1388
A. R. Clark et al. / Tetrahedron Letters 43 (2002) 1387–1389
Scheme 2. Preparation of diaryl ditellurides from arylboronic acids.
Similarly, two non-symmetrical diaryl tellurides were
prepared by condensation of 2- and 3-nitrophenyl-
followed by flash chromatography (neutral alumina/
dichloromethane). The product was crystallized from
toluene.
boronic acids with 3,5-dimethylphenyltellurium tribro-
mide, followed by reduction (Scheme 3). Yields for
these reactions were improved by the addition of cop-
per(I) bromide, but were lower than those of ditel-
lurides. All syntheses are summarized in Table 1, yields
refer to isolated products and were calculated based on
boronic acids as limiting reactants.
Example 2: Preparation of 3,5-dimethylphenyl 2%-nitro-
phenyl telluride. A 50 mL round bottom flask equipped
with magnetic stirring and a reflux condenser was
charged with 0.50 g (3.0 mmol) 2-nitrophenylboronic
acid, 1.28 g (3.0 mmol) 3,5-dimethylphenyltellurium
tribromide, 50 mg copper(I) bromide and 15 mL dry
nitromethane. The mixture was heated to reflux for 24
h, then allowed to cool and poured into 50 mL ice
water. Reduction was achieved by the addition of 2 g
sodium bisulfite and stirring for 12 h. The product was
extracted with 2×50 mL dichloromethane, purified by
flash chromatography (neutral alumina/dichloro-
methane) and crystallized from petroleum ether, fol-
lowed by recrystallization from ethanol.
Example 1: Preparation of bis(2-nitrophenyl) ditelluride.
A 50 mL round bottom flask equipped with magnetic
stirring and a reflux condenser was charged with 0.50 g
(3.0 mmol) 2-nitrophenylboronic acid, 0.89 g (3.3
mmol) tellurium tetrachloride and 10 mL dry
nitromethane. The mixture was heated to reflux for 30
min, then allowed to cool and poured into 50 mL ice
water. The mixture was buffered by addition of 2 g
sodium acetate, followed by addition of 2 g sodium
bisulfite and 50 mL dichloromethane. Stirring for 12 h
completed the reduction of 2-nitrophenyltellurium chlo-
ride. The organic phase was collected and the aqueous
phase extracted with 5×25 mL dichloromethane. Sol-
vents were removed from the combined organic phases,
2-Phenethylboronic acid did not react with tellurium
tetrachloride to generate any isolable organotellurium
compounds, suggesting that only aryltellurium com-
pounds can be prepared from boronic acids.
Scheme 3. Preparation of diaryl ditellurides from arylboronic acids.
Table 1. Diaryl ditellurides and diaryl tellurides prepared from arylboronic acids
Reactants
Isolated product
Yield (%)
References
Phenylboronic acid; tellurium tetrachloride
Diphenyl ditelluride
95
85
81
60
80
46
3
2-Nitrophenylboronic acid; tellurium tetrachloride
3-Nitrophenylboronic acid; tellurium tetrachloride
4-Methylphenylboronic acid; tellurium tetrachloride
2-Chlorophenylboronic acid; tellurium tetrachloride
Bis(2-nitrophenyl) ditelluride
Bis(3-nitrophenyl) ditelluride
Bis(4-methylphenyl) ditelluride
Bis(2-chlorophenyl) ditelluride
23,24
25
3
3a,24
(None)b
2-Nitrophenylboronic acid; 3,5-dimethylphenyltellurium tribromide 3,5-Dimethylphenyl 2%-nitrophenyl
telluride
3-Nitrophenylboronic acid; 3,5-dimethylphenyltellurium tribromide 3,5-Dimethylphenyl 3%-nitrophenyl
telluride
54
(None)c
a Previously characterized as red oil. Orange crystals, mp 41–2°C.
b Previously unreported. Orange crystals, mp 131–2°C, 1H NMR (CD3COCD3, 400 MHz): l 8.43 (dd, 1H), 7.61 (s, 2H), 7.48 (m, 1H), 7.42 (m,
1H), 7.29 (dd, 1H), 7.19 (s, 1H), 2.35 (s, 6H). 13H NMR (CDCl3, 300 MHz): l 21.3, 117.9, 123.4, 126.4, 126.8, 131.6, 133.6, 134.7, 139.1, 139.8,
147.7. 125Te NMR (CDCl3, 300 MHz): l 797.8. EIMS, m/z 356.9991 (M+).
c Previously unreported. Yellow crystals, mp 52–4°C, 1H NMR (CDCl3, 400 MHz): l 8.40 (m, 1H), 8.06 (m, 1H), 8.46 (s, 2H), 7.31 (t, 1H), 7.99
(s, 1H), 2.28 (s, 6H). 13H NMR (CDCl3, 300 MHz): l 21.2, 112.8, 117.3, 122.4, 129.9, 130.8, 131.1, 137.4, 139.7, 142.2, 148.5. 125Te NMR
(CDCl3, 300 MHz): l 728.0. EIMS, m/z 356.9997 (M+).