Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 13.1 Extrusion of Ph3P from sulfinyl ylides and reactivity of the resulting sulfinyl carbenes

Article abstract of DOI:10.1039/a806182c

Six α-sulfinyl phosphorus ylides 6 have been prepared and are found upon flash vacuum pyrolysis at 500°C to undergo mainly extrusion of Ph₃P to give thioesters, presumably by 1,2-oxygen transfer in the initially formed sulfinyl carbenes; for α-arylsulfinyl ylides loss of Ph₃PO to give additional products is also observed.

Full text of DOI:10.1039/a806182c

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Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 13.1
Extrusion of Ph3P from sulfinyl ylides and reactivity of the
resulting sulfinyl carbenes
R. Alan Aitken,* Martin J. Drysdale and Bruce M. Ryan
School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife,
UK KY16 9ST
Received (in Cambridge) 5th August 1998, Accepted 1st September 1998
Six α-sulfinyl phosphorus ylides 6 have been prepared and are found upon flash vacuum pyrolysis at 500 ЊC to
undergo mainly extrusion of Ph3P to give thioesters, presumably by 1,2-oxygen transfer in the initially formed
sulfinyl carbenes; for α-arylsulfinyl ylides loss of Ph3PO to give additional products is also observed.
Although the thermal extrusion of Ph3PO from α-acyl-
phosphonium ylides 1 to give alkynes is well established,2 the
corresponding reaction of ylides bearing other oxygen contain-
ing functional groups on the α-position has been little investi-
gated. Sulfonyl cyanides have been prepared by spontaneous
extrusion from α-nitroso ylides 2 at Ϫ40 ЊC,3 and there is evi-
dence for extrusion of Ph3PO from α-nitro ylides 3 to give
nitrile oxides.4 In Part 12 of this series,1 we reported that
sulfonyl ylides 4 undergo loss of Ph3P rather than Ph3PO upon
flash vacuum pyrolysis (FVP) to give products derived from
sulfonyl carbenes. We now report the preparation and pyrolytic
behaviour of representative α-sulfinyl ylides 6.5
For the alkanesulfinyl ylides 6a–c, FVP at 500 ЊC and 10Ϫ2
Torr (contact time ca. 10Ϫ2 s) resulted mainly in extrusion of
Ph3P to give the thioesters 7 (Table 1). Since spectroscopic data
for the thioester 7c have apparently not been reported before, an
authentic sample of this was prepared for comparison. The
reaction can be explained by a 1,2-oxygen transfer in the ini-
tially formed sulfinyl carbenes via the zwitterionic oxathiirane
intermediate 14 (Scheme 1). Sulfinyl carbenes are a little known
Ph3P
Ph
Ph
R
Ph
R
FVP
– Ph3PO
Ph
R
FVP
•
•
–
•
[1,2-O]
•
O
S
S
S+
S
– Ph3P
O
R
O
6
14
R1
R2
R1
R2
[1,2-R]
Ph3P
O
SO2Ar Ph3P
O
R
Ph3P
O
Ph3P
O
[1,2-R]
Ph
+H•
Ph
+2H•
N
N+
S
O–
R
O
O
Ph
R
Ph
•
2
4
1
3
S
O
Ph
R
S
S
S
R
15
R
10
8
S
Ph3P
O
Ph
R
O
2 SO2Cl2
AcOH
2 Ph3P=CHPh
?
7
RSH
S
S
R
Ph
R
Cl
R
Ph
PhCH: + RS •
6
5
O
S
– S
O
9
x2
Results and discussion
PhCH=CHPh RSSR + RSH
11 12 13
The sulfinyl ylides are little known and there were, until
recently, only two reports of their synthesis,6 both involving
additional stabilisation by an ester group. Synthesis of the first
examples without additional stabilisation, a range of (alkyl-
sulfinylmethylene)diphenylmethylphosphoranes, was recently
described by reaction of a lithium phosphonium diylide with
sulfinate esters.7 The required ylides 6 were readily formed in
low to moderate yield (Table 1) in analogy to the acyl ylides 1,
by reaction of Ph P᎐CHPh (2 equiv.) with sulfinyl chlorides 5.
