Photoreactions of 3-tosyl- and 6-tosyldihydro-1,3-diazaazulanones to form 1,3-diazaazulanones and ionic pairs between p-toluenesulfonate anion and 1,3-diazadihydroazulanone cations

Article abstract of DOI:10.3987/COM-01-9341

A solvent effect was found on the photoreactions of 1-aryl-3-tosyldihydro-1,3-diazaazulanones with a low pressure mercury lamp. Thus, ion pairs between p-toluenesulfonate anion and the corresponding 1-aryl-1,3-diazadihydroazulanone cations were afforded b

Full text of DOI:10.3987/COM-01-9341

HETEROCYCLES, Vol. 55, No. 12, 2001, pp. 2315 - 2324, Received, 17th September, 2001
PHOTOREACTIONS OF 3-TOSYL- AND 6-TOSYLDIHYDRO-1,3-
DIAZAAZULANONES TO FORM 1,3-DIAZAAZULANONES AND
IONIC PAIRS BETWEEN p-TOLUENESULFONATE ANION AND 1,3-
DIAZADIHYDROAZULANONE CATIONS
Katsuhiro Saito, * Tomoko Kunisada, Hiroyuki Ishiguro, Michie Sato,
and Tadayuki Doi
Department of Applied Chemistry, Nagoya Institute of Technology,
Gokiso-cho, Showa-ku, Nagoya 466-8555, J apan
Abstract——A solvent effect was found on the photoreactions of 1-aryl-
3
-tosyldihydro-1,3-diazaazulanones with a low pressure mercury lamp.
Thus, ion pairs between p-toluenesulfonate anion and the correspond-
ing 1-aryl-1,3-diazadihydroazulanone cations were afforded by the
reactions in THF. On the other hand, the corresponding 1-aryl-1,3-
diazaazulanones were formed by the reactions in the other solvents.
The analogous photoreactions with 1-aryl-6-tosyldihydro-1,3-diaza-
azulanones afforded the corresponding 1-aryl-1,3-diazaazulanones.
Not only as precursors of azulanones, a member of nonbenzenoid aromatic compounds, but
also from theoretical stand point, dihydroazulanones have attracted attention of chemists.
A considerable amount of papers have been published on the synthesis or elucidation of
1
reactivities, but the documents concerning the photochemistry of dihydroazulanones are
2
few in number. As a member of dihydroazulanone analogue, dihydro-1,3-diazaazulanones
(
1) have unique structural characteristics. The system of 1 is constructed from two
moieties, i.e., a cycloheptatirene (tropilidene) moiety and a diazacyclopentanone moiety. A
combination of these two moieties generates a cross-conjugated delocalized system,
2
composed from a cyclic triene system, a carbonyl group, and two sp hybridized nitrogen
atoms. The UV spectrum, which has two absorption maxima at ca. 250 nm (log ε = 4.5)
and ca. 310 nm (log ε = 3.5) well supports the existence of this long delocalized system.3

The photochemistry of tropilidene system has been researched extensively to make clear
the existence of 1,7-hydrogen shift and/or 4π ring contraction reactions.4 However,
considering the characteristic nature of the tropilidene moieties as a component of the
system of 1, unique behaviors in photochemistry can be expected. As a series of our study
on the chemistry of azulanone and dihydroazulanone systems, we investigated
photoreactions of 1.2 Herein, the results are reported.
CH3
Ar
N
Ar
N
THF
O
O
N
Ts
hν(254 nm)
N
H
O S O
O
2
1
1
1
1
a:p-ClC H
6 4
b:p-BrC H
6
4
c:p-CH C H
3
6
4
Ar
N
d:p-CH OC H
3
6
4
CH CN
3
O
hν(254 nm)
N
3
Scheme1
A
THF solution of 1-p-chlorophenyl-3-tosyldihydro-1,3-diazaazulanone (1a) was
photoirradiated with a low pressure mercury lamp at room temperature under a nitrogen
stream for 4 h. As the reaction proceeded, an ion pair (2a, 52 % yield) was deposited from
the reaction solution as pale yellow crystals. The analogous irradiation with the
diazaazulanone derivatives (1b, 1c, 1d) afforded the corresponding ion pairs （2b, 2c, and
2
d）in 53, 35, and 27 % yields, respectively.
Figure 1 shows an existence of a substituent effect in the yield of 2, i.e., the electron
withdrawing groups promoted the yields.
When the photoirradiation of 1 was carried out in acetonitrile,a different result from that in
THF was obtained. Thus, an anhydrous acetonitrile solution of 1a was irradiated with a
low pressure mercury lamp for 4 h under the same reaction conditions as above. After
evaporation of the solvent, the resulted residue was separated with thin-layer
chromatography on silica gel to give 1-p-chlorophenyl-1,3-diazaazulanone (3a) in 53 % yield.

