Safe Preparation of Alkyl Aryl and Diaryl Sulfides
J . Org. Chem., Vol. 65, No. 18, 2000 5605
arenediazonium o-benzenedisulfonimides (1; Ar ) Ph; 2-, 3-,
and 4-MeC6H4; 2-, 3-, and 4-MeOC6H4; 2-, 3-, and 4-ClC6H4;
2-, 3-, and 4-BrC6H4; 2-, 3- and 4-O2NC6H4; 2-MeSC6H4;
2-naphthyl; 2,4-(O2N)2C6H3; 2,6-Me2C6H3; 2,6-F2C6H3; 2,6-
Cl2C6H3; 2,6-Br2C6H3) were prepared as described previously
by us.1 The crude salts were virtually pure and could be used
in the next alkyl- and arylthiodediazoniations, without further
crystallization.
(1, Ar ) Ph; 1.62 g, 5 mmol) was added in one portion with
vigorous stirring to a solution of sodium methanethiolate (4,
R ) Me; 0.39 g, 5.5 mmol) in anhydrous MeOH (10 mL),
previously cooled at 0-5 °C with an ice bath. The salt dissolved
at once, and the resultant solution became temporary deep
orange and then cleared quickly to yellow. Simultaneously a
plentiful evolution of nitrogen took place and a fine solid
substance constituted of sodium o-benzenedisulfonimide (5)
began to precipitate. A test of azo coupling with 2-naphthol,
carried out immediately after the addition of the salt, was
negative. This confirmed a sudden reaction of the diazonium
salt. TLC (PE), GC, and GC-MS analyses of the reaction
mixture showed the presence of dimethyl disulfide (6; R ) Me),
MS m/z 94 (M+), and the title compound, MS m/z 124 (M+), as
major product. GC-MS analysis showed also the presence of
benzene (7; Ar ) Ph), MS m/z 78 (M+). The intermediate
(methylsulfanyl)(phenyl)diazene (2; Ar ) Ph, R ) Me) was not
observed on TLC. The products were isolated according to the
following procedures.
Dr y Ar en ed ia zon iu m o-Ben zen ed isu lfon im id es (1).
Rep r esen ta tive P r oced u r e. Dr y 4-Cya n oben zen ed ia zo-
n iu m o-Ben zen ed isu lfon im id e (1; Ar ) 4-NCC6H4). Ac-
cording to the procedure previously reported,1 diazotization
of 4-cyanoaniline (1.18 g, 10 mmol) was carried out with
isopentyl nitrite (1.29 g, 11 mmol) in the presence of o-
benzenedisulfonimide (8; 2.63 g, 12 mmol) in glacial AcOH (60
mL) at 0-5 °C. The virtually pure (NMR, dp) title compound
was obtained in 92% yield (3.20 g). For analytical purposes, a
sample was purified by dissolution in hot anhydrous acetoni-
trile and precipitation with anhydrous Et2O after cooling: dp
(dec point) 126-128 °C; 1H NMR (CF3COOD) δ 7.40-7.75 (m,
4 H), 7.88 and 8.42 ppm (2 d, 1:1, J ) 8.5 Hz, 4 H). Anal. Calcd
for C13H8N4O4S2: C, 44.82; H, 2.31; N, 16.08; S, 18.41. Found:
C, 44.93; H, 2.40; N, 16.17; S, 18.34. Yields and physical and
specral data of the new diazonium salts are given below.
Ca u tion ! In our laboratory was no case of sudden decom-
position during the preparation, purification, and handling of
salts 1. Nevertheless it must be born in mind that all
diazonium salts in the dry state are potentially explosive.
Therefore they must be carefully stored and handled.
Dr y 4-Ca r boxyben zen ed ia zon iu m o-Ben zen ed isu lfon -
P r oced u r e A: the reaction mixture was poured into Et2O-
water (100 mL, 1:1). The aqueous layer was separated and
extracted with Et2O (2 × 50 mL). The combined organic
extracts were washed with water (2 × 50 mL), dried over Na2-
SO4, and evaporated under reduced pressure. The crude
residue was chromatographed on
a short column, using
pentane as eluent. The first eluted product was dimethyl
disulfide (it was isolated in variable amounts, because no
particular device was adopted to avoid its loss during the
solvent evaporation). The second eluted product was the pure
(GC, GC-MS, TLC, NMR) title compound (0.51 g, 82% yield).
Identical physical and spectral data and retention time, by co-
injection, for the product and a commercially available sample
of analytical purity were observed. The aqueous layer and the
aqueous washings containing the salt 5 were collected and
evaporated under reduced pressure. The residue was passed
through a column of Dowex 50X8 ion-exchange resin (1.6 g
for 1 g of product), eluting with water (about 35 mL). After
removal of the water under reduced pressure, virtually pure
(NMR) o-benzenedisulfonimide (8) was recovered in 81% yield
(0.89 g); mp 192-194 °C (toluene) (lit.1 mp 192-194 °C).
1
im id e (1; Ar ) 4-HOOCC6H4). 94% (3.44 g); dp 136 °C; H
NMR (CF3COOD) δ 7.55-7.95 and 8.25-8.70 ppm (2 m, 1:1).
