[2+2] Cycloadditions of electron-poor acetylenes to (5Z)-5-[(dimethylamino) methylene]imidazolidine-2,4-diones

Article abstract of DOI:10.1002/hlca.200800297

Microwave-assisted [2+2] cycloadditions of acetylene mono- and acetylenedicarboxylates 2 to (5Z)-5-[(dimethylamino)methylene]imidazolidine-2,4- dione 4a or to the corresponding thioxo derivative 4b in MeCN furnished the highly functionalized imidazolidine

Full text of DOI:10.1002/hlca.200800297

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[2 þ 2] Cycloadditions of Electron-Poor Acetylenes to (5Z)-5-
[(Dimethylamino)methylene]imidazolidine-2,4-diones
by Urosˇ Ursˇicˇ, Urosˇ Grosˇelj, Anton Meden, Jurij Svete, and Branko Stanovnik*
ˇ
ˇ
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, P.O. Box 537, 1000
Ljubljana, Slovenia
(e-mail: branko.stanovnik@fkkt.uni-lj.si)
Microwave-assisted [2 þ 2] cycloadditions of acetylene mono- and acetylenedicarboxylates 2 to
(5Z)-5-[(dimethylamino)methylene]imidazolidine-2,4-dione 4a or to the corresponding thioxo deriva-
tive 4b in MeCN furnished the highly functionalized imidazolidine-2,4-dione derivatives 5 and 6 or the
corresponding thioxo derivatives 5 – 7 as single isomers or mixtures of two isomers (Schemes 2 and 3,
Table 1). When the reaction of (5Z)-5-[(dimethylamino)methylene]imidazolidine-2,4-dione (4c) with
acetylenedicarboxylate 2a was performed in DMF, hydrolysis of the (dimethylamino)methylene group
took place to give (2E)-2-(2,5-dioxoimidazolidin-4-ylidene)butanedioate 11 (Scheme 5).
Introduction. – In the last few decades, there have been some reports of reactions of
simple tertiary enamines with electron-poor acetylenes, such as alkyl propiolates
(¼alkyl prop-2-ynoates) and dialkyl acetylenedicarboxylates (¼dialkyl but-2-yne-
dioates) [1]. It has been generally accepted that these reactions initially proceed by a
[2 þ 2] cycloaddition. However, the structure of the final product is strongly dependent
on the structure of the starting compound and reaction conditions [1d]. The geometry
of the obtained products was, in some cases, unambiguously determined by Reinhoudt
and co-workers in the early eighties [1d]. When these reactions were extended to other
functionalized enamines and enaminones, in some cases, a Michael-type addition took
place preferentially over the [2 þ 2] cycloaddition [2].
The 3-(dimethylamino)propenoates and related enaminones have been demon-
strated to be useful building blocks in the synthesis of many heterocyclic systems [3],
including the preparation of natural products and their analogs, such as aplysinopsins
[4], meridianines [5], dipodazines [6], and tryprostatins [7]. We have also reported an
efficient method for the preparation and functionalization of highly substituted 1-
amino-2,3-dihydro-1H-pyrrole, 1-amino-1H-pyrrole, and fused pyrrolo[3,2-d]oxazole
systems from ꢀ1,2-diazabuta-1,3-dienesꢁ and 3-(dimethylamino)prop-2-enoates [8] and
the regio- and stereoselective one-pot synthesis of oxazolo-fused pyridazines via a
ꢀMichael-addition – pyridazine-cyclization – oxazoline cyclizationꢁ cascade reaction [9].
As an extension of our research, we recently reported on microwave assisted
regiospecific [2 þ 2] cycloadditions of electron-poor acetylenes 2 to (2Z)-2-(acyla-
mino)-3-(dimethylamino)prop-2-enoates 1, which resulted in the formation of
(1E,3E)-1-(acylamino)-4-(dimethylamino)buta-1,3-dienes 3 (Scheme 1) [10].
ꢂ 2009 Verlag Helvetica Chimica Acta AG, Zꢃrich

