Lithiacarboranes and 1,2,4-triazine 4-oxides: SNH reactions and ring transformations

Article abstract of DOI:10.1023/B:RUCB.0000042277.99035.a8

The reactions of 1-lithia-1,2- or 1,7-dicarba-closo-dodecaborane with 1,2,4-triazine 4-oxides can follow two competitive pathways: deoxygenative nucleophilic substitution of hydrogen to form 1-(1,2,4-triazin-5-yl)-1,2- or 1,7-dicarba-closo-dodecaboranes and the transformation of the 1,2,4-triazine ring into the triazoline ring giving rise to 1-(2-acetyl-1-aroyl-3-aryl-1,2,4- triazolin-5-yl)-1,2-dicarba-closo-dodecaboranes. Introduction of the electron-withdrawing triazine ring into the carborane cage substantially facilitates deboronation to give 1-(1,2,4-triazin-5-yl)-1,2-1,7-dicarba-nido- undecaboranes.

Full text of DOI:10.1023/B:RUCB.0000042277.99035.a8

Russian Chemical Bulletin, International Edition, Vol. 53, No. 6, pp. 1223—1231, June, 2004
1223
Lithiacarboranes and 1,2,4ꢀtriazine 4ꢀoxides:
SNH reactions and ring transformations
O. N. Chupakhin,a A. M. Prokhorov,a D. N. Kozhevnikov,a V. L. Rusinov,aꢀ I. A. Glukhov,b
Z. A. Starikova,b V. A. Ol´shevskaya,b V. N. Kalinin,b and M. Yu. Antipinb
aUrals State Technical University,
19 ul. Mira, 620002 Ekaterinburg, Russian Federation.
Fax: +7 (343 2) 74 0458. Eꢀmail: rusinov@htf.ustu.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085. Eꢀmail: vkalinin@ineos.ac.ru
The reactions of 1ꢀlithiaꢀ1,2ꢀ or 1,7ꢀdicarbaꢀclosoꢀdodecaborane with 1,2,4ꢀtriazine
4ꢀoxides can follow two competitive pathways: deoxygenative nucleophilic substitution of
hydrogen to form 1ꢀ(1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ1,2ꢀ or 1,7ꢀdicarbaꢀclosoꢀdodecaboranes and the transꢀ
formation of the 1,2,4ꢀtriazine ring into the triazoline ring giving rise to 1ꢀ(2ꢀacetylꢀ1ꢀaroylꢀ3ꢀ
arylꢀ1,2,4ꢀtriazolinꢀ5ꢀyl)ꢀ1,2ꢀdicarbaꢀclosoꢀdodecaboranes. Introduction of the electronꢀwithꢀ
drawing triazine ring into the carborane cage substantially facilitates deboronation to give
1ꢀ(1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ1,2ꢀ1,7ꢀdicarbaꢀnidoꢀundecaboranes.
Key words: nucleophilic substitution of hydrogen, ring transformation, 1,2,4ꢀtriazine,
carborane, hetarylcarboranes.
The construction of new materials possessing unique
physicochemical properties is a major endeavor in orꢀ
ganic chemistry, which generates a need for new types of
organic and organometallic compounds. In the present
study, we attempted to combine two radically different
and interesting classes of compounds, such as 1,2,4ꢀtriazꢀ
ines and carboranes. 1,2,4ꢀTriazines are of interest1 from
the viewpoint of medical and analytical chemistry as well
as efficient agents for extraction and separation of rareꢀ
earth metals.2 Carboranes attract attention because of their
unique physicochemical properties.3 In medicine, comꢀ
pounds bearing the carborane cage serve as the basis for
boron neutron capture therapy (BNCT) for cancer and
proton emission tomography (PET).4
The available procedures for the preparation of hetarylꢀ
carboranes involve the nucleophilic substitution of haloꢀ
gen or crossꢀcoupling of haloheteroarenes with Cꢀmetallaꢀ
carboranes5,6 and the addition of metallacarboranes to
highly electrophilic heterocycles followed by dehydrogeꢀ
nation of intermediates.7
1ꢀlithiaꢀorthoꢀcarborane 3 in THF at low temperatures to
form σHꢀadducts A, which can be isolated in the free form.
For example, 1ꢀ(4ꢀhydroxyꢀ3,6ꢀdiphenylꢀ4,5ꢀdihydroꢀ
1,2,4ꢀtriazinꢀ3ꢀyl)ꢀ2ꢀphenylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaꢀ
borane (4) was isolated and characterized upon treatment
of the reaction mixture with water. However, σHꢀadducts
are unstable and readily undergo aromatization with elimiꢀ
nation of a water molecule to form the corresponding
1,2,4ꢀtriazinylcarboranes 5a—c and 6 (Scheme 1). Aroꢀ
matization occurs even more easily with the use of mild
acylating agents, such as dimethylcarbamoyl chloride or
acetic anhydride. In this case, σHꢀadducts were not isoꢀ
lated and the acylating agent was added directly to the
reaction mixture. Triazinylcarboranes 5 were prepared in
20—40% yields. When performing the reaction with
unsubstituted carborane 3, no precautions9 were taken to
prevent the formation of dilithiacarborane and to ensure
against the reaction at both carbon atoms. In spite of this
fact, monotriazinylcarborane 6 was isolated from the reꢀ
action mixture as the only reaction product.
