Nucleophilic reactions of 5-(aryl)thianthrenium bromides with sodium aryl oxides

Article abstract of DOI:10.1002/poc.585

Reactions between 5-(aryl)thianthrenium bromides (1a-e) with aryl (Ar) groups phenyl (a), p-tolyl (b), p-anisyl (c), p-chlorophenyl (d) and p-bromophenyl (e) and sodium aryl oxides (7a-c, Ar′ONa, Ar′ = phenyl, p-tolyl and p-chlorophenyl) were carried out in acetonitrile at 80°C. Results are compared with those of earlier reactions of 1a-e with corresponding sodium aryl thiolates (Ar′SNa). In contrast with the thiolate reactions, those with 7a-c were too slow at room temperature to be useful. Reactions of 1a-c at 80°C gave small amounts of benzene and toluene from la and b, small amounts of diaryl ethers ArOAr′ (9) and thianthrene (Th) and large amounts (90-97%) of 2-(ArS)-2′-(Ar′O)diphenyl sulfide (10). Compared with reactions of 1a-c, those of 1d and e gave larger amounts (10-17%) of 9, lesser amounts (25-30%) of 10 and substantial amounts (42-55%) of 2-[4-(Ar′O)-ArS]-2′-(Ar′O)diphenyl sulfide (12). Small amounts of 1,4-di(Ar′O)benzene (11) were also obtained from reactions of Id and e. Formation of 11 and 12 is preceded by replacement of halogen by Ar′O^-. Structures of products 10 and 12 were deduced by comparison with earlier products from thiolate reactions, elemental analyses, mass spectrometry molecular masses and, in the case of 10, the crystal structure of 10d. It is proposed that products 9-12 are formed by nucleophilic reactions of Ar′O^- at ipso positions in 1. Copyright

Full text of DOI:10.1002/poc.585

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
J. Phys. Org. Chem. 2003; 16: 142–147
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/poc.585
Nucleophilic reactions of 5-(aryl)thianthrenium bromides
with sodium aryl oxides
Ding-Quan Qian,1 Henry J. Shine,1* John H. Thurston2 and Kenton H. Whitmire2
1Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA
2Department of Chemistry, Rice University, Houston, Texas 77005, USA
Received 3 June 2002; revised 27 September 2002; accepted 3 October 2002
ABSTRACT: Reactions between 5-(aryl)thianthrenium bromides (1a–e) with aryl (Ar) groups phenyl (a), p-tolyl (b),
epoc
p-anisyl (c), p-chlorophenyl (d) and p-bromophenyl (e) and sodium aryl oxides (7a–c, Ar'ONa, Ar' = phenyl, p-tolyl
and p-chlorophenyl) were carried out in acetonitrile at 80°C. Results are compared with those of earlier reactions of
1a–e with corresponding sodium aryl thiolates (Ar'SNa). In contrast with the thiolate reactions, those with 7a–c were
too slow at room temperature to be useful. Reactions of 1a–c at 80°C gave small amounts of benzene and toluene
from 1a and b, small amounts of diaryl ethers ArOAr' (9) and thianthrene (Th) and large amounts (90–97%) of 2-
(ArS)-2'-(Ar'O)diphenyl sulfide (10). Compared with reactions of 1a–c, those of 1d and e gave larger amounts (10–
17%) of 9, lesser amounts (25–30%) of 10 and substantial amounts (42–55%) of 2-[4-(Ar'O)-ArS]-2'-(Ar'O)diphenyl
sulfide (12). Small amounts of 1,4-di(Ar'O)benzene (11) were also obtained from reactions of 1d and e. Formation of
11 and 12 is preceded by replacement of halogen by Ar'OÀ. Structures of products 10 and 12 were deduced by
comparison with earlier products from thiolate reactions, elemental analyses, mass spectrometry molecular masses
and, in the case of 10, the crystal structure of 10d. It is proposed that products 9–12 are formed by nucleophilic
reactions of Ar'OÀ at ipso positions in 1. Copyright  2003 John Wiley & Sons, Ltd.
