Triarylbismuthane Oxides
Organometallics, Vol. 23, No. 23, 2004 5479
4-bromobenzyl alcohol-d2 (12-d2),50 1-phenyl-1,4-butanediol,51
2,2′-dimethoxydiphenyl ether (8a),52 and 2,2′-dimethyldiphenyl
ether (8b)53 were prepared according to the known procedures.
Other reagents were used as commercially received.
procedure similar to that described for the synthesis of 3. After
several hours in vacuo, 5 was obtained in an anhydrous,
1
dimeric form. H NMR: δ 3.24 (s, 18H), 6.94 (d, 6H, J ) 8.0
Hz), 7.01 (t, 6H, J ) 7.6 Hz), 7.48 (ddd, 6H, J ) 8.0, 7.6, 1.5
Hz), 7.65 (dd, 6H, J ) 7.6, 1.5 Hz). In the presence of a suitable
amount of water, the hydrated species was observed together
with the anhydride. 1H NMR: δ 1.87 (s, ca. 1.5H), 3.78 (s, 9H),
6.70 (d, 3H, J ) 8.0 Hz), 7.13 (t, 3H, J ) 7.6 Hz), 7.45 (ddd,
3H, J ) 8.0, 7.6, 1.5 Hz), 7.88 (dd, 3H, J ) 7.6, 1.5 Hz).
Thermal Decomposition of 3. Typical Procedure.
Compound 3 (0.3 mmol) was heated for 0.5-15 h in 10 mL of
refluxing benzene. The insoluble substance that formed was
removed by filtration. The formation of biphenyl 7, diaryl ether
8, and arene 9 was confirmed by GC and GCMS spectrometry.
The filtrate was concentrated under reduced pressure to leave
an oily residue, which was chromatographed on a silica gel
column (hexane/EtOAc ) 50/1) to give bismuthane 6. The
eluted compounds 7 and 8 were characterized by comparison
with authentic specimens. During the thermal decomposition
of 3a, both the vapor phase and the liquid phase of the reaction
mixture were analyzed at several intervals by GC fitted with
a 5 Å molecular sieves column, but O2 gas could not be detected
in all cases examined. When the thermolysis of 3a was carried
out in the presence of an excess (>5 equiv) of a trapping agent
or a hydrogen source such as 1,4-cyclohexadiene, 1,3-cyclo-
octadiene, trans-stilbene, or 9,10-dihydroanthracene, 6a was
obtained and the trapped products were not detected by GCMS
or 1H NMR. In the competition experiments, a 1/1 (v/v)
benzene/toluene or benzene/anisole mixture was used as the
solvent.
Synthesis of Triarylbismuthane Oxides 3. General
Procedure. Water (50 µL, 2.8 mmol) was added to a mixture
of triarylbismuth dichloride 1 (0.50 mmol), KO-t-Bu (123 mg,
1.10 mmol), and CH2Cl2 (10 mL), and the resulting mixture
was stirred for 2 h at 0 °C. The mixture was then passed
quickly through a plastic filter (Nacalai, Cosmo Nicefilter S),
and acetonitrile (1 mL) was added to the filtrate. The resulting
solution was concentrated under reduced pressure at 0-10 °C
to give 3 as a pale yellow or colorless solid. The 1H NMR
analysis of the solid showed that 3 was formed quantitatively
in a high state of purity (>99%). Triarylbismuth diacetates
2a-e also reacted with H2O/KO-t-Bu to give 3 quantitatively.
Compounds 3a-c,e did not show definite melting points.
3a: 1H NMR δ 3.84 (s, 18H), 7.13-7.19 (m, 12H), 7.43-
7.47 (m, 6H), 8.02 (br-d, 6H); IR νmax 1580, 1566, 1471, 1431,
1302, 1275, 1244, 1231, 1182, 1175, 1156, 1117, 1051, 1020,
937, 851, 789, 756, 748, 710, 638, 588, 574, 565, 534, 473, 436
cm-1; FABMS m/z (%) 1831 (7), 1301 (14), 969 (63), 879 (8),
755 (24), 637 (100), 423 (32), 316 (20), 209 (28). Weak fragment
ion peaks due to the tetramer (m/z 1831) and trimer (m/z 1301)
were also detected. Due to the thermal and chemical instability
of 3a, we have not been successful in obtaining satisfactory
analytical data of an accuracy within (0.4%.
3b (n ) 1): 1H NMR δ 1.07 (s, ca. 2H, OH), 2.68 (s, 18H),
7.35-7.52 (m, 18H), 7.86 (d, 6H, J ) 7.2 Hz); IR νmax 1582,
1559, 1509, 1472, 1458, 1442, 1377, 1272, 1206, 1157, 1115,
1007, 920, 797, 739, 642, 548, 532, 471, 424 cm-1; FABMS m/z
889. Anal. Calcd for C42H44Bi2O3: C, 49.71; H, 4.37. Found:
C, 49.39; H, 4.49.
Reaction of 3a with Ph3M (M ) P, As, Sb). Ph3M (M )
P, As, Sb; 0.5 mmol) was added to a CH2Cl2 solution (10 mL)
of 3a (273 mg, 0.25 mmol) at room temperature. After 30 min,
the reaction was concentrated under reduced pressure and
1
3c (n ) 0): mp 96-105 °C dec; H NMR δ 0.56 (s, ca. 2H,
1
examined by H NMR spectroscopy. Bismuthane 6a and the
OH), 3.83 (s, 9H), 7.09 (d, 6H, J ) 8.8 Hz), 8.19 (d, 6H, J )
8.8 Hz); 13C{1H} NMR δ 55.4, 116.0, 135.4, 144.2, 161.6; IR
νmax 1580, 1487, 1460, 1441, 1396, 1294, 1248, 1175, 1117,
1101, 1026, 997, 824, 785, 611, 584, 511, 475 cm-1. Anal. Calcd
for C21H23BiO5: C, 44.69; H, 4.11. Found: C, 44.55; H, 3.90.
