A novel route to spin-labeled dihydrooxepines and o-benzoquinones

Article abstract of DOI:10.1007/s11172-011-0356-8

A reaction of a lithiated derivative of 4,4,5,5-tetramethyl-3-oxido-4,5- dihydro-1H-imidazole 1-oxyl with 3,6-di-tert-butyl-o-benzoquinone at -80 °C predominantly gave spin-labeled dihydrooxepine via nucleophilic 1,2-addition of the paramagnetic carbanion to the CO group of the benzoquinone followed by insertion of the O atom into the ring. At lower temperatures, this reaction was accompanied by 1,4-addition of the organolithium compound to the benzoquinone followed by oxidation of the resulting adduct into spin-labeled o-benzoquinone. This one pot process is a novel approach to organic derivatives that can further be converted into di- and polyradicals combining nitronyl nitroxide and semiquinolate fragments.

Full text of DOI:10.1007/s11172-011-0356-8

Russian Chemical Bulletin, International Edition, Vol. 60, No. 11, pp. 2325—2330, November, 2011
2325
A novel route to spinꢀlabeled dihydrooxepines and oꢀbenzoquinones*
E. V. Tretyakov,a S. E. Tolstikov,a G. V. Romanenko,a A. S. Bogomyakov,a
V. K. Cherkasov,b D. V. Stass,c and V. I. Ovcharenkoa
aInternational Tomography Center, Siberian Branch of the Russian Academy of Sciences,
3a ul. Institutskaya, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383) 333 1399. Eꢀmail: Victor.Ovcharenko@tomo.nsc.ru
bG. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation
cInstitute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences,
3 ul. Institutskaya, 630090 Novosibirsk, Russian Federation
A reaction of a lithiated derivative of 4,4,5,5ꢀtetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidꢀ
azole 1ꢀoxyl with 3,6ꢀdiꢀtertꢀbutylꢀoꢀbenzoquinone at –80 °C predominantly gave spinꢀlabeled
dihydrooxepine via nucleophilic 1,2ꢀaddition of the paramagnetic carbanion to the CO group
of the benzoquinone followed by insertion of the O atom into the ring. At lower temperatures,
this reaction was accompanied by 1,4ꢀaddition of the organolithium compound to the benzoꢀ
quinone followed by oxidation of the resulting adduct into spinꢀlabeled oꢀbenzoquinone. This
"one pot" process is a novel approach to organic derivatives that can further be converted into
diꢀ and polyradicals combining nitronyl nitroxide and semiquinolate fragments.
Key words: nitronyl nitroxides, oꢀbenzoquinones, ring expansion reactions, SNHꢀreactions.
Design of molecular magnets based on heterospin comꢀ
plexes of transition metals with organic radicals is an acꢀ
tively developed interdisciplinary scientific field. One of
these goals is the design of novel types of magnetically
active compounds liable to either a phase transition into
a magnetically ordered state or structural rearrangements
giving rise to a physical anomaly in the paramagnetic
range.1—3 The ability of heterospin complexes to demonꢀ
strate various magnetic anomalies is due to the presence of
exchangeꢀcoupled spin systems (also called exchange clusꢀ
ters, multispin ensembles, or multispin clusters).4,5 The
largest groups of paramagnetic ligands used to design such
clusters are constituted by stable nitroxides, in which the
unpaired electron density is efficiently delocalized over
several donor atoms,2,6 and sterically hindered oꢀsemiꢀ
quinolate anions.7,8 In a considerable number of comꢀ
plexes with such ligands, the solid phases can be magneꢀ
tized and exhibit thermomagnetic or photo/thermomeꢀ
chanical properties.9—11
anion and stable nitroxides derived from 2ꢀimidazoline)
have been recently12,13 obtained and characterized. They
exhibit nontrivial properties. For instance, when coordiꢀ
nating to an extra ligand, CuII semiquinolate begins to
function as a sensor of its nearest environment, using the
changes in the ferromagnetic/antiferromagnetic exchange
ratio as a quantum inducing device.12 Heterospin cobalt
complexes containing both the oꢀsemiquinolate and nitrꢀ
oxide ligands show magnetic anomalies at room temperaꢀ
ture, which is promising for the design of new inducing
devices and molecular actuators.13 Active investigations14—16
are being done to obtain complexes with diradical anions
Ln in which the oꢀsemiquinone ring is linked directly or
Simultaneous introduction of various paramagnetic
fragments (nitroxide and oꢀsemiquinolate groups) into the
ligand environment of a metal ion gives greater scope to
the design and functionalization of multispin ensembles.