Anal. Calcd for C13H9N3O6S2: C, 42.51; H, 2.47; N, 11.44; S,
17.45. Found: C, 42.41; H, 2.48; N, 11.34; S, 17.53.
Dr y 4-Meth oxyca r bon ylben zen ed ia zon iu m o-Ben zen e-
d isu lfon im id e (1; Ar ) 4-MeOOCC6H4). 97% (3.69 g); dp
1
103-105 °C; H NMR (CF3COOD) δ 3.93 (s, 3 H), 7.60-7.90
and 8.12-8.52 ppm (2 m, 1:1,
8 H). Anal. Calcd for
14H11N3O6S2: C, 44.09; H, 2.91; N, 11.02; S, 16.81. Found:
C
C, 44.20; H, 3.00; N, 11.04; S, 16.70.
Dr y 2-Hyd r oxyben zen ed ia zon iu m o-Ben zen ed isu lfon -
im id e (1; Ar ) 2-HOC6H4). 83% (2.81 g); dp 162 °C; 1H NMR
(CF3COOD) δ 6.60-7.10 and 7.30-7.80 ppm (2 m, 1:3). Anal.
Calcd for C12H9N3O5S2: C, 42.47; H, 2.67; N, 12.38; S, 18.90.
Found: C, 42.56; H, 2.76; N, 12.33; S, 18.82.
P r oced u r e B: the reaction mixture was stirred at 0-5 °C
for a further 30 min, to complete the precipitation of 5, which
was gathered by filtration on a Buchner, washed with cold
MeOH (3-4 mL), and then passed through a Dowex column.
o-Benzenedisulfonimide (8) was recovered in yield comparable
to that obtained in procedure A. The methanolic filtrate and
washings were collected and diluted with Et2O (150 mL). The
organic solution was washed several times with water (4 ×
50 mL) and dried over Na2SO4. By a workup identical to that
described in Procedure A, the pure (GC, GC-MS, TLC, NMR)
title compound was obtained in comparable yield.
Dr y 4-Hyd r oxyben zen ed ia zon iu m o-Ben zen ed isu lfon -
im id e (1; Ar ) 4-HOC6H4). 87% (2.94 g); dp 138-139 °C; 1H
NMR (CF3COOD) δ 6.75 (d, J ) 8.5 Hz, 2 H), 7.25-7.62 (m, 4
H), 7.82 ppm (d,
12H9N3O5S2: C, 42.47; H, 2.67; N, 12.38; S, 18.90. Found: C,
42.40; H, 2.74; N, 12.31; S, 18.80.
J ) 8.5 Hz, 2 H). Anal. Calcd for
C
Dr y 2,6-Diflu or oben zen ed ia zon iu m o-Ben zen ed isu l-
The reaction was also carried out under an atmosphere of
nitrogen. Neither the reaction rate nor yields of the products
changed.
1
fon im id e (1; Ar ) 2,6-F 2C6H3). 93% (3.36 g); dp 170 °C; H
NMR (CF3COOD) δ 7.10-7.50, 7.50-7.90 and 8.00-8.40 ppm
(3 m, 2:4:1). Anal. Calcd for C12H7F2N3O4S2: C, 40.11; H, 1.96;
F, 10.57; N, 11.69; S, 17.84. Found: C, 40.21; H, 2.01; F, 10.66;
N, 11.80; S, 17.75.
All the aryl methyl sulfides (3, R ) Me) reported in entries
2-23 of Table 1 were prepared according to the above
procedure. In particular, entries 13-15 and 23 were carried
out at -15 °C to avoid too fast reactions.
Entry 17 was carried out at -78 °C to minimize the
competitive hydrodediazoniation. Under these conditions the
crude residue was virtually pure (TLC, NMR) 4-(methylsul-
fanyl)benzoic acid. When the same reaction was carried out
at 0 °C, two products were instead obtained, i.e., 4-(methyl-
sulfanyl)benzoic acid and benzoic acid, in a 5:1 GC ratio.
Dr y 2,6-Dibr om oben zen ed ia zon iu m o-Ben zen ed isu l-
fon im id e (1; Ar ) 2,6-Br 2C6H3). 99% (4.76 g); dp 126-128
°C; 1H NMR (CF3COOD) δ 7.45-7.80 ppm (m). Anal. Calcd
for C12H7Br2N3O4S2: C, 29.96; H, 1.47; Br, 33.21; N, 8.73; S,
13.33. Found: C, 29.87; H, 1.51; Br, 33.26; N, 8.65; S, 13.23.
Ca u tion ! Diazosulfides can decompose violently when not
in solution. In the reactions described in this work most of
the diazosulfides formed as intermediates reacted immedi-
ately. However in all cases, also when the conversion of the
diazosulfides in the final products was slow, they were fully
dissolved in MeOH. Although no accident took place during
our work, caution is needed during the handling of the reaction
mixtures till the intermediate diazosulfides are present.
Meth ylth iod ed ia zon ia tion s of Dr y Ar en ed ia zon iu m
o-Ben zen ed isu lfon im id es (1). R ep r esen t a t ive P r oce-
d u r es. Meth yl P h en yl Su lfid e (3; Ar ) P h , R ) Me). In
entry 1 of Table 1 benzenediazonium o-benzenedisulfonimide
Entries 19 and 20 were carried out at room temperature.
In these cases the workup was slightly modified, i.e., the
reaction mixture was directly concentrated under reduced
pressure and the crude residue was column chromatographed,
using at first PE/Et2O (9.5:0.5, v/v) and then water, to elute
2- or 4-(methylsulfanyl)phenol and, respectively, sodium o-
benzenedisulfonimide (5). The aqueous solution was concen-
trated and passed through Dowex to recover o-benzenedi-
sulfonimide (8).