3d (n ) 0): 1H NMR δ 0.56 (s, ca. 2H, OH), 2.39 (s, 9H),
7.39 (d, 6H, J ) 8.0 Hz), 8.14 (d, 6H, J ) 8.0 Hz); 13C{1H}
NMR δ 21.3, 131.4, 134.0, 141.4, 150.3; IR νmax 1481, 1445,
1389, 1306, 1205, 1178, 1113, 1095, 1045, 1007, 844, 804, 694,
595, 475, 428 cm-1; FABMS m/z (%) 1205 (14), 1023 (12), 997
(28), 889 (100), 707 (54), 499 (25), 391 (58). Anal. Calcd for
C21H23BiO2: C, 48.84; H, 4.49. Found: C, 48.84; H, 4.28.
3e (n ) 0): 1H NMR δ 0.65 (s, ca. 2H, OH), 7.47 (t, 3H, J )
7.6 Hz), 7.60 (t, 6H, J ) 7.6 Hz), 8.29 (d, 6H, J ) 7.6 Hz);
13C{1H} NMR δ 130.9, 131.1, 134.2, 153.6; IR νmax 1566, 1472,
1433, 1372, 1325, 1300, 1173, 1051, 1013, 993, 968, 912, 833,
737, 725, 689, 573, 527, 449, 432 cm-1; FABMS m/z (%) 1275
(17), 1121 (15), 913 (12), 835 (32), 819 (100), 759 (28), 665 (48),
457 (20), 363 (20). The peak at δ 0.65 disappeared in the
presence of D2O. When allowed to stand in vacuo for 6 h, 3e
was converted to an amorphous substance, insoluble in most
organic solvents. We have characterized this insoluble sub-
stance as a polymeric triphenylbismuthane oxide. Anal. Calcd
for C18H15BiO: C, 47.38; H, 3.31. Found: C, 47.56; H, 3.35.
The polymeric oxide was reversibly converted to the dihydrox-
ide 3e by treatment with an excess of water in CH2Cl2.
Synthesis of Tris(2-methoxyphenyl)stibane Oxide
(5).17b,20 This compound was prepared from tris(2-methoxyphe-
nyl)antimony dichloride (4), H2O, and KO-t-Bu according to a
oxide Ph3MdO were formed quantitatively. The 1H NMR
monitoring of the same reaction in CDCl3 did not show any
intermediates.
Oxidation of Ethanol and 2-Propanol: NMR Experi-
ments. Compounds 3a,b (1.1-1.2 equiv) were added in one
portion to a CDCl3 solution of alcohol at room temperature.
1
After 5 min, the reaction mixture was measured by H NMR
(9,10-dihydroanthracene as an internal standard). In these
oxidations, anisole (from 3a) or toluene (from 3b) was formed
quantitatively with Ar2BiOBiAr2 (11a,b). Compounds 11a,b
were characterized by comparison with authentic samples
independently prepared from Ar2BiOTf and aqueous NaOH.
Compounds 11a,b gradually underwent disproportionation in
solution to give triarylbismuthanes 6a,b and insoluble solids.
Bis[bis(2-methoxyphenyl)bismuth] Oxide (11a).17b 1H
NMR δ 3.63 (s, 12H), 7.01 (d, 4H, J ) 8.0 Hz), 7.12-7.16 (m,
4H), 7.27-7.32 (m, 4H), 8.15 (dd, 4H, J ) 7.0, 1.4 Hz).
Bis[bis(2-methylphenyl)bismuth] Oxide (11b).17b 1H
NMR δ 2.15 (s, 12H), 7.22-7.32 (m, 8H), 7.38-7.42 (m, 4H),
8.20 (d, 4H, J ) 7.2 Hz). IR νmax 1578, 1560, 1458, 1447, 1375,
1267, 1200, 1155, 1113, 1043, 1028, 752, 746, 617, 588 cm-1
.
Oxidation of Alcohols: General Procedure. Alcohol
(0.45 mmol) was added to a CH2Cl2 solution (10 mL) of 3 (0.5
mmol) at room temperature. Thin-layer chromatography in-
dicated that the reaction was complete within a few minutes
at room temperature. After 5-30 min, the reaction mixture
was concentrated under reduced pressure to leave an oily
residue, which was then chromatographed on a silica gel
column (hexane/EtOAc ) 20/1) to give a carbonyl product.
Competitive Oxidation of Alcohols. A CDCl3 solution
(0.5 mL) containing 12 (0.06 mmol) and 12-d2 (0.06 mmol) was
added to a solution of 3b,d (0.02 mmol) in CDCl3 (0.5 mL) at
23 ( 1 °C. After a few minutes, the resulting mixture was
measured by 1H NMR. The intramolecular competition experi-
ment was carried out using 12-d (0.02 mmol), 3b,d (0.02
mmol), and CDCl3 (1.0 mL). Both intermolecular and intra-
(50) Pollack, S. K.; Raine, B. C.; Hehre, W. J. J. Am. Chem. Soc.
1981, 103, 6308-6313.
(51) Klement, I.; Lu¨tjens, H.; Knochel, P. Tetrahedron 1997, 53,
9135-9144.
(52) Kime, D. E.; Norymberski, J. K. J. Chem. Soc., Perkin Trans.
1 1977, 1048-1052.
(53) Barton, D. H. R.; Finet, J.-P.; Khamsi, J.; Pichon, C. Tetrahe-
dron Lett. 1986, 27, 3619-3622.