Synthesis and transformations of some new 2,4-bismethylene-1,3-ditelluretanes

Article abstract of DOI:10.1016/S0040-4039(03)00245-4

A novel four-membered 1,3-ditelluretane dialdehyde 8/9 was synthesized from trimethylsilylethynyl tellurolate. The dialdehyde was transformed into extended tetrathiafulvalenes (14 and 15). These are the first examples of ditelluretane spaced TTF derivatives.

Full text of DOI:10.1016/S0040-4039(03)00245-4

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 2397–2400
Synthesis and transformations of some new
2,4-bismethylene-1,3-ditelluretanes
Desikan Rajagopal, M. V. Lakshmikantham, Michael P. Cava,* Grant A. Broker and
Robin D. Rogers
Chemistry Department, University of Alabama, PO Box 87-0336, Tuscaloosa, AL 35487-0336, USA
Received 20 September 2002; revised 21 January 2003; accepted 21 January 2003
Abstract—A novel four-membered 1,3-ditelluretane dialdehyde 8/9 was synthesized from trimethylsilylethynyl tellurolate. The
dialdehyde was transformed into extended tetrathiafulvalenes (14 and 15). These are the first examples of ditelluretane spaced TTF
derivatives. © 2003 Elsevier Science Ltd. All rights reserved.
A number of 1,3-dithietane derivatives 1 have been
synthesized via several approaches but mainly by the
reaction of carbon disulfide with anions derived from
active methylene derivatives.1 In contrast, only three
Scheme 1.
examples of 1,3-diselenetane are known.2 These were
sulfur or selenium, where four-membered rings were
not detected.
obtained when selenaketenes produced in a matrix by
pyrolysis of selenadiazoles were warmed up. The only
1,3-ditelluretane to have been unambiguously charac-
terized via X-ray was the 2,4-bis benzylidene derivative
3.3,4 Petrov et al. have also reported the formation of
1,3-ditelluretanes 3 (R=H, R=Me).5 It should be
noted that these arylidene ditelluretanes are not gener-
ally amenable to further transformations.
In the course of our investigations on the synthesis of
1,3-ditellurole-containing radialene-type TTF deriva-
tives,6 it was observed that depending on the proton-
source and conditions of protonation of the
trimethylsilylethynyl tellurolate anion, either the ditellu-
rafulvalene or the 1,3-ditelluretane derivative can be
generated selectively. Thus, the use of t-butanol at
room temperature furnished the ditellurafulvene 5
whereas the use of trifluoroacetic acid in t-butanol at
−20°C led to the formation of ditelluretane 7 pre-
sumably via the telluraketene 6 (Scheme 2).
Ditelluretane 3 (R=H) was obtained as a very minor
bye-product along with cis/trans 1,3-ditellurafulvene 4
from the reaction of phenylacetylide with tellurium
followed by acidification with trifluoroacetic acid
(Scheme 1). This reaction has no parallel in the case of
Keywords: 1,3-ditelluretane dialdehyde; tellurium; Horner–Wittig reaction.
* Corresponding author.
0040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)00245-4

