Preparation of symmetrical divinyl tellurides via an ylidation reaction

Article abstract of DOI:10.1016/S0022-328X(99)00090-X

Symmetrical divinyl tellurides are prepared by sequential reaction of bis-(triphenylmethyl phosphonium) halotellurate with base or by the reaction of triphenylmethylidene phosphoranes with TeCl₄, followed by aldehydes. The products are converted to E-α,β-unsaturated aldehydes by treatment with n-BuLi and DMF.

Full text of DOI:10.1016/S0022-328X(99)00090-X

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 44–47
Preparation of symmetrical divinyl tellurides via an ylidation
reaction
a,
a
a
a
Claudio C. Silveira *, Gelson Perin , Paula Boeck , Antonio L. Braga ,
b
Nicola Petragnani
a
Departamento de Qu ´ı mica, UFSM, 97119-900, Santa Maria, RS, Brazil
b
Instituto de Qu ´ı mica, Uni6ersidade de S a˜ o Paulo, Caixa Postal 20780, S a˜ o Paulo, SP, Brazil
Received 7 December 1998
Abstract
Symmetrical divinyl tellurides are prepared by sequential reaction of bis-(triphenylmethyl phosphonium) halotellurate with base
or by the reaction of triphenylmethylidene phosphoranes with TeCl , followed by aldehydes. The products are converted to
4
E-a,b-unsaturated aldehydes by treatment with n-BuLi and DMF. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Tellurium; Phosphorus; Wittig; Divinyl tellurides
1. Introduction
Tellurium compounds have recently attained a re-
markable development as synthetic reagents and inter-
mediates [1]. Among the many classes of
organotellurium compounds, vinylic tellurides play an
important role [2], justifying a recent review concerning
their preparation and reactivity [3].
The most important synthetic applications of vinylic
tellurides are certainly the detellurative coupling reac-
tions and the transmetalation reaction, i.e. the substitu-
tion of the tellurium moiety by the organic moiety of
different organocuprates [4], and the Li/Te or Cu/Te
exchange giving, respectively, vinyllithium [5] or vinyl-
copper reagents [6].
A straightforward method for the preparation of
symmetrical divinyl tellurides is based on the hydrotel-
luration of acetylenes with the system Te/NaBH4/
EtOH, THF/aq NaOH [6a]. However, this method,
which produces predominantly Z adducts, works well
only with acetylenes conjugated to aryl groups, CꢀC
double bonds or other electron-withdrawing groups. By
contrast, alkylacetylenes are fairly unreactive, in accor-
dance with the unsatisfactory results described for the
addition of organotellurolates to these acetylenes [5b,6].
Symmetrical divinyl tellurides are especially useful in
transmetalation reactions since by treating them with
two equivalents of Li or copper reagents, both of the
vinyl groups are displaced. This process occurs with
retention of the carbon–carbon bond geometry and the
resulting Li derivative can be trapped by a variety of
electrophiles.
2. Results and discussion
New methods for the preparation of symmetrical
divinyl tellurides deserve additional efforts. In this pa-
per we describe the preparation of these compounds in
*
Corresponding author. Fax: +55-55-220-8754.
E-mail address: silveira@quimica.ufsm.br (C.C. Silveira)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00090-X

C.C. Sil6eira et al. / Journal of Organometallic Chemistry 584 (1999) 44–47
45
accordance with the approach previously reported by
us for the preparation of arylvinyl tellurides [7] employ-
ing aryltellurophosphoranes. The method consists in
the sequential treatment of bis-(triphenylmethylphos-
phonium) halotellurate [8] 1 with excess of base (six
equivalents LICA–lithium dicyclohexylamide) and then
with the aldehyde in THF at −78°C. This sequence
involves the step by step deprotonation of 1, generating
the bis-dichlorotellurophosphonium salt 2 and in se-
quence the bis-dichlorotellurophosphorane 3. Reaction
with two equivalents of the aldehyde should have pro-
duced the divinyl tellurium dichloride 4. However, 4
was not isolated and instead, the divinyltelluride 8 was
obtained [9]. This intriguing result can be rationalized
on the basis of the known reaction of phosphoranes
with dihalogen sources giving a-haloalkyl/phosphonium
halides [10]. Once 3 is formed, it suffers dehalogenation
by disproportionation to give the bis-tellurophospho-
rane 5 and mono-chloro or di-chlorophosphonium
chlorides 6 or 7. The divinyl telluride 8 is then pro-
duced by the Wittig reaction of 5 with the aldehyde
Scheme 2.