The same type reactions in acetonitrile with 1b, 1c, and 1d afforded the corresponding
diazaazulanone derivatives (3b, 3c, 3d) in 60, 33, and 45 % yields, respectively. The
analogous substituent effects as the case of 2 were found on the yields of 3 as shown in
Figure 1.
7
6
5
4
3
2
1
0
0
0
0
0
0
0
2
3
p- Br
p- Cl
p- CH3
p- OCH3
-
0.3
-0.2
-0.1
0
0.1
0.2
0.3
Sigma value
Figure 1
The analogous photoreactions of 1d in the another solvents proceeded through the same
path as that in acetonitrile to form 3d. However, the yields of 3d depended on the solvent
used. The Table 1 summarizes the yields of 3d and the dielectric constants of the solvents
used suggesting that the polar solvents promoted the yield.
Table 1. Yields of 3d and dielectric constants of the solvents
Solvents
C
2
H
5
OH
CH
3
CN
DMSO
67 %
3
d
31 %
24.55
45 %
37.50
Dielectric constants
46.68
The interconversion between 2 and 3 was examined under some reaction conditions as
follows. A treatment of a methanol solution of 2b with potassium hydroxide at rt for 2 h
converted 2b to 3b in an almost quantitative yield.
The ion pair （2 ）was formed in the reaction of 3 with an equimolar amount of p-
toluenesulfonic acid. The reaction conditions and the yields of 2 are summarized in Table 2
with the case of 2b.

O
O S O
SO H
Ar
N
Ar
N
3
O
O
+
N
H
N
CH3
3
CH3
2
Scheme 2
Table 2.
Yields of 2b under various conditions
Entry
Solvent
THF
Reaction temperature Reaction time (h) Yields of 2b (%)
1
2
3
4
rt
6
6
6
6
23
88
67
90
THF
Reflux
rt
CH
CH
3
3
CN
CN
Reflux
These facts suggested the structure of 2 to be close to a complex between 3 and p-toluene
sulfonate.
The structures of 3 were deduced on the basis of their spectral properties and confirmed by
6
the coincidences of these properties with those of the authentic samples. The structures of
2
were deduced on the basis of their spectral properties and finally decided by a single
crystal X-Ray analysis.2
Figure 2
Figure 2
Figure 2

A photoirradiation of 2a in acetonitrile with a low pressure mercury lamp generated 3a in
0 % yield. However, the reaction proceeded slowly, and a prolonged photoirradiation (30
6
h) was required by the complete consumption of the starting material (2a). This fact
demonstrates that 3 can be formed in the photoreaction of 2. However, considering the
difference of the reaction rate between the formation of 3 from 1 and from 2, the formation
of 3 from 1 cannot proceed through 2.
CH3
Ar
N
Ar
N
Ar
N
O
O
O
N
N
N
Ts
Ts
S
4
O
O
5
1
CH3
CH3
Ar
N
Ar
N
O
O
N
H
N
Non-Polar
Solvent
H
S
O S O
O
O
O
2
6
Polar
Solvent
Ar
N
Ar
N
O
O
N
N
H
3
7
Scheme 3
Table 3. Charge distribution of 1
Ar
Ground State
0.1173
Excited State
0.1936
1
N
2
3
N1
C2
O3
N4
C
O
N 4
0.3139
0.3011
Ts
-0.3687
-0.2842
1
-0.5385
-0.4750

The reaction is considered to proceed as follows.
Photoirradiation of 1 generates an
excited state (4) of 1, which is thought to have an ionic character as shown in Scheme 3.
The charge distribution of the ground state and the excited state of 1 are summarized in
Table 3. In the excited state, the electron density on the heterocyclic part is diminished.
4
This fact suggests a shift of the electron density away from N to the tropilidene moiety,
4
resulting weakening of the bond between N and the tosyl group.
4
A bond cleavage between N and the tosyl group generates an ionic pair intermediate (5).
The effect of the solvents shown in Figure 1 is considered to reflect thestabilities of the
tropylium ion part of the intermediate (5).
In the nonpolar solvent (THF) the anionic part and the cationic part of 5 remain in contact
each other. A hydrogen migration in the cationic part and an appropriate oxidation of the
anionic part can form the final product (2).
Table 4. Yields of 2b under various reaction conditions
Dry
THF
Dry
Entry
THF
N
2
Reaction time (h)
Yields of 2 (%)
O
2
1
2
3
○
○
○
4
4
4
53
6
○
○
○
44
Table 4 demonstrates the yields of 2b in the photoreactions of 1b under various reaction
conditions. In the reaction in anhydrous THF as a solvent under a nitrogen stream (Entry
2
), only a small amount of 2b was formed. On the other hand, uses of usual (wet) THF
(
Entry 1)or a oxygen stream (Entry 3) resulted in the formation of 2b in considerable yields.
This fact suggests that the anionic part of 5 is oxidized by water or oxygen dissolved in the
solvents.
Ar
N
Ar
N
THF
Ts
O
O
N
H
hν(254 nm)
N
8
8
8
a:p-ClC H
3a:p-ClC H
6 4
6
4
b:p-BrC H
3b:p-BrC H
6
4
6 4
c:p-CH C H
3c:p-CH C H
3 6 4
3
6
4
Scheme 4

