153.71 (quat), 136.25 (quat), 133.74, 130.22 (quat), 129.71, 128.93,
128.29 (2CH), 128.05 (quat), 127.61, 127.30, 126.58 (2CH), 121.13,
114.10, 112.03, 111.73, 110.05, 70.31 (CH2) and 51.14 (CH3); m/z
333 (M+, 35%), 274 (12), 170 (34), 168 (23), 154 (23) and 91 (100).
2-Formyl-N-[2-(allylthio)phenyl]pyrrole 6 (0.486 g, 2 mmol)
(8 h) gave methyl 3-{N-[2-(allylthio)phenyl]pyrrol-2-yl}prope-
Torr) (found: M+ 187.0644. C11H9NO2 requires M 187.0633); dH
9.42 (1H, s), 7.39–6.94 (4H, m) and 6.46–6.25 (3H, m) (OH not
apparent); dC 178.40, 150.39 (quat), 131.16, 129.29, 127.26, 120.13,
116.98, 113.92 and 110.78 (two quaternaries not apparent); m/z
187 (M+, 100%), 170 (28), 159 (93), 158 (50), 131 (23) and 130 (55),
and 3-formyl-N-(2-hydroxyphenyl)pyrrole 15 (0.058 g, 16%), bp
150–155 ◦C (0.5 Torr), (found: M+ 187.0625. C11H9NO3 requires M
187.0633); dH 9.69 (1H, s), 7.72 (1H, t, 4J 1.8), 7.30–6.91 (5H, m)
and 6.76 (1H, dd, 3J 3.0 and 4J 1.8) (OH not apparent); dC 186.45,
149.91 (quat), 131.11, 129.03, 128.88 (quat), 128.06 (quat), 125.42,
124.78, 120.51, 117.41 and 108.68; m/z 187 (M+, 92%), 170 (40),
159 (100), 158 (60), 130 (32) and 94 (27).
◦
noate 10 (0.342 g, 60%), bp 145–150 C (0.05 Torr) (found: M+
299.0984. C17H17NO2S requires M 299.0980); dH 7.41 (2H, m),
7.27–7.14 (3H, m), 6.85–6.80 (2H, m), 6.36 (1H, dd, 3J 3.3),
5.93 (1H, d, 3J 15.9), 5.81–5.64 (1H, m), 5.18–5.03 (2H, m),
3
3.67 (3H, s) and 3.40 (2H, d, J 6.6); dC 167.85 (quat), 137.36
(quat), 135.97 (quat), 133.08, 132.62, 129.88 (quat), 129.23, 128.88,
128.75, 127.04, 126.21, 118.24 (CH2), 112.48, 112.13, 110.33,
51.20 (CH3) and 35.40 (CH2); m/z 299 (M+, 41%), 258 (81),
226 (100), 199 (44), 198 (69), 197 (31), 186 (53), 167 (23) and
41 (22).
Methyl 3-{N-(2-hydroxyphenyl)pyrrol-2-yl}propenoate 12 and
methyl (4H-5-oxa-9b-aza-cyclopenta[a]naphthalen-4-yl)acetate 13
2-Formyl-1-(2-hydroxyphenyl)pyrrole 14 (0.070 g, 0.37 mmol)
was dissolved in dry THF (50 cm3). Methyl (triphenylphos-
phoranylidene)acetate (0.38 g, 1.12 mmol) was added and the
mixture was then heated under reflux until TLC showed that
all the aldehyde had been consumed (36 h). The mixture was
pre-adsorbed onto silica (1 g) and purified by dry-flash chro-
matography (20% ethyl acetate–hexane: 5% gradient). This gave
two products: methyl (4H-5-oxa-9b-aza-cyclopenta[a]naphthalen-
4-yl)acetate 13 (0.031 g, 34%), bp 130–135 ◦C (0.1 Torr) (found: M+
243.0883. C14H13NO3 requires M 243.0895); dH 7.33 (1H, m), 7.15
Flash vacuum pyrolysis experiments
The substrate was volatilised under vacuum through an electrically
heated empty silica tube (35 × 2.5 cm) and the products were
collected in a liquid nitrogen cooled U-tube, situated at the
exit point of the furnace. Conditions for the pyrolyses were
established in small-scale experiments in which the product(s) were
dissolved in a deuterated solvent and analysed immediately by 1H
NMR spectroscopy. The precursor, pyrolysis conditions [quantity
of precursor, furnace temperature (Tf), inlet temperature (Ti),
pressure range (P) and pyrolysis time (t)] and, where appropriate,
approximate yields are given.