Scheme 1
class of reactive intermediates,9 but this type of oxygen transfer
has been observed before in two cases.10,11 The analogous
rearrangement of nitro carbenes to acylnitroso compounds has
been described,12 as has 1,4-O-transfer from sulfur in an
N-sulfonylimidoyl carbene to give the sulfinylimidoyl ketone.13
For 6a,b there was also some loss of Ph3PO to give other
minor products, and for the ylides 6c–f competing processes
were more important, although 7 was still formed in each case.
Since 7e,f appear to be previously unknown, authentic samples
were prepared by an alternative route and characterised. To
confirm that these compounds were stable under the pyrolysis
conditions and would not give rise to any secondary products,
they were each subjected to FVP at 500 ЊC but were recovered
unchanged. In Table 1 the balance of the phosphorus products
is accounted for in each case by Ph3PS, presumably formed by
interaction of Ph3P with sulfur containing products. The most
obvious feature for 6d–f was the production of an intense dark
᎐
3
The sulfinyl chlorides which are notoriously unstable and
difficult to purify were used directly as obtained from the
improved method8 involving treatment of RSH with 2 equiv.
SO2Cl2 and 1 equiv. AcOH. The ylides were easily recognised
from the characteristic doublet (1JP–C 122–128 Hz) due to the
ylide carbon in their 13C NMR spectra (see Table 2). The com-
pounds proved to be rather unstable and difficult to purify and
the low yield in the case of 6c meant that correct analytical data
could not be obtained, although the consistent pattern of 13C
NMR data across the series leaves little doubt as to its identity.
Significantly the majority of the compounds showed a peak for
Mϩ Ϫ O as the highest signal in the mass spectrum.
J. Chem. Soc., Perkin Trans. 1, 1998, 3345–3348
3345

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Table 1 Formation of sulfinyl ylides 6 and results of their pyrolysis at 500 ЊC
Products from FVP of 6 (%)
Yield
R
of 6 (%)
δP
Ph3P
Ph3PO
7
9
10
11
12
13
a
b
c
d
e
f
Et
24
33
4
29
45
31
ϩ19.7
ϩ20.2
ϩ18.7
ϩ20.4
ϩ20.2
ϩ19.7
80
84
50
64
82
27
13
9
40
32
15
67
53
37
30
20
25
9
—
—
—
—
5
—
—
2
4
—
7
—
—
10
10
—
7
—
—
—
10
6
—
—
—
8
20
25
Pri
CH2Ph
Ph
4-Me-C6H4
4-Cl-C6H4
18
17
Table 2 13C NMR Spectra of ylides 6, δC (JP–C
)
P–Phenyl
C-1
P᎐C–Ph signals
᎐
R
P᎐C
᎐
C-2
C-3
C-4
C-1
C-2
C-3
C-4
R signals
a
b
Et
47.9 (126) 127.7 (86) 134.2 (10) 128.6 (12) 131.9 (2)
47.2 (123) 127.5 (89) 134.3 (10) 128.6 (12) 132.0 (2)
137.1 (14) 131.5 (6) 127.8 124.0
137.3 (11) 131.9 (5) 127.7 124.1
45.4 (12), 10.1
49.6 (12), 19.0,
18.7
Pri
c
d
e
CH2Ph
47.1 (128) 127.0 (90) 134.0 (10) 128.6 (12) 132.1 (<2) 138.3 (12) 131.9 (5) 127.9 123.5
56.3 (12), 133.2,
130.5 (2C), 128.4
(2C), 127.0
147.7 (16), 127.8
(2C), 126.3 (2C),
128.6
144.6 (16), 137.7,
128.7 (2C), 126.3
(2C), 21.1
Ph
52.2 (122) 126.8 (89) 134.3 (10) 128.8 (12) 132.4 (2)
137.2 (12) 129.7 (6) 127.3 122.7
4-Me-C6H4
52.1 (125) 128.0 (78) 134.3 (10) 128.8 (12) 132.3 (<2) 137.4 (12) 132.0 (7) 127.3 122.6
blue colour in the cold trap which faded rapidly upon
warming. This is attributed to the thioketones 8 although they
were only present in trace quantities and could not be detected
spectroscopically despite authentic samples being prepared for
comparison. The formation of these products may be due to
rearrangement of the sulfenyl carbenes resulting from Ph3PO
extrusion and the failure to detect them spectroscopically is
explained by their rapid reaction with Ph3P in solution to give
Ph3PS (δP ϩ42.8) as confirmed by a control experiment using 8d.
