A novel method for the synthesis of telluroesters

Article abstract of DOI:10.1002/jccs.200400053

Diaryl ditellurides were conveniently reduced by a system consisting of cerium trichloride and samarium intetrahydrofuran to produce the aryltellurolates. This "living" tellurolate anion species reacted smoothly with acid chlorides and acid anhydrides to

Full text of DOI:10.1002/jccs.200400053

Journal of the Chinese Chemical Society, 2004, 51, 347-349
347
A Novel Method for the Synthesis of Telluroesters
Xue Lia,b
(
), Songlin Zhang*a (
) and Yongmin Zhangb (
)
aCollege of Chemistry and Environmental Science, Henan Normal University, Xinxiang, 453002, P. R. China
bDepartment of Chemistry, Zhejiang University at Xixi Campus, Hangzhou, 310028, P. R. China
Diaryl ditellurides were conveniently reduced by a system consisting of cerium trichloride and samarium
intetrahydrofuran to produce the aryltellurolates. This “living” tellurolate anion species reacted smoothly
with acid chlorides and acid anhydrides to afford telluroesters in good yields under mild and neutral condi-
tions.
Keywords: Ditellurides; Samarium; CeCl3; Reductive; Aryltelluroester.
INTRODUCTION
Organotellurium compounds have attracted consider-
ing our research in this area, herein we wish to report the
CeCl3/Sm system promoted reductive cleavage of Te-Te
bond in ditellurides to produce aryltellurolates, which re-
acted with acid chlorides and acid anhydrous to afford tellu-
roesters.
able interest recently as reagents and intermediates in organic
synthesis.1 Considering that the C-Te bond of the telluro-
esters is weak and very easily broken, telluroesters have been
employed as mild acyltransfer reagents,2 precursors of acyl
radicals,3 or anions.4 And the findings of its liquid crystal
properties have also been attractive.5
EXPERIMENTAL SECTION
A number of synthetic methods have been found to pre-
pare organotellurium derivatives. A convenient and general
method to introduce a tellurium moiety into organic mole-
cules is the reaction of metal tellurolates with appropriate
electrophiles.6 It can be prepared by the reaction of a benzoyl
chloride with NaTeAr.7 The use of ditellurides and samarium
diiodide in THF/HMPA,8 Sm/ZrCl4,9 Sm/CrCl3 (Cat.)10 have
also recently been reported to give the telluride anions.
In 1980, Kagan and cowoekers11 published a seminal
paper on the usage of samarium diiodide. Following the pio-
neering work of Kagan, a number of important individual re-
actions induced by SmI2 have been found useful in organic
synthesis.12 Although SmI2 is a useful reagent, its sensitivity
to air limits its application in organic synthesis. On the other
hand, metallic samarium is stable in air and its strong reduc-
ing power (Sm3+/Sm = -2.41V) is similar to that of magne-
sium (Mg2+/Mg = -2.37V) and superior to that of Zinc
(Zn2+/Zn = -0.71). These properties encouraged us and other
workers to use the more convenient and cheaper metallic sa-
marium directly instead of samarium diiodide.13
Melting points were uncorrected. IR spectra were ob-
1
tained on a PE-683 infrared spectrophotometer. H NMR
spectra were recorded on a JEOL-90Q NMR instrument in
carbon tetrachloride as solvent and tetramethylsilane as an
internal standard. Tetrahydrofuran was freshly distilled from
sodium benzophenone ketyl before use. Acyl halides and an-
hydrides were commercially available and were used without
further purification. The reaction was performed in a Schlenk
type apparatus and under a nitrogen atmosphere.
GENERAL PROCEDURE
Under nitrogen atmosphere, metallic samarium powder
(3 mmol), cerium trichloride (1 mmol) and ditelluride (0.5
mmol) were placed in a three-necked reaction flask and THF
(10 mL) was added in one portion. The resulting mixture was
magnetically stirred at 30 °C for 4 h, and the cleavage of the
Te-Te bond was indicated by the dissipation of the red color
of the mixture due to ditelluride. To the mixture was added
successively the acid chloride (1.5 mmol) or the acid anhy-
dride (1.5 mmol) and stirred for given times (see Table 1,
TLC as monitored). When the reaction was finished, dilute
HCl (0.1 M, 10 mL) and diethyl ether (50 mL) were added.
The organic layer was washed with water (20 mL ´ 2) and
In our previous work, we investigated the reductive
cleavage of Se-Se bond by a new reductive system CeCl3/Sm
to afford organic seleno compounds.14 And we also reported
the CeCl3/Sm system promoted pinacolic coupling of aro-
matic aldehydes and ketones to afford 1,2-diols.15 In continu-

