Selenadiazolo[3,4-b]pyrazines: Synthesis from 3,4-Diamino-1,2,5-selenadiazole and Generation of Persistent Radical Anions

Article abstract of DOI:10.1002/ejoc.201500742

Previously unknown 3,4-diamino-1,2,5-selenadiazole (6) was prepared by hydrolysis of [1,2,5]selenadiazolo[3,4-c][1,2,5]selenadiazole (7b) and used in synthesis of novel 1,2,5-selenadiazolo[3,4-b]pyrazines by the Koerner-Hinsberg reaction covering the parent compound 4 and its substituted derivatives 5a-g. The compounds synthesized were characterized by solution and solid-state⁷⁷Se NMR, and 6, 5-Ph and 5,6-Me₂[1,2,5]selenadiazolo[3,4-b]pyrazines (5a, g, respectively) by X-ray diffraction. Electrochemical reduction of 5,6-R₂[1,2,5]selenadiazolo[3,4-b]pyrazines 5c, g (R = Ph, Me) into novel persistent radical anions (RAs) was studied by cyclic voltammetry and the RAs [5c]^-and [5g]^-were characterized by EPR spectroscopy combined with DFT calculations. 3,4-Diamino-1,2,5-selenadiazole was synthesized and used for preparing novel [1,2,5]selenadiazolo[3,4-b]pyrazines. Electrochemical reduction of the latter into persistent radical anions (RAs) was studied by CV and the RAs were characterized by EPR combined with DFT calculations.

Full text of DOI:10.1002/ejoc.201500742

FULL PAPER
DOI: 10.1002/ejoc.201500742
[1,2,5]Selenadiazolo[3,4-b]pyrazines: Synthesis from 3,4-Diamino-1,2,5-
selenadiazole and Generation of Persistent Radical Anions
Lidia S. Konstantinova,[a] Irina E. Bobkova,[a] Yulia V. Nelyubina,[b] Elena A. Chulanova,[c,d]
Irina G. Irtegova,[c,d] Nadezhda V. Vasilieva,[c] Paula S. Camacho,[e] Sharon E. Ashbrook,[e]
Guoxiong Hua,[e] Alexandra M. Z. Slawin,[e] J. Derek Woollins,[e] Andrey V. Zibarev,[c,f,g]
and Oleg A. Rakitin*[a]
Keywords: Synthetic methods / Selenium heterocycles / Nitrogen heterocycles / Radical anions / Cyclovoltammetry / EPR
spectroscopy / DFT calculations
Previously unknown 3,4-diamino-1,2,5-selenadiazole (6) was
prepared by hydrolysis of [1,2,5]selenadiazolo[3,4-c][1,2,5]-
selenadiazole (7b) and used in synthesis of novel 1,2,5-selen-
adiazolo[3,4-b]pyrazines by the Koerner–Hinsberg reaction
covering the parent compound 4 and its substituted deriva-
tives 5a–g. The compounds synthesized were characterized
by solution and solid-state 77Se NMR, and 6, 5-Ph and 5,6-
Me2[1,2,5]selenadiazolo[3,4-b]pyrazines (5a, g, respectively)
by X-ray diffraction. Electrochemical reduction of 5,6-
R2[1,2,5]selenadiazolo[3,4-b]pyrazines 5c, g (R = Ph, Me) into
novel persistent radical anions (RAs) was studied by cyclic
voltammetry and the RAs [5c]– and [5g]– were characterized
by EPR spectroscopy combined with DFT calculations.
logues,[2,4,7,12–14] whereas chemistry of 1,2,5-telluradiazoles
is only emerging.[4–7,15,16] Very recent interest to these com-
pounds, especially fused with benzene and heterocyclic
rings, is due to their actual or potential applications as
building blocks in organic functional materials such as light
emitters, solar cells, synthetic metals, as well as drugs for
preventive and therapeutic medical treatment and fluores-
cent imagine probes.[1,4,7,13,14,17]
Introduction
The chemistry of chalcogen–nitrogen π-heterocycles, par-
ticularly 1,2,5-chalcogenadiazoles, is an important part of
contemporary organic and organoelement chemistry and its
applications in the field of biomedicine and molecule-based
functional materials.[1–9] Amongst 1,2,5-chalcogenadiazoles
the best studied are the sulfur derivatives[1–4,7,10,11] though
there are scattered reports on the selenium ana-
Recently, it was shown that many classes of chalcogen–
nitrogen π-heterocycles possess positive electron affinity
(EA) making them suitable precursors for thermodynami-
cally stable radical anions (RAs) which are possible build-
ing blocks for magnetically-active functional materials.[7–9]
Whereas some 1,2,5-thiadiazolidyl RAs, including [1,2,5]-
thiadiazolo[3,4-b]pyrazinidyl, have already been isolated in
the form of thermally stable salts,[7–9,18] investigation of
their Se congeners is restricted by synthetic accessibility.