A major product for 6e,f was the ketone 9 which most likely
results from rearrangement of the sulfinyl carbene to a sulfine
followed by loss of sulfur. A closely related example, dimethyl-
vinyl(p-tolylsulfinyl)carbene, has been reported to give the
ketone in excellent yield in an analogous way,14 and the absence
of this process for 6a–c probably reflects the poorer migratory
aptitude of alkyl vs. aryl groups. In fact there seems to be a fine
balance in the reactivity of sulfinyl carbenes between under-
going 1,2-oxygen transfer to give thioesters and the alternative
Wolff-type rearrangement to sulfines. While rhodium catalysed
reaction of cephalosporin-derived α-diazo sulfoxides results
in oxygen transfer,11 photolysis of the same precursors give
the sulfines.15 In very recent work, Maguire and coworkers
have found that rhodium catalysed reaction of cyclic α-diazo
sulfoxides also proceeds by way of a sulfine.16
Experimental
Melting points were recorded on a Reichert hot-stage micro-
scope and are uncorrected. UV–visible spectra were recorded
using a Pye-Unicam SP-800 instrument. Infrared spectra were
recorded as Nujol mulls for solids and as thin films for liquids
on a Perkin-Elmer 1420 instrument. NMR spectra were
1
obtained for H at 300 MHz and for 13C at 75 MHz using a
Bruker AM300 instrument, and for 31P at 32 MHz using a
Varian CFT 20 instrument. All spectra were run on solutions in
CDCl3 with internal Me4Si as reference for H and 13C and
1
external 85% H3PO4 as reference for 31P. Chemical shifts are
reported in ppm to high frequency of the reference and
coupling constants J are in Hz. In the reporting of 13C NMR
spectra, 4ry refers to quaternary carbon. Mass spectra were
obtained on an AEI/Kratos MS-50 spectrometer using electron
impact at 70 eV. GC–MS data were obtained using a Hewlett
Packard 5890A chromatograph coupled to a Finnigan Incos
mass spectrometer. The column used was a 25 m capillary
column HR17 with a phenyl methyl silicone stationary phase.
Toluene was dried by storing over sodium wire.
The sulfinyl chlorides 5a–f were prepared according to the
literature procedure,8 by treatment of the corresponding thiols
with one equiv. acetic acid and two equiv. sulfuryl chloride at
Ϫ45 ЊC.
The remaining products can be accounted for by alternative
reactions of the sulfenyl carbene resulting from extrusion of
Ph3PO. The benzyl sulfide 10 is clearly formed by hydrogen
atom abstraction, but the formation of stilbene 11 is more dif-
ficult to explain. Although the disulfide 12 and thiol 13 may be
Preparation of the sulfinyl ylides 6
A suspension of benzyltriphenylphosphonium chloride (10.0 g,
26 mmol) in dry toluene (100 cm3) was stirred at 0 ЊC under
nitrogen while a solution butyllithium (2.5 M, 10.3 cm3, 26
mmol) was added. After stirring for 30 min, a solution of the
appropriate sulfinyl chloride 5 (13 mmol) in dry toluene (10
cm3) was added dropwise. After stirring at room temperature for
12 h, the mixture was filtered and the filtrate evaporated. Tritur-
ation of the residual oil with ethyl acetate gave the product.
ؒ
formed by a variety of radical processes which generate RS , it
is attractive to speculate that all three products may result as
shown from an α-elimination process of radical 15 formed by
abstraction of a single hydrogen atom by the sulfenyl carbene,
although we are not aware of any precedent for this process. In
control experiments, FVP of 10e,f and 9e,f at 500 ЊC established
that they are stable under these conditions and do not lead to
any secondary products. A further complication is the possibil-
ity of disproportionation of 6 in the inlet tube which has been
observed for other sulfinyl ylides,17 and would lead to further
products from pyrolysis of sulfenyl and sulfonyl ylides.
[Ethylsulfinyl(phenyl)methylene]triphenylphosphorane
6a.