For instance, heterospin CuII and CoII complexes with
various paramagnetic ligands (an oꢀsemiquinolate radical
* Dedicated to Academician of the Russian Academy of Sciences
O. M. Nefedov on the occasion of his 80th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2280—2285, November, 2011.
1066ꢀ5285/11/6011ꢀ2325 © 2011 Springer Science+Business Media, Inc.

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Tretyakov et al.
through the paraꢀphenylene spacer with the 3ꢀoxidoꢀ1ꢀ
oxylimidazolinꢀ2ꢀyl fragment. Precursors of Ln are spinꢀ
labeled catechols prepared by condensation of appropriate
aldehydes with 2,3ꢀbis(hydroxyamino)ꢀ2,3ꢀdimethylꢀ
butane followed by oxidation of intermediate imidazolꢀ
idineꢀ1,3ꢀdiols. The methodological basis for the synthesis
of such ligands Ln is provided by Ullman´s approach.17,18
In the present work, we propose a novel method for the
synthesis of such organic paramagnetics. The method inꢀ
volves nucleophilic addition reactions of organometallic
compounds of Li, Zn, Cd, and Al (Scheme 1) with steriꢀ
cally shielded 3,6ꢀdiꢀtertꢀbutylꢀoꢀbenzoquinone (2). Subꢀ
sequent hydrolysis and oxidation give the corresponding
substituted oꢀquinones.19 If the reaction followed the
1,4ꢀaddition pattern, the reaction product could a priori
be expected to be 2ꢀ(2,5ꢀdiꢀtertꢀbutylꢀ3,4ꢀdioxocyclohexaꢀ
1,5ꢀdienyl)ꢀ4,4,5,5ꢀtetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ
1Hꢀimidazole 1ꢀoxyl (5) (see Scheme 1), which is a poꢀ
tential precursor of the diradical anion L3. This was eviꢀ
denced by a 1,4ꢀaddition reaction of benzoquinone 2 with
PhLi at one carbonyl group: the resulting lithium semiꢀ
quinolate was subjected to in situ hydrolysis and oxidation
leading to phenylꢀoꢀbenzoquinone.20 At the same time, it is
known21 that the first step in reactions of benzoquinone 2
with lithium acetylenides (PhC≡CLi or Me3CC≡CLi) inꢀ
volves 1,2ꢀaddition of the organolithium compound to the
oꢀquinone to yield the corresponding lithium salts of hydrꢀ
oxycyclohexadienones, which in polar solvents undergo
rearrangement into sevenꢀmembered lactones. Thus, the
problem of introduction of a paramagnetic substituent into
quinone 2 via its reaction with compound 1 remained
unsolved up to the present study.
methylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole 1ꢀoxyl) with
oꢀquinone 2 in THF gives a mixture of products varying
with the reaction temperature and time (see Scheme 1).
For instance, when compounds 1 and 2 were stirred at
–80 °C for 2 h, the final mixture contained dihydroꢀ
oxepine 4 (23%) and its transformation product 3 (26%).
When the reagents were mixed at –80 °C, warmed to room
temperature, and stirred for 24 h, we detected no dihydroꢀ
oxepine 4, while the yield of compound 3 increased to
47%. When the reaction was carried out at –105 °C (the
gel transition temperature of THF) for 2 h, workup of the
reaction mixture mainly gave nitroxides 3 and 4; minor
amounts of quinone 5 were also isolated. When the stirꢀ
ring time was extended to 24 h, dihydrooxepine 4 was
transformed into compound 3 (42%), while the yield of
quinone 5 did not exceed 5%.
