393.1551); δH 7.77–6.69 (18H, m), 3.91 (2H, s) and 2.22 (3H, s);
δC 166.71 (quat), 147.99 (quat), 138.97 (quat), 138.06 (quat),
136.72 (quat), 134.56 (quat), 132.96 (quat), 130.4–120.5
(aromatics), 38.44 (CH2) and 20.73 (CH3); m/z 393 (Mϩ, 1%),
302 (55) and 91 (100).
Pyrolysis of N-[(2-benzylthio)benzylidene]aniline 18. N-[(2-
Benzylthio)benzylidene]aniline 18 (0.40 g, 1.32 mmol) (Tf
650 ЊC; Ti 165 ЊC; P 0.005 Torr; tp 15 min) gave a mixture of
products which was separated by dry-flash column chroma-
tography (0.5% ethyl acetate–hexane, 10% gradient): biphenyl
24 (trace), δH 7.6–7.2 (10H, m); δC 141.10 (quat), 128.63, 127.12
and 127.04; m/z 154 (Mϩ): diphenylmethane 28 (0.030 g, 14%),
δH 7.5–7.2 (10H, m) and 4.05 (2H, s); δC 140.99 (quat), 128.80,
128.33, 125.94 and 41.81 (CH2) (spectra consistent with litera-
ture data24); m/z 168 (Mϩ): bibenzyl 29 (0.030 g, 12%), δH 7.47–
7.22 (10H, m) and 3.00 (4H, s); δC 141.65 (quat), 128.33, 128.21,
125.79 and 37.83 (CH2) (spectra consistent with literature
data24); m/z 182 (Mϩ): benz[d]isothiazole 26 (0.060 g, 34%), δH
8.91 (1H, s), 8.07–7.92 (2H, m) and 7.56–7.38 (2H, m) (spec-
trum consistent with literature data as above12); δC 154.81,
151.49 (quat), 135.88 (quat), 127.61, 124.72, 123.90 and 119.42;
m/z 135 (Mϩ, 100%), 108 (17) and 91 (15): an impure fraction
which contained a small amount of 2-(phenylthio)benzonitrile
30 (≈0.010 g, 4%), δH 7.65–7.05 (aromatics); δC (CH resonances
only) 133.51, 133.43, 132.82, 129.76, 129.62, 128.76 and 126.29
(data consistent with those reported above for this compound):
an impure fraction which may contain dibenzo[b,f][1,4]-
thiazepine 31 (≈10%) δH 8.91 (1H, s), 8.15 (1H, m) and 7.49–
7.10 (aromatics) [lit.,13 8.7 (1H, s) and 7.40–7.05 (8H, m)];
m/z 211 (Mϩ, 67%), 210 (100), 184 (10) and 91 (32): 2,2Ј-
disulfanediyldibenzonitrile 32 (0.032 g, 9%) (Found: Mϩ,
268.0129. C14H8N2S2 requires M, 268.0129); νmax 2221 cmϪ1
(lit.,15 2220 cmϪ1); δH 7.79–7.25 (8H, m); δC 139.76 (quat),
133.63, 133.46, 129.77, 128.26, 116.08 (quat) and 113.01 (quat)
(1H NMR spectrum consistent with literature data,15 though
the 13C NMR spectrum15 shows discrepancies at δC 129 and
110); m/z 268 (Mϩ, 100%) and 134 (29).
Pyrolysis experiments
The substrates were sublimed or distilled under reduced pres-
sure through a silica tube (35 × 2.5 cm) which was held at the
required temperature by an electrical tube furnace. Products
were collected in a U-tube trap cooled by liquid nitrogen that
was situated immediately after the hot zone. The work-up
involved dissolution of the pyrolysate in dichloromethane
followed by dry-flash chromatography over silica, unless
otherwise stated using hexane–ethyl acetate mixtures as eluent
(starting with 99.5% hexane and increasing the proportion
of the more polar solvent by 0.1% each time). Results are
quoted as follows: quantity of substrate, furnace temperature
(Tf), inlet temperature (Ti), pressure range (P), pyrolysis time
(tP) and products (quoted in the order of elution from the
column).