By performing the olefination reaction in the presence
of 30% HMPA as a co-solvent, the Z,Z isomer becomes
predominant (doublets at l 7.00 and 7.43 ppm with
1
J=10.6 Hz) as deduced from H-NMR (200 MHz) and
by comparison with an authentic sample prepared by
another route [6b]. The predominant formation of Z
geometry was confirmed by treatment with n-BuLi
followed by benzaldehyde giving the corresponding al-
lylic alcohol, PhCHꢀCHCH(OH)Ph, in 64% yield (see
1
Section 3.2) and in a 1:5 ratio as assessed by H-NMR
(
E:Z).
In the case of aliphatic aldehydes, the Z geometry
from the Z,Z and Z,E isomers) is preferred in both
(
1
solvent systems, as can be deduced from the H-NMR
(
Scheme 1).
1
(
400 MHz). For example, H-NMR of the reaction
Our efforts to isolate the chlorinated phosphonium
salts 6 or 7 as pure compounds were unsuccessful due
to the intractable nature of these materials.
product with isobutyraldehyde shows a doublet of dou-
blets at l 6.06 ppm (J=9.2 and 8.8 Hz) and two
doublets at 6.40 (J=8.8 Hz) and 6.43 ppm (J=9.2
Hz). With n-butyraldehyde and using HMPA as co-sol-
vent, the Z geometry is also predominant ( H-NMR,
00 MHz, a doublet at l 6.55 ppm, H a to Te, J=9.2
The reactions with aromatic aldehydes were not
stereoselective under the conditions employed, giving
Z,Z, E,Z and E,E isomer mixtures, with a preferential
E geometry (from the E,Z and E,E isomers). This fact
1
4
Hz). A small doublet at l 6.51 ppm (J=16.0 Hz; H a
to Te) can be identified for the E-isomer.
1
can be easily deduced from the H-NMR spectra of the
reaction with benzaldehyde where a 16.6 Hz coupling
constant of the doublets at l 7.12 and 7.13 ppm (H a to
Te) and 7.44 and 7.48 ppm (for H b to Te) was
observed. The formation of E geometry on the double
bonds is also confirmed by treatment with n-BuLi and
capture of the intermediate vinyllithium with benzalde-
hyde [6b]. The allylic alcohol was isolated with 50%
A metal salt and base dependence was observed both
on the stereochemistry of the divinyl tellurides as well
as on the yield (for the reaction with benzaldehyde).
Using KH instead of n-BuLi in THF, the Z,Z-product
was formed almost exclusively, but in only 12% isolated
yield. Other bases like LDA and LiN(SiMe ) also gave
3
2
1
the products in very low yield.
yield in a ca. 4:1 ratio as assessed by H-NMR (E:Z).
An alternative methodology was also studied. The
starting bis-tellurophosphorane 5 was prepared in situ
by means of a transylidation reaction between TeCl4
and an excess of alkylidenetriphenylphosphorane (gen-
erated from the corresponding phosphonium salt and
n-BuLi) 9. The tellurobisphosphorane 5 reacted with
aldehydes giving the expected divinyl tellurides 8 in
acceptable yields (Scheme 2). Again, inversion of the
stereochemistry was observed by the use of HMPA as a
co-solvent. The yields obtained by both methods are in
the same range. The reactions were also performed on
a larger scale (3 or 5 mmol, see Table 1) with compara-
ble yields.