Therefore, lithiated derivative 1 reacts with the startꢀ
ing oꢀquinone 2 predominantly according to the 1,2ꢀaddiꢀ
tion mechanism to give adduct 6, which undergoes in situ
rearrangement into lactone 7 (Scheme 2).
One can believe that warming of the reaction mixture
results in a further transformation of lactone 7: the Li
atom migrates to the nitronyl O atom to give isomer 8,
which then recombines with imino nitroxide 9 gradually
accumulating in the reaction mixture through deoxygenꢀ
ation of the starting 4,4,5,5ꢀtetramethylꢀ3ꢀoxidoꢀ4,5ꢀdiꢀ
hydroꢀ1Hꢀimidazole 1ꢀoxyl (Scheme 3).
Single crystals of nitroxides 3—5 were grown and exꢀ
amined by Xꢀray diffraction. In structures 3 and 4, the
dihydrooxepine ring has a boat conformation. The C(8),
C(9), C(22), and C(23) atoms in compound 3 (pairs of the
doubly bonded atoms: C(8)=C(9), 1.330(3) Å; C(22)=C(23),
1.331(3) Å) and the C(14), C(22), C(28), and O(5) atoms
in compound 4 form the bottom of the boat; the deviaꢀ
We found that a reaction of lithiated derivative 1 (genꢀ
erated by the action of LiN(SiMe3)2 on 4,4,5,5ꢀtetraꢀ
Scheme 1

Spinꢀlabeled dihydrooxepines and oꢀbenzoquinones Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2327
Scheme 2
are equal (1.277(2) Å). The intermolecular contacts
O(1)...C(14´) (2.888(2) Å) between the molecules of comꢀ
pound 5 are substantially shorter than the sum of the van
der Waals radii (–0.332 Å) (Fig. 2, b). Apparently, the
presence of such contacts accounts for the difference beꢀ
tween the geometrical parameters of two molecular fragꢀ
ments (O=)C—CBut. In the fragment (O=)C—CBut with
the carbonyl C atom approaching the O atoms of the N—O
groups of adjacent molecules, the C(9)—C(14) and
C(14)—O(3) bond lengths are 1.498(3) and 1.215(3) Å,
respectively. The corresponding bond lengths in the other
fragment are different: C(22)—C(23), 1.467(3) Å;
C(22)—O(4), 1.225(3) Å. The μeff value of compound 5 in
a temperature range from 40 to 300 K is close to the theoꢀ
retical value for a monoradical (1.73 0.01μB).
The ESR spectra of compounds 3—5 are similar, conꢀ
sisting of a quintet for two virtually equivalent N nuclei.
The spectra show no finer substructure, which is probably
due to the steric hindrances presented by the bulky substitꢀ
uents to the rotation of the radicals in solution (in Fig. 3,
the ESR spectrum of nitroxide 5 is shown as an example).
Nevertheless, for satisfactory modeling of the spectral lines,
we should take account of the HFC with 12 methyl proꢀ
tons with a characteristic constant of 0.024 mT. The calꢀ
culated HFC constants and g factors are given below (the
accuracy of the calculation is 0.005 mT and 0.0001, reꢀ
spectively).
tions of the aforementioned atoms from the meanꢀsquare
plane do not exceed 0.025 Å (Fig. 1, Table 1). The other
atoms of the dihydrooxepine ring are distant from the bottom
plane by 0.71—0.77 and 0.75—0.83 Å in compounds 3
and 4, respectively. The angles between the planes of the
fragment N(1)C(7)N(2) of the imidazoline ring and
the fragment O(5)C(8)C(9) of the dihydrooxepine ring
are 81.5° and 76.6° in compounds 3 and 4, respectiveꢀ
ly. The N—O bond lengths in nitroxides 3 and 4 are
1.277(2)—1.280(2) Å, which is characteristic of nitronyl
nitroxides.22 The paramagnetic centers of adjacent moleꢀ
cules (the O atoms of the N—O groups) are spaced apart
at more than 4.5 Å. The considerable intermolecular disꢀ
tances make the spins virtually separate, so the experiꢀ
mental effective magnetic moments μeff of compounds 3
and 4 in a temperature range from 300 to 30 K are conꢀ
stant and close to a theoretical value of 1.73μB.