On the other hand, in polar solvents, the cationic part of 5 behaves apart from the anionic
part. An elimination of hydrogen from 5 can form the final product (3).
Photoreactions of the isomers of 1, 1-aryl-6-tosyl-1,3-diazadihydroazulanones (8) were
investigated. A THF solution of 1-p-chlorophenyl-6-tosyl-1,3-diazadihydroazulanobne (8a)
was irradiated with a low pressure mercury lamp at room temperature under a nitrogen
stream for 3 h. The usual treatment of the reaction mixture gave 3a in 19 % yield, which
was also formed in the analogous reaction but using acetonitrile as a solvent in 32 % yield.
The product yields in the reactions with some isomers of 8 are summarized in Table 5.
Table 5. Yields of 3 in the reaction of 8
3
a
3b
3c
THF
CH CN
19 % (3 h) 22 % (3 h) 17 % (3 h)
32 % (3 h) 37 % (3 h) 26 % (3 h)
3
The charge distributions of 8 in the ground state and in the excited state calculated with
MINDO 3 method are as shown in the Table 6. In the excited state, the electron cloud
4
1
seems to shift from N to N . Considering these electron densities, the excited state of 8 is
thought to have a contribution of an ionic form (9). The reaction is considered to proceed
through an elimination of the tosyl group in 9 to form the cationic intermediate (10), which
then removes a hydrogen to generate the final product.
Ar
N
Ar
N
hν
Ts
O
Ts
O
N
H
N
H
9
8
Ar
N
Ar
N
-
O
O
+
-Ts
-H
N
H
N
3
10
Scheme 5

Table 6. Charge distribution of 8
Ground State Excited State
Ar
1
N1
C2
O3
N4
0.0973
0.1932
-0.3788
0.1524
0.1349
0.2117
-0.3383
0.0806
N
2
3
Ts
C O
N4
H
8
ACKNOWREDGEMENT
The authors are indebted to Prof. Hideki Masuda of Nagoya Institute of Technology for his
measurement of a single crystal X-Ray analysis.
EXPERIMENTAL
Photoirradiation was performed with six low pressure mercury lamps National GL-15 in a
5
0 ml quartz pear shaped flask. MS and NMR spectra were measured with Hitachi 220A
and Varian GEMINI 200/300 spectrometers, respectively. IR spectra were measured with
a J ASCO FT/IR-5300 spectrophotometer. Wakogel C200 and B5F were used for column
and thin-layer chromatography, respectively.
Only typical reactions are mentioned below.
Photoreaction of 1a in THF.
A solution of 1a (200 mg, 0.5 mmol) in THF (20 mL ) was
photoirradiated with low pressure mercury lamps at rt under a nitrogen stream for 4 h.
The deposited crystals were filtered off to give 2a (102 mg, 52 %).
o
2
5
2
a: Pale yellow crystals. mp 238-239 C (from ethanol).
Anal. Calcd for C21
H
17
N
2
O ClS: C,
4
8.81; H, 4.00; N, 6.53. Found: C, 58.67; H, 3.68; N, 6.55. MS m/z (rel intensity): 258 (35),
56 (100), 221 (19), 119 (80). IR (KBr): 3489, 1751, 1228, 1032 cm . 1H NMR (DMSO- d
),
-1
6
δ: 2.28 (s, 3 H), 7.10 (d, 2 H, J = 8.5 Hz, tosyl), 7.46 (s, 2 H, tosyl), 7.65 (d, 2 H, J = 7.5 Hz
aryl), 7.80 (d, 2H, aryl), 8.08 (d, 1H, J = 9.7 Hz), 8.27 (dd, 1H, J = 9.7 and 9.7 Hz), 8.42 (dd,
1
2
5
H, J = 9.7 and 9.7 Hz), 8.46 (d, 1H, J = 9.7 Hz), 8.58 (dd, 1H, J = 9.7 and 9.7 Hz).
o
b: Pale yellow crystals. mp 238-239 C (from ethanol).
Anal. Calcd for C21H17BrS: C,
3.29; H, 3.62; N, 5.92. Found: C, 52.75; H, 3.47; N, 5.99. MS m/z (rel intensity): 302
-1
(
(
83), 300 (81), 221 (26), 119 (100). IR (KBr): 3443, 1749, 1226, 1032 cm . 1H NMR
DMSO- d ), δ: 2.28 (s, 3 H), 7.10 (d, 2 H, J = 8.5 Hz, tosyl), 7.46 (s, 2 H, tosyl), 7.58 (d, 2 H,
6

