K. Kobayashi et al.
Bull. Chem. Soc. Jpn., 74, No. 6 (2001) 1113
ring for 40 min at the same temperature, the reaction mixture was
diluted with CH2Cl2 (20 mL), and aqueous Na2CO3 (20 mL) suc-
cessively, and the organic phase was separated and dried over an-
hydrous Na2SO4. Evaporation of the solvent gave a residue,
which was purified by column chromatography on silica gel to
give 23 (0.10 g, 47%) and 28 (27 mg, 13%). 23: mp 90–91 ˚C
(hexane); IR 3350, 3130 and 1614 cmꢀ1; 1H NMR δ 1.39 (3H, d, J
ꢁ 6.3 Hz), 2.99 (1H, dd, J ꢁ 16.4 and 9.5 Hz), 3.17 (1H, dd, J ꢁ
16.4 and 2.1 Hz), 4.45–4.55 (1H, m), 5.40 (1H, br s), 6.8–6.9 (2H,
m), 7.42 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.52 (1H, td, J ꢁ 7.9 and
1.6 Hz), 7.84 (1H, dd, J ꢁ 7.9 and 1.6 Hz), 7.88 (1H, dd, J ꢁ 7.9
and 1.6 Hz), and 7.92 (1H, dd, J ꢁ 2.6 and 1.1 Hz); MS m/z (%)
226 (Mꢂ, 7.4) and 182 (100). Found: C, 74.11; H, 6.32; N,
12.16%. Calcd for C14H14N2O: C, 74.31; H, 6.24; N, 12.38%. 28:
Rf 0.31 (1 : 2 EtOAc–hexane); IR (neat) 3335, 3127, and 1614
7.19; N, 9.99%.
The reaction of 5 with 2,2-dimethyloxirane under conditions
similar to those described for the preparations of 23–28 gave 9.
4-(1-Ethoxyethyl)pyrrolo[1,2-a]quinoxaline 35.
Typical
Procedure for the Reaction of 1-(2-Isocyanophenyl)pyrroles 5
or 6 with Acetals 29–33. To a stirred solution of 5 (1.0 mmol,
0.17 g) and actaldehyde diethyl acetal 30 (1.0 mmol, 0.12 g) in
CH2Cl2 (10 ml) at 0 ˚C under argon was added dropwise three por-
tions of 14 mg (0.10 mmol) each of diethyl ether–boron trifluoride
at 30 min intervals. After completion of the addition of diethyl
ether–boron trifluoride, stirring was continued for 40 min at the
same temperature. The reaction mixture was worked up in a man-
ner similar to that described above, and the crude product was pu-
rified by column chromatography on silica gel to give 35 (0.21 g,
85%): Rf 0.52 (1 : 2 EtOAc–hexane); IR (neat) 3143 and 1612
1
1
cmꢀ1; H NMR δ 1.52 (3H, d, J ꢁ 7.4 Hz), 3.25–3.55 (2H, m),
cmꢀ1; H NMR δ 1.22 (3H, t, J ꢁ 6.9 Hz), 1.67 (3H, d, J ꢁ 6.9
4.00 (1H, dd, J ꢁ 11.1 and 4.8 Hz), 4.19 (1H, dd, J ꢁ 11.1 and 3.2
Hz), 6.87 (1H, dd, J ꢁ 4.2 and 2.6 Hz), 6.93 (1H, dd, J ꢁ 4.2 and
1.1 Hz), 7.43 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.50 (1H, td, J ꢁ 7.9
and 1.6 Hz), 7.84 (1H, dd, J ꢁ 7.9 and 1.6 Hz), 7.88 (1H, dd, J ꢁ
7.9 and 1.6 Hz) and 7.93 (1H, dd, J ꢁ 2.6 and 1.1 Hz); MS m/z
(%) 226 (Mꢂ, 36), 209 (85) and 168 (100). Found: m/z 226.1127.
Calcd for C14H14N2O: M, 226.1107.
Hz), 3.4–1.69 (2H, m), 4.78 (1H, q, J ꢁ 6.9 Hz), 6.86 (1H, dd, J ꢁ
4.2 and 2.6 Hz), 7.27 (1H, dd, J ꢁ 4.2 and 1.1 Hz), 7.42 (1H, td, J
ꢁ 7.9 and 1.6 Hz), 7.49 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.83 (1H,
dd, J ꢁ 7.9 and 1.6 Hz), and 7.9–8.0 (2H, m); MS m/z (%) 240
(Mꢂ, 15) and 195 (100). Found: m/z 240.1270. Calcd for
C15H16N2O: M, 240.1264.