To illustrate the usefulness of the prepared com-
pounds, we performed the transmetalation of bis-vinyl
tellurides with n-BuLi at −78°C, which can be em-
ployed to prepare a,b-unsaturated aldehydes 10 by
treatment of the intermediate vinyllithiums with DMF
Scheme 1.

46
C.C. Sil6eira et al. / Journal of Organometallic Chemistry 584 (1999) 44–47
Table 1
Divinyl tellurides prepared from the tellurophosphonium salt 1 (Scheme 1) and from TeCl4 (Scheme 2)
Product
R
Yield (%) from Te-salt 1
Yield (%) from TeCl4
THF
THF
THF/HMPA
THF/HMPA
8a
8b
8c
8d
8e
8f
C H
4-MeC H
2-Furyl
4-ClC H
44 (33 a)
43 (43 a)
48 (45 b)
30
28
42
30
15
34
6
5
47
30
45
20
22
25
24
27
45
27
46
42
20
34
25
6
4
6
4
(CH ) CH
3
2
CH CH CH
3
2
2
a
Reaction performed on 3 mmol scale.
Reaction performed on 5 mmol scale.
b
(
Scheme 3). These aldehydes, irrespective of the geometry
a solution of LICA–lithium dicyclohexylamide (3 mmol)
in THF (3 ml) was added dropwise. After 3 h of stirring
at this temperature, benzaldehyde (0.159 g, 1.5 mmol)
was added. The temperature was raised to room temper-
ature, the mixture was stirred for 2 h and then treated
with water and extracted with ethyl acetate (3×25 ml).
of the starting bis-vinyl telluride, were formed with
E-stereochemistry under the conditions employed (DMF
added at −78°C, followed by stirring at room temper-
ature for 2 h). For reactions performed only at −78°C,
an isomeric mixture of E:Z isomers 10b is isolated (8:1
ratio, for Ar=4-MeC H ), in essentially the same yield.
The organic layer was dried over MgSO and the solvent
6
4
4
Considering that the described reaction is feasible for
both aromatic and aliphatic aldehydes, thus providing
dialkyl vinylic tellurides which can hardly be obtained by
hydrotelluration of alkyl acetylenes, and that the yields,
in spite of being moderate, are obtained under simple
experimental conditions and are not far from the theoret-
ical, the described method is certainly a useful contribu-
tion for the preparation of symmetrical divinyl tellurides.
removed under vacuum. The residue was purified by
column chromatography over silica gel, eluting with
hexane, to afford the bis-(2-phenylethenyl)telluride 8a
1
(mixture of isomers). Yield 0.073 g, 44%. H-NMR (200
MHz, CDCl , l ppm) 7.00 (d, 1H, J=10.6 Hz); 7.09 (d,
3
1H, J=10.6 Hz); 7.12 (d, 1H, J=16.6 Hz); 7.13 (d, 1H,
J=16.6 Hz); 7.20–7.38 (m, 10H); 7.43 (d, 1H, J=10.6
Hz); 7.44 (d, 1H, J=16.6 Hz); 7.48 (d, 1H, J=16.6 Hz);
7
.49 (d, 1H, J=10.6 Hz); Anal. Calcd for C H Te
16 14
(
333.88): C, 57.56; H, 4.23. Found: C, 57.28; H, 4.19. MS
+
3. Experimental
(m/z): 337 [M +1], 256, 167 (100%), 77.
3.1. General
3
.2.2. Preparation of 8e by TeCl method
4
1
13
To a solution of methyltriphenylphosphonium iodide
2.43 g, 6 mmol) in dry THF (25 ml) under nitrogen, at
H- and C-NMR spectra of CDCl solutions were
3
(
recorded on a 200 MHz (Bruker DPX 200), or a 400 MHz
Bruker DPX 400) spectrometer as noted. Chemical
room temperature, n-BuLi (6 mmol) was added drop-
wise. After stirring at room temperature for 20 min the
solution was cooled to −78°C and a solution of TeCl4
0.270 g, 1 mmol) in dry THF (10 ml) was added. The
mixture was stirred for 20 min and isobutyraldehyde
0.216 g, 3 mmol) was added. The temperature was raised
(
shifts are expressed as parts per million (ppm) with
respect to tetramethylsilane as an internal standard.
Mass spectra (EI) were obtained at 70 eV with a
Hewlett–Packard EM/CG HP-5988A spectrometer. Ele-
mental analyses were performed on a Vario EL Elemen-
tar Analysensysteme. Reactions were conducted in
oven-dried (120°C) glassware under a nitrogen atmo-
sphere. Merck silica gel (230–400 mesh) was used for
flash chromatography. THF was distilled over sodium/
benzophenone immediately before use.
(
(
to room temperature, the mixture was stirred for 3 h and
then treated with water and extracted with ethyl acetate
(
3×25 ml). The organic layer was dried over MgSO and
4
the solvent removed under vacuum. The residue was
purified by column chromatography over silica gel,
eluting with hexane, to afford 8e (mixture of isomers).
3.2. Synthesis of symmetrical di6inyl tellurides. Typical
procedures
3
.2.1. Preparation of 8a from tellurophosphonium salt 1
To a solution of tellurophosphonium salt 1 (0.539 g,
.5 mmol) in dry THF (5 ml) at −78°C under nitrogen,
0
Scheme 3.

C.C. Sil6eira et al. / Journal of Organometallic Chemistry 584 (1999) 44–47
47
1
1
Yield 0.09 g, 34%. H-NMR (400 MHz, CDCl , l ppm)
210°C). H-NMR (200 MHz, CDCl , l ppm) 2.37 (s,
3
3
0
.95–1.12 (m, 12H); 2.2–2.5 (m, 2H); 6.06 (dd, 1H,
3H); 6.65 (dd, 1H, J=15.9, 7.6 Hz); 7.21 (d, 2H,
J=8.0 Hz); 7.37–7.46 (m, 3H); 9.65 (d, 1H, J=7.6
Hz).
J=9.2 Hz, J=8.8 Hz); 6.20 (dd, 1H, J=16.2 Hz,
J=6.6 Hz); 6.21 (dd, 1H, J=16.2 Hz, J=6.6 Hz);
6.40 (d, 1H, J=8.8 Hz); 6.43 (d, 1H, J=9.2 Hz); 6.48
(
1
dd, 1H, J=16.4 Hz, J=1.2 Hz); 6.49 (dd, 1H, J=
6.4 Hz, J=1.2 Hz). MS (m/z): 268 [M ], 95, 69
+
Acknowledgements
(
100%), 41.
The authors thank CNPq, CAPES and FAPERGS
for financial support.
3
.3. (Z,E)-Phenyl-1-hydroxy-3-phenylprop-2-ene from
(Z,Z; E,Z and E,E)-bis-(2-phenyl ethenyl) telluride
To
a solution of bis(2-phenylethenyl) telluride
References
(
0.334g, 1 mmol) in THF (4 ml) at −78°C under
nitrogen, a solution of n-BuLi (0.91 ml, 2.2 mmol, 2.42
M solution in hexane) was added dropwise. After 20
min of stirring at this temperature, benzaldehyde (0.265
g, 2.5 mmol) was added. The mixture was stirred for 30
min, then diluted with ethyl acetate (30 ml) and washed
with brine (4×15 ml). The organic layer was separated,
[
1] For recent reviews on the application of tellurium reagents in
organic synthesis see: (a) N. Petragnani, J.V. Comasseto, Synthe-
sis (1986) 1; (1991) 793 and 897. (b) N. Petragnani, Best Syn-
thetic Methods—Tellurium in Organic Synthesis, Academic
Press, New York, 1994. (c) I.D. Sadekov, V.I. Minkin, Russ.
Chem. Rev. 64 (1995) 491. (d) N. Petragnani, in: McKillop (ed.),
Comprehensive Organometallic Chemistry II, vol. 11, 1995,
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2] (a) N.K. Gusarova, A.A. Takarinova, M. Sirregovskaya, Sulfur
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dried over MgSO and solvent removed under vacuum.
4
The residue was purified by column chromatography
over silica gel. Elution with hexane removed dibutyl
telluride, and elution with ethyl acetate gave an oil.
[
1
Yield 0.269 g, 64%, E:Z=1:5. H-NMR (200 MHz,
CDCl , l ppm) E+Z isomers: 2.59 (s, 1H); 7.10–7.40
3
[3] J.V. Comasseto, W.L. Lo, N. Petragnani, H.A. Stefani, Synthesis
(1997) 373.
[
[
(
1
m, 10H). Z isomer: 5.55 (d, 1H, J=9.2 Hz); 5.85 (dd,
H, J=11.4, 9.2 Hz); 6.59 (d, 1H, J=11.4 Hz). E
4] Ref. [3], Section 3.2.2.
5] (a) Ref. [3], Section 3.3. (b) F.C. Tucci, A. Chieffi, J.V. Comas-
seto, J.P. Marino, J. Org. Chem. 61 (1996) 4975.
6] (a) H. Takahashi, K. Ohe, S. Uemura, N. Sugita, Nippon
Kagaku Kaishi (1987) 1508. (b) S.M. Barros, M.J. Dabdoub,
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7] C.C. Silveira, G. Perin, A.L. Braga, N. Petragnani, Synlett
isomer: 5.25 (d, 1H, J=6.2 Hz); 6.29 (dd, 1H, J=15.8
Hz, J=6.2 Hz); 6.59 (d, 1H, J=15.8 Hz).
[
3.4. (E)-p-Methylcynnamaldehyde 10b from (Z,Z; E,Z
[
[
and E,E)-bis-[2(p-tolyl)ethenyl] telluride
(
1995) 58.
8] (a) A very stable colored salt prepared by the reaction of TeCl
4
To a solution of bis-[2-(p-tolyl) ethenyl] telluride
+ −
with two equivalents of Ph PCH ]
I
. (b) N. Petragnani, L.
3
3
(
0.362 g, 1 mmol) in THF (4 ml) at −78°C under
Torres, J. Organomet. Chem. 76 (1974) 241.
nitrogen, a solution of n-BuLi (0.91 ml, 2.2 mmol, 2.42
M solution in hexane) was added dropwise. After 20
min of stirring at this temperature, DMF (0.2 ml, 2.58
mmol) was added. The temperature was raised to room
temperature and stirred for 2 h, then diluted with ethyl
acetate (30 ml), and washed with water (3×20 ml). The
[9] The yield was not increased by treatment of the crude of reaction
mixture with NaBH4 to reduce any divinyl tellurium dichloride
to 8.
10] (a) D.B. Densey, S.T. Ross, J. Org. Chem. 26 (1962) 99. (b) A.N.
Pudovik, I.M. Aladzheva, L.N. Yakovenko, Zh. Obsch. Khim.
[
[
3
5 (1965) 1210 [C.A., 63 (1965) 11609]. (c) A.J. Speziale, K.W.
Rath, J. Org. Chem. 28 (1963) 465. (d) E. Zbiral, M. Rasberger,
Tetrahedron 25 (1969) 1871. (e) R. Amos, J. Org. Chem. 50
organic layer was separated, dried with MgSO and
4
(
6
1985) 1311. (f) X.Y. Li, Y.S. Hu, Tetrahedron Lett. 28 (1987)
317. (g) K. Yamagata, M. Takaki, M. Yamazaki, Liebigs Ann.
solvent removed under vacuum. Elution with hexane
removed dibutyl telluride, and elution with ethyl acetate
gave a low m.p. solid, 0.175 g, 60% (characterized as
the semicarbazone: m.p. 208.4–209.4°C; Literature [11]
Chem. (1993) 1109.
11] M. Scholtz, A. Wiedemann, Ber. Dtsch. Chem. Ges. 36 (1903)
845.
.