Reaction as above using ethanesulfinyl chloride gave yellow
crystals (24%), mp 169–172 ЊC (Found: C, 75.4; H, 5.9. C27H25-
OPS requires C, 75.7; H, 5.9%) (HRMS: found Mϩ Ϫ O,
3346
J. Chem. Soc., Perkin Trans. 1, 1998, 3345–3348

View Article Online
412.1436. C27H25OPS requires M Ϫ O, 412.1415); νmax/cmϪ1
1591, 1489, 1436, 1255, 1240, 1101, 1093, 999, 977, 917, 754 and
694; δH 7.7–6.9 (20 H, m), 2.86 (2 H, q, J 7) and 1.08 (3 H, t,
J 7); δC see Table 2; δP ϩ19.7; m/z 412 (Mϩ Ϫ O, 5%), 383 (10),
351 (1), 300 (1), 277 (12), 262 (12), 183 (32) and 121 (100).
which was shown by 31P and 1H NMR and GC–MS to consist
of Ph3P, Ph3PO and Ph3PS in a ratio of 80:13:7: Ph3P; δP Ϫ5.4;
m/z 262 (12%), 183 (45), 152 (16) and 108 (100). Ph3PO;
δP ϩ28.6; m/z 277 (Mϩ Ϫ H, 100%), 201 (28), 183 (27) and 152
(10). Ph3PS; δP ϩ43.6; m/z 294 (Mϩ, 91%), 262 (15), 217 (15)
and 183 (100). The liquid in the cold trap was shown to be
almost pure S-ethyl thiobenzoate 7a (53%); δH 8.1–7.9 (2 H, m),
7.3–7.5 (3 H, m), 3.08 (2 H, q, J 7) and 1.35 (3 H, t, J 7);
δC 192.1, 23.4 and 14.8; m/z 166 (Mϩ, 5%) and 105 (100).
FVP of the ylide 6b (200 mg) gave a solid at the furnace exit
which was shown by 31P and 1H NMR and GC–MS to consist
of Ph3P, Ph3PO and Ph3PS in a ratio of 84:9:7. The liquid in
the cold trap was shown to be almost pure S-isopropyl thio-
benzoate 7b (37%); δH 8.2–8.0 (2 H, m), 7.7–7.5 (3 H, m), 3.92
(1 H, septet, J 7) and 1.44 (6 H, d, J 7); δC 192.1, 137.4, 133.1,
128.5 (2C), 127.1 (2C), 34.7 and 23.1 (2C); m/z 180 (Mϩ, 5%),
138 (1), 105 (100) and 77 (45).
[Phenyl(isopropylsulfinyl)methylene]triphenylphosphorane 6b.
Reaction as above using propane-2-sulfinyl chloride gave yellow
crystals (33%), mp 145–148 ЊC (Found: C, 75.6; H, 5.8. C28H27-
OPS requires C, 76.0; H, 6.1%) (HRMS: found Mϩ Ϫ Pri,
399.0956. C28H27OPS requires M Ϫ Pri, 399.0972); νmax/cmϪ1
1190, 1114, 1100, 1031, 988, 925, 752, 722 and 697; δH 7.7–6.9
(20 H, m), 3.08 (1 H, septet of d, J 7, 2), 1.28 (3 H, dd, J 7, 1)
and 1.08 (3 H, d, J 7); δC see Table 2; δP ϩ20.2; m/z 426
(Mϩ Ϫ O, 1%), 400 (12), 399 (41), 263 (43), 262 (71), 183 (78),
121 (76) and 105 (100).
FVP of the ylide 6c (105 mg) gave a solid at the furnace exit
which was shown by 31P and 1H NMR and GC–MS to consist
of Ph3P, Ph3PO and Ph3PS in a ratio of 50:40:10. The liquid in
the cold trap was shown by NMR, GC–MS and comparison
with authentic samples to consist of S-benzyl thiobenzoate 7c
(30%); δH 7.96 (2 H, m) and 4.32 (2 H, s); m/z 228 (Mϩ, 5%) and
105 (100) together with smaller quantities of bibenzyl (4%); m/z
182 (Mϩ, 10%), 91 (100), (Z)-stilbene 11 (2%) and (E)-stilbene
11 (8%); m/z 180 (Mϩ, 82%) and dibenzyl sulfide 10e (2%);
m/z 214 (Mϩ, 6%), 123 (22) and 91 (100).
