5776
S. A. Al-Awadi et al. / Tetrahedron 61 (2005) 5769–5777
7.2–7.4 (m, 5H, ArH), 12.19 (s, 1H, OH); 13C NMR
(CDCl3): d 29.4, 34.7, 127.4, 129.7, 130.9, 135.4, 178.1.
Anal. Calcd for C9H10SO2 (182.24): C, 59.34; H, 5.49; S,
17.58. Found: C, 59.85; H, 5.58; S, 17.37.
7.4 Hz, 2H, ArH). Anal. Calcd for C10H12O2S (196.26): C,
61.20; H, 6.16; S, 16.34. Found: C, 61.12; H, 6.10; S, 16.30.
3.2.7. 3-Phenoxypropropionitrile (8). A mixture of phenol
(0.25 mol), acrylonitrile (2–4 mol) and triton B (dimethyl
benzyl acetylammonium hydroxide) (2–5 mL) was heated
under reflux for 20 h. The reaction mixture was diluted with
two volumes of solvent (ether or CHCl3) filtered and washed
successively with 5% sodium hydroxide, dilute hydro-
chloric acid followed by water. The solvent was evaporated
and the residue was recrystallized from benzene/petroleum
ether (40:60) to yield 3-phenoxypropionitrile (70%), mp
3.2.3. Ethyl 3-phenoxypropanoate (4). 3-Phenoxypropa-
noic acid (1.66 g, 0.01 mol) was dissolved in 17 mL of
absolute ethanol saturated with dry hydrogen chloride. The
solution was heated under reflux for 1 h. Normal work up
resulted in a colourless oil (lit.10 bp 170 8C, 40 Torr), yield
1
is 1.74 g (90%). MS: m/zZ194 (MC); H NMR (CDCl3):
d 1.30 (t, JZ7.1 Hz, 3H, CH2CH3), 2.82 (q, JZ7.1 Hz, 2H,
CH2CH2CO), 4.22 (q, JZ7.1 Hz, 2H, OCH2CH3), 4.26
(q, JZ7.1 Hz, 2H, OCH2CH2), 6.95–7.00 (m, 3H, ArH),
7.30–7.32 (m, 2H, ArH); 13C NMR (CDCl3): d 14.79, 35.25,
61.34, 63.96, 115.24, 121.58, 130.04, 159.09, 171.69. Anal.
Calcd for C11H14O3 (194.23): C, 68.04; H, 7.20. Found; C,
68.10; H, 7.09.
1
59–60 8C (lit.14 mp 59–60 8C). MS: m/zZ147 (MC); H
NMR (CDCl3): d 2.85 (t, JZ6.2 Hz, 2H, CH2), 4.22 (t, JZ
6.2 Hz, 2H, CH2), 6.93 (d, JZ7.6 Hz, 2H, ArH), 7.03 (t, JZ
7 Hz, 1H, ArH), 7.28–7.35 (m, 2H, ArH). Anal. Calcd for
C9H9NO (147.18): C, 73.45; H, 6.16; N, 9.52. Found: C,
73.00; H, 5.92; N, 9.57.
3.2.4. Methyl 3-phenoxypropanoate (5). 3-Phenoxypro-
panoic acid (1.66 g, 0.01 mol) was dissolved in 15 mL dry
methanol saturated with dry hydrogen chloride. The mixture
was heated under reflux for 1 h. Normal work up resulted in
colourless oil (lit.11 bp 85 8C, 0.4 Torr), yield is 1.5 g (90%).
3.3. Product analysis
Both kinetic (Section 3.4 below) and reaction product
analyses were conducted using a Chemical Data System
(CDS) custom-made pyrolyzer comprising an insulated
aluminium alloy block fitted with a platinum resistance
thermocouple connected to a Comark microprocessor
thermometer for reactor temperature read-out. The tem-
perature of the reactor is controlled by means of a
Eurotherm 093 precision temperature regulator.
1
MS: m/zZ180 (MC%); H NMR (CDCl3): d 2.83 (t, JZ
6.4 Hz, 2H, CH2), 3.75 (s, 3H, CH3), 4.27 (t, JZ6.4 Hz, 2H,
CH2), 6.92 (d, JZ8.2 Hz, 2H, ArH), 6.98 (t, JZ7.8 Hz, 1H,
ArH), 7.30 (t, JZ7.8 Hz, 2H, ArH). Anal. Calcd for
C10H12O3 (180.20): C, 66.65; H, 6.71. Found; C, 66.55;
H, 6.63.
