,
2005, 15(3), 103–105
3
5
-Methyl- and 4-methyl-2-chlorobenzo[d]-λ -1,3,2-dioxaphos-
†
pholanes 1 and 2 can react with chlorine in a molar ratio of
:2. The first equivalent of the halogen adds very readily to the
1
C6D
O1D
C6A
C1A
phosphorus atom similarly to the behaviour of other related
C5D
O1A
C5A
C4A
1
1
C1D
C4D
phospholes to give derivatives of pentacoordinate phosphorus,
Cl4D
C2D
C2A
Cl4A
5
C7C
C3C
namely, 2,2,2-trichlorobenzo[d]-λ -1,3,2-dioxaphospholes 3 and
O2D
O2A
C5B
C3A
C7A
‡
4
, which can be isolated in high yields and purified by distil-
Cl4C
C3D
O2C
C6B
Cl4B
C3B
lation in vacuo.
C4B
C2B
C4C
C1C
C2C
C5C C7D
C1B
O1B
O
O
O
O
C7B
Cl2
O1C
O2B
R
PCl
R
PCl3
C6C
1
, 2
3, 4
Figure 1 Geometry of four independent molecules of pyrocatechol 7 in a
In the presence of an excess of chlorine, phospholes 3 and 4
unexpectedly undergo a further selective chlorination at the
aromatic ring to give phospholes 5 and 6, respectively. The
crystal.
do not undergo direct spin-spin coupling with protons. The
1
13
resonance of the C7 carbon atom in the C–{ H} spectrum
13
1
structures of compounds 3–6 were determined by H, C and
3
1
31
3
P NMR spectroscopy. In the P NMR spectrum, the signal of
manifests itself as a doublet with J
POCC7
17.4 Hz. The nuclei of
7a
phospholes 5 and 6 chlorinated at the ring is somewhat shifted
towards weaker fields in comparison with that of non-substituted
derivatives 3 and 4, which suggests the retention of a penta-
coordinate environment of the phosphorus atom and the cyclic
structure of the phosphole. The stability of compounds 5 and 6
in the presence of free chlorine and the hydrogen halide mole-
cule formed suggest that the aromaticity of the benzene ring is
preserved. The relative positions of substituents in the phenylene
ipso C3a and C atoms are also easily distinguishable due to not
Me
Me
4
3
O
O
O
Cl
3a
Cl2
2
5
6
PCl3
PCl3
1
– HCl
7a
O
7
3
5
1
Me
fragment was determined based on the H NMR spectra of phos-
Cl
OH
OH
pholes 5 and 6. These compounds showed spectra typical of
H O
2
1
,2,3,4- and 1,2,4,5-tetrasubstituted benzenes (the AB system
–
H PO
3 4
6
7
4
7
of the H and H protons and two singlets of the H and H
protons, respectively) in the weak-field region.
–
HCl
7
1
3
1
The weak-field region of the C–{ H} NMR spectra of com-
§
pounds 5 and 6 contains signals from four carbon atoms that
4
3
O
O
Cl
3a
7a
†
Cl2
2
2
-Chloro-4-methylbenzo[d]-1,3,2-dioxaphosphole 1. A mixture of
5
PCl3
PCl3
1
,2-dihydroxy-3-methylbenzene (12.8 g), PCl (14 ml) and a few drops
– HCl
1
3
O
6
O
of water was stirred for 1.5 h at 100 °C. An excess of PCl was removed
Me
Me
3
7
in vacuo (12 Torr). The residue (phosphole 1) was distilled to give 17.3 g
4
6
1
(
89%), bp 65 °C (1 Torr), n D2 0 1.5630. H NMR (CDCl ) d: 2.41 (s, 3H,
3
5
6
7
31
1
Me), 6.99–7.10 (m, 3H, H , H , H , ABC spectrum). P-{ H} NMR
Cl
OH
OH
(
36.46 MHz, CDCl ) d : 174.2.
H2O
3
P
2
-Chloro-5-methylbenzo[d]-1,3,2-dioxaphosphole 2. A mixture of
–
H PO
3
4
1
,2-dihydroxy-4-methylbenzene (10 g), PCl (22.2 ml) and a few drops
– HCl
Me
3
of water was stirred for 1 h at 100–110 °C and kept in vacuo to remove
8
an excess of PCl . The residue (phosphole 3) was distilled, yield 13.7 g
3
31
1
§
(
91%), bp 65 °C (1 Torr). P-{ H} NMR, d : 176.6.