The aim of the present study was to use the nucleoꢀ
philic substitution of hydrogen in the series of 1,2,4ꢀtriꢀ
azine 4ꢀoxides8 as a new approach to the synthesis of
heteroarylcarboranes.
The structures of compounds 5 and 6 were established
1
by H, 13C, and 11B NMR spectroscopy and mass specꢀ
trometry and were confirmed by the independent syntheꢀ
sis using ipsoꢀsubstitution10 in 5ꢀcyanoꢀ3,6ꢀdiphenylꢀ
1,2,4ꢀtriazine (7) with 1ꢀlithiaꢀ2ꢀphenylꢀorthoꢀcarborane
2 resulting in the replacement of the cyano group. New
carborane derivatives 5 and 6 are easily crystallizable,
which made it possible to study the structures of new
compounds 5a,b by Xꢀray diffraction analysis (Fig. 1).
Results and Discussion
It was found that 1,2,4ꢀtriazine 4ꢀoxides 1a—c readily
react with 1ꢀlithiaꢀ2ꢀphenylꢀorthoꢀcarborane 2 and
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1175—1182, June, 2004.
1066ꢀ5285/04/5306ꢀ1223 © 2004 Plenum Publishing Corporation

1224
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
Chupakhin et al.
Scheme 1
R1 = R2 = Ph (1a, 5a, 6, 7); R1 = R2 = pꢀTol (1b, 5b); R1 = pꢀTol, R2 = Ph (1c, 5c); R3 = Ph (2, 5), H (3, 6)
It was demonstrated that the 1,2,4ꢀtriazine ring bound
to the carborane icosahedron substantially changes the
properties of the latter. When studying the 1H NMR specꢀ
tra of triazinylcarboranes 5 in DMSOꢀd6, we found that
these compounds were slowly transformed into new comꢀ
pounds, which proved to be deboronation products, viz.,
C(28)
C(30)
C(29)
C(27)
N(16)
N(17)
C(15)
C(26)
C(21)
C(20)
C(31)
C(19)
C(23)
C(32)
C(22)
C(18)
C(34)
C(24)
C(36)
C(37)
N(14)
C(25)
C(35)
C(13)
C(1)
C(38)
B(3)
C(33)
B(6)
B(4)
B(8)
B(5)
B(7)
C(2)
B(9)
B(11)
B(10)
B(12)
Fig. 1. Crystal structure of triazinylꢀorthoꢀcarborane 5b. The H atoms are omitted. Selected bond lengths (Å): C(1)—C(13), 1.525(2);
C(1)—C(2), 1.709(3); C(2)—C(33), 1.502(3).

Reactions of 1,2,4ꢀtriazine 4ꢀoxides with carboranes Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
1225
Scheme 2
tion. It was found that deboronation in DMSOꢀd6 conꢀ
taining 5% of water at room temperature was completed
in less than one day. Heating of the reaction mixture or an
increase in the concentration of water to 20% led to a
sharp increase in the reaction rate. The fact that carboranes
5 readily undergo deboronation is attributable to the strong
electronꢀwithdrawing properties of the 1,2,4ꢀtriazine ring,
which facilitates the nucleophilic attack on the boron
atom adjacent to the carbon atom of the carborane fragꢀ
ment. An analogous effect of electronꢀwithdrawing subꢀ
stituents on the ease of deboronation has been observed
earlier for carbonylꢀ, alkoxycarbonylꢀ, and other substiꢀ
tuted carboranes.11 The introduction of two 1,2,4ꢀtriazine
residues into orthoꢀcarborane gives bis(1,2,4ꢀtriaziꢀ
nyl)carborane, which cannot virtually be isolated in the
closo form. 1,2ꢀBis(1,2,4ꢀtriazinꢀ3ꢀyl)ꢀ1,2ꢀdicarbaꢀclosoꢀ
dodecaborane B, which was formed in the reaction of
1,2,4ꢀtriazine 4ꢀoxide 1d with dilithiaꢀorthoꢀcarborane,
was rapidly transformed into 1,2ꢀbis[6ꢀ(4ꢀchlorophenyl)ꢀ
3ꢀphenylꢀ1,2,4ꢀtriazinꢀ3ꢀyl]ꢀ1,2ꢀdicarbaꢀnidoꢀundecaꢀ
borane (9) in the course of isolation.
When studying the reactions of 1,2,4ꢀtriazine 4ꢀoxꢀ
ides 1 with lithiacarboranes, we unexpectedly found that
the reaction with the use of a more severe acylating agent,
viz., acetyl chloride, did not afford the expected products
of nucleophilic substitution of hydrogen (5 and 6). The
IR spectra of the reaction products have stretching abꢀ
sorption bands of two (!) carbonyl groups, which cannot
be explained in terms of the known concepts. Based on
the results of Xꢀray diffraction analysis and spectroscopic
data, we established the structure of one of the reaction
Scheme 3
R1 = R2 = Ph (a); R1 = R2 = pꢀTol (b);
R
1 = 4ꢀClꢀC6H4, R2 = Ph (1d, 9)
Reagents and conditions: i. 1) orthoꢀCarborane (0.5 equiv.),
ButLi (1 equiv.), –50 °C; 2) 1d; 3) Me2NCOCl.
1ꢀ(1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ2ꢀphenylꢀ1,2ꢀdicarbaꢀnidoꢀunꢀ
decaboranes 8a,b (Scheme 2). Deboronation of triazinylꢀ
carboranes 5 occurs very readily on heating in wet (less
than 5% of water) DMSO even over a short period. The
course of this process is conveniently monitored by
1H NMR spectroscopy. The spectra show the characterisꢀ
tic highꢀfield signal (δ –2.75) of the bridging hydrogen
atom and the lowꢀfield signal (δ 10) of the "acidic" proꢀ
ton. The fact that deboronation occurred was confirmed
by the fact that the 1H NMR spectra show a signal of
molecular hydrogen, which was eliminated in this reacꢀ
tion. The signal with the same chemical shift (δ 4.61) was
observed in the 1H NMR spectrum in DMSOꢀd6 after
bubbling of gaseous hydrogen through the reaction soluꢀ
R1 = R2 = Ph (a); R1 = R2 = pꢀTol (b); R1 = pꢀTol, R2 = Ph (c);
R
1 = Tol, R2 = 2ꢀfuryl (e)
Reagents and conditions: i. 1) 1ꢀPhenylꢀorthoꢀcarborane (2 equiv.),
ButLi (2 equiv.), –50 °C; 2) 1a—c,e; 3) AcCl.

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Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
Chupakhin et al.
C(24)
C(25)
C(23)
C(22)
C(26)
C(21)
C(20)
C(29)
C(18)
C(27)
O(28´)
C(29´)
O(19)
B(8)
O(28)
N(16)
C(36)
N(17)
C(35)
B(4)
B(9)
C(15)
C(13)
C(33)
C(30)
N(14)
C(34)
B(5)
B(3)
B(12)
C(32)
C(1)
B(10)
C(31)
B(7)
C(2)
B(11)
B(6)
C(37)
C(38)
C(42)
C(39)
C(41)
C(40)
Fig. 2. Crystal structure of triazolinylꢀorthoꢀcarborane 10b. The H atoms are omitted. Selected bond lengths (Å): C(1)—C(13),
1.554(3); C(1)—C(2), 1.695(3); C(2)—C(33), 1.515(3). The O(28) and C(29) atoms are disordered over two positions with equal
occupancies.
products as 1ꢀ(2ꢀacetylꢀ1ꢀtoluoylꢀ3ꢀtolylꢀ1,2,4ꢀtriazolinꢀ
5ꢀyl)ꢀ2ꢀphenylꢀorthoꢀcarborane (10b) (Fig. 2).
We propose the mechanism of this transformation
(Scheme 4) taking into account that the latter occurs only
in the reactions with lithiacarboranes (reactions with
phenyllithium, phenylethynyllithium, or Grignard reꢀ
agents12 led only to the replacement of hydrogen). The
structures of the reaction products are indicative of the
transfer of the oxygen atom from the nitrogen atom at
position 4 of the heterocycle to the carbon atom at posiꢀ
tion 6 accompanied by the cleavage of the C(5)—C(6)
bond. The addition of lithiacarborane to 1,2,4ꢀtriazine
4ꢀoxide 1 results in the formation of intermediate
σꢀadduct D, in which the Li atom is adjacent to the
carborane cage and is involved in the Coulomb interacꢀ
tion with the electronegative hydrogen atoms of the B—H
groups. Subsequent acylation of the intermediate D at the
N(2) atom gives a cationic intermediate, which can be
represented as two mesomeric structures E and F. The
further E → H transformation can be considered as the
The following conditions are required for the reaction
of 1,2,4ꢀtriazine 4ꢀoxides 1a—c,e with lithiacarborane 2
to proceed as the transformation into the triazoline ring
giving rise to 1,2,4ꢀtriazolinylcarboranes 10a—c,e: AcCl
as the acylating agent and a 1.5—2ꢀfold excess of lithiaꢀ
carborane (Scheme 3).
For example, the reactions with the use of equimolar
amounts of the reagents and acetyl chloride (only the first
condition was fulfilled) did not provide unambiguous reꢀ
sults and yielded either products of nucleophilic substituꢀ
tion of hydrogen (5) or products of ring transformation
(10) depending on the nature of substituents in the startꢀ
ing triazine oxide 1. On the contrary, the reactions with
the use of a twofold excess of lithiacarborane and diꢀ
methylcarbamoyl chloride (only the second condition was
fulfilled) always gave triazinylcarborane 5.