Comꢀ
pound
aN1
aN2
a12H
giso
mT
3
4
5
0.736
0.747
0.728
0.712
0.712
0.717
0.024
0.024
0.024
2.0066
2.0065
2.0066
To sum up, we found that a reaction of 3,6ꢀdiꢀtertꢀ
butylꢀoꢀbenzoquinone with a lithium derivative of 4,4,5,5ꢀ
tetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole 1ꢀoxyl
occurs at the carbonyl group of the quinone according to
the 1,2ꢀaddition pattern followed by insertion of the
O atom into the ring. The resulting substituted dihydrooxeꢀ
pine 4 can react with lithium 4,4,5,5ꢀtetramethylꢀ4,5ꢀdiꢀ
hydroꢀ1Hꢀimidazolꢀ1ꢀolate to give more substituted diꢀ
The structure of nitroxide 5 has a plane of mirror symꢀ
metry passing through the C and O atoms of the quinone
fragment and the C(10), C(11), C(24), and C(27) atoms
of the tertꢀbutyl groups (Fig. 2, a). The planar imidazoline
ring is perpendicular to the plane of the benzene ring. The
N—O bond lengths in the nitronyl nitroxide fragment
Scheme 3

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Tretyakov et al.
a
b
C(25)
C(26)
C(27)
C(24)
C(26)
C(23)
C(22)
C(14)
C(27)
O(4)
O(1)
C(24)
O(4)
C(3)
C(2)
C(25)
C(2)
C(28)
O(1)
C(28)
C(23)
C(22)
N(1)
C(7)
O(5)
C(8)
C(9)
C(1)
C(3)
C(6)
C(1)
C(5)
O(5)
C(8)
N(1)
C(7)
C(4)
N(2)
O(3)
C(17)
C(11)
C(14)
N(3)
C(15)
C(21)
C(18)
C(12)
N(2)
C(4)
C(9)
C(10)
C(6)
O(2)
C(10)
C(5)
C(16)
C(20)
O(2)
C(13)
C(13)
N(4)
C(11)
C(12)
C(19)
Fig. 1. Structures 3 (a) and 4 (b).
Table 1. Selected bond lengths d in structures 3 and 4
Bond
d/Å
Bond
d/Å
3
4
3
4
N(1)—O(1)
N(2)—O(2)
O(4)—C(28)
O(5)—C(28)
O(5)—C(8)
C(7)—C(8)
C(8)—C(9)
C(9)—C(14)
C(14)—C(22)
1.280(2)
1.279(2)
1.196(2)
1.386(2)
1.406(2)
1.463(3)
1.330(3)
1.525(3)
1.497(3)
1.280(2)
1.277(2)
1.193(2)
1.395(2)
1.411(2)
1.473(3)
1.333(3)
1.473(3)
1.317(3)
C(22)—C(23)
C(23)—C(28)
O(3)—N(3)
O(3)—C(14)
N(3)—C(21)
N(3)—C(15)
N(4)—C(21)
N(4)—C(18)
1.331(3)
1.484(3)
1.427(2)
1.447(2)
1.390(3)
1.490(3)
1.266(3)
1.487(3)
1.500(3)
1.505(3)
—
—
—
—
—
—
a
b
C(27)
C(28)
C(24)
C(26)
C(22)
O(4)
C(23)
C(8)
C(7)
C(3)
C(14)
N(1)
C(1)
C(9)
C(10)
2.888(2) Å
O(3)
C(2)
O(1)
C(11)
C(12)
Fig. 2. Structure 5 (a) and the intermolecular contacts O(1)...C(14´) in structure 5 (b). The symmetry operation code is 1 – x,
–1/2 + y, 1 – z.

Spinꢀlabeled dihydrooxepines and oꢀbenzoquinones Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2329
isotropic g factors were determined with solidꢀstate diphenylpicꢀ
rylhydrazyl as a standard.
Reaction of a lithiated derivative of 4,4,5,5ꢀtetramethylꢀ3ꢀ
oxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole 1ꢀoxyl (1) with 3,6ꢀdiꢀtertꢀbuꢀ
tylꢀoꢀbenzoquinone (2) (general procedure A). A 1.0 M solution of
LiN(SiMe3)2 (2.1 mL, 2.1 mmol) in THF was added at –80 °C
to a stirred solution of 4,4,5,5ꢀtetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ
1Hꢀimidazole 1ꢀoxyl (300 mg, 1.91 mmol) in THF (40 mL). The
resulting redꢀorange solution was stirred for 30 min and cooled
until a jellyꢀlike mass formed (~–105 °C). Then a solution of
benzoquinone 2 (300 mg, 1.36 mmol) in THF (5 mL) was added.
The reaction mixture was stirred without cooling for 20 h
and concentrated. The residue was chromatographed on SiO2
(2×10 cm) with CH2Cl2 and AcOEt as eluents used in succesꢀ
345
346
347
348
349
350
Н/mT
sion. The yield of nitroxide 3 was 294 mg (42% from quinone 2).
A mixture of compounds 5 and 2 was separated by column
chromatography on Al2O3 (2×10 cm) with benzene and AcOEt as
eluents used in succession. The yield of nitroxide 5 was 23 mg (5%).
General procedure B. A 1.0 M solution of LiN(SiMe3)2
(2.1 mL, 2.1 mmol) in THF was added at –80 °C to a stirred
solution of 4,4,5,5ꢀtetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidꢀ
azole 1ꢀoxyl (1.91 mmol) and compound 2 (1.36 mmol) in THF
(40 mL). The reaction mixture was stirred without cooling for an
additional 2 h and concentrated. The residue was chromatoꢀ
graphed on SiO2 (2×10 cm) with CH2Cl2 and AcOEt as eluents
used in succession. The yield of nitroxide 3 was 186 mg (26%
from quinone 2). A mixture of compounds 4 and 2 was separated
by column chromatography on Al2O3 (2×10 cm) with benzene
and AcOEt as eluents used in succession. The yield of nitroxide 4
was 120 mg (23%).
2ꢀ[3,6ꢀDiꢀtertꢀbutylꢀ2ꢀoxoꢀ5ꢀ(4,4,5,5ꢀtetramethylꢀ4,5ꢀdiꢀ
hydroꢀ1Hꢀimidazolꢀ1ꢀyloxy)ꢀ2,5ꢀdihydrooxepinꢀ7ꢀyl]ꢀ4,4,5,5ꢀ
tetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole 1ꢀoxyl (3). Vioꢀ
let needles, m.p. 147—149 °C (from ethyl acetate—toluene),
Rf 0.40 (CH2Cl2, N/UV254 Al2O3 plates (0.2 mm, Machereyꢀ
Nagel)); Rf 0.33 (AcOEt, Silica gel 60 F254 plates (Merck)). IR,
ν/cm–1: 544, 610, 647, 678, 700, 737, 752, 824, 842, 870, 920,
941, 962, 983, 1024, 1046, 1072, 1094, 1121, 1164, 1217, 1249,
Fig. 3. ESR spectrum of a 1•10–5 M solution of nitroxide 5 in
toluene.
hydrooxepine 3. At low temperatures (–105 °C), the above
process is accompanied by 1,4ꢀaddition of the organolithꢀ
ium compound leading to spinꢀlabeled quinone 5, which
is formally derived from compound 2 by an SNHꢀreaction
at the quinonoid ring.
As noted above, L1 and L2 were earlier accessible from
appropriate catechols,14—16 which were oxidized into
diradical anions for complexation reactions with metal
ions. The method we proposed here for the synthesis of
spinꢀlabeled derivatives affords quinone 5, which can be
reduced to diradical anion L3 and, like L1 and L2, used in
complexation reactions. The latter calls for further invesꢀ
tigations.
Experimental
4,4,5,5ꢀTetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole
1ꢀoxyl (1)23 and 3,6ꢀdiꢀtertꢀbutylꢀoꢀbenzoquinone (2)24 were
prepared according to known procedures. Commercial reagents
and solvents were used as purchased. Reactions were carried out
under argon. Silica gel (0.063—0.200 mm, column chromatoꢀ
graphy grade, Merck) and Al2O3 (chromatography grade, the
Donetsk Plant of Chemicals) were used for chromatographic
purposes. IR spectra (KBr pellets) were recorded on a Vectorꢀ22
spectrophotometer (Bruker). Melting points were measured on
a Boetius microscope stage. Microanalyses were performed at
the N. N. Vorozhtsov Novosibirsk Institute of Organic Chemisꢀ
try (Siberian Branch of the Russian Academy of Sciences) on
a Euro EA3000 CHNSꢀanalyzer. Magnetochemical measureꢀ
ments were carried out on a MPMSXL SQUID magnetometer
(Quantum Design) in the 2—300 K range. The effective magnetic
moments were calculated by the equation
1337, 1371, 1410, 1464, 1611, 1735, 2873 (w), 2982. μeff = 1.73μ
(200—300 K). Found (%): C, 64.8; H, 8.6; N, 10.7. C28H45N4O5.
Calculated (%): C, 65.0; H, 8.8; N, 10.8.
B
2ꢀ(3,6ꢀDiꢀtertꢀbutylꢀ2ꢀoxoꢀ2,3ꢀdihydrooxepinꢀ7ꢀyl)ꢀ4,4,5,5ꢀ
tetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole 1ꢀoxyl (4). Vioꢀ
let crystals, m.p. 158—159 °C (from CH2Cl2—heptane), Rf 0.62
(CH2Cl2, Al2O3); Rf 0.77 (AcOEt, silica gel). IR, ν/cm–1: 543,
617, 650, 667, 688, 731, 755, 777, 837, 871, 885, 932, 949, 965,
978, 1003, 1030, 1060, 1077, 1089, 1137, 1172, 1218, 1257, 1338,
1371, 1408, 1454, 1592, 1785, 2872 (w), 2968, 2999, 3056 (w),
3400 (br). μeff = 1.73μB (250—300 K). Found (%): C, 66.3; H, 8.8;
N, 7.4. C21H33N2O4. Calculated (%): C, 66.8; H, 8.8; N, 7.4.
2ꢀ(2,5ꢀDiꢀtertꢀbutylꢀ3,4ꢀdioxocyclohexaꢀ1,5ꢀdienyl)ꢀ
4,4,5,5ꢀtetramethylꢀ3ꢀoxidoꢀ4,5ꢀdihydroꢀ1Hꢀimidazole 1ꢀoxyl
(5). Redꢀbrown needles, m.p. 204—206 °C (from CH2Cl2—heptꢀ
ane), Rf 0.73 (CH2Cl2, Al2O3); Rf 0.74 (AcOEt, silica gel). IR,
ν/cm–1: 551, 644, 673, 734, 870, 939, 1142, 1173, 1216, 1273,
1370, 1398, 1451, 1488, 1657, 1673, 1688, 2920 (w), 2958, 2993.
μ
eff(T) = 2.84(χ´MT)1/2
,
where χ´M is the paramagnetic molar susceptibility corrected to
the diamagnetic contribution. The steadyꢀstate Xꢀband ESR
spectra of 1•10–5 M solutions of nitroxyl radicals in toluene were
recorded at room temperature on a Bruker EMX spectrometer
and modeled with the Winsim v.0.96 program package;25 the
μeff = 1.68μB (250—300 K). Found (%): C, 67.0; H, 8.1; N, 7.5.
C21H31N2O4. Calculated (%): C, 67.2; H, 8.3; N, 7.5.
Xꢀray diffraction study of compounds 3—5. Reflection intenꢀ
sities were collected on a SMART APEX II CCD diffractometer
(Bruker AXS) (MoꢀKα radiation, λ = 0.71073 Å, T = 240 K).

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Tretyakov et al.
