An efficient synthesis and structural aspects of hexakis(arylseleno) benzenes and hexakis(arylselenomethyl)benzenes

Article abstract of DOI:10.1016/j.tetlet.2004.07.020

An efficient synthesis and structural aspects of a novel class of selenium bearing hexa-hosts by the reaction of hexafluorobenzene or hexakis(bromomethyl) benzene with RSe^- ions is demonstrated. However, under identical reaction conditions, our attempts to prepare tellurium analogues by the reaction of RTe^- (R = Ph or p-CH₃C₆H₄-) with hexafluorobenzene or hexakis(bromomethyl)benzene to obtain (RTe) ₆C₆ and (RTeCH₂)₆C₆ proved to be difficult.

Full text of DOI:10.1016/j.tetlet.2004.07.020

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 6611–6613
An efficient synthesis and structural aspects of hexakis
(arylseleno)benzenes and hexakis(arylselenomethyl)benzenes
Naveen Kumar, Marilyn Daisy Milton and Jai Deo Singh*
Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India
Received 3 June 2004; revised 29 June 2004; accepted 6 July 2004
Available online 24 July 2004
Respectfully dedicated to Professor Tej Narayan Srivastava, who passed away on 27 December 2003
Abstract—An efficient synthesis and structural aspects of a novel class of selenium bearing hexa-hosts by the reaction of hexafluoro-
benzene or hexakis(bromomethyl) benzene with RSeꢀ ions is demonstrated. However, under identical reaction conditions, our
attempts to prepare tellurium analogues by the reaction of RTeꢀ (R=Ph or p-CH3C6H4-) with hexafluorobenzene or hexa-
kis(bromomethyl)benzene to obtain (RTe)6C6 and (RTeCH2)6C6 proved to be difficult.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Currently considerable efforts are being devoted to the
synthesis of hexasubstituted benzene derivatives with
1,3,5- or 2,4,6-substitution pattern, leading to character-
istically preorganized systems and a wide range of inclu-
sion behavior has been established for hexa-host type
molecules.1 Certain structural features present in host
compounds, such as size, shape, and the symmetry of
the host molecule, can maximize opportunities for inclu-
sion complex formation. Furthermore, the modification
of a known host might lead to new hosts with properties
significantly different from those of the parent in terms
of both cavity size and selective inclusion behavior. In
this regard a wide range of hexa-hosts containing either
oxygen2 or sulfur1,3 have been studied in detail for their
multimolecular inclusion behavior. In contrast, compar-
atively little work has appeared concerning the structur-
ally related selenium analogues.4,5 For example, the
investigations on (PhSe)6C6, (PhSeCH2)6C6, and
(ptBuC6H4SeCH2)6C6 are limited to their synthesis and
the structures of the resulting products remain unex-
plored despite the fact that these systems might exhibit
self-organizing properties and may create useful nonhy-
drogen-bonded networks through chalcogenꢁ ꢁ ꢁchalco-
gen interactions.
R'
R'
R
R
R
R
Se
R'
Se
R
R
Se
Se
R
R
Se
R'
R
R
Se
R
R
R'
R'
R' = R = H 1 ; R' = Me, R =H 2 ; R' = OMe, R = H 3 ;
R' = R = Me 4 ; R' = R = CHMe 5 ; R' = R = CMe
6
3
2
Our curiosity regarding the structures of these hexa-
hosts was stimulated by our continuing interest in the
search for potential organoselenium or tellurium-con-
taining molecules whereby the chalcogen atoms could
play an important role in the design and synthesis of
highly diverse spatially arranged single components with
a view to creating nonhydrogen-bonded networks. In
the present study a new and different strategy is em-
ployed for the selenium-containing hexa-hosts, the main
objective being the design and synthesis of new hosts
with no direct structural relationship to any other host.
Sodium areneselenolate ions,6 can be generated in situ
by the reduction of the corresponding diaryldiselenide
in aqueous THF with sodium borohydride at 0ꢁC. A
ÔproblemÕ we encountered immediately was that NaBH4
Keywords: Selenium; Hexa-host; Inclusion complexes; X-ray structure.