Reactions of 1,2,4ꢀtriazine 4ꢀoxides with carboranes Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
1227
Scheme 4
Scheme 5
R1 = R2 = Ph (1a, 11, 13a); R1 = pꢀTol, R2 = 4ꢀClꢀC6H4 (1f, 12, 13b)
Reagents and conditions: i. 1) metaꢀCarborane, ButLi (1 equiv.), –50 °C; 2) 1a; 3) Ac2O. ii. 1) metaꢀCarborane (0.5 equiv.), ButLi
(1 equiv.), –50 °C; 2) 1f; 3) Me2NCOCl. iii. 1) metaꢀCarborane (2 equiv.), ButLi (2 equiv.), –50 °C; 2) 1a,f; 3) AcCl.

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Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
Chupakhin et al.
C(29´)
C(30´)
Cl(1´)
N(16´)
N(17´)
C(28´)
C(15´)
C(25´)
C(27´)
C(20´)
C(21´)
C(18´)
C(22´)
C(26´)
C(19´)
N(14´)
C(24´)
C(23´)
C(13´)
Cl(1)
C(29)
C(1)
C(30)
B(6)
C(28)
C(27)
B(2)
B(5)
B(3)
C(7)
C(25)
B(4)
N(14)
B(11)
B(12)
B(10)
B(9)
C(26)
C(15)
B(8)
C(13)
N(16)
N(17)
C(18)
C(19)
C(24)
C(20)
C(21)
C(23)
C(22)
Fig. 3. Crystal structure of bistriazinylꢀmetaꢀcarborane 12. The H atoms are omitted. Selected bond lengths (Å): C(1)—C(13´),
1.520(3); C(1)—B(3), 1.713(3); C(7)—B(3), 1.719(3); C(7)—C(13), 1.520(3).
sigmatropic shift of OLi proceeding through transition
state G. The subsequent cleavage of the C(5)—C(6) bond
affords the openꢀchain intermediate I, and recyclization
gives the final triazoline 10.
monolithiated carborane and then with acetyl chloꢀ
ride yielded 1,2,4ꢀtriazolinꢀ5ꢀylꢀmetaꢀcarboranes 13a,b
(Scheme 5).
Hence, the reaction pathway can be controlled by
varying the conditions. As a result, one can prepare either
the products of transformation of the triazine ring, which
leads to the ring contraction and the formation of 1,2,4ꢀtriꢀ
azolinylcarboranes, or the products of deoxygenative
nucleophilic substitution of hydrogen. The latter pathway
provides an approach to the synthesis of a broad spectrum
of 1,2,4ꢀtriazinylcarboranes. It should be noted that analoꢀ
gous transformations accompanied by the cleavage of the
C—C bond have not been described in the literature.
The aboveꢀmentioned substitutions of hydrogen and
transformations occur also in reactions with the use of the
Cꢀlithium derivative of unsubstituted metaꢀcarborane as a
nucleophile. For example, the reaction of 1,2,4ꢀtriazine
4ꢀoxide 1a with monolithiated metaꢀcarborane (equivaꢀ
lent amounts of metaꢀcarborane and ButLi) followed by
treatment of the reaction mixture with acetic anhydride
gave 1ꢀ(3,6ꢀdiphenylꢀ1,2,4ꢀtriazinꢀ3ꢀyl)ꢀ1,7ꢀdicarbaꢀ
closoꢀdodecaborane (11). The reaction of a twofold exꢀ
cess of ButLi with 1,2,4ꢀtriazine 4ꢀoxide 1a followed by
treatment of the reaction mixture with dimethylcarbamoyl
chloride afforded 1,7ꢀbistriazinylꢀmetaꢀcarborane 12. The
structure of the latter was studied by Xꢀray diffraction
analysis (Fig. 3). It was established that the aboveꢀ
described transformation of the 1,2,4ꢀtriazine ring ocꢀ
curs also in the reactions with metaꢀcarborane. Treatꢀ
ment of 1,2,4ꢀtriazine 4ꢀoxides 1a,f with an excess of
Experimental
The NMR spectra were recorded on a Bruker WMꢀ250 specꢀ
trometer (250 MHz) using DMSOꢀd6 as the solvent and Me4Si
as the internal standard. The electronꢀimpact ionization mass
spectra were obtained on a Varian MATꢀ311A instrument. Comꢀ
mercially available carboranes were used as nucleophiles. The

Reactions of 1,2,4ꢀtriazine 4ꢀoxides with carboranes Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
1229
Table 1. Crystallographic data and main details of structure refinement for compounds 5a,b,
10b, and 12
Parameter
5a
5b
10b
12
Molecular formula
Molecular weight
Space group
a/Å
b/Å
c/Å
C23H25B10N3
C25H29B10N3
479.55
Pbca
11.6446(8)
13.2237
35.230(3)
90
С27H33B10N3O2 C32H28B10Cl2N6
451.55
P43
11.3890(6)
—
18.7520(14)
90
539.69
P1
675.64
P1(bar)
8.665(4)
35.230(3)
16.947(7)
79.56(3)
77.11(4)
75.39(3)
1680.2(12)
2
10.439(6)
11.925(7)
13.574(7)
82.664(15)
77.032(16)
64.479(10)
1485.2(14)
2
α/deg
β/deg
90
90
90
90
γ/deg
V/Å3
2432.3(3)
4
1.233
0.67
5424.8(7)
8
1.174
Z
dcalc/g cm–3
1.207
1.335
µ/cm–1
0.63
0.070
2.29
Number of measured
reflections, Rint
Number of reflections
with I > 2σ(I )
Number of parameters
in refinement
R1(I > 2σ(I ))