Absorption corrections were applied with the SADABS program
(v. 2.10, Bruker). The structures were solved by direct methods
and refined anisotropically (for all nonꢀhydrogen atoms) by the
fullꢀmatrix leastꢀsquares method. The H atoms were partially
located from difference electronꢀdensity maps. All calculations
were performed with the Bruker SHELXTL program package
(version 6.14).
8. A. I. Poddel´sky, V. K. Cherkasov, G. A. Abakumov, Coord.
Chem. Rev., 2009, 253, 291.
9. M. Fedin, V. Ovcharenko, R. Sagdeev, E. Reijerse, W. Luꢀ
bitz, E. Bagryanskaya, Angew. Chem., Int. Ed., 2008, 47, 6897.
10. N. N. Smirnova, G. A. Abakumov, V. K. Cherkasov, K. A.
Kozhanov, A. V. Arapova, M. P. Bubnov, J. Chem. Thermoꢀ
dyn., 2006, 38, 678.
Compound 3. C28H45N4O5, M = 517.68, monoclinic crysꢀ
tals, space group P21/c, a = 19.461(7) Å, b = 11.770(4) Å,
11. G. A. Abakumov, G. A. Razuvaev, V. I. Nevodchikov, V. K.
Cherkasov, J. Organomet. Chem., 1988, 341, 485.
3
c = 13.410(5) Å, β = 96.928(8)°, V = 3049.3(18) Å , Z = 8, dcalc
=
12. V. I. Ovcharenko, E. V. Gorelik, S. V. Fokin, G. V. Roꢀ
manenko, V. N. Ikorskii, A. V. Krashilina, V. K. Cherkasov,
G. A. Abakumov, J. Am. Chem. Soc., 2007, 129, 10512.
13. E. Yu. Fursova, O. V. Kuznetsova, E. V. Tretyakov, G. V.
Romanenko, A. S. Bogomyakov, V. I. Ovcharenko, R. Z.
Sagdeev, V. K. Cherkasov, M. P. Bubnov, G. A. Abakumov,
Izv. Akad. Nauk, Ser. Khim., 2011, 791 [Russ. Chem. Bull.,
Int. Ed., 2011, 60, 809].
= 1.128 g cm–3, μ = 0.078 mm–1, 23 736 measured reflections
(2.03° < θ < 27.95°), 7211 independent reflections, 2965 refꢀ
lections with I > 2σ(I), 347 parameters refined, R1 = 0.0532,
wR2 = 0.1302.
Compound 4. C21H33N2O4, M = 377.49, orthorhombic crysꢀ
tals, space group Pbca, a = 10.3434(13) Å, b = 12.3847(16) Å,
3
c = 34.433(5) Å, V = 4410.8(10) Å , Z = 8, dcalc = 1.137 g cm–3
,
μ = 0.078 mm–1, 35 427 measured reflections (2.37° < θ < 28.04°),
5271 independent reflections, 1890 reflections with I > 2σ(I),
377 parameters refined, R1 = 0.0439, wR2 = 0.1001.
14. D. A. Shultz, S. H. Bodnar, K. E. Vostrikova, J. W. Kampf,
Inorg. Chem., 2000, 39, 6091.
15. E. C. Depperman, S. H. Bodnar, K. E. Vostrikova, D. A.
Shultz, M. L. Kirk, J. Am. Chem. Soc., 2001, 123, 3133.
16. D. A. Shultz, K. E. Vostrikova, S. H. Bodnar, H.ꢀJ. Koo,
M.ꢀH. Whangbo, M. L. Kirk, E. C. Depperman, J. W. Kampf,
J. Am. Chem. Soc., 2003, 125, 1607.
17. E. F. Ullman, J. H. Osiecki, D. G. B. Boocock, R. Darcy,
J. Am. Chem. Soc., 1972, 94, 7049.
18. US Pat. 3927019; Chem. Abstrs, 1976, 84, 180213.
19. G. A. Abakumov, V. K. Cherkasov, L. G. Abakumova, V. I.
Nevodchikov, N. O. Druzhkov, N. P. Makarenko, Yu. A.
