Photo-Stevens rearrangement reaction of S-naphthylmethyl-N-p-tosylsulfimides

Article abstract of DOI:10.1039/a703455e

Photolysis sulfimides unexpectedly led to Stevens rearrangement products.

Full text of DOI:10.1039/a703455e

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Photo-Stevens rearrangement reaction of S-naphthylmethyl-N-p-tosylsulfimides
Hiroyuki Morita,* Hideo Kamiyama, Miho Kyotani, Takayoshi Fujii, Toshiaki Yoshimura, Shin Ono and
Choichiro Shimasaki
Department of Chemical and Biochemical Engineering, Faculty of Engineering, Toyama University, 3190 Gofuku, Toyama 930,
Japan
Photolysis sulfimides unexpectedly led to Stevens rearrange-
ment products.
did not proceed at all. This result suggests that a napthyl group
is necessary in this reaction as a useful chromophore to accept
photoirradiation and to initiate the photoreaction. Therefore,
measurements of the UV–VIS spectra of 1a–d were carried out
and showed, as expected, the existence of a strong absorption
band (loge = 4.9) around 230 nm, extending beyond the 300 nm
region as shoulders, while 1e showed no absorption beyond 300
nm.
In the thermal reaction of sulfimides, the products derived via
Stevens rearrangement were reported to be formed.1 In the
photolysis of sulfimides, however, it is reported that nitrenes are
initially generated via a photo-induced cleavage of the S–N
linkage.2 In contrast to this mechanistic route for photolytic
decomposition of sulfimides, another route via Stevens re-
arrangement was recently reported for the particular case of a
cyclic sulfimide derivative, i.e. N-tosylnaphtho[1,8-de]-
A
further study of the photolysis of S-(2-pyridyl)-
S-(1-naphthylmethyl)-N-p-tosylsulfimide 1a in several solvents
was carried out under the same conditions. The products formed
were found to depend significantly on the nature of solvents
used. In aprotic solvents such as CH2Cl2 and MeCN, the
primary rearranged product 2a¶ was formed as the major
product; however, in acetone the secondary products 3a and 4a
were the major products, presumably due to acceleration of the
photochemical excitation of 2a by probable triplet sensitization
of acetone, as suggested by Guo and Jenks in the photolysis of
sulfoxide.4 Meanwhile, in alcoholic solvents, another mecha-
nistic path is apparently involved and toluene-p-sulfonamide 6,
as well as the products 3a and 4a via Stevens-type rearrange-
ment, was formed predominantly. One possibility for this
mechanism is the nitrene pathway, which would immediately
lead to sulfonamide 6 and the corresponding sulfide, which is
observed to decompose to 3a and 5a under the same conditions.
Another possibility is a pathway involving the initial protona-
tion at the iminonitrogen atom of the sulfimide and subsequent
4
1l ,3-dithiin-1-imine, which rearranged to naphtho[1,8-ef]-