Pyrolysis of 2-(phenylthio)benzaldehyde O-methyloxime 12.
2-(Phenylthio)benzaldehyde O-methyloxime 12 (0.50 g, 2.1
mmol) (Tf 650 ЊC; Ti 50 ЊC; P 0.01 Torr; tP 30 min) gave a
mixture of products which was separated by dry-flash chrom-
atography: dibenzothiophene 23 (trace), δH 7.85–8.20 (8H, m);
δC 139.33 (quat), 135.43 (quat), 126.58, 124.23, 122.67 and
121.44 (NMR data consistent with literature values24): biphenyl
24 (trace), m/z 154 (Mϩ): diphenyl sulfide 25 (trace), m/z 186
(Mϩ): benz[d]isothiazole 26 (0.231 g, 48%), δH 8.89 (1H, s),
7.90–8.04 (2H, m) and 7.28–7.56 (2H, m) (data consistent with
literature values12); δC 154.67, 151.40 (quat), 135.80 (quat),
127.48, 124.60, 123.76 and 119.29; m/z 135 (Mϩ): 2-(phenylthio)-
benzyl alcohol 31, δH 7.17–7.49 (9H, m) and 4.76–4.79 (2H, d,
3J 5.6); δC (quaternary signals not reported) 133.98, 129.34,
129.15, 128.53, 128.44, 126.53 and 63.64 (CH2) (two peaks
overlapping) (NMR data consistent with literature values25);
m/z 216 (Mϩ).
Pyrolysis of N-{1-[2-(benzylthio)phenyl]ethylidene}aniline
19. N-{1-[2-(Benzylthio)phenyl]ethylidene}aniline 19 (0.51 g,
1.61 mmol) (Tf 650 ЊC; Ti 195 ЊC; P 0.005 Torr; tp 15 min)
gave a mixture of products which was separated by dry-flash
column chromatography (0.5% ethyl acetate–hexane, 10%
gradient): biphenyl 24 (trace); m/z 154 (Mϩ): diphenylmethane
28 (0.015 g, 5%), δH 7.4–7.2 (10H, m) and 4.01 (2H, s); m/z 168
(Mϩ): bibenzyl 29 (0.060 g, 20%), δH 7.4–7.2 (10H, m) and 2.95
(4H, s); m/z 182 (Mϩ): N-benzo[b]thiophen-3-ylaniline 36
(0.107 g, 30%), mp (crude sample) 66–68 ЊC (lit.,29 88 ЊC);
δH 7.85 (1H, m), 7.66 (1H, m), 7.40–7.25 (5H, m) 7.03–6.87 (3H,
m) and 5.73 (1H, br s); δC 144.52 (quat), 138.70 (quat), 134.86
(quat), 134.42 (quat), 129.23, 124.72, 123.76, 123.06, 120.45,
119.99, 115.94 and 108.90; δH ([2H6]benzene; 360 MHz) 7.67
(1H, m), 7.47 (1H, m), 7.26–7.18 (4H, m), 6.92 (1H, m), 6.86–
6.82 (2H, m), 6.71 (1H, s) and 5.18 (1H, br s); δC ([2H6]benzene;
90 MHz) 145.18 (quat), 139.28 (quat), 135.41 (quat), 135.12
(quat), 129.41, 124.91, 123.87, 123.22, 121.19, 120.12, 116.24
and 110.14; m/z 225 (Mϩ, 100%), 224 (97), 183 (13) and 91 (17):
3-methylbenz[d]isothiazole 35 (0.060 g, 25%), δH 8.12–6.85 (4H,
m) and 2.75 (3H, s); δC 162.71 (quat), 151.93 (quat), 134.92
(quat), 127.35, 124.32, 123.27, 119.72 and 17.26 (CH3) (spectra
consistent with literature values26); m/z 149 (Mϩ, 100%), 121
(12) and 108 (8): 2-phenylbenzothiazole 37 (0.030 g, 9%),
δH 8.14–7.88 (4H, m) and 7.56–7.34 (5H, m); δC 167.96 (quat),
154.01 (quat), 134.93 (quat), 133.49 (quat), 130.86, 128.91,
127.44, 126.20, 125.08, 123.11 and 121.51 (spectra consistent
with literature values24); m/z 211 (Mϩ, 37%), 210 (100) and
108 (12).