Additional material for this paper is available from the epoc website at http://www.wiley.com/epoc
KEYWORDS: 5-(aryl)thianthrenium; nucleophilic reactions; sodium aryl oxides
INTRODUCTION
RESULTS AND DISCUSSION
Reactions of 5-(aryl)thianthrenium bromides (1a–e) with
aryl thiolates (Ar'SÀ) were reported recently from these
laboratories.1 Diaryl sulfides (2), thianthrene (Th) and
tetraaryltrisulfides (3), Scheme 1, were the main products
from reactions of 1a–c. From 1a and b small amounts of
benzene and toluene were also formed. Reactions of 1d
and e gave smaller amounts of 2 and 3, but considerable
amounts of 1,4-(diarylthio)benzenes (4) and pentaaryl-
tetrasulfides (5). It was deduced that the products 2–5 and
Th were formed by ligand coupling routes within
sulfurane intermediates (6). We have now studied for
comparison the reactions of 1a–e with analogous sodium
aryl oxides, NaOAr' (7a–c), Ar' = phenyl (a), p-tolyl (b)
and p-chlorophenyl (c).
The structures of reactants 7 and of products 8–12 are
given in Scheme 2. Structures of 10 and 12 were
deduced from analogous reactions with aryl thiolates,1
1
analytical data, satisfactory H NMR spectroscopy and,
in the case of 10, the crystal structure of 10d. In contrast
with reactions of 1a–e with aryl thiolates, which
occurred readily at room temperature, reactions with
the aryl oxides at room temperature were too slow to
follow to completion. These reactions, therefore, were
carried out at 80°C. As in the earlier work, the tabulated
results are divided into two groups, those of 1a–c
reactions in Table 1 and those of 1d and e reactions in
Table 2. The main product (91–97%) from reactions of
1a–c was a 2-(arylthio)-2'-(aryloxy)diphenyl sulfide
(10). Small amounts of diaryl ether (9) were formed,
the yields of those from 1a being notably larger than
from 1b and c. Small amounts of benzene (8a) and
toluene (8b) were obtained from 1a and b. In the
reactions of 1d and e substantial amounts (10–17%) of
diaryl ether (9) were formed, a contrast, particularly,
with the amounts of 9 (ꢀ1%) that were obtained from 1b
and c. Opening of the thianthrenium ring of 1d and e,
giving products 10 and 12, was again the dominant
*Correspondence to: H. J. Shine, Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
E-mail: qvhjs@ttacs.ttu.edu
Contract/grant sponsor: Robert A. Welch Foundation; Contract/grant
number: D-0028; Contract/grant number: C-0976.
Contract/grant sponsor: National Science Foundation; Contract/grant
number: CHE-9983352.
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 142–147

NUCLEOPHILIC REACTIONS OF 5-(ARYL)THIANTHRENIUM BROMIDES WITH Na ARYL OXIDES
143
Scheme 1
reaction. In these reactions, the formation of 12,
representing 60–70% of ring-opening reaction, had to
be preceded by replacement of the halogen atom in 1.
Surprisingly, very little 1,4-(diaryloxy)benzene (11) was
formed, in contrast with the reactions of 1d and e with
thiolates,1 in which substantial amounts (33–70%) of the
analogous 1,4-(diarylthio)benzene were obtained. The
last column in each table is an account of the fate of the
thianthrene ring in 1, amounting to 93–101% in Table 1
and 92–101% in Table 2. In principle, the sum of yields
of 8 and 9 in Table 1 and of 9 and 11 in Table 2 should
equal the yield of Th, an accounting that is met only
approximately.