*
Corresponding author. Tel.: +91-11-26596455; fax: +91-11-
26862037; e-mail: jaideo@chemistry.iitd.ernet.in
0040-4039/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.07.020

6612
N. Kumar et al. / Tetrahedron Letters 45 (2004) 6611–6613
was not very soluble in anhydrous THF. However, the
addition of a few drops of water to the anhydrous
THF apparently facilitated dissolution (giving clear
solutions as observed), and generated the corresponding
ArSeꢀ anion.7 It reacted cleanly with hexabromomethyl-
benzene and, after completion of the reaction, the prod-
uct in solution was recovered by conventional aqueous
workup in excellent yields (>90%) and high purity. In
particular, compound 2 was easily isolated as white crys-
tals after removal of the solvent.8 We also attempted the
synthesis of hexakis(phenylseleno)benzene [(PhSe)6C6] 7
via a modified route. The synthesis of the first example
of hexakis(phenylseleno)benzene has been reported in
the literature; it was prepared by the reaction of PhSeNa
with C6Cl6 in HMPA at ambient temperature for four
days, furnishing a 51% yield of hexakis(phenylse-
leno)benzene.4 This compound can easily be obtained
by the reaction of 1mol of hexafluorobenzene with
6mol of the PhSeꢀ anion generated in situ for a stoichio-
metric and complete reaction.9 However, under identical
conditions, our attempts to prepare tellurium analogues
by the reaction of RTeꢀ (R=Ph or p-CH3C6H4-) with
hexakis(bromomethyl)benzene and hexafluorobenzene
to afford (RTe)6C6 and (RTeCH2)6C6 proved to be dif-
ficult and recovery of R2Te2 from the reaction mixture
was the typical outcome (Scheme 1).
crystal X-ray diffraction studies of the compound
(PhSeCH2)6C6 1 revealed that the molecule crystallizes
in a monoclinic, C2/c, space group.11 The distribution
of the side-chain phenylseleno units of compound 1
was regular as they were arranged alternatively above
and below the central benzene ring plane (ababab con-
formation, a=above and b=below).
In summary, we have demonstrated that multi-selenium
aromatic compounds can be synthesized easily. The
hexa-host compounds of oxygen and sulfur have been
prepared and encouragingly formed a number of inclu-
sion complexes with solvent molecules and are capable
of binding metal cations in solution as well. However,
we could not find any inclusion phenomenon in our sys-
tems. Due to their sterically congested structures, they
might be regarded as building blocks for larger p-conju-
gated systems aiming at star-shaped molecules with new
properties. We are currently involved in examining
their applications and results will be reported in due
course.
Acknowledgements
Financial support from the Department of Science and
Technology (DST), India is gratefully acknowledged.
We are also thankful to CSIR and UGC for providing
research fellowships to N.K. and M.D.M. Thanks are
also due to RSIC, Lucknow, India for providing
ES-MS spectra.
Compounds (1–7) are crystalline in nature and poorly
soluble in common organic solvents when freshly pre-
pared and the solubility further decreased after crystalli-
zation. They can be crystallized from a solution of
benzene or toluene. Physicochemical and spectral stud-
ies are in good agreement with the proposed stoichio-
metry. 1H and 13C NMR spectral data showed no
unusual features, suggesting in all cases, the equivalence
of the REꢀ groups as well as the ring carbons indicating
symmetrical structures. The electrospray mass spectral
(ES-MS) technique was found to be quite helpful in
establishing structures on the basis of fragmentations.
Although the parent molecular ion peaks were not ob-
served, in each case the loss of one arylseleno group
was always observed from the parent ion and the result-
ing signals were attributable to the consecutive loss of
the arylseleno groups as part of their fragmentation pat-
tern.10 The stepwise fragmentation pattern further con-
firms the symmetrical nature of the product. Single
References and notes
1. For general discussions on hexa-hosts, see: (a) Toda, F. In
Inclusion Compounds; Atwood, J. L., Davies, J. E. D.,
MacNicol, D. D., Eds.; Oxford University Press: Oxford,
1991; Vol. 4, pp 126; (b) MacNicol, D. D.; Downing, G.
A. In Comprehensive Supramolecular Chemistry; MacNi-
col, D. D., Toda, F., Bishop, R., Eds.; Elsevier Science:
Oxford, 1996; Vol. 6, pp 421; (c) Weber, E. In Compre-
hensive Supramolecular Chemistry; MacNicol, D. D.,
Toda, F., Bishop, R., Eds.; Elsevier Science: Oxford,
1996; Vol. 6, pp 535.