Pyrolysis of 2Ј-(phenylthio)acetophenone O-methyloxime 13.
2Ј-(Phenylthio)acetophenone O-methyloxime 13 (0.50 g, 1.9
mmol) (Tf 650 ЊC; Ti 105 ЊC; P 0.01 Torr; tp 30 min) gave a
mixture of products which was separated by dry-flash chrom-
atography: dibenzothiophene 23 (trace), δH 7.8–8.2 (8H, m); m/z
184 (Mϩ): biphenyl 24 (trace), m/z 154 (Mϩ): 3-methylbenz-
[d]isothiazole 35 (0.135 g, 45%), δH 7.95–7.88 (2H, m), 7.55–
7.25 (2H, m) and 2.74 (3H, s); δC 162.71 (quat), 151.92 (quat),
134.91 (quat), 127.33, 124.31, 123.26, 119.71 and 17.26 (CH3)
(spectra consistent with literature values26); m/z 149 (Mϩ,
100%), 148 (26), 121 (33) and 108 (21): 2-(phenylthio)benzo-
nitrile 30 (0.024 g, 8%), δH 7.09–7.65 (9H, m) (consistent with
literature data27); δC 142.24 (quat), 133.53, 133.45, 132.85,
131.70 (quat), 129.78, 129.64, 128.79, 126.32, 116.82 (quat)
and 112.70 (quat); m/z 211 (Mϩ, 100%), 210 (40) and 184 (24);
νmax 2219 cmϪ1 (lit.,16 2220 cmϪ1).
Pyrolysis of 2-(phenylthio)benzophenone O-methyloxime 14.
2-(Phenylthio)benzophenone O-methyloxime 14 (0.50 g, 1.6
mmol) (Tf 650 ЊC; Ti 115 ЊC; P 0.01 Torr; tp 30 min) gave a
mixture of products which was separated by dry-flash chrom-
atography: biphenyl 24 (trace), m/z 154 (Mϩ): diphenyl sulfide
25 (trace), m/z 186 (Mϩ): diphenyl disulfide 40 (trace), m/z 218
(Mϩ): 3-phenylbenz[d]isothiazole 41 (0.037 g, 48%), δH 8.18
(1H, m), 7.98 (1H, m), 7.90–7.85 (2H, m) and 7.59–7.42 (5H, m)
(spectrum consistent with literature data28); δC 164.25 (quat),
153.36 (quat), 135.07 (quat), 133.65 (quat), 129.20, 128.67,
128.57, 127.36, 124.87, 124.71 and 119.81; m/z 211 (Mϩ, 100%),
210 (80), 184 (11), 105 (15) and 77 (18).
Pyrolysis
of
N-[2-(benzylthio)-ꢀ-phenylbenzylidene]-4-
methylaniline 20. N-[2-(Benzylthio)-α-phenylbenzylidene]-4-
methylaniline 20 (0.47 g {80% pure}, 0.96 mmol) (Tf 650 ЊC; Ti
285 ЊC; P 0.006 Torr; tp 20 min) gave a mixture of products
which was separated by dry-flash column chromatography
(0.5% ethyl acetate–hexane, 10% gradient): dibenzothiophene
23 (0.038 g, 22%), δH 8.18–8.14 (2H, m), 7.88–7.84 (2H, m) and
1084
J. Chem. Soc., Perkin Trans. 1, 2001, 1079–1085