In the reactions of 1a–e with aryl thiolates, we have
argued the case that the formation of diaryl sulfides (2)
and opening of the thianthrenium ring occurred by ligand
coupling (LC) within sulfurane intermediates (6, X = H,
Me, MeO, Cl, Br, Ar'S). Developing such a case for the
reactions of 1a–e with 7a–c is not so compelling. There
are differences in the relative amounts of products in the
thiolate and aryl oxide reactions that prompt this
conclusion. Most striking is the paucity in the amounts
(0–3.4%) of 1,4-di(aryloxy)benzenes (11a–c) as com-
pared with the amounts (33–70%) of 1,4-(diarylthio)ben-
zenes (4).1 Formation of 11, as with formation of 4,
requires first the replacement of halogen in 1 by the
nucleophile, Ar'OÀ in the present case. It is evident from
the yields of 12a–c (42–55%) that this is a facile reaction.
Once replacement had occurred (13, Scheme 3), however,
continuation to formation of 11 and thianthrene (Th) was
apparently inhibited. Instead, 13 was carried on mostly to
12 by further reaction with Ar'OÀ. Inhibition of formation
of 11 could result from the formation of a sulfurane (14,
Scheme 4) in which the aryloxyaryl and aryloxy groups
were both apical, allowing LC to give 12 but incapable of
leading to 11. Apical alkyloxy groups (RFO) in a stable
sulfurane of thianthrene have been reported by Perozzi
and Martin.2 If this were the case with 11, we would have
to abandon it, however, for example, for 9i–k, which were
obtained in significant amounts (11–17%). That is,
analogously oriented apical groups in the sulfurane 15
would not allow for the formation of 9. A more consistent
interpretation of formation of 9 and 11, then, is ipso
nucleophilic attack (Scheme 5). The trend in yields of 9
(Tables 1 and 2), in the order X = Br >Cl >H >Me
ꢁMeO, suits the electronic effects of X on nucleophilic
attack at the position in XC6H4 ipso to the sulfonium
sulfur atom, with Hammett ꢀp = 0.232 (Br), 0.227 (Cl),
À0.170 (Me) and À 0.268 (MeO).3 Inhibition of forming
11 by nucleophilic attack of Ar'OÀ on the ipso position in
13 is similarly understandable, with, for example, sp
(PhO) = À0.320.3
The formation of small amounts of benzene from 1a
and of toluene from 1b no doubt requires the reaction of
7a–c at the sulfonium sulfur atom of 1a and b.
Nevertheless, the thiophilicity of the aryl thiolates
appears not to be shared by the aryl oxides, so that the
formation of the other products of these reactions is better
attributable to aromatic nucleophilic substitution rather
than to LC reactions, as is shown in Scheme 5. In this
Scheme, path a, which leads to 9 or 11, is inhibited by
electron-donating groups (Me, MeO, Ar'O), causing path
b, which leads to 10 or 12, to be dominant.
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 142–147

144
D.-Q. QIAN ET AL.
Marriott, Rice University, and elemental analyses were
carried out by Desert Analytics (Tucson, AZ, USA).
Some diaryl ethers and phenols for preparing sodium aryl
oxides were obtained from commercial sources. The
preparation of 5-(aryl)thianthrenium bromides (1a–e) has
been described earlier.1
Sodium aryl oxides (7a±c). An example is given with
sodium phenoxide (7a). A solution of 43 g (0.46 mmol)
of phenol in 50 ml of dry diethyl ether was added to a
protected, stirred suspension of 5.5 g (0.24 mmol) of
sodium in 100 ml of diethyl ether. Stirring was continued
until sodium could no longer be seen. The white solid
product was filtered, washed with hexane to remove
phenol and dried under vacuum, to give 24 g (0.21 mmol,
87%) of 7a.
Diaryl ethers (9) and 1,4-(diaryloxy)benzenes (11).
These were prepared essentially as described.5 A stirred
mixture of the appropriate phenol (48 mmol) and KOH
(30 mmol) was heated to 140°C until water no longer
distilled off. Next, the appropriate aryl halide (20 mmol)
and 240 mg of electrolytic grade Cu powder were added,
and heating was continued at 170–180°C for 14–18 h.