wR2
7043
5859
5780
5865
6460
1729
4233
4341
1.003
0.804
1.142
0.994
0.0464
0.1091
0.0471
0.0865
0.0654
0.1519
0.0477
0.1162
starting 1,2,4ꢀtriazine 4ꢀoxides 1 were prepared from isonitrosoꢀ
acetophenone hydrazones according to known procedures.13
5ꢀCyanoꢀ3,6ꢀdiphenylꢀ1,2,4ꢀtriazine was synthesized by direct
cyanation of 3,6ꢀdiphenylꢀ1,2,4ꢀtriazine 4ꢀoxide.14
then concentrated at ~20 °C. The residue was treated with waꢀ
ter. The resulting suspension was extracted with chloroform, the
extract was concentrated, the residue was treated with acetoꢀ
nitrile, and the precipitate that formed was filtered off. The yield
was 230 mg (11%), m.p. 201 °C. 1H NMR, δ: 1.10—3.10 (m,
10 H, B—H); 4.82 (br.s, 1 H, H(5)); 7.00—8.10 (m, 15 H).
Synthesis of 1ꢀ(1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ1,2ꢀ and 1,7ꢀdicarbaꢀ
closoꢀdodecaboranesꢀ12 (5a—c, 6, 11) (general procedure).
A solution of lithiacarborane in THF, which was prepared by
the addition of a 1.6 M ButLi solution in pentane (2.5 mL) to a
solution of carborane (4 mmol) in dry THF (20 mL), was added
to a suspension of the corresponding triazine oxide (4 mmol) in
dry THF (10 mL) under argon at –50 °C. The reaction mixture
was kept until the starting triazine oxide was dissolved (~15 min).
After 20 min, carbamoyl chloride (4 mmol) was added to the
reaction mixture at the same temperature. The reaction mixture
was concentrated under reduced pressure, the residue was exꢀ
tracted with toluene, the extract was concentrated, the residue
was treated with acetonitrile, and the precipitate that formed
was filtered off.
1ꢀ(3,6ꢀDiphenylꢀ1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ2ꢀphenylꢀ1,2ꢀdicarbaꢀ
closoꢀdodecaborane (5a). The yield was 670 mg (37%), m.p.
205 °C. Found (%): C, 61.03; H, 5.65; N, 9.22. C23H25B10N3.
Calculated (%): C, 61.17; H, 5.58; N, 9.31 (M = 451.55).
1H NMR, δ: 1.20—3.20 (m, 10 H, B—H); 7.21—7.68 (m, 13 H);
8.33 (m, 2 H). MS (EI, 70 eV), m/z (Irel (%)): 452 [M]+ (100).
1ꢀ[3,6ꢀDi(4ꢀmethylphenyl)ꢀ1,2,4ꢀtriazinꢀ5ꢀyl]ꢀ2ꢀphenylꢀ
1,2ꢀdicarbaꢀclosoꢀdodecaborane (5b). The yield was 750 mg
(39%), m.p. 165 °C. Found (%): C, 62.55; H, 6.06; N, 9.00.
C25H29B10N3. Calculated (%): C, 62.61; H, 6.09; N, 8.76
(M = 479.55). 1H NMR, δ: 1.20—3.20 (m, 10 H, B—H);
2.43 and 2.46 (both s, 3 H each, Me); 7.18—7.46 (m, 11 H);
8.21 (m, 2 H).
Xꢀray diffraction study. Crystals of compounds 5a,b were
prepared by crystallization from acetonitrile. The intensities of
reflections were measured on a Smart 1000 CCD diffractometer
at 110 K (5a,b and 10b) and a Nonius CAD4 diffractometer at
298 K (12) (λ(MoKα) = 0.71072 Å, ω scanning technique for
5a,b and 10b; θ/2θ scanning technique for 12, 2θ < 60°). The
crystallographic data and selected parameters of structure reꢀ
finement for compounds 5a,b, 10b, and 12 are given in Table 1.*
The structures were solved by direct methods and refined by the
leastꢀsquares method with anisotropic and isotropic thermal paꢀ
rameters for nonhydrogen and hydrogen atoms, respectively. All
calculations were carried out using the SHELXTL PLUS 5.0
program package.
1ꢀ(4ꢀHydroxyꢀ3,6ꢀdiphenylꢀ4,5ꢀdihydroꢀ1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ
2ꢀphenylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (4). A solution of
lithium salt 2 in THF, which was prepared by the addition of a
1.6 M ButLi solution in pentane (2.5 mL) to a solution of the
corresponding carborane (4 mmol) in dry THF (20 mL), was
added to a suspension of triazine oxide 1a (4 mmol) in dry THF
(10 mL) under argon at –50 °C. The reaction mixture was kept
until the starting triazine oxide was dissolved (~15 min) and
* The crystallographic data were deposited with the Camꢀ
bridge Structural Database (CCDC 205482—205484;
www.ccdc.cam.ac.uk/conts/retrieving.html; the Cambridge
Crystallographic Data Centre, 12, Union Road, Camꢀ
bridge CB2 1EZ, UK; Fax: +44ꢀ1223/336ꢀ033; Eꢀmail:
deposit@ccdc.cam.ac.uk).

1230
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
Chupakhin et al.
1ꢀ[6ꢀ(4ꢀMethylphenyl)ꢀ3ꢀphenylꢀ1,2,4ꢀtriazinꢀ5ꢀyl]ꢀ2ꢀpheꢀ
nylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (5c). The yield was 300 mg
(21%), m.p. 155 °C. Found (%): C, 62.01; H, 5.93; N, 9.00.
C24H27B10N3. Calculated (%): C, 61.91; H, 5.84; N, 9.02
(M = 465.61). 1H NMR, δ: 1.20—3.20 (m, 10 H, B—H); 2.46 (s,
3 H, Me); 7.21—7.68 (m, 12 H); 8.33 (m, 2 H).
1ꢀ(3,6ꢀDiphenylꢀ1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ1,2ꢀdicarbaꢀclosoꢀ
dodecaborane (6). The yield was 600 mg (40%), m.p. 220 °C.
Found (%): C, 54.59; H, 5.64; N, 10.75. C17H21B10N3. Calcuꢀ
lated (%): C, 54.38; H, 5.64; N, 11.19 (M = 375.49). 1H NMR,
δ: 1.00—3.00 (br.s, 10 H, B—H); 5.95 (br.s, 1 H, C—H);
7.56—7.76 (m, 8 H); 8.46 (m, 2 H).
(m, 10 H, B—H); 2.40 (s, 3 H, Me); 5.56 (s, 1 H, H(5));
7.33—7.80 (m, 14 H).
1ꢀ[2ꢀAcetylꢀ3ꢀfurylꢀ1ꢀ(pꢀtoluoyl)ꢀ1,2,4ꢀtriazolinꢀ5ꢀyl]ꢀ2ꢀ
phenylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (10e). The yield was
410 mg (21%), m.p. 193 °C. Found (%): C, 55.79; H, 5.60;
N, 8.14. C24H29B10N3O3. Calculated (%): C, 55.91; H, 5.67;
N, 8.15 (M = 515.63). 1H NMR, δ: 1.82 and 2.38 (both s,
3 H each, Me); 1.50—3.10 (m, 10 H, B—H); 5.54 (s, 1 H,
H(5)); 6.78 (m, 1 H); 7.28—7.77 (m, 10 H); 8.07 (m, 1 H).
1ꢀ(2ꢀAcetylꢀ1ꢀbenzoylꢀ3ꢀphenylꢀ1,2,4ꢀtriazolinꢀ5ꢀyl)ꢀ1,7ꢀ
dicarbaꢀclosoꢀdodecaborane (13a). The yield was 800 mg
(50%), m.p. 189 °C. Found (%): C, 52.63; H, 5.76; N, 9.45.
1ꢀ(3,6ꢀDiphenylꢀ1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ1,7ꢀdicarbaꢀclosoꢀ
dodecaborane (11). The yield was 300 mg (20%), m.p. 165 °C.
Found (%): C, 54.30; H, 5.49; N, 10.95. C17H21B10N3. Calcuꢀ
lated (%): C, 54.38; H, 5.64; N, 11.19 (M = 375.49). 1H NMR,
δ: 1.00—3.10 (br.m, 10 H, B—H); 4.19 (br.s, 1 H, C—H);
7.50—7.69 (m, 8 H); 8.48 (m, 2 H).
C19H25B10N3O2. Calculated (%): C, 52.40; H, 5.79; N, 9.65
1
(M = 435.54). H NMR, δ: 1.50—3.10 (m, 10 H, B—H); 4.18
(br.s, 1 H, H(2)); 5.99 (s, 1 H, H(5)); 7.53—7.75 (m, 10 H).
1ꢀ[2ꢀAcetylꢀ1ꢀbenzoylꢀ3ꢀ(4ꢀchlorophenyl)ꢀ1,2,4ꢀtriazolinꢀ5ꢀ
yl]ꢀ1,7ꢀdicarbaꢀclosoꢀdodecaborane (13b). The yield was 357 mg
(19%), m.p. 191 °C. Found (%): C, 48.73; H, 5.36; N, 9.25.
1,7ꢀBis[3ꢀ(4ꢀchlorophenyl)ꢀ6ꢀ(4ꢀmethylphenyl)ꢀ1,2,4ꢀtriꢀ
azinꢀ5ꢀyl]ꢀ1,7ꢀdicarbaꢀclosoꢀdodecaborane (12) was prepared
analogously to monotriazinylcarboranes 5 from triazine oxide 1f
(1.13 g, 4 mmol), metaꢀcarborane (290 mg, 2 mmol), and a
1.6 M ButLi solution in pentane (2.5 mL). The yield was 450 mg
(16%), m.p. 227 °C. Found (%): C, 56.74; H, 4.27; N, 12.29.