4-(1-Methoxyethyl)pyrrolo[1,2-a]quinoxaline 34: Rf 0.49
(1 : 2 EtOAc–hexane); IR (neat) 3134 and 1613 cmꢀ1; 1H NMR δ
1.67 (3H, d, J ꢁ 6.9 Hz), 3.39 (3H, s), 4.70 (1H, q, J ꢁ 6.9 Hz),
6.79 (1H, dd, J ꢁ 4.2 and 2.6 Hz), 7.21 (1H, dd, J ꢁ 4.2 and 1.1
Hz), 7.43 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.52 (1H, td, J ꢁ 7.9 and
1.6 Hz), 7.86 (1H, dd, J ꢁ 7.9 and 1.6 Hz), and 7.9–8.0 (2H, m);
MS m/z (%) 226 (Mꢂ, 17), 196 (92), and 195 (100). Found: m/z
226.1107. Calcd for C14H14N2O: M, 226.1107.
4-(2-Hydroxy-2-phenylethyl)pyrrolo[1,2-a]quinoxaline 24:
1
mp 114–115 ˚C (hexane); IR 3330, 3179, and 1610 cmꢀ1; H
NMR δ 3.08 (1H, dd, J ꢁ 13.7 and 7.9 Hz), 3.36 (1H, dd, J ꢁ
13.7 and 7.9 Hz), 4.7–4.8 (1H, m), 5.25–5.35 (1H, m), 6.85–6.95
(2H, m), 7.2–7.3 (5H, m), 7.44 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.53
(1H, td, J ꢁ 7.9 and 1.6 Hz), 7.89 (1H, dd, J ꢁ 7.9 and 1.6 Hz),
7.92 (1H, dd, J ꢁ 7.9 and 1.6 Hz), and 7.97 (1H, dd, J ꢁ 2.1 and
1.6 Hz); MS m/z (%) 288 (Mꢂ, 25), 168 (60), and 197 (100).
Found: C, 79.39; H, 5.42; N, 10.00%. Calcd for C19H16N2O: C,
79.16; H, 5.59; N, 9.72%.
4-Methylpyrrolo[1,2-a]quinoxaline.2a This compound was
1
obtained along with 34, and identified by a comparison of its H
NMR spectrum with that reported by Cheeseman et al.;2a mp 138–
140 ˚C (Ref. 2a, 137 ˚C).
trans-4-(2-Hydroxycyclohxyl)pyrrolo[1,2-a]quinoxaline 25:
mp 164–167 ˚C (hexane–Et2O); IR 3350, 3131, and 1614 cmꢀ1
;
4-(1-Ethoxy-1-methylethyl)pyrrolo[1,2-a]quinoxaline 36:
Rf 0.74 (1 : 2 EtOAc–hexane); IR (neat) 3143 and 1608 cmꢀ1; 1H
NMR δ 1.15 (3H, t, J ꢁ 6.9 Hz), 1.73 (6H, s), 3.30 (2H, q, J ꢁ 6.9
Hz), 6.85 (1H, dd, J ꢁ 4.2 and 2.6 Hz), 7.35–7.45 (2H, m), 7.49
(1H, td, J ꢁ 7.9 and 1.6 Hz), 7.83 (1H, dd, J ꢁ 7.9 and 1.6 Hz),
and 7.85–7.95 (2H, m); MS m/z (%) 254 (Mꢂ, 5) and 210 (100).
Found: m/z 254.1433. Calcd for C16H18N2O: M, 254.1420.
4-(1-Ethoxy-2-propenyl)pyrrolo[1,2-a]quinoxaline 37: Rf
0.15 (1 : 10 EtOAc–hexane); IR (neat) 3135, 1643, and 1613
cmꢀ1; 1H NMR δ 1.26 (3H, t, J ꢁ 6.9 Hz), 3.5–3.7 (2H, m), 5.12
(1H, dt, J ꢁ 6.0 and 1.3 Hz), 5.27 (1H, dt, J ꢁ 10.3 and 1.3 Hz),
5.54 (1H, dt, J ꢁ 17.1 and 1.3 Hz), 6.23 (1H, dt, J ꢁ 17.1, 10.3,
and 6.0 Hz), 6.86 (1H, dd, J ꢁ 4.2 and 2.6 Hz), 7.22 (1H, dd, J ꢁ
4.2 and 1.1 Hz), 7.42 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.50 (1H, td, J
ꢁ 7.9 and 1.6 Hz), 7.84 (1H, dd, J ꢁ 7.9 and 1.6 Hz), 7.92 (1H,
dd, J ꢁ 2.6 and 1.1 Hz), and 7.97 (1H, dd, J ꢁ 7.9 and 1.6 Hz);