2. (a) Gilmore, C. J.; MacNicol, D. D.; Mallinson, P. R.;
Murphy, A.; Russell, M. A. J. Inclusion Phenom. 1984, 1,
295–301; (b) Gilmore, C. J.; MacNicol, D. D.; Murphy,
A.; Russell, M. A. Tetrahedron Lett. 1983, 24, 3269–3272;
(c) Goodgame, D. M. L.; Grachvogel, D. A.; White, A. J.
P.; Williams, D. J. Inorg. Chim. Acta 2003, 344, 214–220;
(d) Freer, A. A.; MacNicol, D. D.; Mallinson, P. R.;
Vallance, I. Tetrahedron Lett. 1992, 33, 261–264; (e)
Ranganathan, S.; Muraleedharan, K. M.; Chandrashe-
khar Rao, C. H.; Vairamani, M.; Karle, I. L.; Gilardi, R.
D. Chem. Commun. 2001, 2544–2545; (f) Kobayashi, K.;
Shirasaka, T.; Horn, E.; Furukawa, N. Tetrahedron Lett.
2000, 41, 89–93; (g) Kobayashi, K.; Sato, A.; Sakamoto,
S.; Yamaguchi, K. J. Am. Chem. Soc. 2003, 125,
3035–3045; (h) Elwahy, A. H. M. Tetrahedron Lett.
2001, 42, 5123–5126; (i) Kobayashi, K.; Shirasaka, T.;
Sato, A.; Horn, E.; Furukawa, N. Angew. Chem., Int. Ed.
1999, 38, 3483–3486.
-
RSe / DMF
R = Ph, n = 0, X = F
X
ER
-
( )
( )
RSe / THF
( )
( )
X
ER
( )
n
n
( )
n
( )
n = 1, X = Br
n
( )
n
n
X
ER
-
X
RE
RTe / THF
( )
( )
( )
X
( )
n
n
n
n
X
n = 1, X = Br;
R = Ph, p-CH C H -
ER
n
n
X
RE
3
6 4
-
RTe / DMF
n = 0, X = F;
X
R = Ph, p-CH C H -
3
6 4
Scheme 1. Reagents and conditions: E=Se, n=1, R=Ph 1 (90%); p-
4
CH3C6H4
2
(92%); MeO–C6H4
3
(95%); 2,4,6-Me3C6H2
(92%); 2,4,6-iPrC6H2 5 (91%); 2,4,6-tBuC6H2 6 (93%); E=Se, n=0,
R=Ph 7 (91%).
3. (a) Vo¨gtle, F.; Weber, E. Angew. Chem., Int. Ed. Engl.
1974, 13, 814–816; (b) Freer, A.; Gilmore, C. J. Tetrahe-

N. Kumar et al. / Tetrahedron Letters 45 (2004) 6611–6613
6613
dron Lett. 1980, 21, 205–208; (c) MacNicol, D. D.;
Swanson, S.; Wilson, D. R. J. Chem. Soc., Perkin Trans.
2 1980, 999–1005; (d) Testaferri, L.; Tingoli, M.; Tiecco,
M. J. Org. Chem. 1980, 45, 4376–4380; (e) Barner-
Kowollik, C.; Dalton, H.; Davis, T. P.; Stenzel, M. H.
Angew. Chem., Int. Ed. 2003, 42, 3664–3668; (f) Hiraoka,
S.; Shiro, M.; Shionoya, M. J. Am. Chem. Soc. 2004, 126,
1214–1218.
trated to dryness on a rotary evaporator to give 2 as
essentially white crystals in >90% yield.
9. To a stirred solution of diphenyldiselenide (0.94g, 3mmol)
in DMF (10mL) at 0ꢁC under an N2 atmosphere was
added sodium hydride (60% dispersion in mineral oil,
0.12g, 3mmol) in pinches. After the liberation of H2 gas
had ceased, the reaction mixture was stirred for an
additional 30min. To this mixture, a solution (0.94g,
0.5mmol) of hexafluorobenzene in 5mL of DMF was
added dropwise over 15min, and the resulting reaction
mixture was stirred for an additional 2h. It was then
poured into 100mL of ice-water, and the white precipitate
formed was filtered and dried overnight in air yielding
0.92g (91%) of the desired compound. Crystallization
from chloroform/diethyl ether mixture (50:50) yielded
colorless crystals.