2,2,2,5-Tetrachloro-4-methylbenzo[d]-1,3,2-dioxaphosphole 5. A solu-
P
‡
2
,2,2-Trichloro-4-methylbenzo[d]-1,3,2-dioxaphosphole 3. A solution
tion of chlorine (4 g) in dichloromethane (20 ml) was added to a solution
of dioxaphosphole 1 (3.6 g) in dichloromethane (15 ml) with stirring at
–60 °C. The reaction mixture was slowly heated to 20 °C and kept for
six days. The solvent and an excess of chlorine were removed in vacuo
(12 Torr) to give a residue of phosphole 5, viscous yellowish oil, yield
of chlorine (1.45 g) in dichloromethane (10 ml) was added to a solution
of dioxaphosphole 1 (3.85 g) in dichloromethane (15 ml) with stirring at
–
70 °C in an argon atmosphere. The reaction mixture was kept in vacuo
in order to remove an excess of chlorine and the solvent. The residue
1
7 3
consisted of phosphole 3, viscous yellowish oil, yield 97%, bp 97–101 °C
97%. H NMR (CDCl ) d: 2.32 (s, Me), 6.87 (br. dd, H , J
6
7
8.6 Hz,
3
H CCH
1
7
3
4
6
3
5
(
8
0.8 Torr). H NMR (CDCl ) d: 2.41 (s, Me), 7.17 (br. d, H , J
6
7
JPOCCCH
7
1.0 Hz), 7.04 (br. dd, H , J
6
7
8.6 Hz, J
POCCCCH7
1.4 Hz).
3
5
H CCH
H CCH
6
3
13
13
13
1
.8 Hz), 6.99–7.04 (br. m, H , H , J
6
5
8.5 Hz). C NMR (the param-
C NMR (the parameters of the C-{ H} NMR spectrum in CDCl are
H CCH
3
1
3
1
3a 2
eters of the C-{ H} NMR spectrum in CDCl are given in parentheses)
given in parentheses) d: 141.87 [m (d), C , J
(d), C , J
[dqd (s), C , J
[d (s), C , J
POC3a
2.1 Hz], 120.27 [ddq
3
3a
2
4
3
4
3
3
2
d: 140.10 [m (d), C , JPOC3a 1.3 Hz], 121.28 [ddqd (d), C , JPOCC
4
4
16.5 Hz, J
6
4
6.0–6.2 Hz, J
HCCC5
4
6.0–6.2 Hz], 129.02
POCC
HC CC
HCC
7.0 Hz, 3
J
6.7–6.8 Hz, 3J
7.1 Hz,
2
J
2.0 Hz], 124.81
5.0 Hz], 122.74
167.6 Hz, J
5
3
10.7 Hz, J
3
5.4 Hz, J
2
4.4 Hz], 122.89
1
[
[
1
4
6
4
5
4
7
5
6
5
HCCC
HC CC
HC C
HC CC
HC C
5
1
3
3
6
1
7
1
3
ddq (s), C , J
HC5
160.4 Hz, J
7
5
7.6 Hz, J
HCCC5
HC6
HC7
168.5 Hz], 108.77 [dd (d), C , J 170.2 Hz, J
POCC7
HC CC
6
1
7
1
3
7a
3
2
d (s), C , J
HC6
5
163.9 Hz], 107.99 [ddd (d), C , J
HC7
POCC7
17.4 Hz], 140.33 [br. dd (br. s), C , J 7a 12.0 Hz, J
6
7
7a 3.6 Hz],
HC CC
HC C
31
3
7a
3
12.74 [qd (d), Me, 1JHC 129.9 Hz, 4JPOCCC 1.1 Hz]. P-{ H} NMR
1
8.0 Hz, J
7
8.8 Hz], 142.23 [br. d (br. s), C , J
6
7a 10.2 Hz],
HC CC
HC CC
4
3
31
1
1
4.62 [br. qd (d), Me, J 128.2 Hz, J
1.1 Hz]. P-{ H} NMR
(CDCl ) d : –22.8.