348 J. Chin. Chem. Soc., Vol. 51, No. 2, 2004
Li et al.
Table 1. Synthesis of the Telluroesters
Entry
Ar
R1
R2
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
Ph
Ph
Ph
P-ClC6H4
o-BrC6H4
P-BrC6H4
P-BrC6H4
2
2
2
2
2
2
3
2
70
72
75
67
73
75
68
71
P-MeC6H4
Ph
Ph
Ph
P-MeC6H4
Ph
CH3
Ph
CH3CH2
a Isolated yields based on ditelluride.
dried over anhydrous Na2SO4. The solvent was removed un-
der reduced pressure; the residue was then purified by pre-
parative TLC on Silica gel with light petroleum and ethyl ace-
tate (100:1) as eluent to give the products.
7.70 (m).
617 p-BrC6H4COTeC6H4Me-p m.p.110-112 °C (lit.
111-112 °C); IR n (cm-1) 3100, 3080, 2980, 2880, 1670,
max
1595, 1580, 1530, 1490, 1385, 1250, 1200, 1170, 1070, 1010,
850, 780, 750, 680; 1H NMR 2.35 (3H, s), 6.90-7.20 (2H, m),
7.40-7.90 (6H, m).
In summary, a novel method for the preparation of
telluroesters has been provided. The advantages of which are
easily available and cheap materials, single product, simple
manipulation, and mild and neutral conditions.
716 CH3COTePh oil; IR n (cm-1) 3090, 3085, 2980,
max
1740, 1580, 1520, 1480, 1440, 1350, 1250, 1080, 1020, 1000,
760, 680; 1H NMR 2.40 (3H, s), 7.00-7.33 (3H, m), 7.51-7.80
(2H, m).
Scheme I
816 CH3CH2COTePh oil; IR n
(cm-1) 3080, 3075,
max
R1COCl
ArTeCOR1
ArTeCOR2
CeCl3/Sm
[ArTe-]
2985, 2960, 2890-2860, 1720, 1560, 1480, 1480, 1440, 1380,
1250, 1020, 1000, 740, 680; 1H NMR 1.16 (3H, t), 2.50 (2H,
q), 7.00-7.30 (3H, m), 7.40-7.73 (2H, m).
ArTeTeAr
(R2CO)2O
-
DATA OF THE PRODUCTS
ACKNOWLEDGEMENT
116 PhCOTePh m.p. 70-71 °C (lit. 71-72 °C); IR n
max
(cm-1) 3080, 3040, 1685, 1600, 1590, 1480, 1280, 1200,
The authors are grateful to the Natural Science Founda-
tion of Henan Province (Project No. 004030700) for financial
support.
1
1170, 1010, 1000, 850, 760, 740, 680, 650; H NMR 7.02-
8.03 (m).
217 PhCOTeC6H4Me-p m.p. 64-66 °C (lit. 65-67 °C); IR
n
max (cm-1) 3100, 3080, 2980, 2880, 1680, 1595, 1580, 1530,
Received May 23, 2003.
1490, 1385, 1250, 1200, 1170, 1070, 1010, 850, 780, 750,
690; 1H NMR 2.35 (3H, s), 6.90-7.10 (2H, m), 7.30-7.70 (5H,
m), 7.90-8.15 (2H, m).
32 p-ClC6H4COTePh m.p. 69-72 °C (lit. 71-72 °C); IR
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A Novel Method for the Synthesis of Telluroesters
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