1232 (s), 1204 (s), 1179 (s),
1135 (s, characteristic dihydropyridone fingerprint),
1
702 cmK1 (m, out-of-plane); H NMR (DMSO-d6): d 7.96
(d broad, JZ5.1 Hz, 1H, NH), 7.44 (dd, JZ5.1, 1.6 Hz, 1H,
300-H), 7.29 (dd, JZ7.4, 0.8 Hz, 1H, 6-H), 7.08–7.07 (m, 1H,
5 -H), 6.98 (dd, JZ5.1, 3.1 Hz, 1H, 40-H), 5.00 (ddd, JZ
9.8, 6.3, 1.6 Hz, 1H, 2-H), 4.76 (dd, JZ7.4, 1.2 Hz, 1H,
5-H), 2.55 (dd, JZ16.0, 6.3 Hz, 1H, 3-H), 2.48 (dd, JZ
15.7, 10.2 Hz, 1H, 3-H); 13C NMR (DMSO-d6): d 190.1
(C-4), 152.0 (C-6), 145.0 (C-20), 127.4 (C-40), 126.0 (2C,
C-30CC-50), 98.1 (C-5), 52.2 (C-2), 44.8 (C-3); MS (70 eV)
m/e (rel.int.): 179 (M, 31), 162 (thiophen-2-ylpyridine$HC,
61), 151 (MKCO, 72), 110 (Retro-Diels–Alder-fragment,
100), 106 (2-allylpyridine$HC, 21), 96 (MKthiophenyl,
13), 84 (thiophen, 27), 66 (pyrrole, 53); HRMS (70 eV) m/e
calcd for C9H9NOS: 179.0405, found 179.0381.
6.2.8. 2-(2-Bromophenyl)-2,3-dihydropyridin-4(1H)-one
(6h). Pale-yellow oil, RfZ0.18 (EtOAc/petroleum etherZ
75:25); yield: 52.0 mg (63%); purityO99% (GC); IR (neat):
3252 (broad, –N–H), 3036 (m, –C]C–H), 1676 (s, amide
I), 1559 (s, amide II), 1236 (m)/1202 (s)/1187 (s)/1136
(s, characteristic dihydropyridone fingerprint), 720 cmK1
6.2.11. 2,3-Dihydro-2,20-bipyridin-4(1H)-one (6l). Yellow
oil, RfZ0.36 (EtOAc/MeOH/Me2NEtZ87.5:10:2.5); yield:
23.2 mg (40%); purityO99% (GC); IR (neat): 3226 (broad,
–N–H), 3022 (m, –C]C–H), 2929 (w, –C–H), 1619
(m, amide I), 1562 (s, amide II), 1275 (w)/1236 (m)/1207
(s)/1166 (m, characteristic dihydropyridone fingerprint),
1
(m, out-of-plane); H NMR (DMSO-d6): d 7.90 (d broad,
1
JZ5.5 Hz, 1H, NH), 7.63 (dd, JZ8.0, 1.4 Hz, 1H, 30-H),
7.56 (dd, JZ7.6, 1.8 Hz, 1H, 60-H), 7.48–7.39 (m, 2H,
6-HC50-H), 7.25 (td, JZ7.6, 2.0 Hz, 1H, 40-H), 5.01–4.94
(m, 1H, 2-H), 4.80 (d, JZ7.4 Hz, 1H, 5-H), 2.49 (dd, JZ
16.0, 6.3 Hz, 1H, 3-H), 2.39 (dd, JZ16.0, 11.7 Hz, 1H-
3-H); 13C NMR (DMSO-d6): d 190.0 (C-4), 153.3 (C-6),
139.8 (C-10), 133.7 (C-30), 130.5 (C-40), 128.9 (2C, C-50C
C-60), 122.6 (C-20), 97.8 (C-5), 56.5 (C-2), 42.6 (C-3); MS
(70 eV) m/e (rel.int.): 253 (81BrM, 78), 251 (79BrM, 81),
225 (81BrMKCO, 12), 223 (79BrMKCO, 15), 184
(2-81bromostyreneZRetro-Diels–Alder-fragment, 62), 182
(2-79bromostyreneZRetro-Diels–Alder-fragment, 58), 172
(MKBr, 56), 144 (MKBr–CO, 55), 130 (isoquinolinium,
100), 103 (styrene, 91), 77 (–Ph, 12); HRMS (70 eV) m/e
calcd for C11H10BrNO: 252.9925 (81Br)/250.9946 (79Br),
found 252.9909 (81Br)/250.9924 (79Br).
782, 748 cmK1 (m, out-of-plane); H NMR (DMSO-d6): d
8.57–8.54 (m, 1H, 30-H), 7.96 (d0 broad, JZ5.5 Hz, 1H,
NH), 7.80 (td, JZ7.8, 2.0 Hz, 1H, 5 -H), 7.44 (d, JZ7.8 Hz,
1H, 60-H), 7.39 (t, JZ6.9 Hz, 1H, 6-H), 7.33–7.29 (m, 1H,
40-H), 4.78 (ddd, JZ10.2, 6.3, 2.0 Hz, 1H, 2-H), 4.73
(d, JZ7.4 Hz, 1H, 5-H), 2.64 (dd, JZ16.0, 10.2 Hz, 1H,
3-H), 2.55 (dd, JZ16.0, 6.3 Hz, 1H, 3-H); 13C NMR
(DMSO-d6) d 190.3 (C-4), 159.8 (C-10), 152.4 (C-6), 149.8
(C-30), 137.7 (C-50), 123.5 (C-40), 121.4 (C-60), 97.8 (C-5),
57.5 (C-2), 42.0 (C-3); MS (70 eV) m/e (rel.int.): 174 (M,
14), 146 (MKCO, 63), 130 ([1,7]naphthyridine, 100), 106
(Retro-Diels–Alder-fragment, 18), 96 (MKpyridine, 18),
78 (pyridine, 15); HRMS (70 eV) m/e calcd for C10H10N2O:
174.0793, found 174.0790.
6.2.12. Ethyl 2-methyl-4-oxo-1,2,3,4-tetrahydropyridine-
2-carboxylate (6m). Yellow oil, RfZ0.23 (EtOAc); yield:
20.1 mg (33%); purityO99% (GC); IR (neat): 3291 (broad,
6.2.9. 2-(Furan-2-yl)-2,3-dihydropyridin-4(1H)-one (6i).