4. MacNicol, D. D.; Mallinson, P. R.; Murphy, A.; Sym, G.
J. Tetrahedron Lett. 1982, 23, 4131–4134.
5. (a) MacNicol, D. D.; Wilson, D. R. J. Chem. Soc., Chem.
Commun. 1976, 494–495; (b) Hardy, A. D. U.; MacNicol,
D. D.; Wilson, D. R. J. Chem. Soc., Perkin Trans. 2 1979,
1011–1019.
6. (a) Generation of arylchalcogenolate anions are well
known in nonaqueous media, however, this complicated
procedure involves the reaction of diaryldichalcogenide
using sodium metal in THF for reduction and required
36h refluxing to generate the arylchalcogenolate anions;
(b) Tani, H.; Inamasu, T.; Suzuki, H. Heterocycles 1992,
34, 341–347.
7. On the basis of many experiments, we finally established
that the reaction was most satisfactorily run in THF at
temperatures around 0ꢁC with the molar ratios between
the reactants (Ar2Se2:NaBH4:NaOH) being 1:2.2:2.2 in
anhydrous THF containing 2% water.
8. To a cooled (0ꢁC) and stirred solution of (p-CH3C6H4)2Se2
(1.02g, 3mmol) and sodium hydroxide (0.25g, 6.6mmol)
in aqueous THF (20 mL+0.2mL H2O) under N2(g), was
added NaBH4 (0.419g, 6.6mmol) (exothermic) in pinches.
The yellow color of the selenol was soon generated and
then gradually faded to a colorless solution (usually taking
only a few minutes). This was allowed to warm to room
temperature over 0.5h. The clear colorless solution thus
formed was treated with hexabromomethylbenzene (0.32g,
2.2mmol), which was added as a solid in portions. The
reaction mixture was stirred for 6h at room temperature
and was then diluted with aqueous NH4Cl solution
followed by extraction with chloroform (3·25mL). The
combined organic extracts were washed with water and
brine and dried over anhydrous MgSO4. The drying agent
was removed by filtration, and the filtrate was concen-
10. For compound 2, [Mꢀ(SeC6H4 ꢀCH3-p)]+ [m/z=1006.54
(calcd 1007.68)], [Mꢀ2(SeC6H4 ꢀCH3-p)]+ [m/z=836.47
(calcd 838.60)], [Mꢀ3(SeC6H4 ꢀCH3-p)]+ [m/z=668.38
(calcd 669.52)], [Mꢀ4(SeC6H4 ꢀCH3-p)]+ [m/z=498.37
(calcd 500.44)], [Mꢀ5(SeC6H4 ꢀCH3-p)]+ [m/z=330.42
(calcd 331.55)].
11. Diffraction measurements were made on a Siemens smart
Apex CCD diffractometer with graphite-monochromated
˚
MoKa (k=0.7107A) radiation at room temperature. The
crystal structure was solved by direct methods using the
SHELXTL package. Semi-empirical absorption correction
was applied using the SAD ABS program. All nonhydro-
gen atoms were refined anisotropically, and hydrogen
atoms were located using geometrical constraints. The
heaviest atoms were located first and the remaining atoms
were deducted from subsequent Fourier difference synthe-
ses. The final cycle of full-matrix least-squares refinement
on F2 was based on 4848 observed reflections and 329
variable parameters and converged with unweighted and
weighted agreement factors of: R1=RiF0jꢀjFCi/R—
jF0 i=0.0366 for 3193F0 > 4sig (F0) and 0.0588 for all
2
2 1=2
4848 data; wR2 ¼ ½RðwðF 20 ꢀ F C2 Þ Þ=RwðF 02Þ ꢂ ¼ 0:0772.
Compound 1, colorless cubes (0.50·0.10·0.05mm)
is monoclinic, C48H42Se6, space group C2/c, a=
˚
˚
˚
10.7433(11)A,
b=
25.979(3)A,
c=15.3594(16)A,
3
˚
a=90.00ꢁ, b=102.271(2)ꢁ, c=90.00,ꢁ, V=4188.79A.