Aqueous NaOH was added to the mixture, which was
then extracted with diethyl ether. The residue from
evaporation of the dried ether solution was either distilled
under reduced pressure or passed through a column of
silica gel before crystallization from hot ethanol.
9b, from phenol and 4-bromotoluene, 64%, b.p. 160–
162°C/70 mmHg. Lit.6 b.p. 227–228°C.
9e, from p-cresol and 4-bromochlorobenzene, 75%,
m.p. 54–55°C. Lit.7 m.p. 55–56°C.
9f, from phenol and 4-bromoanisole, 83%, b.p. 176–
178°C/20 mmHg. Lit.8 b.p. 168–170°C/15 mmHg.
9g, from p-cresol and 4-bromoanisole, 82%, m.p. 47–
47.5°C. Lit.9 m.p. 45–46°C.
9h, from 4-chlorophenol and 4-bromoanisole, 83%,
m.p. 54–55°C. Lit.10 oil.
9j, from p-cresol and 1,4-dibromobenzene, 35%, m.p.
68.5–69°C. Lit.5 m.p. 67°C.
9k, from 4-chlorophenol and 1,4-dibromobenzene,
37%, m.p. 40–41°C. Lit.5 m.p. 36°C.
9l, from 4-chlorophenol and 4-bromochlorobenzene,
61%, m.p. 28–29°C. Lit.11 m.p. 30°C.
11a, from phenol and 1,4-dibromobenzene, 38%, m.p.
74.5–75.5°C. Lit.12 m.p. 76°C.
11b, from p-cresol and 1,4-dibromobenzene, separated
chromatographically from 9j, 40%, m.p. 104.5–105.5°C.
Lit.5 m.p. 106°C.
Scheme 2
11c, from 4-chlorophenol and 1,4-dibromobenzene,
separated chromatographically from 9k, 36%, m.p. 99.5–
100.5°C. Lit.5 m.p. 100°C.
EXPERIMENTAL
The method of drying solvent MeCN and the columns A
and B for gas chromatography (GC) have been described
earlier.4 Mass spectrometric data were supplied by Dr T.
Reactions of 5-(aryl)-thianthrenium bromides (1a±e)
with sodium aryl oxides (7a±c) at 80°C. Reactions at
room temperature were found to be too slow to be useful
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 142–147

NUCLEOPHILIC REACTIONS OF 5-(ARYL)THIANTHRENIUM BROMIDES WITH Na ARYL OXIDES
Table 1. Products of reactions of 1a±c with 7a±ca
145
Reactants
Products (%)b
9c
Run
1
7
8c
10d
Thc
Sum (%) (Th ‡ 10)
1
2
3
4
5
6
7
8
9
a
a
a
b
b
b
c
a
b
c
a
b
c
a
b
c
a, 2.9
a, 3.8
b, 6.4
c, 8.7
b, 1.9
d, 0
e, 0.9
f, 0.1
g, 1.2
h, 0.2
a, 90
b, 97
c, 91
d, 92
e, 96
f, 95
g, 91
h, 92
i, 93
6.7
4.1
7.7
3.6
0
2.3
2.9
1.2
1.3
97
101
99
b, 0.8
96
96
97
94
c
93
c
94
a
In MeCN at 80°C.
b
c
d
e
Yields are based on the amount of 1.
GC yield.
Isolated yield.
Average of two runs.
Table 2. Products of reactions of 1d and e with 7a±ca
Reactants
Products (%)b
Run
1
7
9c
10d
11c
12d
Thc
Sum (%) (Th ‡ 10 ‡ 12)
1
2
3
4
5
6
d
d
d
e
a
b
c
a
b
c
c, 10
e, 11
l, 11
i, 17
j, 16
k, 17
m, 25
n, 28
o, 25
j, 30
k, 31
l, 23
a, 1.8
b, 0.3
c, 3.4
a, 0
b, 0.4
c, 3.2
a, 55
b, 49
c, 49
a, 42
b, 42
c, 55
14
15
18
22
24
23
94
92
92
94
97
101
e
e
a
In MeCN at 80°C.