There is a lack of suitable preparative approaches to many
interesting and potentially useful derivatives with enlarged
EA including, for example, [1,2,5]selenadiazolo[3,4-b]pyr-
azines.
In principle, these compounds could be prepared from
2,3-diaminopyrazines[19] and SeO2, i.e. using the standard
Hinsberg approach to the selenadiazole ring-clo-
sure.[2,4,13,14] The diamines, however, are relatively hardly
accessible, and in this work two synthetic alternatives con-
ceptually based on the Yuryev[17] and the Koerner–
Hinsberg[20] reactions were investigated. The first reaction
deals with heteroatom exchange in five-membered heterocy-
cles, and the second with pyrazine ring-closure.
[a] N. D. Zelinsky Institute of Organic Chemistry, Russian Acad-
emy of Sciences,
119991 Moscow, Russia
E-mail: orakitin@ioc.ac.ru;
http://zioc.ru/institute/laboratories/laboratory-of-polysulphur-
nitrogen-heterocycles-n31
[b] A. N. Nesmeyanov Institute of Organoelement Compounds,
Russian Academy of Sciences,
119991 Moscow, Russia
E-mail: unelya@xrlab.ineos.ac.ru
[c] N. N. Vorozhtsov Institute of Organic Chemistry, Siberian
Branch, Russian Academy of Sciences,
630090 Novosibirsk, Russia
E-mail: zibarev@nioch.nsc.ru
[d] Department of Natural Sciences, Novosibirsk State University,
630090 Novosibirsk, Russia
E-mail: chulanovaea@gmail.com
[e] EaStChem. School of Chemistry, University of St. Andrews,
St. Andrews, Fife KY16 9ST, United Kingdom
E-mail: jdw3@st-andrews.ac.uk
[f] Department of Physics, Novosibirsk State University,
630090 Novosibirsk, Russia
E-mail: zibarev@nioch.nsc.ru
[g] Department of Chemistry, Tomsk State University,
634050 Tomsk, Russia
E-mail: zibarev@nioch.nsc.ru
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500742.
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This paper describes the synthesis of previously unknown which can be prepared from [1,2,5]thiadiazolo[3,4-c][1,2,5]-
3,4-diamino-1,2,5-selenadiazole and its use in the synthesis selenadiazole (7a) or its selenium counterpart 7b.[12]
of the title compounds under conditions of the Koerner–
1,2,5-Thia/selenadiazoles are a well-known protected
Hinsberg reaction. The key diamine and the [1,2,5]selenadi- form of 1,2-diamines. Normally, the diamines can be reco-
azolo[3,4-b]pyrazines synthesized were characterized by vered by reduction of the heterocycles[21–23] and in some
multinuclear NMR including solution and solid-state 77Se cases also by hydrolysis. In this work, technically simple hy-
NMR and X-ray diffraction (XRD). The [1,2,5]selenadiaz- drolysis was employed.
olo[3,4-b]pyrazines were used for electrochemical genera-
Treatment of 7a with 3 m ammonium hydroxide solution
tion of their radical anions and the novel persistent RAs at room temperature gave no reaction whereas refluxing of
obtained were characterized by EPR in combination with the reaction for 0.5 h led to a mixture of 3,4-diamino-1,2,5-
DFT calculations.
selenadiazole (6) and 3,4-diamino-1,2,5-thiadiazole (8) in
practically 1:1 ratio (Scheme 4) suggesting that the hydroly-
sis rates of the thia- and selenadiazole rings of 7a are similar
under the conditions used.
Results and Discussion
2.1. Synthesis
Recently, the first representative of the heterocycles un-
der discussion, i.e. [1,2,5]selenadiazolo[3,4-b]quinoxaline
(1), was obtained by direct exchange of the sulfur atom of
the corresponding 1,2,5-thiadiazole 2 by a selenium atom
(Scheme 1).[12]
Scheme 4. Hydrolysis of [1,2,5]thiadiazolo[3,4-c][1,2,5]selenadiaz-
ole 7a.
However, 7b was easily hydrolyzed with 3 m ammonium
hydroxide solution to give the target compound 6 in high
yield (Scheme 5). The structure of 6 was confirmed by XRD
(section 2.2).
Scheme 1. Synthesis of [1,2,5]selenadiazolo[3,4-b]quinoxaline 1
from the corresponding thiadiazole 2.
To explore the synthetic scope of the direct transforma-
tion of 1,2,5-thiadiazoles into 1,2,5-selenadiazoles, the reac-
tion between [1,2,5]thiadiazolo[3,4-b]pyrazine (3) and SeO2
was studied. It was found that heating 3 with SeO2
(1.2 equiv.) at 100 °C in dimethylformamide (DMF) gives
[1,2,5]selenadiazolo[3,4-b]pyrazine (4) in low yield
(Scheme 2) together with several byproducts. Attempts to
purify 4 by crystallization were unsuccessful due to its insta-
bility in DMF and other organic solvents on heating.