[1,4,2]dithiaazepine, followed by de-imination to give N-p-
tosylaldimines and naphtho[1,8-cd]-1,2-dithiole quantita-
tively.3 In this reaction the driving force apparently results from
formation of a stable cyclic disulfide via the through-space
interaction between the two sulfur atoms at the 1,8-positions of
naphthalene.
In order to study more precisely and photolytic behaviour of
acyclic sulfimide derivatives, we prepared several S-naphthyl-
methyl-N-p-tosylsulfimides and carried out their photolysis
using a high-pressure mercury lamp with a Pyrex filter under
nitrogen.† When 1a‡ was irradiated in degassed MeOH under
these conditions, the major products were dipyridyl disulfide 3a
and N-(naphthylmethyl)toluene-p-sulfonamide 4a.§ In view of
the formation of 4a, the reaction is considered to pass through a
rearrangement mechanism, i.e. a Stevens-type rearrangement as
depicted in Scheme 1. Here we report the first examples of this
photo-induced
S-naphthylmethyl-N-p-tosylsulfimide derivatives.
Stevens
rearrangement
reaction
in
a
Table 1 Photolysis of N-tosylsulfimides 1 in CH2Cl2
S-Aryl- or S-alkyl-S-naphthylmethyl-N-p-tosylsulfimides
1a–e were prepared by the reaction of the corresponding
sulfides with the sodium salt of N-chlorotoluene-p-sulfonamide
(Chloramine T) in MeCN in high yields. Photolysis of
S-naphthylmethyl-N-p-tosylsulfimides in degassed CH2Cl2 was
carried out under the previously described conditions for 2 h.
The results are summarized in Table 1. The photolyses of
S-pyridyl-, S-phenyl- and even S-methyl-S-(1-naphthylmethyl)-
or S-(2-naphthyl-methyl)-N-p-tosylsulfimide derivatives 1a–d
(entries 1–4) were found to lead to the Stevens rearrangement
product 2, as well as 3 and 4, which are formed by photolysis of
2 in a secondary photochemical step, while in the photolysis of
S-benzyl-S-phenyl-N-p-tosylsulfimide 1e (entry 5), the reaction
Yield (%)b
Entry
Compound
Conversion (%)
2
3
4
1
2
3
4
5
1a
1b
1c
1d
1e
100
92
94
63
0
27
47
40
54
—
45
37
33
—
—
72
46
30
42
—
c
a Irradiation with a 400 W high-pressure Hg lamp; concentration: 0.2 mmol;
reaction time = 2 h. b Isolated yield. c Dimethyl disulfide not isolated.
Table 2 Photolysis of S-(2-pyridyl)-S-(naphthylmethyl)-N-p-tosylsulfimide
1a in different solventsa
NTs
CH R2
Ts
N
hν (>300 nm)
Yield (%)b
1
R S
R1S
CH2R2
2
CH2Cl2
1a R1 = 2-pyridyl, R2 = 1-naphthyl
b R1 = 2-pyridyl, R2 = 2-naphthyl
c R1 = Ph, R2 = 1-naphthyl
d R1 = Me, R2 = 1-naphthyl
e R1 = Ph, R2 = Ph
2
Solvent
2a
3a
4a
5a
6
hν
MeOH
PriOH
CH2Cl2
MeCN
Me2CO
0
0
27
15
0
25
38
45
33
41
15
34
72
54
74
7
21
trace
trace
4
64
57
0
0
0
Ts
R1SSR1
H
NCH2R
2
3
4
R2C2H4R2
TsNH2
5
6
a Irradiation with a 400 W high-pressure Hg lamp: concentration: 0.2 mmol;
reaction time = 2 h. Isolated yield.
Scheme 1
Chem. Commun., 1997
1347