[Phenylmethylsulfinyl(phenyl)methylene]triphenylphosphorane
6c. Reaction as above using phenylmethanesulfinyl chloride
gave yellow crystals (4%), mp 159–161 ЊC; νmax/cmϪ1 1255,
1190, 1108, 1000, 934, 758, 720 and 698; δH 7.8–6.9 (25 H, m),
4.58 (1 H, half AB pattern of d, J 12, 2) and 4.08 (1 H, half AB
pattern, J 12); δC see Table 2; δP ϩ18.7; m/z (no Mϩ at 490) 415
(3%), 400 (4), 398 (20), 382 (12), 351 (8), 294 (5), 292 (4), 277
(8), 262 (57), 228 (6), 183 (100), 121 (96), 105 (90), 91 (78) and
77 (95).
FVP of the ylide 6d (200 mg) gave a yellow liquid at the
furnace exit which was shown by 31P and 1H NMR and GC–MS
to consist of Ph3P, Ph3PO and Ph3PS in a ratio of 64:32:4. The
bright blue liquid in the cold trap was shown by NMR, GC–
MS and comparison with authentic samples to consist of
benzenethiol 13d (8%); m/z 110 (Mϩ, 100%), (Z)-stilbene 11
(2%); m/z 180 (Mϩ, 38%), (E)-stilbene 11 (8%); m/z 180 (Mϩ,
63%), benzyl phenyl sulfide 10d (4%); m/z 200 (Mϩ, 3%), 109 (5)
and 91 (100), diphenyl disulfide 12d (10%); m/z 218 (Mϩ, 8%),
185 (4), 154 (9) and 109 (100) and S-phenyl thiobenzoate 7d
(20%); m/z 214 (Mϩ, 1%), 184 (1), 152 (1), 105 (90) and 77 (100).
FVP of the ylide 6e (110 mg) gave a yellow liquid at the
furnace exit which was shown by 31P and 1H NMR and GC–MS
to consist of Ph3P, Ph3PO and Ph3PS in a ratio of 82:15:3. The
bright blue liquid in the cold trap was shown by NMR, GC–MS
and comparison with authentic samples to consist of benzalde-
hyde (5%); δH 10.0; m/z 106 (Mϩ, 55%); 4-methylbenzenethiol
13e (20%); δH 3.4 (1 H); m/z 124 (Mϩ, 42%) and 91 (100),
4-methylbenzophenone 9e (5%); m/z 196 (Mϩ, 12%), 119 (100),
105 (37), 91 (54) and 77 (55), S-(4-methylphenyl) thiobenzoate
7e (25%); δH 8.0 (2 H, m) and 2.40 (3 H, s); m/z 228 (Mϩ, 1%),
123 (5) and 105 (100) and bis(4-methylphenyl) disulfide 12e
(6%); m/z 246 (Mϩ, 8%), 214 (1), 182 (4) and 123 (66).
FVP of the ylide 6f (180 mg) gave a yellow liquid at the
furnace exit which was shown by 31P and 1H NMR and GC–MS
to consist of Ph3P, Ph3PO and Ph3PS in a ratio of 26:68:6. The
bright blue liquid in the cold trap was shown by NMR, GC–
MS and comparison with authentic samples to consist of
4-chlorobenzenethiol 13f (25%); δH 3.47 (1 H); m/z 144 (35Cl-
Mϩ, 100%) and 109 (48), (E)-stilbene 11 (7%), 4-chlorobenzo-
phenone 9f (18%); m/z 216 (35Cl-Mϩ, 60%), 181 (20), 139 (95),
111 (40) and 105 (100), benzyl 4-chlorophenyl sulfide 10f (7%);
δH 4.04 (2 H); m/z 234 (35Cl-Mϩ, 19%), 143 (8) and 91 (100),
S-(4-chlorophenyl) thiobenzoate 7f (9%); m/z 248 (35Cl-Mϩ,
4%), 143 (10) and 105 (100) and bis(4-chlorophenyl) disulfide
12f (17%); m/z 286 (35Cl2-Mϩ, 30%), 222 (3), 143 (100) and
108 (50).
[Phenylsulfinyl(phenyl)methylene]triphenylphosphorane
6d.