MS m/z (%) 252 (Mꢂ, 4), 223 (9), and 207 (100). Found: m/z
254.1254. Calcd for C16H16N2O: M, 252.1264.
1H NMR δ 1.45–1.55 (4H, m), 1.8–1.95 (2H, m), 2.15–2.3 (2H,
m), 3.05–3.2 (2H, m), 4.35–4.5 (1H, m), 6.85 (1H, dd, J ꢁ 4.0 and
2.6 Hz), 6.93 (1H, dd, J ꢁ 4.0 and 1.5 Hz), 7.41 (1H, td, J ꢁ 7.9
and 1.6 Hz), 7.47 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.83 (1H, dd, J ꢁ
7.9 and 1.6 Hz), and 7.85–7.95 (2H, m); MS m/z (%) 266 (Mꢂ, 17)
and 195 (100). Found: C, 76.68; H, 6.81; N, 10.55. Calcd for
C17H18N2O: C, 76.66; H, 6.81; N, 10.51%.
4-(2-Hydroxy-5-hexenyl)pyrrolo[1,2-a]quinoxaline 26: mp
79–82 ˚C (hexane–Et2O); IR 3440, 3143, 1638, and 1614 cmꢀ1
;
1H NMR δ 1.6–1.9 (3H, m), 2.2–2.4 (2H, m), 3.01 (1H, dd, J ꢁ
15.8 and 8.9 Hz), 3.19 (1H, dd, J ꢁ 15.8 and 2.6 Hz), 4.25–4.4
(1H, m), 4.95–5.15 (2H, m), 5.8–6.0 (1H, m), 6.86 (1H, dd, J ꢁ
3.7 and 2.6 Hz), 6.90 (1H, dd, J ꢁ 3.7 and 1.5 Hz), 7.42 (1H, td, J
ꢁ 7.9 and 1.6 Hz), 7.49 (1H, td, J ꢁ 7.9 and 1.6 Hz), 7.83 (1H,
dd, J ꢁ 7.9 and 1.6 Hz), 7.89 (1H, dd, J ꢁ 7.9 and 1.6 Hz), and
7.93 (1H, J ꢁ 2.6 and 1.5 Hz); MS m/z (%) 266 (Mꢂ, 0.02), 248
(62), and 207 (100). Found: C, 76.64; H, 6.84; N, 10.80%. Calcd
for C17H18N2O: C, 76.66; H, 6.81; N, 10.51%.
α
4-( -Methoxybenzyl)pyrrolo[1,2-a]quinoxaline 38:
mp
trans-4-(2-Hydroxycyclohxyl)-7-methylpyrrolo[1,2-a]qui-
noxaline 27: mp 127–129 ˚C (hexane); IR 3414, 3144, and
1614 cmꢀ1; 1H NMR δ 1.4–1.55 (4H, m), 1.8–1.95 (2H, m), 2.15–
2.3 (2H, m), 2.48 (3H, s), 3.0–3.15 (1H, m), 3.19 (1H, s), 4.35–4.5
(1H, m), 6.82 (1H, dd, J ꢁ 4.0 and 2.6 Hz), 6.90 (1H, dd, J ꢁ 4.0
and 1.5 Hz), 7.29 (1H, dd, J ꢁ 7.9 and 2.1 Hz), 7.71 (1H, d, J ꢁ
7.9 Hz), 7.73 (1H, br s), and 7.86 (1H, dd, J ꢁ 2.6 and 1.5 Hz);
MS m/z (%) 280 (Mꢂ, 41), 209 (91), and 183 (100). Found: C,
76.99; H, 7.15; N, 10.17%. Calcd for C18H20N2O: C, 77.11; H,
139–142 ˚C (EtOAc–hexane); IR 3141 and 1602 cmꢀ1; 1H NMR δ
3.54 (3H, s), 5.64 (1H, s), 6.80 (1H, dd, J ꢁ 4.2 and 2.6 Hz), 7.12
(1H, dd, J ꢁ 4.2 and 1.1 Hz), 7.15–7.35 (3H, m), 7.4–7.55 (2H,
m), 7.62 (2H, d, J ꢁ 7.4 Hz), 7.82 (1H, dd, J ꢁ 7.9 and 1.6 Hz),
7.88 (1H, dd, J ꢁ 2.6 and 1.1 Hz), and 8.04 (1H, dd, J ꢁ 7.9 and
1.6 Hz); MS m/z (%) 288 (Mꢂ, 9), 273 (16), and 258 (100).
Found: C, 79.11; H, 5.70 N, 9.75%. Calcd for C19H16N2O: C,
79.14; H, 5.59; N, 9.72%.
4-(1-Ethoxyethyl)-7-methylpyrrolo[1,2-a]quinoxaline 39: