An efficient and facile one-pot synthesis of structurally unique 2,4,6-tris(arylchalcogeno)-1,3,5-triazine and 1,3,5-tris(arylchalcogeno)-2,4,6- trimethylbenzene

Article abstract of DOI:10.1016/j.tetlet.2004.06.128

An efficient one-pot synthesis of a novel class of 2,4,6- tris(arylchalcogeno)-1,3,5-triazine (sulfur, selenium and tellurium) and 1,3,5-tris(arylchalcogeno)-2,4,6-trimethylbenzene (sulfur and selenium)-containing ligands has been developed based on the r

Full text of DOI:10.1016/j.tetlet.2004.06.128

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 6453–6455
An efficient and facile one-pot synthesis of structurally unique
2,4,6-tris(arylchalcogeno)-1,3,5-triazine and
1,3,5-tris(arylchalcogeno)-2,4,6-trimethylbenzene
Marilyn Daisy Milton, Naveen Kumar, Sarbjot Singh Sokhi, Sarika Singh
and Jai Deo Singh*
Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India
Received 14 May 2004; revised 25 June 2004; accepted 29 June 2004
Available online 20 July 2004
Dedicated to Professor Ram Charan Mehrotra (UOR) on his 82nd birthday
Abstract—An efficient one-pot synthesis of a novel class of 2,4,6-tris(arylchalcogeno)-1,3,5-triazine (sulfur, selenium and tellurium)
and 1,3,5-tris(arylchalcogeno)-2,4,6-trimethylbenzene (sulfur and selenium)-containing ligands has been developed based on the
reaction of 2,4,6-trichloro-1,3,5-triazine and 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene with the corresponding arylchalco-
genide anions generated in aqueous tetrahydrofuran.
ꢀ 2004 Published by Elsevier Ltd.
There has been significant interest in the design and syn-
thesis of robust organic ligands based on triazine and
trimethylbenzene anchors due to their unique applica-
tions in organic synthesis,1,2 enantiodifferentiating cou-
pling reagents,3 catalysis,4 molecular tectonics,5
polymeric materials6 and in analytical7 and coordina-
tion chemistry.8 We also became interested in develop-
ing synthetic methodology for multifunctional
organochalcogen (S, Se and Te) donors in order to cre-
ate non-hydrogen-bonded networks, whereby chalcogen
atoms could play an important role in the design and
synthesis of highly diverse spatially arranged single com-
ponents that may exhibit self-organizing properties
through chalcogen–chalcogen interactions. In fact, the
directional forces between chalcogen centres may lead
to interesting structures when the chalcogen atoms are
incorporated into fairly rigid ring systems. For these
reasons, we paid attention to the synthesis of
2,4,6-tris(arylchalcogeno)-1,3,5-triazines and 1,3,5-tris-
(arylchalcogeno)-2,4,6-trimethylbenzene.
Sodium areneselenolate and tellurolate ions, generated
in situ by the reduction of the diaryldiselenide or diaryl-
ditelluride in aqueous THF with sodium borohydride at
0ꢁC, react with 2,4,6-trichloro-1,3,5-triazine and 1,3,5-
tris(bromomethyl)-2,4,6-trimethylbenzene cleanly and
afforded the desired 2,4,6-tris(arylchalcogeno)-1,3,5-tri-
azines (selenium and tellurium) and 1,3,5-tris(arylchalco-
geno)-2,4,6-trimethylbenzenes, respectively, in excellent
yields (>90%)9 (Scheme 1). There is only a single report
in the literature regarding the synthesis of (PhE)3C3N3
(E=Se or Te) but the method cited therein is time con-
suming and tedious.10 Moreover, the structural details
of the compounds prepared were not discussed. The pre-
sent method provides an efficient route for the synthesis
of the desired compounds and suitable crystals of X-ray
quality were obtained from diethyl ether solutions.
Compounds 1–8 are crystalline in nature and soluble
in common organic solvents when freshly prepared but
showed decreased solubility after crystallization. Physico-
chemical and spectral studies were in good agreement
with the proposed stoichiometry. 1H and 13C NMR
spectral data showed no unusual features, suggesting
in all cases, the equivalence of the REÀ groups as well
as the ring carbons.
Keywords: Arylchalcogen; Triazine; Sulfur; Selenium; Tellurium.
*
Single crystal X-ray diffraction studies of the compound
(PhTe)3C3N3 2 revealed that the molecule crystallizes in
Corresponding author. Tel.: +91-11-26596455/26591512; fax: +91-
11-26862037; e-mail: jaideo@chemistry.iitd.ernet.in
0040-4039/$ - see front matter ꢀ 2004 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2004.06.128