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D. Rajagopal et al. / Tetrahedron Letters 44 (2003) 2397–2400
Scheme 2.
Some years ago, the synthesis of vinylogous TTF
derivatives bearing a heterocyclic spacer of the type 16
was reported.14 The major difference between 16 and
the present ditelluretane-separated TTF derivatives lies
in the fact that in the former, the dithiole units are
separated by four double bonds whereas in the latter,
the ditelluretane is equivalent to one double bond in
addition to the four double bonds. It can also be
considered to be the equivalent of a cyclohexadiene
unit. No such TTF derivative is reported in the case of
the dithietane and diselenetane series. New approaches
have to be devised so as to make these compounds
available for direct comparison with the ditelluretane
derivatives.
Figure 1. X-Ray structure of trans-bis-2,4-formylmethylene-
1,3-ditelluretane (8).
The use of ethereal hydrogen chloride did not furnish
the telluretane 3 (R=H) exclusively.
Although 5 is reported in the literature,7 we were
unable to isolate it. However, as in the case of 5,
Vilsmeier–Haack reaction on the crude ditelluretane 7
furnished a mixture of trans and cis dialdehydes 8 and
98 in 10% yield (Scheme 2). Their separation proved to
be tedious and involved chromatography via multiple
development on the Chromatotron to isolate small
samples of the pure compounds.
Solutions of ditelluretane 15 were extremely sensitive to
laboratory conditions. Therefore, cyclic voltammetry
was carried out on the ditelluretane derivative 14. The
cyclic voltammogram of 14 showed anodic peaks at
507.1, 715.4, 834.8 and 1318 mV. Only the first oxida-
tion peak was reversible with the corresponding
cathodic peak at 480.2 mV, the difference being 26.9
mV. This behavior is in contrast to that exhibited by
the vinylog 16 (X=O, NMe and S),14 all of which show
two well resolved reversible waves (Table 1).
Both dialdehydes 8 and 9 crystallized readily. However,
only the crystals of the trans isomer 8 were suitable for
X-ray analysis. The crystal structure revealed that 8 is
planar, with the aldehyde groups oriented in the trans
configuration relative to the ditelluretane ring (Fig. 1).
The crystal packing down the crystallographic axis b
revealed the formation of columns through p–p stack-
ing interactions. The distance between molecules in the
,
columns was 6.41 A. The crystal packing down the
No conclusions can be drawn from this result because
of the basic difference between 16 and 14.
crystallographic axis c revealed that the columns were
arranged in a herring-bone fashion. The distance
,
between the molecules in the herring-bone was 4.081 A.
The major difference between 14 and 16 lies in the
species generated during the second oxidation step. The
latter generates a radical cation in the first step and a
dication during the second oxidation step. In contrast,
in the case of 14 the second step can lead to the
formation of a diradical dication (Scheme 4).
In view of the difficulties associated with the separation
of the cis and trans isomers of the dialdehyde, subse-
quent Wittig reactions were carried out on the aldehyde
mixture (8/9). Therefore all the products are E/Z mix-
tures. The stable phosphorane 10 condensed smoothly
with 8/9 to give E/Z diester product 11.9 Diesterdithiole
phosphorane 12 derived from the corresponding phos-
phonium salt,10 as well as the ylid from the dithiole-
phosphonate 1311 condensed smoothly with the
aldehyde mixture to give 14,12 and 15,13 the first exam-
ples of vinylogous TTF derivatives separated by a
1,3-ditelluretane moiety (Scheme 3).
The propensity of tellurium centered radical ions and
cations in five-membered 1,3-ditellurole rings is well
documented.15,16 This is the first example of a cyclic
voltammogram of a functionalized 1,3-ditelluretane. It
will obviously involve synthesis of more 1,3-ditellure-
tane derivatives and extensive electrochemical analysis
to fully understand the behavior of such ion-radicals.

D. Rajagopal et al. / Tetrahedron Letters 44 (2003) 2397–2400
2399
Scheme 3.
Table 1. Oxidation potentialsa of 14 and 16
Compound
Pa1 rev.
Pa2
Pa3 irr.
Pa4 irr.
Pc1 rev.
14
507.1 mV
480.0 mV
690 mV
715.4 mV irr.
810 mV rev.
790 mV
834.8 mV irr.
1.318 V irr.
480.2 mV
16 (X=NMe)
16 (X=S)
16 (X=O)
580 mV
710 mV rev.
a 0.1 molar solution in CH2Cl2 containing TBAHFP, Pt W.E. referenced to SCE.
Scheme 4.
Summary. Preliminary work is presented on the synthe-
sis, and X-ray of the first formyl substituted 1,3-ditel-
luretane. Vinylogous TTF derivatives bearing the
1,3-ditelluretane spacer are described. Cyclic voltamme-
try on one of these vinylogs is presented.
2. Holm, A.; Berg, C.; Bjerre, C.; Bak, B.; Swanholt, H. J.
Chem. Soc., Chem. Commun. 1979, 99.
3. Bender, S. L.; Haley, N. F.; Luss, H. R. Tetrahedron
Lett. 1981, 22, 1495.
4. Lakshmikantham, M. V.; Cava, M. P.; Albeck, M.; Eng-
man, L.; Wudl, F.; Aharon-Shalom, E. J. Chem. Soc.,
Chem. Commun. 1981, 828.
Acknowledgements
5. Laishev, V. Z.; Petrov, M. L.; Petrov, A. A. Zh. Org.
Khimii 1981, 17, 2064 (CA, 1982, 96, 122329).
6. Rajagopal, D.; Lakshmikantham, M. V.; Cava, M. P.
Org. Lett. 2002, 4, 2581.
We thank the National Science Foundation for a grant
(CHE 9910177) in support of this project.
7. Amosova, S. V.; Potapov, V. A.; Bulakhova, Z. A.;
Romanenko, L. Sulfur Lett. 1991, 13, 143.
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