Based on the amount of 1.
GC yield.
b
c
d
Isolated yield.
and were therefore carried out at 80°C in either a septum-
capped flask or in a sealed ampule. Examples are given
with 1a and 1e.
by three extractions with diethyl ether. Evaporation of the
dried ether solution gave a residue which was placed on a
silica gel column. Naphthalene, Th and 9a were washed
from the column with petroleum ether (PE). Elution with
PE–diethyl ether (20:1) gave 260 mg (0.673 mmol, 90%)
of 2-phenoxy-2'-(phenylthio)diphenyl sulfide (10a), m.p.
75–77°C.
Reaction of 1e with 7a. The same procedure was used
with 289 mg (0.640 mmol) of 1e and 372 mg (3.20 mmol)
of 7a, but with the omission of butanone. Elution with
PE–diethyl ether (20:1) gave 50.2 mg of 10j, 94.6 mg of
Reaction of 1a with 7a. A mixture of 279 mg
(0.746 mmol) of 1a, 354 mg (3.05 mmol) of 7a and
naphthalene as GC standard in 20 ml of MeCN was
heated in a septum-capped flask at 80°C for 2 days. After
adding butanone to the cooled solution as a second GC
standard, assay for 9a and thianthrene was carried out on
column A and of benzene (8a) on column B. The solution
was then poured into 50 ml of water, which was followed
Scheme 3
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 142–147

146
D.-Q. QIAN ET AL.
10h, calcd for C26H22S2O2: C, 72.5; H, 5.15; S, 14.9.
Found: C, 72.8; H, 5.11; S, 14.5%.
10i, calcd for C25H19S2O2Cl: C, 66.6; H, 4.25; S, 14.2;
Cl, 7.86. Found: C, 66.5; H, 4.28; S, 14.1; Cl, 7.47%.
10j, calcd for C24H17S2OBr: C, 61.9; H, 3.68; S, 13.8;
Br, 17.2. Found: C, 62.0; H, 3.49; S, 14.0; Br, 16.8%.
10k, calcd for C25H19S2OBr: C, 62.6; H, 3.99; S, 13.4;
Br, 16.7. Found: C, 62.5; H, 3.94; S, 13.8; Br, 16.6%.
10n, calcd for C25H19S2OCl: C, 69.0; H, 4.40; S, 14.7;
Cl, 8.15. Found: C, 69.1; H, 4.29; S, 15.0; Cl, 7.84%.
Scheme 4
12a and a mixture of the two. The mixture was
rechromatographed to give 39.5 mg of 10j and 35.1 mg
of 12a. Thus the yield of 10j (0.193 mmol) was 30% and
that of 12a (0.271 mmol) was 42%. 10j was crystalliized
from hot ethanol and had m.p. 75–75.5°C, but 12a
remained as an oil. All other reactions were carried out
similarly.
Mass spectrometry. Molecular masses were measured
on all products 10 and 12 that did not crystallize. The
error in ppm is given in parentheses.
10c, calcd for C24H17S2OCl: 420.040939. Found:
420.040370 (1.4).
10g, calcd for C25H20S2O2: 416.090475. Found:
416.090354 (0.29).
10l, calcd for C24H16S2OBrCl: 497.951461. Found:
497.951497 (0.072).
10m, calcd for C24H17S2OCl: 420.040939. Found:
420.040821 (0.28).
10o, calcd for C24H16S2OCl2: 454.001966. Found:
454.001535 (0.95).
12a, calcd for C30H22S2O2: 478.106125. Found:
478.106030 (0.20).
Attempted preparation of 1,4-bis(phenoxy)benzene
(11a) by reaction of 4-bromodiphenyl ether (9i) with
7a at 80°C. A mixture of 168 mg (0.674 mmol) of 9i and
287 mg (2.48 mmol) of 7a in 20 ml of MeCN was stirred
for 3 days at 80°C. GC analysis of the cooled solution
failed to show the presence of 11a.
Elemental analyses. Analyses were obtained for all
crystalline products 10.
10a, calcd for C24H18S2O: C, 74.6; H, 4.66; S, 16.6.
Found: C, 74.5; H, 4.68; S, 16.3%.
12b, calcd for C32H26S2O2: 506.137425. Found:
506.137682 (0.51).
12c, calcd for C30H20S2O2Cl2: 546.028181. Found:
546.027669 (0.94).
10b, calcd for C25H20S2O: C, 75.0; H, 5.03; S, 16.0.
Found: C, 74.9; H, 4.83; S, 15.7%.
10d, calcd for C25H20S2O: C, 75.0; H, 5.03; S, 16.0.
Found: C, 74.7; H, 5.07; S, 16.2.
NMR spectroscopy of 10 and 12. 1H NMR spectra were
recorded for most of these compounds in CDCl3 at 300 or
500 MHz; ꢁ in ppm, J in Hz.
10e, calcd for C26H22S2O: C, 75.3; H, 5.35; S, 15.5.
Found: C, 75.0; H, 5.22; S, 15.4%.
10f, calcd for C25H19S2OCl: C, 69.0; H, 4.40; S, 14.7;
Cl, 8.15. Found: C, 69.2; H, 4.21; S, 14.5; Cl, 8.17%.
10b, 300, ꢁ: 7.366–7.078, m, 13H; 7.047–6.996, m,
1H; 6.862, dd, 3H, J = 6.8, 1.7 (av.); 2.322, s, 3H.
10d, 300, ꢁ: 7.336–7.258, m, 5H; 7.142–6.930, two m,
12H; 2.342, s, 3H.
Scheme 5
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 142–147

NUCLEOPHILIC REACTIONS OF 5-(ARYL)THIANTHRENIUM BROMIDES WITH Na ARYL OXIDES
147
as described earlier1 for the Ortep diagram in Fig. 1.
Attempts to grow single crystals of other products 10
were not made.
Supplementary material
Five tables giving crystal data and structural refinements,
atomic coordinates and equivalent isotropic displacement
parameters, bond lengths and angles, anisotropic dis-
placement parameters, and hydrogen coordinates and
equivalent isotropic displacement parameters for 2-(p-
tolylthio)-2'-(phenoxy)diphenyl sulfide, C25H20OS2, are
available at the epoc website at http://www.wiley.com/
epoc. The crystal structure has been deposited at the
Cambridge Crystallographic Data Centre (deposition
number: 193527).
Figure 1. Ortep diagram of 2-(p-tolylthio)-2'-(phenyloxy)di-
phenyl sul®de (10d)
Acknowledgements
10e, 500, ꢁ: 7.307–7.284, m, 3H; 7.190–7.156, m, 1H;
7.134–7.088, m, 7H; 7.028–6.972, m 2H; 6.892–6.857,
m, 3H; 2.342, s, 3H; 2.321, s, 3H.
10f, 300, ꢁ: 7.296–7.234, m, 6H; 7.151–7.090, m, 6H;
6.936–6.876, m, 4H; 2.353, s, 3H.
We thank the Robert A. Welch Foundation for support
under Grants D-0028 (H.J.S) and C-0976 (K.H.W) and
the National Science Foundation under Grant CHE-
9983352 (K.H.W).
10g, 300, ꢁ: 7.398–7.289, m, 5H; 7.200–6.980, m, 8H;
6.930–6.829, m, 4H; 3.815, s, 3H.
10h, 300, ꢁ: 7.406–7.327, m, 3H; 7.187–6.999, m, 7H;
6.915–6.836, m, 6H; 3.820, s, 3H; 2.324, s, 3H.
10i, 300, ꢁ: 7.392–7.245, m, 3H; 7.106–6.939, m, 7H;
6.928–6.841, m, 6H; 3.829, s, 3H.
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