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formation of an alkoxysulfonium salt (counter anion TsNH2)
which eventually decomposes to the corresponding sulfide and
a carbonyl compound.∑ A similar mechanism was suggested by
Oae in the case of the thermolysis of N-p-tosylsulfimides in
MeOH.1a
Footnotes
* E-mail: morita@sci.toyama-u.ac.jp
† All photolyses were carried out in 9 mm i.d. Pyrex glass tubes, sealed with
a septum under nitrogen atmosphere at room temperature, with irradiation
from a 400 W high-pressure mercury lamp.
In order to confirm the mechanistic pathway of this
photoreaction, the product distribution in the course of
photolysis of 1a in CH2Cl2 under the previously described
conditions was determined by quantitative analysis with HPLC.
The result is illustrated in Fig. 1; the amount of starting
sulfimide 1a decreased gradually, and three new species
appeared. Two were found to be di(2-pyridyl) disulfide 3a and
N-(1-naphthylmethyl)toluene-p-sulfonamide 4a by comparing
their HPLC retention times and their spectral data with those of
authentic compounds prepared or separated by chromatog-
raphy. The third species showed a maximum after 40 min and
then gradually decreased. This probably points to the existence
of the intermediate 2 in this reaction, which apparently reacted
to give the products 3a and 4a. Therefore, the reaction mixture
was separated by HPLC after 40 min photolysis and the product
corresponding to this intermediate was identified as 2a. Further,
in order to clarify that 2a is exactly the intermediate of this
reaction, photolysis of 2a thus separated was carried out under
the same conditions to afford the expected products 3a and 4a
in good yields. All these results indicate clearly that this
reaction proceeds via a photo-induced Stevens rearrangement to
afford the intermediate 2a, which subsequently decomposes to
dipyridyl disulfide 3a and N-(1-naphthylmethyl)toluene-
p-sulfonamide 4a together with a small amount of product 5a
via direct cleavage of the S–CH2 linkage.
‡ Compound 1a was prepared by the following procedure: a solution of
pyridyl naphthylmethyl sulfide and Chloramine T (1.5 equiv.) in 100 ml of
MeCN was refluxed for 6 h. After removal of MeCN, washing with water
to remove excess Chloramine T and drying, S-pyridyl-S-naphthylmethyl-
N-p-tosylsulfimide was obtained in 88% yield, mp 164 °C (AcOEt–hexane).
Selected data for 1a: 1H NMR (400 MHz, CDCl3): d 2.20 (s, Me, 3 H), 4.46
(dd, J 13 Hz, 1 H), 5.34 (dd, J 13 Hz, 1 H), 6.63–6.65 (m, 2 H), 7.17–7.34
(m, 5 H), 7.48–7.58 (m, 3 H), 7.75–7.84 (m, 2 H), 7.97–8.08 (m, 2 H),
8.31–8.33 (m, 1 H), 8.70–8.72 (m, 1 H); 13C NMR (100 MHz, CDCl3): d
21.3, 54.8, 122.1, 122.9, 123.7, 125.1, 125.5, 125.7, 126.1, 127.0, 127.8,
128.8, 128.8, 129.5, 130.0, 131.2, 131.3, 133.6, 138.9, 140.8, 149.9; nmax
(KBr)/cm21 1280, 1100 (SO2), 980 (SN); Calc. for C23H20N2O2S2: C,
65.68; H, 4.79; N, 6.66. Found: C, 65.52; H, 4.84; N, 6.49%.
1
§ Selected data for 4a: H NMR (400 MHz, CDCl3): d 2.45 (s, Me, 3 H),
4.53 (d, J 1 Hz, CH2, 2 H), 4.63 (d, J 2 Hz, NH, 1 H), 7.25–7.35 (m, 4 H),
7.46–7.51 (m, 2 H), 7.77–7.90 (m, 5 H); 13C NMR (100 MHz, CDCl3); d
21.5, 45.4, 123.2, 125.1, 126.0, 126.7, 126.9, 127.2, 128.7, 129.1, 129.7,
131.1, 133.7, 136.4, 143.5; nmax (KBr)/cm21 1330, 1160 (SO2), 3300 (NH);
m/z 311 (M+); Calc. for C18H17NO2S: C, 69.42; H, 5.50; N, 4.49. Found: C,
69.51; H, 5.62; N, 4.33%.
1
¶ Selected data for 2a: H NMR (400 MHz, CDCl3): d 2.44 (s, Me, 3 H),
6.70—6.73 (m, 1 H), 6.81–6.83 (m, 1 H), 6.99–7.03 (m, 1 H), 7.30–7.36 (m,
3 H), 7.47–7.49 (m, 1 H), 7.57–7.61 (m, 1 H), 7.65–7.67 (d, J 2 Hz, 1 H),
7.74–7.76 (d, J 2 Hz, 1 H), 7.85–7.88 (m, 2 H), 8.08–8.10 (m, 1 H),
8.44–8.47 (m, 1 H); 13C NMR (100 MHz, CDCl3): d 21.6, 55.8, 118.3,
119.9, 123.8, 124.8, 125.7, 126.7, 127.9, 128.5, 129.3, 129.6, 129.7, 130.0,
131.9, 133.5, 135.0, 136.1, 144.3, 148.1, 160.6; nmax(KBr)/cm21 1351,
1165 (SO2); m/z 78 (C5H5N+), 127 (C10H7+), 141 (C10H7CH2+), 155 (Ts+),
156 (C10H7CH2NH+), 311 (TsNHCH2C10H7+), 420 (M+); Calc. for
C23H20N2O2S2: C, 65.68; H, 4.79; N, 6.66. Found: C, 65.86; H, 4.79; N,
6.60%. The methylene protons (CH2C10H7) were not observed in the 1H
NMR spectrum, even after varying the solvent, although all other analytical
and combustion data confirmed this structure.
We are now pursuing further studies to clarify the limitations
and the detailed mechanism of this reaction.
20
15
10
5
∑ In MeOH the formation of paraformaldehyde was observed.
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0
150
0
30
60
90
t / min
120
180
Fig. 1 Product distribution in the course of photolysis of 1a; (5) 1a, (2) 2a,
(8) 3a and («) 4a
Received in Corvallis, OR, USA, 27th January 1997; revised MS received
19th May 1997; 7/03455E
1348
Chem. Commun., 1997