Kursky, J. Organomet. Chem., 1995, 491, 127.
20. N. P. Makarenko, T. I. Kulikova, N. O. Druzhkov, V. K.
Cherkasov, Ya. I. Yashin, Zh. Fiz. Khim., 2001, 75, 1063
[Russ. J. Phys. Chem. (Engl. Transl.), 2001, 75].
21. G. A. Abakumov, N. N. Vavilina, V. I. Nevodchikov, V. K.
Cherkasov, L. G. Abakumova, Yu. A. Kursky, L. N. Zakhaꢀ
rov, Izv. Akad. Nauk, Ser. Khim., 1999, 351 [Russ. Chem.
Bull. (Engl. Transl.), 1999, 48, 350].
Compound 5. C21H31N2O4, M = 375.48, monoclinic crysꢀ
tals, space group P2/m, a = 9.5529(16) Å, b = 10.1119(18) Å,
3
c = 11.436(2) Å, β = 112.490(12)°, V = 1020.7(3) Å , Z = 8,
dcalc = 1.222 g cm–3, μ = 0.084 mm–1, 14 913 measured reflecꢀ
tions (2.31° < θ < 28.44°), 2680 independent reflections, 993
reflections with I > 2σ(I), 208 parameters refined, R1 = 0.0438,
wR2 = 0.1044.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 09ꢀ03ꢀ00091
and 11ꢀ03ꢀ00027), the Council on Grants at the President
of the Russian Federation (State Support Program for
Young Ph.D. Scientists, Grants MKꢀ4268.2010.3 and
MKꢀ868.2011.3), the V. N. Orekhovich Research Instiꢀ
tute of Biomedicinal Chemistry, and the Russian Acadeꢀ
my of Sciences.
22. Cambridge Structural Database, Version 5.29, Cambridge
Crystallographic Data Center, Cambridge, November 2009
(last update August 2010).
References
23. E. V. Tretyakov, I. A. Utepova, M. V. Varaksin, S. E. Tolꢀ
stikov, G. V. Romanenko, A. S. Bogomyakov, D. V. Stass,
V. I. Ovcharenko, O. N. Chupakhin, ARKIVOC, 2011, viii, 76.
24. I. S. Belostotskaya, N. L. Komissarova, E. V. Dzhuaryan,
V. V. Ershov, Izv. Akad. Nauk SSSR, Ser. Khim., 1972, 1594
[Bull. Acad. Sci. USSR, Div. Chem. Sci. (Engl. Transl.), 1972,
21, 1535].
25. F. B. Sviridenko, D. V. Stass, T. V. Kobzeva, E. V. Tretyaꢀ
kov, S. V. Klyatskaya, E. V. Mshvidobadze, S. F. Vasilevsky,
Yu. N. Molin, J. Am. Chem. Soc., 2004, 126, 2807.
1. H. Iwamura, K. Inoue, in Magnetism: Molecules to Materials
II. MoleculeꢀBased Materials, Eds J. S. Miller, M. Drillon,
Wiley—VCH, Weinheim, 2001, 61.
2. D. Gatteschi, R. Sessoli, J. Villain, Molecular Nanomagnets,
Oxford University Press, Oxford, 2006, 395.
3. V. I. Ovcharenko, in Stable Radicals: Fundamentals and Apꢀ
plied Aspects of OddꢀElectron Compounds, Ed. R. Hicks,
Wiley—VCH, 2010, 461.
4. J. S. Miller, Adv. Mater., 1994, 6, 322.
5. V. I. Ovcharenko, R. Z. Sagdeev, Usp. Khim., 1999, 68, 381
[Russ. Chem. Rev. (Engl. Transl.), 1999, 68, 345].
6. E. V. Tretyakov, V. I. Ovcharenko, Usp. Khim., 2009, 78,
1051 [Russ. Chem. Rev. (Engl. Transl.), 2009, 78].
7. C. G. Pierpont, C. W. Lange, Prog. Inorg. Chem., 1994,
41, 331.
Received March 28, 2011;
in revised form October 13, 2011