J = 7.5 Hz, aryl), 7.92 (d, 2H, aryl), 8.08 (d, 1H, J = 9.7 Hz), 8.27 (dd, 1H, J = 9.7 and 9.7
Hz), 8.42 (dd, 1H, J = 9.7 and 9.7 Hz), 8.46 (d, 1H, J = 9.7 Hz), 8.59 (dd, 1H, J = 9.7 and 9.7
Hz).
o
2
2
c: Pale yellow crystals. mp 183-184 C (from ethanol). MS m/z (rel intensity): 235 (100),
21 (33), 194 (9), 119 (76). IR (KBr): 3491, 1747, 1234, 1043 cm . 1H NMR (DMSO-d
),
-1
6
δ: 2.30 (s, 3 H), 2.45 (s, 3 H), 7.10 (d, 2 H, J = 8.5 Hz, tosyl), 7.48 (d, 2 H, tosyl), 7.50 (s, 4 H,
aryl), 7.95 (d, 1 H, J = 9.7 Hz), 8.20 (dd, 1 H, J = 9.7 and 9.7 Hz), 8.36 (dd, 1 H, J = 9.7 and
9
2
2
.7 Hz), 8.40 (d, 1 H, J = 9.7 Hz), 8.52 (dd, 1 H, J = 9.7 and 9.7 Hz).
o
d: Pale yellow crystals. mp 117-118 C (from ethanol). MS m/z (rel intensity): 252 (100),
37 (64), 221 (8), 210 (8), 133 (95). IR (KBr): 3458, 1745, 1230, 1026 cm . 1H NMR
-1
(DMSO-d
6
), δ: 2.30 (s, 3 H), 3.88 (s, 3 H), 7.11 (d, 2H, J = 8.5 Hz, tosyl), 7.24 (d, 2 H, J = 7.5
Hz, aryl), 7.45 (d, 2H, tosyl), 7.53 (d, 2 H, aryl), 8.05 (d, 1H, J = 9.7 Hz), 8.28 (dd, 1H, J =9.7
and 9.7 Hz), 8.45 (dd, 1H, J = 9.7 and 9.7 Hz), 8.50 (d, 1H, J = 9.7 Hz), 8.60 (dd, 1H, J = 9.7
and 9.7 Hz).
Photoirradiation of 1a in acetonitrile. A solution of 1a (127 mg, 0.31 mmol) in acetonitrile
(
20 mL ) was photoirradiated with low pressure mercury lamps at rt under a nitrogen
stream for 4 h. After evaporation of the solvent the residue was thin-layer
chromatographed on silica gel to give 3a (42 mg, 53 %, ethyl acetate, R = 0.1).
f
Photoirradiation of 4b in acetonitrile. A solution of 4b (67 mg, 0.17 mmol) in THF (15 mL)
was photoirradiated with low pressure mercury lamps at rt under a nitrogen stream for 3 h.
After evaporation of the solvent the residue was thin-layer chromatographed on silica gel to
give 3b (7 mg, 17 %, ethyl acetate, R = 0.1).
f
Reaction of 2b with potassium hydroxide. A solution of 2b (34 mg, 0.07 mmol) and
potassium hydroxide (106 mg, 1.9 mmol) in methanol (30 mL) was stirred at rt for 2 h.
After addition of brine the reaction mixture was extracted with methylene chloride. After
the usual treatment the solvent was evaporated to give crystals of 3b (22 mg, ca. 100 %).
Photoreaction of 2a. A solution of 2a (39 mg, 1 mmol) in acetonitrile (15 mL) was irradiated
with a low-pressure mercury lamp at rt under a nitrogen stream for 30 h. After
evaporation of the solvent, the residue was thin-layer chromatographed on silica gel to give
3
a (25 mg, 60 %). In a short time irradiation (2 h), formation of 3a was not obvious.
Reaction of 3b with p-toluenesulfonic acid. A solution of 3b (142 mg, 0.47 mmol), p-
toluenesulfonic acid (84 mg, 0.49 mmol) in THF (20 mL) was stirred at rt for 6 h. After
evaporation of the solvent, the residue was column chromatographed on silica gel to give 2b

with an eluant of ethyl alcohol (51 mg, 23 %).
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