, 2006, 16(2), 80–82
The formation of assemblies of imidazolidine rings 5 instead
of expected tricyclic structures 3 is probably due to the rigidity
of the molecular frame of original ethyleneurea 1, which prevents
the second NH group from entering into cyclocondensation. An
attempt to obtain tetracyclic system 4 by the condensation of
resulting 5b with 2a yielded polymers, apparently due to the
trans orientation of the imidazolidine rings at the 4- and 5-posi-
tions of compound 5b.
Based on the mechanism3 of formation of glycolurils via
the α-ureidoalkylation of ureas with 4,5-dihydroxyimidazolidin-
2-ones, the formation of compounds 5 can be assumed to occur
as two-step α-ureidoalkylation of imidazolidin-2-one 1 with
4,5-dihydroxyimidazolidin-2-ones 2 (Scheme 2).
At the first reaction stage, the protonation of compound 2
and the elimination of one water molecule gives carbonium-
immonium ion A (shown as two resonance structures) that con-
denses with the first molecule of ethyleneurea 1. At the second
reaction stage, resulting intermediate B, that is, an α-ureido-
alkylating reagent, undergoes protonation and dehydration to
carbonium-immonium ion C, which reacts with another mole-
cule of ethyleneurea 1 to give compound 5.
Thus, a study of the α-ureidoalkylation of imidazolidin-2-one
1 using 4,5-dihydroxyimidazolidin-2-ones 2 as ureidoalkylating
reagents resulted in hitherto unknown assemblies of three
imidazolidine rings, the structures of which were confirmed by
a combination of spectroscopic characteristics and X-ray data.†
Figure 2 A fragment of H-bonded homochiral layer in the crystal struc-
ture of 5a.
Analysis of crystal packing revealed that molecules of 5a in
the crystal are assembled by N–H···O bonds [N···O 2.897(2) Å]
into H-bonded homochiral layers (Figure 2) parallel to the
crystallographic bc plane and the H-bonded rings are centered
by two water molecules O···O [2.796(2)–2.826(2) Å]. In addition,
water molecules interlink the neighbouring layers by N–H···O
bonds [N···O 2.861(2) Å].
The synthesis of these hitherto unknown structures was
optimised for compound 5a as an example. As expected, when
the reaction was carried out with starting compounds 1 and 2a
under the same conditions but in a stoichiometric ratio, the
yield of 5a increased to 44%, while when the reaction time
increased to 1.5 h, the yield of 5a increased to 64%. After com-
†
All new compounds gave satisfactory elemental analyses. Their struc-
tures were confirmed by 1H and 13C NMR spectroscopy and mass
spectrometry. The 1H NMR spectra were recorded on a Bruker AM-300
spectrometer (300.13 MHz). Chemical shifts were measured with reference
to the residual protons of a [2H6]DMSO solvent (d 2.50 ppm). Mass
spectra were measured on an MS 30 spectrometer.
1
pound 5a was separated, the H NMR spectrum of the mother
liquor evaporated to dryness did not contain proton signals from
unreacted compounds 1 and 2a, but only proton signals from
hydantoin and unidentifiable oligomers were detected. The con-
ditions found were used in reactions of ethyleneurea 1 with 1,3-di-
methyl- and 1,3-diethyl-4,5-dihydroxyimidazolidin-2-ones 2b,c.
The yields of compounds 5b and 5c were 53 and 40%, respectively.
General procedure for the synthesis of 1,3-dihydro- and 1,3-dialkyl-
4,5-di(2-oxoimidazolidin-1-yl)imidazolidin-2-ones 5a–c. A catalytic amount
of hydrochloric acid (pH 1) was added to a solution of ethyleneurea 1
(imidazolidin-2-one) (0.02 mol) and corresponding 4,5-dihydroxyimi-
dazolidin-2-one 2a–c (0.01 mol). The reaction mixture was refluxed for
1.5 h. In the case of compound 5a, the precipitate formed was filtered off
and recrystallised from water. The yield of 5a was 64%. In the case of
compounds 5b,c, the reaction mixtures were concentrated into oils and
solidified with a methanol–acetone mixture. The resulting precipitates
were recrystallised from MeOH. The yields were 53 and 40%, respectively.
5a: yield 61–64%, mp 250–252 °C. 1H NMR ([2H6]DMSO) d: 3.35
(m, 8H, CH2CH2), 5.17 (s, 2H, CHCH), 6.50 (br. s, 2H, 2NH), 6.90 (s,
2H, 2NH). MS, m/z (%): 168 (5, M+ – 86), 86 (100), 69 (8), 56 (11).
5b: yield 50–53%, mp 263–264 °C. 1H NMR ([2H6]DMSO) d: 2.61 (s,
6H, NMe), 3.40 (m, 8H, CH2CH2), 5.10 (s, 2H, CHCH), 6.75 (br. s, 2H,
2NH). MS, m/z (%): 196 (100, M+ – 86), 141 (10), 128 (11), 112 (12),
97 (9), 86 (8), 70 (10).
R
R
R
OH
OH
N
N
N
H+
O
O
O
H2O
N
N
N
OH
OH
R
R
R
2
A
H
O
O
N
R
HN
NH
N
N
H+
5c: yield 37–40%, mp 270–273 °C. 1H NMR ([2H6]DMSO) d: 1.10
(m, 6H, 2Me), 2.75 (m, 2H, 2CH2), 3.11 (m, 2H, 2CH2), 3.37 (m, 8H,
CH2CH2), 5.20 (s, 2H, CHCH), 6.70 (s, 2H, 2NH). MS, m/z (%): 224
(63, M+ – 86), 196 (15), 168 (14), 140 (33), 127 (25), 113 (27), 97 (31),
86 (100), 83 (32), 70 (62), 69 (37), 60 (18).
O
H+
H2O
N
OH
R
B
X-ray diffraction analysis: at 120 K crystals of 5a (C9H18N6O5)
are monoclinic, space group C2/c, a = 11.759(2), b = 9.335(2), c =
= 11.386(3) Å, b = 92.977(6)°, V = 1248.2(5) Å3, Z = 4 (Z' = 0.5),
M = 290.29, dcalc = 1.545 g cm–3, m(MoKα) = 1.27 cm–1, F(000) = 616.
Intensities of 2478 reflections were measured with a Smart 1000 CCD
diffractometer at 120 K (2q < 54°), and 1285 independent reflections
(Rint = 0.04711) were used in the further refinement. The structure was
solved by a direct method and refined by the full-matrix least-squares
technique against F2 in the anisotropic-isotropic approximation. The
hydrogen atoms were located from the Fourier density synthesis.
The refinement converged to wR2 = 0.1020 and GOF = 0.917 for all
independent reflections [R1 = 0.0504 was calculated against F for 684
observed reflections with I > 2s(I)]. All calculations were performed
using SHELXTL PLUS 5.0.
Atomic coordinates, bond lengths, bond angles and thermal param-
eters have been deposited at the Cambridge Crystallographic Data Centre
conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336 033; or deposit@ccdc.cam.ac.uk).
Any request to the CCDC for data should quote the full literature citation
and CCDC reference number 603575. For details, see ‘Notice to Authors’,
Mendeleev Commun., Issue 1, 2006.
H
H
O
O
N
N
R
R
N
N
N
N
O
O
N
N
R
R
C
H
O
O
N
R
HN
– H+
NH
N
N
O
O
N
N
NH
R
5
Scheme 2 Mechanism of formation of assemblies 5 of three imidazo-
lidine rings.
Mendeleev Commun. 2006 81
Sigachev, Andrey S.
