A new method for the synthesis of organotellurium compounds by the use of reductive cleavage of the tellurium-tellurium bond with lanthanum metal

Article abstract of DOI:10.1246/bcsj.78.341

It was confirmed that lanthanum metal is an efficient reagent for the reductive cleavage of the tellurium-tellurium bond of ditelluride. Alkyl phenyl tellurides were prepared by the reaction of diphenyl ditelluride with primary and secondary alkyl halides

Full text of DOI:10.1246/bcsj.78.341

Short Articles
Bull. Chem. Soc. Jpn., 78, 341–343 (2005)
341
Table 1. Reaction of PhTeTePh with HalododecaneaÞ
La, cat.I2
A New Method for the Synthesis
of Organotellurium Compounds
by the Use of Reductive Cleavage
of the Tellurium–Tellurium Bond
with Lanthanum Metal
PhTeTePh
+
C12H25TePh
C12H25
X
THF
(1)
(2)
Entry
RX
Temp./ꢁC
Yeild/%bÞ
1
2
3
4cÞ
5
6
7cÞ
C12H25I
C12H25Br
25
67
25
25
25
67
25
90
89
37
87
trace
49
90
C12H25Cl
ꢀ
Toshiki Nishino, and Noboru Sonoda
Yutaka Nishiyama, Mitsuo Okada,
ꢀ
a) Reaction conditions: PhTeTePh (1.0 mmol), C12H25X (2.0
mmol), La (1.0 mmol), I2 (0.2 mmol), and THF (3.0 mL)
for 5 h. b) GC yield based on C12H25X. c) HMPA (1.0 mL)
was added.
Department of Applied Chemistry, Faculty of Engineering,
Kansai University, Suita, Osaka 564-8680
Received September 2, 2004; E-mail: nishiya@ipcku.kansai-
u.ac.jp
Table 2. Synthesis of Alkyl Phenyl TellurideaÞ
Entry
1
RX
Temp./ꢁC
25
Product
Yield/%bÞ
92
It was confirmed that lanthanum metal is an efficient re-
agent for the reductive cleavage of the tellurium–tellurium
bond of ditelluride. Alkyl phenyl tellurides were prepared
by the reaction of diphenyl ditelluride with primary and sec-
ondary alkyl halides in the presence of lanthanum metal and
a catalytic amount of iodine in moderate to good yields. The
reaction was accelerated by the addition of HMPA. In addi-
tion, the reduction of ditelluride with lanthanum metal, fol-
lowed by the addition of acyl or aroyl chlorides or ꢀ,ꢁ-unsat-
urated ester, provided the Te-phenyl tellurol esters and the ꢁ-
phenyl telluro ester in moderate yields.
C4H9I
C4H9TePh
(3)
C6H13TePh
(4)
2
3
C6H13I
25
67
91
54
(CH3)2CHI
(CH3)2CHTePh
(5)
(5)
C2H5CH(CH3)TePh
4cÞ
5
25
67
93
65
C2H5CH(CH3)I
(6)
(6)
6cÞ
7
25
67
100
11
I
TePh
(7)
(7)
8cÞ
9
25
67
67
0
There is increasing interest in the chemistry of organotellu-
rium compounds, and much effort is being devoted to accom-
plish the synthesis of organotellurium compounds.1 Although
there have been numerous reports on the synthesis of organo-
tellurium compounds, it usually requires the handling of
reagents that are unstable in air and moisture, under strongly
basic or acidic reaction conditions, and involving the use of
multi-step procedures for the preparation of the tellurium
reagents.1a,1d,2 Thus, the development of a one-step synthetic
procedure using a stable tellurium reagent under neutral condi-
tions has attracted much attention. In this paper, we report on a
new approach for the synthesis of organotellurium compounds
by using reductive cleavage of the tellurium–tellurium bond of
ditelluride with lanthanum metal (Scheme 1).3
I
TePh
a) Reaction conditions: PhTeTePh (1.0 mmol), RI (2.0 mmol),
La (1.0 mmol), I2 (0.2 mmol), and THF (3.0 mL) for 5 h.
b) GC yield based on RX. c) HMPA (1.0 mL) was added.