Each of the substrates (0.2 g) was introduced in the reaction
tube, which is cooled in liquid nitrogen, sealed under
vacuum and placed in the pyrolyzer for 900 s at a
temperature comparable with that used to achieve complete
pyrolysis in the kinetic studies. The contents of the tube
were then analysed by NMR and LC/MS, and quantitative
estimates were obtained by HPLC. A sample of known mass
was subjected to complete pyrolysis. The pyrolysate was
dissolved in a known volume of solvent and then injected in
the HPLC chromatograph. The percentage yield of each
product was estimated by comparing the area under the peak
of the product with that of an authentic sample of known
concentration. The spectral data of the pyrolysates were
compared with reference spectra.
3.2.5. Ethyl 3-(phenylthio)propanoate (6). A mixture of
thiophenol (11.2 g, 0.1 mol) and THF (25 mL) and triethyl
amine (9 g, 0.1 mol) was cooled at 0 8C, and then ethyl
acrylate (10 g, 0.1 mol) was added to the mixture. The
mixture was stirred and kept on ice for 2 h and then over
night at room temperature. The product was extracted with
ether (50 mL), washed with aqueous sodium hydroxide
(10 mL, 1 M), dried over sodium sulfate and filtered. After
removal of the solvent, the product was subjected to vacuum
distillation and a residue was obtained as yellow oil (15 g,
71%), (lit.12 bp 116–117 8C, 3 Torr). MS: m/zZ210 (MC);
IR (KBr): 1734 cmK1 (CO); 1H NMR (CDCl3): d 1.27
(t, JZ7.1 Hz, 3H, CH3), 2.63 (t, JZ7.4 Hz, 2H, CH2), 3.18
(t, JZ7.4 Hz, 2H, CH2), 4.15 (q, JZ7.2 Hz, 2H, CH2), 7.22
(t, JZ6.8 Hz, 1H, ArH), 7.28 (t, JZ7.2 Hz, 2H, ArH), 7.38
(d, JZ7.6 Hz, 2H, ArH); 13C NMR (CDCl3): d 14.8, 29.6,
35.0, 61.3, 127.1, 129.6, 130.7, 135.8, 172.3. Anal. Calcd
for C11H14O2S (210.29): C, 62.85; H, 6.66; S, 15.23. Found:
C, 63.11; H, 6.86; S, 15.38.
3.4. Kinetic runs and data analysis
A stock solution (7 mL) was prepared by dissolving
6–10 mg of the substrate in acetonitrile as solvent to give
a concentration of 1000–2000 ppm. An internal standard
was then added, the amount of which was adjusted to give
the desired peak area ratio of substrate to standard (2.5:1).
The solvent and the internal standard are selected because
both are stable under the conditions of pyrolysis, and
because they do not react with either substrate or product.
The internal standard used in this study is chlorobenzene,
1,3-dichlorobenzene or 1,2,4-trichlorobenzene. Each solu-
tion was filtered to ensure that a homogeneous solution is
obtained. The weight ratio of the substrate with respect to
the internal standard was calculated from the ratio of the
substrate peak area to the peak area of the internal standard.
The kinetic rate was obtained by tracing the rate of
disappearance of the substrate with respect to the internal
3.2.6. Methyl 3-(phenylthio)propanoate (7). Methyl
acrylate (20 g) was added to 17 mL thiophenol containing
0.1 g of concentrated HCl. The mixture was kept cold in an
ice bath for 16 h. The product was extracted with ether
(50 mL), washed with aqueous sodium hydroxide (10 mL,
1 M), dried over anhydrous sodium sulfate and filtered.
After removal of the solvent, the product was distilled under
vacuum and the residue obtained was yellow oil (16 g,
60%), (lit.13 bp 113–116 8C, 2 Torr). MS: m/zZ196 (MC);
1H NMR (CDCl3): d 2.61 (t, JZ7.4 Hz, 2H, CH2), 3.15
(t, JZ7.4 Hz, 2H, CH2), 3.62 (s, 3H, CH3), 7.18 (t, JZ
7.2 Hz, 1H, ArH), 7.27 (t, JZ7.4 Hz, 2H, ArH), 7.34 (d, JZ