C19H24B10ClN3O2. Calculated (%): C, 48.56; H, 5.15; N, 8.94
(M = 469.98). 1H NMR, δ: 1.98 (s, 3 H, Me); 1.50—3.10 (m,
10 H, B—H); 4.18 (br.s, 1 H, H(2)); 5.98 (s, 1 H, H(5));
7.56—7.75 (m, 9 H).
Deboronation of triazinylcarboranes 5 (general procedure).
The corresponding 1,2,4ꢀtriazinylcarborane 5 (1 mmol) was disꢀ
solved in DMSO (5 mL). Then water (1 mL) was added to the
reaction solution and the mixture was kept at ~20 °C for one
day, after which water (10 mL) was added. The precipitate that
formed was filtered off and recrystallized from acetonitrile.
1ꢀ(3,6ꢀDiphenylꢀ1,2,4ꢀtriazinꢀ5ꢀyl)ꢀ2ꢀphenylꢀ1,2ꢀdicarbaꢀ
nidoꢀundecaborane (8a). The yield was 410 mg (90%),
m.p. >250 °C (decomp.). Found (%): C, 62.49; H, 5.81; N, 9.69.
C
32H28B10Cl2N6. Calculated (%): C, 56.89; H, 4.18; N, 12.44
(M = 675.64). 1H NMR, δ: 1.20—3.20 (m, 10 H, B—H); 2.43
and 2.46 (both s, 3 H each, Me); 7.18—7.46 (m, 11 H);
8.21 (m, 2 H).
Synthesis of 1ꢀ(2ꢀacetylꢀ1ꢀaroylꢀ1,2,4ꢀtriazolinꢀ5ꢀyl)ꢀ1,2ꢀ
and 1,7ꢀdicarbaꢀclosoꢀdodecaboranes (10a—c,e and 13a,b) (genꢀ
eral procedure). A solution of lithiacarborane in THF, which
was prepared by the addition of a 1.6 M ButLi solution in penꢀ
tane (5 mL) to a solution of the corresponding carborane
(8 mmol) in dry THF (20 mL), was added to a suspension of
triazine oxide (4 mmol) in dry THF (10 mL) under argon at
–50 °C. The reaction mixture was kept until the starting triazine
oxide was dissolved (~15 min). After 20 min, acetyl chloride
(8 mmol) was added to the reaction mixture at the same temꢀ
perature. Then the reaction mixture was concentrated and exꢀ
tracted with toluene. The extract was concentrated, the residue
was treated with acetonitrile, and the precipitate that formed
was filtered off.
C
23H26B9N3. Calculated (%): C, 62.53; H, 5.93; N, 9.51
(M = 441.78). 1H NMR, δ: –2.85 (br.s, 1 H); 1.20—3.20 (m,
9 H, B—H); 6.60—6.80 (m, 5 H, carborane Ph); 7.31—7.67 (m,
8 H); 8.33 (m, 2 H); 10.21 (br.s, 1 H). MS (EI, 70 eV),
m/z (Irel (%)): 442 [M]+ (100).
1ꢀ[3,6ꢀDi(4ꢀmethylphenyl)ꢀ1,2,4ꢀtriazinꢀ5ꢀyl]ꢀ2ꢀphenylꢀ1,2ꢀ
dicarbaꢀnidoꢀundecaborane (8b). The yield was 415 mg (90%),
m.p. >250 °C (decomp.). Found (%): C, 63.91; H, 6.44; N, 8.94.
C
25H30B9N3. Calculated (%): C, 63.73; H, 6.43; N, 8.81
(M = 469.84). 1H NMR, δ: –2.85 (br.s, 1 H); 1.20—3.20 (m,
9 H, B—H); 6.65—6.89 (m, 5 H, Ph); 7.20—7.46 (m, 6 H); 8.39
(m, 2 H); 11.00 (br.s, 1 H).
1ꢀ(2ꢀAcetylꢀ1ꢀbenzoylꢀ3ꢀphenylꢀ1,2,4ꢀtriazolinꢀ5ꢀyl)ꢀ2ꢀpheꢀ
nylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (10a). The yield was 1.30 g
(63%), m.p. 201 °C. Found (%): C, 58.60; H, 5.76; N, 8.35.
1,2ꢀBis[6ꢀ(4ꢀchlorophenyl)ꢀ3ꢀphenylꢀ1,2,4ꢀtriazinꢀ5ꢀyl]ꢀ
1,2ꢀdicarbaꢀnidoꢀundecaborane (9). A solution of 1,2ꢀdilithiaꢀ
carborane in THF, which was prepared by the addition of a
1.6 M ButLi solution in pentane (2.5 mL) to a solution of
carborane (2 mmol, 290 mg) in dry THF (20 mL), was added to
a suspension of the corresponding triazine oxide (4 mmol,
1.13 mg) in dry THF (10 mL) under argon at –50 °C. The
reaction mixture was kept until the starting triazine oxide was
dissolved (~15 min). After 20 min, carbamoyl chloride (4 mmol,
0.5 mL) was added to the reaction mixture at the same temperaꢀ
ture. Then the reaction mixture was concentrated under reꢀ
duced pressure, the residue was extracted with toluene, the exꢀ
tract was concentrated, the residue was treated with acetoniꢀ
trile, and the precipitate that formed was filtered off. The yield
was 330 mg (95%), m.p. >250 °C (decomp.). Found (%):
C, 57.73; H, 4.39; N, 12.62. C32H29B9Cl2N6. Calculated (%):