were efficiently utilized in the reaction. The reaction of chloro-
and bromododecane was successfully carried out by elevating
the reaction temperature to produce 2 in 49 and 89% yields,
respectively (entries 2 and 6). It is of interest to note that the
reaction was accelerated by the addition of HMPA, and 2
was obtained in good yield, even when the reaction was carried
ꢁ
out at 25 C (entries 4 and 7).10
When diphenyl ditelluride (1) (1.0 mmol) was allowed to
react with two equivalent amounts of 1-iodododecane (2.0
mmol) in the presence of lanthanum metal (1.0 mmol) and a
catalytic amount of iodine (0.2 mmol) in THF (5 mL) as a sol-
The results of the reaction of diphenyl ditelluride (1) with
various alkyl halides in the presence of lanthanum metal are
given in Table 2. When 1 was allowed to react with primary
alkyl iodides under the same reaction conditions as entry 1
in Table 1, the yields of the primary alkyl phenyl telluride
were high (entries 1 and 2). For the secondary alkyl iodide,
such as 2-iodopropane and 2-iodobutane, the yields of the tel-
luride were slightly lower under similar reaction conditions to
that of the primary alkyl iodides; however, the yields were im-
proved by the addition of HMPA (entries 4 and 6). Cyclohexyl
phenyl telluride was also obtained in 67% yield (entry 8). In
ꢁ
vent at 25 C for 5 h, 1.80 mmol of dodecyl phenyl telluride
(2) was obtained (90% yield based on 1-iodododecane)
(Table 1, entry 1).9 Two phenyltelluro groups contained in 1
La, cat.I2
PhTeTePh
RX
PhTeR
+
THF
Scheme 1.
Published on the web February 11, 2005; DOI 10.1246/bcsj.78.341

342 Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
Ó 2005 The Chemical Society of Japan
the reaction of tertiary alkyl iodide, no alkyl phenyl telluride
was formed, and the alkyl halide was recovered (entry 9).
The reaction of benzyl bromide resulted in the formation of
benzaldehyde in 62% yield.11
metal with alkyl halides (Path 1). Another pathway including
the SH2 reaction of alkyl radicals, which was generated by
the reduction of alkyl halides with lanthanum metal, with ditel-
luride was suggested (Path 2). To better understand the reac-
tion pathway, we carried out some experiments, and obtained
the following results. When PhTeTePh was treated with lan-
thanum metal, lanthanum metal was gradually dissolved to
give a brown solution. Subsequently, the addition of 1-iododo-
decane to the solution provided dodecyl phenyl telluride in
87% yield. On the other hand, when 1-chlorododecane was
added to the brown solution, no alkyl phenyl telluride was
formed. Furtheremore, the addition of HMPA to the resulting
solution caused the formation of dodecyl phanyl telluride
(67%). Based on these results, at the present time, while the
preparation pathway of organotellurium compounds was not
clearly shown, the reaction pathway including the alkylation
of lanthanum phenyltellurolate with alkyl halides was strongly
suggested.
Although the syntheses of the Te-phenyl tellurol esters by
the lanthanum metal-assisted reaction of diphenyl ditelluride
(1) with acyl or aroyl chlorides were next carried out, the
yields of Te-phenyl tellurol esters were low, due to the forma-
tion of various by-products. The product yields were improved
by using a two-step procedure. Diphenyl ditelluride (1) was al-
lowed to react with lanthanum metal in the presence of a cat-
ꢁ
alytic amount of iodine at 25 C for 5 h, and then the acyl or
aroyl chloride was added to the resulting solution, producing
Te-phenyl tellurol esters in 42–75% yields (Scheme 2). Simi-
larly, a reaction of the ꢀ,ꢁ-unsaturated ester efficiently occur-
red to afford the ꢁ-phenyltelluro ester in 63% yield (Scheme 3).
In the case of epoxide, such as 1,2-epoxybutane, the yield of
2-hydroxy-1-phenyltellurobutane was very low (7%) owing
the preparation of various by-products.