Reaction as above using benzenesulfinyl chloride gave yellow
crystals (29%), mp 172–174 ЊC (HRMS: found Mϩ Ϫ O,
460.1423. C31H25OPS requires M Ϫ O, 460.1415); νmax/cmϪ1
(CH2Cl2) 1590, 1487, 1440, 1243, 1190, 1102, 1000 and 960; δH
7.8–6.7 (25 H, m); δC see Table 2; δP ϩ20.4; m/z 460 (Mϩ Ϫ O,
2%), 399 (1), 277 (13), 262 (21), 218 (40), 200 (40), 183 (12), 143
(15), 105 (50) and 91 (100).
[4-Methylphenylsulfinyl(phenyl)methylene]triphenylphosphor-
ane 6e. Reaction as above using 4-methylbenzenesulfinyl
chloride gave yellow crystals (45%), mp 168–173 ЊC (Found: C,
78.6; H, 5.5. C32H27OPS requires C, 78.3; H, 5.5%) (HRMS:
found Mϩ Ϫ O, 474.1476. C32H27OPS requires M Ϫ O,
474.1520); νmax/cmϪ1 (CH2Cl2) 1590, 1490, 1440, 1243, 1190,
1102, 1000, 928 and 812; δH 8.0–6.8 (24 H, m) and 2.28 (3 H, s);
δC see Table 2; δP ϩ20.2; m/z 474 (Mϩ Ϫ O, 0.2%), 394 (0.5), 379
(1), 351 (0.2), 277 (14), 262 (26), 183 (45), 105 (67) and 77 (100).
[4-Chlorophenylsulfinyl(phenyl)methylene]triphenylphosphor-
ane 6f. Reaction as above using 4-chlorobenzenesulfinyl
chloride gave yellow crystals (31%), mp 194–196 ЊC (HRMS:
found Mϩ Ϫ O, 494.1020. C31H2435ClOPS requires; M Ϫ O,
494.1025); νmax/cmϪ1 1590, 1485, 1440, 1248, 1190, 1100, 1000,
982, 822, 752 and 697; δH 7.8–6.8 (24 H, m); δC see Table 2;
δP ϩ19.7; m/z 496 (37Cl-Mϩ Ϫ O, 0.3%), 494 (35Cl-Mϩ Ϫ O, 1),
383 (1), 309 (0.5), 277 (33), 262 (12), 233 (5), 183 (10), 121 (23)
and 77 (100).
Flash vacuum pyrolysis of ylides
The apparatus used was as described previously.18 All pyrolyses
were conducted with a furnace temperature of 500 ЊC and at
pressures in the range 10Ϫ3–10Ϫ1 Torr and were complete within
1 h. Under these conditions the contact time in the hot zone was
estimated to be ≈10 ms.
In all cases the phosphorus containing products collected at
the furnace exit and the more volatile products were recovered
from the cold trap. Yields were determined by calibration of the
1H NMR spectra by adding an accurately weighed quantity of a
solvent such as CH2Cl2 and comparing integrals, a procedure
estimated to be accurate to 10%.
Preparation of authentic samples of pyrolysis products
Preparation of thiobenzoates 7. A solution of the appropriate
thiol (80 mmol) and triethylamine (8.3 g, 82 mmol) in dry tolu-
ene (100 cm3) was stirred while a solution of benzoyl chloride
FVP of the ylide 6a (110 mg) gave a solid at the furnace exit
J. Chem. Soc., Perkin Trans. 1, 1998, 3345–3348
3347

View Article Online
(11.3 g, 82 mmol) in dry toluene (10 cm3) was added dropwise.
After 2 h, the mixture was filtered, washed with water, dried and
evaporated. Using this method the following compounds were
prepared.
S-Benzyl thiobenzoate 7c. From phenylmethanethiol (32%) as
a colourless oil which crystallised with time, bp 110 ЊC (oven
temp.) at 2 Torr, mp 34–36 ЊC (lit.,19 39.5 ЊC); δH 8.0–8.2 (2 H,
m), 7.2–7.6 (8 H, m) and 4.35 (2 H, s).
(4ry), 144.8 (4ry), 143.1 (4ry), 131.7, 129.9 (2 C), 129.5 (2 C),
128.7 (2 C), 127.9 (2 C) and 21.6.
4-Chlorothiobenzophenone 8f. Blue liquid (20%), bp 170 ЊC
(oven temp.) at 0.1 Torr (lit.,25 145–146 ЊC at 0.22 Torr)
(HRMS: found Mϩ, 232.0102. C13H935ClS requires M,
232.0113); νmax/nm 592; δH 7.2–7.8 (10 H, m); δC 236.2 (C᎐S),
᎐
146.9 (4ry), 145.3 (4ry), 138.5 (4ry), 132.1, 130.8 (2 C), 129.4
(2 C), 128.2 (2 C) and 128.0 (2 C).