C
25H29B10N3O2. Calculated (%): C, 58.69; H, 5.71; N, 8.21
(M = 511.64). 1H NMR, δ: 1.85 (s, 3 H, Me); 1.50—3.10 (m,
10 H, B—H); 5.60 (s, 1 H, H(5)); 7.48—7.80 (m, 15 H).
1ꢀ[2ꢀAcetylꢀ3ꢀ(4ꢀmethylphenyl)ꢀ1ꢀ(pꢀtoluoyl)ꢀ1,2,4ꢀtriꢀ
azolinꢀ5ꢀyl]ꢀ2ꢀphenylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (10b).
The yield was 890 mg (41%), m.p. 210 °C. Found (%): C, 60.05;
H, 6.06; N, 7.71. C27H33B10N3. Calculated (%): C, 60.09;
H, 6.16; N, 7.79 (M = 539.69). 1H NMR, δ: 1.86 and 2.39
(both s, 3 H each, Me); 1.50—3.10 (m, 10 H, B—H); 2.41 (s,
3 H, Me); 5.53 (s, 1 H, H(5)); 7.32—7.80 (m, 13 H).
1ꢀ[2ꢀAcetylꢀ3ꢀphenylꢀ1ꢀ(pꢀtoluoyl)ꢀ1,2,4ꢀtriazolinꢀ5ꢀyl]ꢀ2ꢀ
phenylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (10c). The yield was
1.39 g (67%), m.p. 228 °C. Found (%): C, 59.21; H, 5.78;
N, 8.02. C26H31B10N3O2. Calculated (%): C, 59.41; H, 5.94;
N, 7.99 (M = 525.67). 1H NMR, δ: 1.86 (s, 3 H, Me); 1.50—3.10
1
C, 57.63; H, 4.33; N, 12.51 (M = 665.83). H NMR, δ: –2.75

Reactions of 1,2,4ꢀtriazine 4ꢀoxides with carboranes Russ.Chem.Bull., Int.Ed., Vol. 53, No. 6, June, 2004
1231
(br.s, 1 H); 1.20—3.20 (m, 9 H, B—H); 7.09—7.44 (m, 14 H);
8.07 (m, 4 H); 11.00 (br.s, 1 H).
6. W. Gill, P. Herbertson, J. MacBrig, and K. Wade,
J. Organomet. Chem., 1996, 507, 249.
7. A. V. Kazantsev and L. E. Litovchenko, Zh. Obshch. Khim.,
1970, 41, 1057 [J. Gen. Chem. USSR, 1970, 41 (Engl.
Transl.)].
8. D. N. Kozhevnikov, V. L. Rusinov, and O. N. Chupakhin,
1,2,4ꢀTriazine Nꢀoxides, in Adv. Heterocycl. Chem., Ed. A. R.
Katritzky, 2002, 82, 261.
9. C. Viñas, R. Benakki, F. Teixidor, and J. Casabó, Inorg.
Chem., 1995, 34, 3844.
10. S. Ohba, S. Konno, and H. Yamanaka, Chem. Pharm. Bull.,
1991, 39, 486.
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 02ꢀ03ꢀ32635)
and INTAS (Grant YSF 2002ꢀ103).
References
1. H. Neunhoeffer, Compr. Heterocycl. Chem. II, Eds. A. R.
Katritzky, C. W. Rees, and E. F. V. Scriven, Pergamon
Press, Oxford, 1996, 6, 507.
11. J. J. Schaeck and S. B. Kahl, Inorg. Chem., 1999, 38, 204.
12. A. M. Prokhorov, D. N. Kozhevnikov, V. L. Rusinov, and
O. N. Chupakhin, Polish J. Chem., 2003, 77, 1157.
13. E. C. Taylor, K. L. Perlman, I. P. Sword, M. SequinꢀFrey,
and P. A. Jacobi, J. Am. Chem. Soc., 1973, 95, 6407.
14. S. Ohba, S. Konno, and H. Yamanaka, Chem. Pharm. Bull.,
1991, 39, 486.
2. Z. Kolarik, U. Mullich, and F. Gassner, Solv. Extr. Ion
Exch., 1999, 17, 23.
3. J. Plesek, Chem. Rev., 1992, 92, 269.
4. J. F. Valiant, K. J. Guenther, A. S. King, P. Morel,
P. Schafer, O. O. Sogbein, and K. A. Stephenson, Coord.
Chem. Rev., 2002, 232, 173; A. H. Soloway, W. Tjarks, B. A.
Barnum, F.ꢀG. Rong, R. F. Barth, I. M. Codogni, and J. G.
Wilson, Chem. Rev., 1998, 98, 1515.
5. D. Armspach, E. C. Constable, C. E. Housecroft,
M. Neuburger, and M. Zehnder, J. Organomet. Chem., 1998,
550, 193.
Received December 29, 2003;
in revised form April 21, 2004