3
3
(1H, dd, J 2.9 and 1.4), 7.09–7.00 (3H, m), 6.32 (1H, t, J 3.4),
3
4
3
6.02 (1H, dt, J 3.5 and J 1.3), 5.62 (1H, ddd, J 7.0 and 6.0,
4J 0.7), 3.77 (3H, s) and 3.00 (2H, m); dC 170.24 (quat), 144.85
(quat), 126.24 (quat), 126.07 (quat), 124.95, 122.28, 118.12, 114.91,
114.58, 110.51, 104.15, 70.25, 51.83 (CH3) and 38.72 (CH2); m/z
243 (M+, 30%), 171 (15) and 170 (100), and methyl 3-[N-(2-
hydr◦oxyphenyl)pyrrol-2-yl]propenoate 12 (0.024 g, 27%), bp 145–
150 C (0.1 Torr) (found: M+ 243.0887. C14H13NO3 requires M
243.0895); dH 7.33–7.12 (3H, m), 7.01–6.97 (2H, m), 6.87 (1H, m),
6.80 (1H, d, 3J 3.8), 6.38 (1H, t, 3J 3.0), 6.16 (1H, br), 5.97 (1H,
FVP of methyl 3-{N-[2-(benzyloxy)phenyl]pyrrol-2-yl}propenoate
9
Methyl 3-{N-[2-(benzyloxy)phenyl]pyrrol-2-yl}propenoate
9
(0.204 g, 6 mmol) (Tf 650 ◦C, Ti 140–160 ◦C, P 0.005 Torr,
t 20 min), gave a number of products, only three of which
could be separated by dry-flash chromatography. The first
to elute was bibenzyl. The second was methyl (4H-5-oxa-9b-
aza-cyclopenta[a]naphthalen-4-yl)acetate 13 (0.006 g, 4%), bp
3
d, J 15.7) and 3.66 (3H, s); m/z 234 (M+, 10%), 241 (13), 227
(21), 226 (78), 213 (86), 198 (100), 197 (75) and 183 (56). These
data are consistent with those reported above for the pyrolysis
of 9.
◦
120–125 C (0.05 Torr) (found: M+ 243.0879. C14H13NO3
requires M 243.0895); dH 7.33 (1H, m), 7.14 (1H, dd, 3J 2.9
4
3
and J 1.3), 7.05–7.00 (3H, m), 6.31 (1H, apparent t, J 3.2),
3
4
3
6.01 (1H, dt, J 3.5 and J 1.3), 5.61 (1H, apparent t, J 6.3),
3.76 (3H, s) and 2.99 (2H, m); dC 170.26 (quat), 144.88 (quat),
126.25 (quat), 126.09 (quat), 124.98, 122.31, 118.16, 114.90,
114.57, 110.48, 104.18, 70.26, 51.88 (CH3) and 38.72 (CH2);
m/z 243 (M+ 30%), 171 (13) and 170 (100). The third product
could not be isolated in a pure form but was identified as methyl
3-[1-(2-hydroxyphenyl)pyrrol-2-yl]propenoate 12 by comparison
with authentic data (see below); dH 7.06–6.99 (2H, m), 6.87 (1H,
m), 6.80 (1H, m), 6.35 (1H, t), 5.99 (1H, d, 3J 15.8) and 3.68 (3H,
s) two aryl protons, one alkenyl proton and OH not assigned; m/z
243 (M+).
FVP of methyl 3-{N-[2-(allylthio)phenyl]pyrrol-2-yl}propenoate
10
Methyl 3-{N-[2-(allylthio)phenyl]pyrrol-2-yl}propenoate 10
◦
◦
(0.250 g, 8 mmol) (Tf 650 C, Ti 140–160 C, P 0.001 Torr, t 20
min), gave one major product which was purified by dry-flash
chromatography (1% ethyl acetate–hexane: 10% gradient) and
identified as methyl pyrrolo[1,2-a]quino◦line-4-carboxylate 17 (see
discussion) (0.084 g, 41%) bp 125–130 C (0.2 Torr) (found: M+
225.0784. C14H11NO2 requires M 225.0790); dH (600 MHz,
[2H6]acetone, see Fig. 2 for atom labels) 8.11 (1H, dd, 3J 2.9 and
4J 1.5, proton B), 8.08 (1H, br. d, 3J 8.5, proton D), 7.87 (1H, s,
3
4
n
proton H), 7.83 (1H, ddt, J 7.8, J 1.4, J 0.7 and 0.7, proton
2-Formyl-N-(2-hydroxyphenyl)pyrrole 14
3
4
K), 7.63 (1H, ddd, J 8.5 and 7.2, J 1.4, proton L), 7.36 (1H,
Application of the general formylation procedure described above
to N-(2-hydroxyphenyl)pyrrole 1 gave, after dry flash chromatog-
raphy (15% ethyl acetate–hexane: 5% gradient), 2-formyl-1-(2-
hydroxyphenyl)pyrrole 14 (0.092 g, 25%), bp 134–139 ◦C (0.2
ddd, 3J 7.8 and 7.2, 4J 1.1, proton G), 7.21 (1H, dd, 3J 3.9 and 4J
3
1.5, proton A), 6.83 (1H, dd, J 3.9 and 2.9, proton C) and 3.95
(3H, s); dC (150 MHz, [2H6]acetone, see Fig. 2 for atom labels)
165.5 (quat P), 134.8 (quat M), 131.1 (L), 130.8 (K), 127.9 (quat
2450 | Org. Biomol. Chem., 2006, 4, 2446–2451
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The Royal Society of Chemistry 2006
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