Scheme 5. Synthesis of 3,4-diamino-1,2,5-selenadiazole 6.
Compound 6 was used in synthesis of the title com-
pounds by the Koerner–Hinsberg reaction. With glyoxal
(40% water solution), it was found that the yield of the
parent selenadiazolopyrazine 4 depends strongly upon the
solvent used. Refluxing in methanol and heating in ethanol
at 60–65 °C for 3 h gave 4 in moderate yields (53 and 51%,
respectively). Using the same reagents in glacial acetic acid
for 1 h at room temperature increased the yield of 4 to 79%
(Scheme 6).
Scheme 2. Synthesis of [1,2,5]selenadiazolo[3,4-b]pyrazine 4 from
[1,2,5]thiadiazolo[3,4-b]pyrazine 3 and SeO2.
Retrosynthetic analysis suggested that the reliable pre-
cursor of the parent [1,2,5]thiadiazolo[3,4-b]pyrazine (4)
and its substituted derivatives 5 would be the previously
unknown 3,4-diamino-1,2,5-selenadiazole (6) (Scheme 3)
Scheme 6. Synthesis of the parent [1,2,5]selenadiazolo[3,4-b]pyr-
azine 4.
Under the same conditions, the reaction was extended to
other 1,2-diketones including fused systems with aromatic
groups. With phenylglyoxal (a) and ninhydrine (b), the reac-
tion proceeded at room temperature, though with benzyl
(c), phenanthren-9,10-dione (d) and acenaphthylen-1,2-di-
one (e) refluxing in acetic acid for 3 h was required. Target
products 5a–e were obtained in moderate to high yields
(Scheme 7). The structure of 5a was confirmed by XRD
(section 2.2).
Scheme 3. Retrosynthetic route for the [1,2,5]selenadiazolo[3,4-b]-
pyrazines preparation.
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Synthesis of Chalcogen-Nitrogen Heterocycles
for insoluble compounds by solid-state 77Se NMR spec-
troscopy.
According to XRD (Figure 1 and Figure 2), geometries
of the selenadiazole rings of 6 and 5a, g are quite similar.
For 6 (Figure 1), the geometry of the selenadiazole moiety
is similar to that reported for 3,4-R2-1,2,5-selenadiazoles
(9a, R = Ph;[24] 9b, R = CN[25]). In 5a, g, the Se–N (1.786
and 1.806 Å), C–N (1.321 and 1.327 Å) and C–C (1.436 Å)
distances have typical values and are statistically indistin-
guishable in the two compounds. In 5a, the Ph substituent
is slightly twisted out of the mean plane of the main ring
with the torsion angle being 10.2°. In 5g, the Me groups lie
slightly above and below the mean plane of the ring, the
torsion angle is 5.7° (Figure 2).
In the solid state, 1,2,5-selenadiazoles normally reveal
propensity to secondary bonding interactions Se···N. Those
lead to 1–3 dimensional architectures via the formation of
the [Se···N]2 four-membered rings. The architectures are of
current interest for supramolecular chemistry and crystal
engineering.[26,27]
In 6, the presence of two NH2 groups results in an exten-
sive H-bonded network in the crystals. The strongest N–
H···N bond (N···N 3.035 Å, NHN 171°) assembles the mol-
ecules into homochiral infinite chains (Figure 1) that inter-
connect via weaker N–H···N bonds (N···N 3.189–3.278 Å,
NHN 128–173°) to give a non-centrosymmetric crystal
packing (space group P212121). There are also shortened
Se···Se (3.319 Å) and Se···N (3.129 Å) contacts. In the case
of 9a these interactions give rise to centrosymmetric dimers
(space group P21/c), while with 9b they result in homochiral
chains (space group P212121).
Scheme 7. Synthesis of the [1,2,5]selenadiazolo[3,4-b]pyrazines
5a–e.
It was found that 2-oxopropanal and diacetyl were de-
composed in acetic acid, and their reaction with 6 led to
complex mixtures with no significant amount of desired
compounds 5. Changing the solvent to ethanol gave better
results and treatment of 6 with these diketones at room tem-
perature for 12 h afforded derivatives 5f, g in good yields
(Scheme 8). The structure of 5g was confirmed by XRD
(section 2.2).
In 5a, the molecules pack the crystal in slipped herring-
bone fashion and these tow stacks are linked by Se···N in-
teractions (3.022 Å) and weak N···H contacts (2.49 Å), as
well as edge to face interactions of the phenyl rings. In 5g,
the molecules pack in parallel stacks along the c axis, the
pyrazine rings lying approximately above and below each
other in both stacks, with lateral contacts Se···N (3.264 Å)
Scheme 8. Synthesis of the substituted [1,2,5]selenadiazolo[3,4-b]-
pyrazines 5f, g.
2.2. Structure Elucidation by XRD and 77Se NMR
The authenticity of the compounds synthesized was con- connecting the sheets (Figure 2). Overall, the main packing
1
firmed by solution H, 13C and 77Se NMR and XRD, and motifs are rather different in 6 and 5a,h.
Figure 1. ORTEP plot of 6 showing 50% probability ellipsoids (left) and fragment of a homochiral H-bonded chain in its crystal (right).
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Figure 3. CP MAS 77Se NMR spectra of 5f (above) and 5e (below)
with isotropic resonances indicated by asterisks.
The solid-state δ77Se for compounds 5e,f agree well with
those measured in solution for compounds 5a–c, g (δ77Se,
1425–1470; see Exp. Sect.). A whole set of obtained data is
in accordance with the results of previous studies on similar
Se–N heterocycles including 2,1,3-benzoselenadiazoles and
their polyfluorinated derivatives.[12,21,28,29] For compound 6,
δ77Se is 1315 thus highlighting deshielding effect of elec-
tron-withdrawing pyrazine ring in derivatives 5.
Figure 2. Left: ORTEP plots of 5a (above) and 5g (below) showing
50% probability ellipsoids. Right: Corresponding packing patterns.
Cross-polarization magic angle spinning (CP MAS) 77Se
solid-state NMR spectra were measured for compounds
5e,f. As shown in Figure 3, a single Se site was observed in
2.3. Electrochemical Properties and Radical Anions
Derivatives 5c and 5g were selected for evaluation of the
both cases, consistent with the molecular symmetry, at δiso potential of the title compounds for persistent RAs.
1449 for 5e and 1454 for 5f. The manifold of spinning side- According to the gas-phase (U)B3LYP/6-31+G(d) calcu-
bands confirms the presence of a significant chemical shift lations, the first adiabatic electron affinity (EA) of com-
anisotropy in each molecule. pounds 5g and 5c are 1.55 and 1.93 eV, respectively, as com-
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Synthesis of Chalcogen-Nitrogen Heterocycles
pared with 0.22 eV for 1,2,5-selenadiazole and 1.06 eV for
2,1,3-benzoselenadiazole (10).[7]
In the potential range 0 to –2 V, the cyclic voltammog-
1C
ram (CV) of 5g contains three reduction peaks Ep
=
–0.98, Ep2C = –1.67 and Ep = –1.96 V, and that of 5c two
3C
1C
2C
reduction peaks Ep = –0.75 and Ep = –1.49 V (Fig-
1C
ure 4). For comparison, for 10 Ep = –1.40 V.[30] For both
5g and 5c the first reduction peak is reversible, diffusion-
1A
1C
controlled and one-electron (Ep – Ep1C = 0.06 V, Ep/2
–
1C
Ep = 0.06 V), i.e. corresponding to the formation of RAs
[5g]– and [5c]–, respectively. For both compounds the first
reduction peaks are reversible even at slow potential sweep
rates of 0.01 Vs–1 thus revealing relative stability of RAs
[5g]– and [5c]–. Thus, according to both CV and DFT data,
compound 5c is stronger electron acceptor than compound
5g.
Figure 5. Experimental and simulated EPR spectra of RA [5g]–.
Figure 4. CV of 5g (above) and 5c (below) in MeCN.
Electrochemical generations of RAs [5g]– and [5c]– for
EPR measurements were performed in the temperature
range 295–220 K with quartz tube in the resonator shifting
the spectra downfield by 145–150 G (14.5–15 mT). At
295 K, EPR spectra of only moderate quality were obtained
for both RAs. Examples of low-temperature experimental
spectra together with simulated ones are shown in Figures 5
and 6 for RAs [5g]– and [5c]–, respectively, and the experi-
mental and DFT-calculated hfc constants are given in
Table 1. Figure 7 shows Mulliken atomic charges, atomic
spin densities, π*-SOMOs and spin density distribution on
the van der Waals (VdW) surfaces of RAs [5g]– and [5c]–
from the UB3LYP/6-31+G(d) calculations. As follows from
the calculations, the π*-SOMO in both cases is essentially
antibonding. The spin density on the VdW surfaces of both
RAs is mostly positive featuring negative values only in the
area of C3a–C7a bond.
Figure 6. Experimental and simulated EPR spectra of RA [5c]–.
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O. A. Rakitin et al.
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Figure 7. Top to bottom: Mulliken atomic charges, atomic spin densities, π*-SOMOs and spin density distributions on the VdW surfaces
of RAs [5g]– (left) and [5c]– (right) from the UB3LYP/6-31+G(d) calculations. Color code: S – yellow, N – blue, C – grey, H – light grey.
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Synthesis of Chalcogen-Nitrogen Heterocycles
Table 1. Experimental/calculated[a] hfc constants of RAs [5g]– and
[5c]–.
all samples transverse magnetization was obtained by cross polar-
ization from H using optimized contact pulse durations of 40 ms,
1
and two-pulse phase modulation 1H decoupling during acquisition.
Spectra were acquired with recycle intervals of between 5 and 55 s,
depending on the longitudinal relaxation time of the samples. The
positions of the isotropic resonances within the spinning sidebands
patterns were unambiguously determined by recording a second
spectrum at a higher MAS rate. MS spectra (EI, 70 eV) were ob-
tained with a Finnigan MAT INCOS 50 instrument. High-resolu-
tion MS spectra were measured on a Bruker micrOTOF II instru-
ment using electrospray ionization (ESI). The measurements were
operated in a positive ion mode (interface capillary voltage
–4500 V) or in a negative ion mode (3200 V); mass range was from
m/z 50 to m/z 3000 Da; external or internal calibration was done
with Electrospray Calibrant Solution (Fluka). A syringe injection
was used for solutions in acetonitrile, methanol, or water (flow rate
RA
a(N1,3), 2N
a(N4,7), 2N
a(H)[b]
[5g]–
0.413/0.401
0.387/0.358
0.228/0.291
0.258/0.320
0.319/0.317
[5c]–
–[c]/0.044, 0.040,
0.028,0.021, 0.010
[a] UB3LYP/6-31+G(d). [b] 6 H. [c] Not determined by simulation.
We anticipate that the stability of the RAs [5c]– and
[5g]– under the CV conditions will lead to the eventual iso-
lation of [1,2,5]selenadiazolo[3,4-b]pyrazinidyls in the form
of salts after their chemical generation (cf. ref. 18), and this
will be a direction of our further work. Due to the spin
polarization of RAs (Figure 7), within the McConnell I
model antiferromagnetic effects should be expected for their 3 μLmin–1). Nitrogen was applied as a dry gas; interface tempera-
ture was set at 180 °C. IR spectra were measured with a Specord
M-80 instrument in KBr pellets. CV measurements on solution of
compounds 5c, g in dry MeCN (C = 2ϫ10–3 mm) were performed
at 298 K in an argon atmosphere with a PG 310 USB potentiostat
(HEKA Elektronik). A spherical platinum electrode (S = 0.08 cm2)
was used. The supporting electrolyte was 0.1 m Et4NClO4. The
sweep rates were v = 0.01–1.0 Vs–1. Peak potentials were quoted
with reference to a saturated calomel electrode (SCE). EPR mea-
surements on electrochemically generated RAs [5c]– and [5g]– (C =
2 mm in MeCN) were carried out with a ELEXSYS-II E500/540
spectrometer (MW power 10 mW, modulation frequency 100 kHz
and modulation amplitude 0.005 mT) using a standard cell with
platinum working electrode for EPR measurements under anaero-
bic conditions. Simulations of the experimental EPR spectra were
performed with the Winsim 2002 program[32] using the Simplex al-
gorithm for many-parameter optimization of hfc values and line
homospin salts where only RA is paramagnetic. For ferro-
magnetic effects, heterospin salts are required where both
ions are paramagnetic with cations featuring negative spin
density on their VdW surfaces.[7–9]
Conclusions
A convenient route to the previously unknown 3,4-di-
amino-1,2,5-selenadizole 6 has been developed. Compound
6 is promising starting material for variety of organic syn-
theses. In this work, novel [1,2,5]selenadiazolo[3,4-b]pyr-
azines including the parent compound 4 and its substituted
derivatives 5a–g have been prepared from 6 and 1,2-diket-
ones by the Koerner–Hinsberg reaction. The compounds
synthesized have been characterized by XRD and multinu- widths. The accuracy of calculating the hfc values was 0.001 mT.
clear NMR including 77Se solid-state NMR spectroscopy.
DFT calculations were performed at the (U)B3LYP/6-31+G(d)
level of theory with full geometry optimization with the Gaussian-
According to the DFT calculations, [1,2,5]selenadiazolo-
09
program
package.[33]
[1,2,5]Selenadiazolo[3,4-c][1,2,5]-
[3,4-b]pyrazines obtained possess positive EA. They are
precursors of novel persistent RAs under CV conditions.
The identity of the electrochemically generated RAs has
selenadiazole (7b) was prepared according to the published pro-
cedure.[12]
been confirmed by EPR spectroscopy in combination with X-ray Diffraction: Crystal data for 5a: C10H5N4Se, Mr
=
260.14 gmol–1, monoclinic, space group P21/c, a = 14.661(3), b =
5.7089(9), c = 11.488(2) Å, β = 107.427(5), V = 917.4(3) Å3, Z =
4, ρcalc = 1.883 gm–3, μ = 40.59 mm–1, F(000) = 508. Rigaku XRF
generator, [λ(Mo-Kα) = 0.71072 Å], Dectris P200 detector, T =
DFT calculations. Stability of [1,2,5]selenadiazolo[3,4-b]-
pyrazinidyls under the CV conditions motivates experi-
ments towards their eventual isolation in the form of mag-
netically-active salts after chemical generation.
173 K, 9396 reflections, 1680 independent reflections (Rint
=
0.0361). wR2 = 0.0788 and GOF = 0.892 for all independent reflec-
tions [R1 = 0.0223 was calculated against F for 1515 observed re-
flections with IϾ2σ(I)]. All calculations were performed using
SHELXL.[34]
Experimental Section
General: Elemental analyses for C, H and N were performed with
Perkin–Elmer 2400 Elemental Analyser, analyses for Se by spectro-
photometric method described in ref.[31] Melting points were deter-
mined on a Kofler hot-stage apparatus and are uncorrected. Solu-
Crystal Data for 5g: C6H6N4Se, Mr = 213.13 gmol–1, monoclinic,
space group P21/c, a = 12.105(8), b = 9.012(5), c = 6.811(4) Å, β
= 100.059(19)°, V = 731.6(8) Å3, Z = 4, ρcalc = 1.935 gm–3, μ =
50.65 mm–1, F(000) = 416. Rigaku MMoo7 generator, [λ(Mo-Kα)
= 0.71072 Å], Saturn 724 detector, T = 125 K, 9119 reflections,
1328 independent reflections (Rint = 0.1008). wR2 = 0.2133 and
GOF = 1.153 for all independent reflections [R1 = 0.0776 was cal-
culated against F for 1023 observed reflections with IϾ2σ(I)]. All
calculations were performed using SHELXL.[34]
1
tion H (300.1 MHz), 13C (75.5 MHz) and 77Se (76.3 MHz) NMR
spectra were taken for CDCl3 solutions (unless otherwise indicated)
with a Bruker AM-300 machine and referred to TMS (1H and 13C)
and (CH3)2Se (77Se), J values are given in Hz. CP MAS 77Se solid-
state NMR experiments were performed at 298 K using a Bruker
Avance III spectrometer operating at a magnetic field strength of
9.4 T corresponding to a 77Se Larmor frequency of 76.3 MHz. Ex-
periments were carried out using conventional 4 mm MAS probes
and with MAS rates between 5 and 12.5 kHz. Chemical shifts are
referenced relative to (CH3)2Se at 0 ppm, using the isotropic reso-
nance of solid H2SeO3 at 1288.1 ppm as a secondary reference. For
Crystal Data for 6: C2H4N4Se, Mr = 163.05 gmol–1, orthorhombic,
space group P212121, a = 3.93580(10), b = 8.8682(3), c =
12.8796(4) Å, V = 449.54(2) Å3, Z = 4 (ZЈ = 1), ρcalc = 2.409 gm–3,
μ = 81.98 mm–1, F(000) = 312. Intensities of 9009 reflections were
Eur. J. Org. Chem. 2015, 5585–5593
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5591

O. A. Rakitin et al.
FULL PAPER
measured with a Bruker APEXII CCD diffractometer [λ(Mo-Kα)
= 0.71072 Å, ω-scans, θ Ͻ 58°], and 1195 independent reflections
(Rint = 0.0215) were used in further refinement. The structure was
solved by direct method and refined by the full-matrix least-squares
technique against F2 in the anisotropic-isotropic approximation.
Hydrogen atom positions were found in difference Fourier synthe-
sis and refined in the isotropic approximation within the riding
model. The refinement converged to wR2 = 0.0322 and GOF =
1.002 for all independent reflections [R1 = 0.0119 was calculated
against F for 1177 observed reflections with IϾ2σ(I)]. All calcula-
tions were performed using SHELXTL PLUS 5.0.[34]
5,6-Diphenyl[1,2,5]selenadiazolo[3,4-b]pyrazine (5c): Yellow solid,
yield 69 mg (64%), m.p. 261–263 °C. C16H10N4Se (337.24): calcd.
C 56.98, H 2.99, N 16.61, Se 23.41; found C 57.12, H 3.18, N 16.42,
Se 23.50. NMR: 1H: δ = 7.37 (m, 4 H, Ph), 7.47 (m, 2 H, Ph), 7.60
(m, 4 H, Ph)v ppm; 13C: δ = 128.3, 130.1, 130.3, 137.6, 156.5, 159.0
ppm; 77Se: δ = 1452 ppm. IR: ν = 2922 and 2852 (CH), 1659, 1579,
˜
1393, 1277, 1211, 876, 719, 697, 642, 575, 509 cm–1. MS: m/z (%)
= 340 (11) [M + 2], 338 (50) [M+], 336 (18), 183 (28), 129 (17), 105
(47). ESI-MS: found m/z 360.9960; calcd. for C16H10N478Se [M]+
360.9963.
Dibenzo[f,h][1,2,5]selenadiazolo[3,4-b]quinoxaline (5d): Dark red so-
lid, yield 40.2 mg (67%), m.p. Ͼ 350 °C. C16H8N4Se (335.22):
calcd. C 57.33, H 2.41, N 16.71; found C 57.22, H 2.16, N 16.93.
CCDC-1401703 (for 5a), -1401704 (for 5g) and 1045610 (for 6) con-
tain the supplementary crystallographic data for this article. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
IR: ν = 3074 and 3056 (CH), 1601, 1450, 1330, 756, 721, 500 cm–1.
˜
MS: m/z (%) = 338 (14) [M + 2], 336 (92) [M+], 334 (33), 232 (10),
230 (100), 228 (1), 178 (66), 176 (86), 80 (97). ESI-MS: found m/z
358.9825; calcd. for C16H8N478Se [M + Na]+ 358.9807.
3,4-Diamino-1,2,5-selenadiazole 6: A mixture of compound 7b
(141 mg, 0.58 mmol) and a solution of NH4OH in water (3 m,
2.2 mL) was stirred at room temperature for 1 h. The reaction mix-
ture was extracted with EtOAc (4ϫ 5 mL), washed with brine (3ϫ
10 mL) and evaporated under reduced pressure. Colorless solid,
yield 0.90 g (61%), m.p. 177–179 °C. C2H4N4Se (163.04): calcd. C
14.73, H 2.47, N 34.36; found C 14.52, H 2.32, N 34.65. NMR, δ,
Acenaphtho[1,2-e][1,2,5]selenadiazolo[3,4-b]pyrazine (5e): Yellow so-
lid, yield 77 mg (83%), m.p. Ͼ 350 °C. C14H6N4Se (309.18): calcd.
C 54.38, H 1.96, N 18.12; found C 54.17, H 1.88, N 17.95. NMR,
δ, 77Se (solid state): 1449. IR: ν = 3077 and 3055 (CH), 1610, 1421,
˜
1210, 1110, 827, 775, 508 cm–1. MS: m/z (%) = 312 (13) [M + 2],
310 (67) [M+], 308 (33), 306 (13), 230 (15), 204 (100), 178 (30), 152
(33). ESI-MS: found m/z 332.9652; calcd. for C14H6N478Se [M +
Na]+ 332.9650.
1H: 6.36 (s, 4 H, 2NH2); 13C: 153.0; 77Se: 1315. IR: ν = 3420, 3278
˜
and 3155 (NH), 1618 (C=N), 1514, 1418, 702 cm–1. MS: m/z (%)
= 166 (16) [M + 2], 164 (100) [M+], 162 (50), 160 (20), 124 (16),
122 (90), 120 (45), 80 (33), 42 (30). ESI-MS: found m/z 164.9667;
calcd. for C2H5N4Se [M + H]+ 164.9674.
General Procedure for the Reaction of 3,4-Diamino-1,2,5-selenadi-
azole 6 with 1,2-Diketones in Ethanol: A mixture of compound 6
(49 mg, 0.3 mmol) and 1,2-diketone (1.5 mmol) in EtOH (3 mL)
was stirred at room temperature for 12 h, the precipitate was fil-
tered off and washed with EtOH. Combined mother liquids were
evaporated under reduced pressure. The residue was triturated with
diethyl ether (2 mL), precipitate was filtered, washed by ether and
dried.
General Procedure for the Reaction of 3,4-Diamino-1,2,5-selenadi-
azole 6 with 1,2-Diketones in Acetic Acid: A mixture of compound
6 (49 mg, 0.3 mmol) and 1,2-diketone (0.33 mmol) in AcOH (3 mL)
was stirred at room temperature for 12 h or heated under reflux for
3 h and cooled to room temperature. Precipitate was filtered off,
washed by ether and dried.
[1,2,5]Selenadiazolo[3,4-b]pyrazine (4): Pale grey solid, yield 28 mg
(61%), m.p. Ͼ 300 °C. C4H2N4Se (185.05): calcd. C 25.96, H 1.09,
N 30.28; found C 25.72, H 1.01, N 30.58. NMR ([D6]DMSO): 13C:
5-Methyl[1,2,5]selenadiazolo[3,4-b]pyrazine (5f): Dark red solid,
yield 35 mg (58%), m.p. 188–190 °C. C5H4N4Se (199.07): calcd. C
30.17, H 2.03, N 28.14; found C 30.34, H 1.83, N 27.96. NMR
([D6]DMSO): 1H: δ = 3.35 (s, 3 H, Me), 8.93 (s, 1 H, Ar) ppm;
13C: δ = 23.1 (Me), 152.6(CH), 156.0, 156.9, 160.6 ppm; 77Se: δ =
δ = 148.5, 150.8 ppm. IR: ν = 1479, 1395, 1254, 1168, 1008, 880,
˜
742, 692, 521, 469 cm–1. MS: m/z (%) = 186 (100) [M+], 184 (34),
107 (11), 105 (7), 80 (28), 78 (8), 45 (17), 43 (69). ESI-MS: found
m/z 183.9442; calcd. for C4H2N478Se [M]+ 183.9447.
1444 ppm; NMR 77Se (solid state): δ = 1454 ppm. IR: ν = 2982
˜
and 2937 (CH), 1625, 1526, 1356, 1092, 712, 603, 512 cm–1. MS:
m/z (%) = 202 (13) [M + 2], 200 (100) [M+], 198 (57), 123 (4), 121
(79), 89 (4), 87 (58), 85 (23), 82 (8), 80 (62), 69 (9), 67 (76), 65 (4).
ESI-MS: found m/z 222.9497; calcd. for C5H4N478Se [M + Na]+
222.9493.
5-Phenyl[1,2,5]selenadiazolo[3,4-b]pyrazine (5a): Yellow solid, yield
60 mg (77%), m.p. 219–221 °C. C10H6N4Se (261.14): calcd. C
45.99, H 2.32, N 21.45; found C 46.14, H 2.45, N 21.21. NMR
1
([D6]DMSO): H: δ = 7.64 (m, 3 H, Ph), 8.41 (m, 2 H, Ph), 9.73
(s, 1 H, CH) ppm; 13C: δ = 128.8, 129.8, 132.1, 135.5, 149.8, 155.2,
5,6-Dimethyl[1,2,5]selenadiazolo[3,4-b]pyrazine (5g): Yellow solid,
yield 58 mg (87%), m.p. 205–207 °C. C6H6N4Se (213.10): calcd. C
30.17, H 2.03, N 28.14, Se 37.05; found C 30.34, H 1.83, N 27.96,
Se 37.15. NMR (CDCl3): 1H: δ = 2.78 (s, 6 H, Me) ppm; 13C: 24.0,
156.7, 157.3 ppm; 77Se: δ = 1462 ppm. IR: ν = 3062 (CH), 1552,
˜
1482, 1274, 1215, 1030, 957, 771, 687, 507, 479 cm–1. MS: m/z (%)
= 264 (17) [M + 2], 262 (70) [M+], 260 (61), 185 (1), 183 (27), 181
(4), 131 (7), 129 (52), 105 (15), 103 (51), 101 (11), 79 (21), 77 (11).
ESI-MS: found m/z 284.9659; calcd. for C10H6N478Se [M + Na]+
284.9650.
156.4, 160.3 ppm; 77Se: δ = 1426 ppm. IR: ν = 2992 and 2956 (CH),
˜
1479, 1395, 1254, 1168, 1008, 880, 742, 692, 521, 469 cm–1. MS:
m/z (%) = 216 (1) [M + 2], 214 (39) [M+], 212 (18), 123 (1), 121
(54), 80 (38), 69 (4), 67 (100), 65 (16). ESI-MS: found m/z 236.9650;
calcd. for C6H6N478Se [M + Na]+ 236.9650.
9H-Inden[1,2-e][1,2,5]selenadiazolo[3,4-b]pyrazin-9-one (5b): Yellow
solid, yield 75 mg (87%), m.p. 347–349 °C. C11H4N4OSe (287.14):
calcd. C 46.01, H 1.40, N 19.51; found C 46.23, H 1.11, N 19.29.
1
NMR ([D6]DMSO): H: δ = 7.82 (d, 1 H, Ar; J = 6.0), 7.98 (m, 2
H, Ar), 8.22 (d, 1 H, Ar; J = 6.0) ppm; 13C: δ = 123.8, 124.8, 134.7,
Acknowledgments
138.0, 139.7, 140.6, 155.8, 157.7, 157.8, 160.0, 188.1 (C=O) ppm;
77Se: δ = 1469 ppm. IR: ν = 3078 and 3056 (CH), 1724 (C=O),
The authors gratefully acknowledge financial support from the
Russian Foundation for Basic Research (project number 13-03-
00072), the Presidium of the Russian Academy of Sciences (pro-
gramme number 8, project 8.14) and the Leverhulme Trust (project
IN-2012-094). I. G. I., N. V. V., E. A. C. and A. V. Z. are grateful to
˜
1579, 1213, 928, 745, 480 cm–1. MS: m/z (%) = 290 (8) [M + 2],
288 (63) [M+], 286 (3), 132 (10), 130 (100), 128 (1), 104 (3), 102
(43), 100 (13). ESI-MS: found m/z 309.9441; calcd. for
C11H4N4O78Se [M + Na]+ 309.9443.
5592
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Eur. J. Org. Chem. 2015, 5585–5593

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Published Online: July 23, 2015
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5593