S-Phenyl thiobenzoate 7d. From thiophenol (75%) as colour-
less flakes, mp 50–51 ЊC (lit.,20 56 ЊC); δH 8.0 (2 H, m) and 7.3–
7.6 (8 H, m).
S-(4-Methylphenyl) thiobenzoate 7e. From 4-methylthio-
phenol (45%) as colourless crystals, mp 65 ЊC (Found: C, 73.7;
H, 5.6. C14H12OS requires C, 73.7; H, 5.3%) (HRMS: found
Mϩ, 228.0612. C14H12OS requires M, 228.0609); νmax/cmϪ1 1670,
1605 and 1590; δH 8.02 and 7.18 (4 H, AB pattern, J 9), 7.35–
Acknowledgements
We thank British Petroleum Research International Ltd for
Research Studentships (M. J. D. and B. M. R.) and the Royal
Society for a Warren Research Fellowship (R. A. A.).
References
7.55 (5 H, m) and 2.34 (3 H, s); δC 191.0 (C᎐O), 140.3 (4ry),
᎐
1 Part 12, R. A. Aitken, M. J. Drysdale, G. Ferguson and A. J. Lough,
J. Chem. Soc., Perkin Trans. 1, 1998, 875.
2 For a recent review see: R. A. Aitken and A. W. Thomas, in
Chemistry of the Functional Groups, Supplement A3, ed. S. Patai,
Wiley, Chichester, 1997, p. 503.
3 A. M. Van Leusen, A. J. W. Iedema and J. Strating, J. Chem. Soc.,
Chem. Commun., 1968, 440.
137.3 (4ry), 135.7 (2 C), 134.2, 130.7 (2 C), 129.4 (2 C), 128.1
(2 C), 124.5 (4ry) and 22.0; m/z 228 (Mϩ, 15%), 123 (5), 105
(100), 91 (4) and 77 (65).
S-(4-Chlorophenyl) thiobenzoate 7f. From 4-chlorothio-
phenol (16%) as colourless crystals, mp 57–59 ЊC (HRMS:
found Mϩ, 248.0057. C13H935ClOS requires M, 248.0063); νmax
/
cmϪ1 1680; δH 8.0–8.15 (2 H, m) and 7.2–7.7 (7 H, m); δC 190.0
4 L. Horner and H. Oediger, Chem. Ber., 1958, 91, 437; S. Trippett
and D. M. Walker, J. Chem. Soc., 1959, 3874.
(C᎐O), 136.9 (2 C), 136.5 (C-Cl), 134.5, 130.1 (2 C), 129.9 (4ry),
᎐
5 Preliminary communication, R. A. Aitken, M. J. Drysdale and
B. M. Ryan, J. Chem. Soc., Chem. Commun., 1993, 1699.
6 A. M. Hamid and S. Trippett, J. Chem. Soc. C, 1968, 1612; A. D.
Josey, USP 3 647 856/1972 (Chem. Abstr., 1972, 76, 141023).
7 M. Mikolajczyk, W. Perlikowska, J. Omelanczuk, H.-J. Cristeau and
A. Perraud-Darcy, Synlett, 1991, 913; H.-J. Cristeau, A. Perraud,
E. Manginot and E. Torreiles, Phosphorus Sulfur Silicon Relat.
Elem., 1993, 75, 7.
8 J.-H. Youn and R. Herrmann, Synthesis, 1987, 72.
9 C. G. Venier, H. J. Barager III and M. A. Ward, J. Am. Chem. Soc.,
1975, 97, 3238; K. Schank, in Houben-Weyl Methoden der
Organischen Chemie, 4th edn., Vol. E19b, ed. M. Regitz, Thieme,
Stuttgart, 1989, p. 1713.
129.4 (2 C), 128.1 (2 C) and 126.4 (4ry); m/z 250 (37Cl-Mϩ, 3%),
248 (35Cl-Mϩ, 10), 226 (4), 198 (2), 176 (4), 145 (6,), 143 (18),
122, (6), 105 (100), 91 (75) and 77 (92).