Nakamura and Mashima et al. have shown a direct synthetic
method toward lanthanoid thiolate complexes (La ¼ Sm and
Eu) via the reaction of diaryl disulfide with samarium or euro-
pium metal in the presence of a catalytic amount of iodine.12
We have recently found that alkyl radicals were easily gener-
ated by the reduction of alkyl halides with lanthanum metal,
which coupled to form the corresponding dimerization prod-
ucts.13 Based on these bachgrounds, two reaction pathways
for the formation of organotellurium compounds are shown
in Scheme 4.14 One is the reaction of lanthanum phenyltellu-
rolate, prepared by the reduction of ditelluride with lanthanum
We found a new method for synthesizing alkyl phenyl tel-
lurides by the reaction of diphenyl ditelluride with alkyl hal-
ides in the presence of lanthanum metal. Te-Phenyl tellurol es-
ters or ꢁ-phenyltelluro ester were synthesized by the reduction
of ditelluride with lanthanum metal, followed by the addition
of acid chloride or ꢀ,ꢁ-unsaturated esters.
Experimental
1
General Procedures. The H and 13C NMR spectra were re-
corded on 400 and 99.5 MHz spectrometers using CDCl3 as the
solvent with tetramethylsilane as the internal standard. The IR
spectra were recorded on a FT-IR spectrophotometer. Gas chro-
matography (GC) was carried out using a flame-ionizing detec-
tor-equipped instrument and a capillary column (0.25 mm ꢂ
25 m). HPLC separation was performed using recycling prepara-
tive HPLC equipped with GPC columns (20 mm ꢂ 1200 mm).
Reagents. The organic halides and iodine were commercially
available high-grade products, and were used without purification.
The lanthanum metal was a commercially available high-grade
product, which was used after powderization with a rasp. The met-
al was stocked under a nitrogen atmosphere. Diphenyl ditelluride
was synthesized as described in the literature.15 The other reagents
and solvents were purified before use by the usual methods.
General Procedure for the Reaction of Diphenyl Ditelluride
with Organic Halides in the Presence of Lanthanum Metal.
Lanthanum powder (1.0 mmol, 139 mg), iodine (0.2 mmol, 51
mg) and diphenyl ditelluride (1.0 mmol, 409 mg) were placed
in a two-necked flask. THF (5 mL) and the organic halide (2.0
mmol) wꢁere added to the flask, and the mixture was stirred at
25 or 67 C for 5 h under a nitrogen atmosphere. After the reac-
tion, aqueous HCl (1 M) was added to the reaction mixture, and
the mixture was extracted with diisopropyl ether. The organic lay-
er was dried over MgSO4 and filtered. The organic solvent was re-
moved under reduced pressure. Purification of the residue by
HPLC afforded the corresponding alkyl phenyl telluride. The
products were characterized by a comparison of their spectra data
with those of authentic samples (2,9 3,16 4,17 5,17 6,17 and 718).
General Procedure for the Synthesis of Alkyl Phenyl Tellu-
ride in the Presence of HMPA. Lanthanum powder (1.0 mmol,
139 mg), iodine (0.2 mmol, 51 mg), PhTeTePh (1.0 mmol, 409
mg), RI (2.0 mmol), HMPA (1 mL) and THF (5 mL) were added
La (1.0 mmol)
cat. I2 (0.2 mmol)
RCOCl
(2.0 mmol)
PhTeTePh
1.0 mmol
RCOTePh
69 %
25 °C, 3 h
THF (5 mL)
25 °C, 5 h
R = CH3 (8)
R = C5H11 (9)
R = C6H5 (10)
75 %
42 %
Scheme 2.
La (1.0 mmol)
cat. I2 (0.2 mmol)
COOEt
(5.0 mmol)
PhTeTePh
1.0 mmol
THF (5 mL)
25 °C, 5 h
25 °C, 3 h
COOEt
PhTe
63 %
(11)
Scheme 3.
Path 1
La
RX
PhTeTePh
Path 2
RX
La(TePh)n
RTePh
RTePh
PhTeTePh
La
R
ꢁ
Scheme 4.
to the flask, and the mixture was stirred at 25 C for 5 h under a

Y. Nishiyama et al.
Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
343
nitrogen atmosphere. After the reaction, the same workup as de-
scribed in general procedure for the reaction of diphenyl ditellu-
ride with organic halide was carried out to give the corresponding
alkyl phenyl tellurides.