HC
POCCC
3
P
(
36.46 MHz, CDCl ) d : –25.7.
2
2,2,2,6-Tetrachloro-5-methylbenzo[d]-1,3,2-dioxaphosphole 6. A solu-
tion of chlorine (5 g) in dichloromethane (25 ml) was added to a solution
of phosphite 2 (6.2 g) in dichloromethane (30 ml) with stirring at –60 °C.
The resulting mixture was slowly heated to 20 °C and kept for three
days. The solvent and an excess of chlorine were removed in vacuo. The
residue (phosphole 6) was a viscous yellowish oil, yield 96% (9.3 g).
3
P
,2,2-Trichloro-5-methylbenzo[d]-1,3,2-dioxaphosphole 4. A solution
of chlorine (2.8 g) in dichloromethane (15 ml) was added to phosphite 2
7.4 g) at –60 °C; then, the solvent and an excess of chlorine were
removed. The residue consisted of phosphole 4 as a viscous yellowish
(
1
3
oil. Yield 97%, bp 95–100 °C (0.8 Torr). C NMR (the parameters of
the C-{ H} NMR spectrum in CDCl are given in parentheses), d:
1
13
1
13
13
1
C NMR (the parameters of the C-{ H} NMR spectrum in CDCl are
3
3
3
a
3
2
2
7a
2
3
42.84 [ddd (d), C , J
7
3a 7.1 Hz, J
4
3a 3.6 Hz, J
POC3a
6
0.8 Hz],
given in parentheses) d: 141.04 [ddd (d), C , J
POC7a
0.9 Hz, J
4
7a
HC CC
HC C
POCC4
HC CC
4
1
3
3
7.5 Hz, 2
7
1
5
170.8 Hz, 3J
1
11.32 [dddqd (d), C , J 164.0 Hz, J
HC4
17.6 Hz, J
4
7.7 Hz,
7.8 Hz,
7.0 Hz,
J
7
3a 4.3 Hz], 111.62 [dd (d), C ,
J
HC7
POCC7
HC CC
HC C
3
4
5
3
4
2
3
JHCCC
4
5.1 Hz, J
7
4
1.4 Hz], 133.81 [dq (s), C , J
7
5
6
17.7 Hz, J
12.0 Hz], 128.08 [dqd (s), C , J
5.2 Hz], 112.63 [ddqd (d), C , J
HCCCC7
0.8–0.9 Hz], 131.28 [qd (s), C , J
HCC5
6.0 Hz, J
7
5
HCCC6
HCCC4
HC CCC
HC CC
HC CC
2
3
3
6
1
3
6
3
2
3
JHCC
JHCCC
JPOCC
5
6.1 Hz], 123.51 [ddqd (s), C , J
HC6
161.4 Hz, J
4
4
6
10.3 Hz, J
7
6
5.1 Hz, J
17.3 Hz, J
7a 7.5 Hz, J
HC CC
HC CC
HC C
5.1 Hz, 2
J
1.1 Hz], 110.43 [dd (d), C , JHC
7
1
166.7 Hz,
4
1
166.4 Hz, J
3
3
6
7
6
7
HC4
POCC4
HC C
7a
2
3
7a
3
2
7
17.7 Hz], 140.40 [m (d), C , J
POC7a
0.8 Hz], 21.21 [qdd (d), Me,
5.2 Hz, J
7
4
1.3 Hz], 141.03 [ddd (d), C , J
4
7 7a
HC CCC
HC CC
HC C
3.0 Hz].
1J
(
127.2 Hz,
3
J
4.7 Hz,
3
J
4.7 Hz]. P-{ H} NMR
31
1
4.3 Hz, J
POC7a
2
0.9 Hz], 20.03 [qd (s), Me, J 132.6 Hz, J
1
3
4
6
4
HC
HC CC
HC CC
HC
HC CC
31
1
36.46 MHz, C H ) d : –27.3.
P-{ H} NMR (CDCl ) d : –24.1.
6
6
P
3 P
1
04 Mendeleev Commun. 2005