Preparation of substituted benzophenones. These were pre-
pared by Friedel–Crafts acylation of benzene with the
appropriate substituted benzoyl chloride in the presence of
aluminium chloride.
4-Methylbenzophenone 9e. Yellow solid (52%), mp 49–50 ЊC
(lit.,21 50–51 ЊC); δH 7.7–7.9 (4 H, m), 7.4–7.6 (3 H, m), 7.2–7.3
(2 H, m) and 2.43 (3 H, s); δ 196.3 (C᎐O), 143.2 (C-Me), 137.9
᎐
C
10 D. Hodson and G. Holt, J. Chem. Soc. (C), 1968, 1602.
11 C. F. Ebbinghaus, P. Morrissey and R. L. Rosati, J. Org. Chem.,
1979, 44, 4697.
12 P. E. O’Bannon and W. P. Dailey, Tetrahedron Lett., 1988, 29, 987,
5719.
(4ry), 134.9 (4ry), 132.1, 130.2 (2 C), 129.9 (2 C), 128.9 (2 C),
128.2 (2 C) and 21.6.
4-Chlorobenzophenone 9f. Off-white solid (84%), mp 72–73 ЊC
(lit.,22 75.5–76 ЊC); δH 7.7–7.8 (4 H, m) and 7.4–7.7 (5 H, m); δC
13 D. Frank, G. Himbert and M. Regitz, Chem. Ber., 1978, 111, 183.
14 M. Franck-Neumann and J. J. Lohmann, Tetrahedron Lett., 1979,
2397.
195.4 (C᎐O), 138.9 (C–Cl), 137.2 (4ry), 135.9 (4ry), 132.6, 131.4
(2 C), 129.9 (2 C), 128.6 (2 C) and 128.4 (2 C).
᎐
15 R. L. Rosati, L. V. Kapili, P. Morrissey, J. Bordner and E.
Subramanian, J. Am. Chem. Soc., 1982, 104, 4262.
16 A. R. Maguire, P. G. Kelleher and S. E. Lawrence, Tetrahedron Lett.,
1998, 39, 3849.
17 M. Mikolajczyk, University of Lodz, personal communication.
18 R. A. Aitken and J. I. Atherton, J. Chem. Soc., Perkin Trans. 1, 1994,
1281.
19 R. Otto and R. Lüders, Ber. Dtsch. Chem. Ges., 1880, 13, 1283.
20 R. Schiller and R. Otto, Ber. Dtsch. Chem. Ges., 1876, 9, 1634.
21 E. Ador and A. A. Rillet, Ber. Dtsch. Chem. Ges., 1879, 12, 2298.
22 M. Kollarits and V. Mertz, Ber. Dtsch. Chem. Ges., 1873, 6, 563.
23 L. Gatterman, Ber. Dtsch. Chem. Ges., 1895, 28, 2877.
24 B. F. Gofton and E. A. Braude, Org. Synth., 1955, 35, 98.
25 H. Tokunaga, K. Akiba and N. Inamoto, Bull. Chem. Soc. Jpn.,
1972, 45, 506.
Preparation of thiobenzophenones 8. These were prepared
according to the method of Gattermann23 by reaction of the
corresponding benzophenone 9 with an excess of phosphorus
pentasulfide in boiling xylene followed by evaporation and
distillation.
Thiobenzophenone 8d. Blue liquid (69%), bp 170 ЊC (oven
temp.) at 0.1 Torr (lit.,24 174 ЊC at 14 Torr) (HRMS: found, Mϩ,
198.0541. C13H10S requires M, 198.0503); λmax/nm 570; δH 7.25–
7.85 (10 H, m); δC 238.3 (C᎐S), 147.2 (2 C, 4ry), 131.9 (2 C),
᎐
129.6 (4 C) and 127.9 (4 C).
4-Methylthiobenzophenone 8e. Blue liquid (37%), bp 170 ЊC
(oven temp.) at 0.1 Torr (lit.,25 136–138 ЊC at 0.3 Torr) (HRMS:
found Mϩ, 212.0648. C14H12S requires M, 212.0660); λmax/nm
585; δ 7.1–7.8 (9 H, m) and 2.38 (3 H, s); δ 237.7 (C᎐S), 147.6
Paper 8/06182C
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J. Chem. Soc., Perkin Trans. 1, 1998, 3345–3348