6
a) S.-L. Zhang and Y.-M. Zhang, Synth. Commun., 30, 285
(2000). b) S.-L. Zhang and Y.-M. Zhang, Org. Prep. Proced. Int.,
31, 450 (1999).
7
(1999).
8
16, 267 (1996). b) W.-L. Bao and Y.-M. Zhang, Synth. Commun.,
25, 1913 (1995). c) H.-J. Jiang and Y.-M. Zhang, Youji Huaxue,
14, 307 (1994).
L.-H. Zhou and Y.-M. Zhang, Synth. Commun., 29, 533
Two Step Procedures for Synthesis of Organotellurium
Compounds. A THF (5 mL) solution of lanthanum powder
(1.0 mmol, 139 mg), iodine (0.2 mmol, 51 mg) and PhTeTePh
a) W.-L. Bao, Y.-M. Zhang, and J.-Q. Zhou, Youji Huaxue,
ꢁ
(1.0 mmol, 409 mg) was stirred at 25 C for 5 h under a nitrogen
atmosphere. The acyl or aroyl chlorides or ꢀ,ꢁ-unsaturated ester
(2.0 mmol) was added to the resulting solution, and the mixture
9
We have already reported that the reaction of diphenyl di-
ꢁ
was stirred at 25 C for 3 h. After the reaction, the same workup
selenide with alkyl halides in the presence of lanthanum metal was
an convenient method for the synthesis of alkyl phenyl selenide.
In this manuscript, we have shown only one example of the prep-
aration of dodecyl phenyl telluride by the reaction of diphenyl
ditelluride with dodecyl iodide. See: T. Nishino, M. Okada, T.
Kuroki, T. Watanabe, Y. Nishiyama, and N. Sonoda, J. Org.
Chem., 67, 8696 (2002).
as described in the general procedure for the reaction of diphenyl
ditelluride with organic halide, was carried out to give the corre-
sponding organotellurium compound. The product was character-
ized by comparing its spectra data with those of authentic samples
(8,19 10,20 and 1121). The structures of the product (9) were as-
1
signed by their H and 13C NMR and IR spectra.
Te-Hexyl Tellurobenzoate (9): 1H NMR (CDCl3) ꢂ 0.86–
1.00 (m, 3H, CH3), 1.25–1.34 (m, 4H, CH2), 1.60–1.68 (m, 2H,
CH2), 2.67 (t, J ¼ 7:6 Hz, 2H, CH2), 7.25–7.76 (m, 5H);
13C NMR (CDCl3) ꢂ 13.2, 14.5, 22.3, 24.6, 54.9, 114.0, 128.8,
130.3, 139.3, 140.8, 202.9; IR (neat) 3054.8, 2929.3, 1719.0,
10 It is well-known that the nucleophilic addition of organo-
metallic compounds such as alkyllithium compounds is promoted
by the addition of HMPA or THEDA due to the deaggregation of
organometallic compound by these reagents. From the backgroud,
we suggested that the deaggregation of lanthanum tellurolate with
HMPA raised the nucleophilicity of tellurolate.
1572.2, 1474.3, 1434.7, 1115.7, 997.7, 731.3, 690.0 cmꢃ1
.
11 It is known that benzyl tellurolate is oxidized in air at room
temperature to produce benzaldehyde. See: a) H. K. Spencer and
M. P. Cava, J. Org. Chem., 42, 2937 (1977). b) H. K. Spencer, M.
V. Lakshmikantham, and M. P. Cava, J. Am. Chem. Soc., 99, 1470
(1977).
This research was supported by a Grant-in-Aid for Science
Research (No. 15550096) and Research and Development Or-
ganization of Industry-University Cooperation from the Minis-
try of Education, Culture, Sports, Science and Technology.
12 K. Mashima, Y. Nakayama, H. Fukumoto, N. Kanehisa, Y.
Kai, and A. Nakamura, J. Chem. Soc., Chem. Commun., 1994,
2523.
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