6454
M. D. Milton et al. / Tetrahedron Letters 45 (2004) 6453–6455
R
Cl
E
N
N
N
N
R
Cl
N
Cl
E
R
N
E
room temp. 2 h
R = Ph, E = Se 1 (95%) or Te 2 (91%)
R = p-CH -C H -, E = Se 3 (92%)
3
6 4
R = 2,4,6-CH -C H -, E = Se 4 (91%)
3
6 3
NaBH / THF
4
R = p-F-C H -, E = Te 5 (93%)
-
6
4
REER
RE
o
Br
NaOH / 0 C
R = 2-NC H -,
E =S 6 (92%)
5
4
R
E
Br
Br
R
E
room temp. 2 h
E R
R = 2-NC H -,
E =S 7 (94%)
E =Se 8 (92%)
5
4
R = 2-NC H -,
5
4
Scheme 1.
a monoclinic, P21/n, space group with four molecules
per unit cell (Fig. 1). The triazine ring is essentially pla-
nar as the C–N bonds are consistent with a delocalized
system11 [1.325(8)–1.338(8)A]. However, the triazine is
˚
shorter than the sum of the corresponding van der
14
˚
Waals radii (3.61A).
In summary, we have demonstrated a new and facile
method for the reduction of diaryldiselenide or ditellu-
ride with sodium borohydride in aqueous tetrahydro-
furan for the generation of arylselenolate or tellurolate
anions. Regrettably, the reduction of R2Se2 or R2Te2
has never received great attention in organic chalcogen
chemistry due to its poor reactivity. However, addition
of a few drops of water in tetrahydrofuran (aqueous
THF) makes the reaction quite facile and generates aryl-
selenolate or tellurolate ions, within a few minutes,
which are both stable and easy to handle. We have also
demonstrated a general, versatile and high yielding
method for the construction of an aryl-heteroatom bond
by preparing novel classes of 2,4,6-tris(arylchalcogeno)-
1,3,5-triazines and 1,3,5-tris(arylchalcogeno)-2,4,6-tri-
methylbenzenes (sulfur, selenium and tellurium based
robust ligands). Compounds 1–8 are quite appealing
building blocks for the synthesis of metal complexes
not a regular hexagon, as the N–C–N bond angles and
the C–N–C bond angles differ and a distortion similar
to that found in s-triazine itself was observed.12
In compound 2 we encountered TeÁ Á ÁTe distances of the
˚
order of 3.937A which is less than the van der Waals
distance13 (TeÁ Á ÁTe=4.40A). The distances between
˚
Te(1)–Te(2), Te(2)–Te(3) and Te(3)–Te(1) are 5.778,
˚
5.810 and 6.033A, respectively, which further indicate
that the triazine ring is distorted and forces the orienta-
tions of the two phenyltelluro rings towards each other.
The substituted telluriums at the 2,4,6-positions are in
close proximity with the nitrogens of the 1,3,5-triazine
ring. Nevertheless, the atomic distances are worth men-
tioning (Te(1)Á Á ÁN(1), Te(2)Á Á ÁN(2) and Te(3)Á Á ÁN(3) are
˚
3.015, 2.942 and 2.871A, respectively) and are larger
than the sum of their covalent radii but significantly
Figure 1. Crystal structure of [(PhTe)3C3N3] 2 and crystal packing along the a-axis.

M. D. Milton et al. / Tetrahedron Letters 45 (2004) 6453–6455
6455
A.; Atwood, D. A. J. Organomet. Chem. 2001, 623,
185–190.
where the S, Se and Te atoms may participate in bond-
ing with metal ions. We are currently involved in exam-
ining their applications in creating extended-reach
structures and results will be reported in due course.
8. (a) Haiduc, I.; Mahon, M. F.; Molloy, K. C.; Venter, M.
M. J. Organomet. Chem. 2001, 627, 6–12; (b) Cecconi, F.;
Ghilardi, C. A.; Midollini, S.; Orlandini, A. J. Organomet.
Chem. 2002, 645, 101–104; (c) Mahon, M. F.; Molloy, K.
C.; Venter, M. M.; Haiduc, I. Inorg. Chim. Acta 2003, 348,
75–81.
Acknowledgements
9. Typical procedure for the synthesis of 2. To a stirred
solution of diphenylditelluride (2.05g, 5mmol) and
sodium hydroxide (0.040g, 10mmol) in aqueous THF
(20mL+0.2mL H2O) under N2 (g) and cooled to 0ꢁC was
added NaBH4 (0.419g, 11mmol) carefully. The orange-
yellow colour of the ditelluride disappeared within a few
minutes. The resulting mixture was allowed to warm to
room temperature over 0.25h. To the clear solution thus
formed was added 2,4,6-trichloro-1,3,5-triazine (0.615g,
3.33mmol) in anhydrous THF (10mL). The reaction
mixture was stirred for 2h at room temperature and
reaction completion was monitored by thin layer chroma-
tography. The reaction mixture was concentrated to
dryness and treated with saturated NH4Cl solution
(10mL) and extracted with chloroform (3·20mL). The
combined organic extracts were washed with water
(2·20mL) and dried (MgSO4), and concentrated to afford
a colourless oil. This was washed with diethyl ether to
yield the desired product of sufficient analytical purity.
Diethyl ether washings also produced crystals of the
desired species of X-ray quality on evaporation of the
diethyl ether at room temperature. mp 98ꢁC. Elemental
analysis for C21H15N3Te3 (%) calcd: C 36.44; H, 2.18; N,
6.07; found: C 36.32, H 2.03 and N 5.91. FAB-MS: m/z
The authors especially thank Dr. Yoshiaki Nishibayashi
at Kyoto University, Japan for crystallographic charac-
terization of the [(PhTe)3C3N3] derivative isolated dur-
ing the course of this study. This research was
supported by the Department of Science and Technol-
ogy (DST) Government of India (Grant SP/S1/F-18/
1998).We are also thankful to UGC and CSIR for pro-
viding research fellowships to M.D.M., N.K. and S.S.
Thanks are also due to RSIC, Lucknow, India, for pro-
viding FAB-MS spectra.
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