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Scheme 1
Results and Discussion. – Since (5Z)-5-[(dimethylamino)methylene]imidazolidine-
2,4-diones 4a,c and the corresponding thioxo derivative 4b have already been
established as very useful intermediates in the synthesis of natural products such a
aplysinopsins [4], we report in this article on [2 þ 2] cycloadditions of electron-poor
acetylenes 2a – 2d to these compounds, which are cyclic analogues of (2Z)-2-
(acylamino)-3-(dimethylamino)prop-2-enoates 1 [10].
When (5Z)-5-[(dimethylamino)methylene]-3-methylimidazolidine-2,4-dione (4a)
and acetylenedicarboxylates (¼ but-2-ynedioates) 2a,b were heated in MeCN under
microwave (MW) irradiation, (2(1’)E,3(4’’)E)-2-[(dimethylamino)methylene]-3-(1-
methyl-2,5-dioxoimidazolidin-4-ylidene)butanedioates 5a,b were formed as the only
isomers. On the other hand, the reactions of imidazolidine-2,4-dione 4a with electron-
poor but-2-ynoate 2c and of (5Z)-5-[(dimethylamino)methylene]-3-phenyl-2-thioxoi-
midazolidin-4-one (4b) with acetylene derivatives 2a,c produced mixtures of two
isomers. In these cases, the major (2(1’)E,3(4’’)E)-isomers 5c – 5d were accompanied by
(2(1’)E,3(4’’)Z)-isomers 6c – 6d (Scheme 2, Table 1).
Scheme 2
Table 1. Synthesis of Compounds 5a – 5e and 6c – 6e
5, 6
R1
X
R2
R3
Yield [%]
5/6
Time [min]
a
b
c
d
e
Me
Me
Ph
Me
Ph
O
O
S
O
S
COOMe
COOEt
COOMe
CF3
COOMe
COOEt
COOMe
COOEt
COOEt
84
62
89
97
95
100 : 0
100 : 0
54 : 46
65 : 35
54 : 46
120
120
120
120
60
CF3
The structures of products 5 and 6 were determined by elemental analysis, IR, 1H-
and 13C-NMR, HMBC technique, HR-MS, and X-ray analysis. The configurations of
the C(2)¼C(1’) bond of compounds 5a,d and 6d were established by the 2D-HMBC

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483
3
NMR technique. The magnitude of the heteronuclear coupling constant, J(C,H), for
nuclei O¼CꢀC¼CꢀH with cis configuration of the C¼C bond are smaller (2 – 6 Hz)
than those for the trans-oriented ones (8 – 12 Hz) [3b,d][11]. Accordingly, the
heteronuclear coupling constant of compounds 5a,d and 6d indicate the (2E)-
configuration (Fig. 1). The same (2E)-configurations of the C(2)¼C(1’) bonds indicate
that isomers 5 and 6 differ in the configuration of the C(3)¼C(4’’) bonds. Additionally,
the structures of both isomers 5d (Fig. 2) and 6d (Fig. 3) were confirmed by X-ray
analysis.
Fig. 1. Coupling constant 3J(C,H) of the O¼CꢀC¼CꢀH moiety of 5a,d and 6d
Fig. 2. ORTEP View of compound 5d at the 50% probability level. H-Atoms are drawn as spheres of
arbitrary radii. The molecule of the co-crystallized solvent (CHCl3) is omitted for clarity. Very large
displacement parameters of C(223) indicate disorder of the Me group and a somewhat lower quality of
the crystals; the molecular geometry is, however, unambiguous.
The reaction of 4b with ethyl propiolate (¼ethyl prop-2-ynoate; 2d) also furnished
a mixture of two isomers 5f and 7f (Scheme 3). However, in this case, the major
(2(4’)E,3Z)-isomer 5f was accompanied by the minor (2(4’)E,3E)-isomer 7f, which is

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Fig. 3. ORTEP View of compound 6d at the 50% probability level. H-Atoms are drawn as spheres of
arbitrary radii.
Scheme 3
structurally different from the minor isomers 6c – 6e mentioned previously. The
1
structures of isomers 5f and 7f were determined by H-NMR spectroscopy, where
characteristic coupling constants for cis-oriented (3J(H,H) ¼ 10.1 Hz) and trans-
oriented protons (3J(H,H) ¼ 15.9 Hz) were observed (Fig. 4).
Two major pathways can be envisioned for the cycloadditions of acetylenes 2 to 4, a
concerted and a stepwise one. In the case of a concerted cycloaddition, the reaction
should proceed as a [2s þ 2a] cycloaddition resulting in cyclobutene intermediate 9’,
which would undergo
a conrotatory retro-electrocyclization to afford the
(2(1’)E,3(4’’)Z)-isomer 6 (R3=H) and/or (2(1’)Z,3(4’’)E)-isomer 7 (R3=H), or
(2(4’)Z,3Z)-isomer 6 (R3 ¼ H) and/or (2(4’)E,3E)-isomer 7 (R3 ¼ H). In the two-step
mechanism, the initially formed intermediate 8 can cyclize to cyclobutene 9’ or it may
be transformed into intermediate 8’, which cyclizes to cyclobutene intermediate 9.
From the latter, two different products can be formed by conrotatory retro-electro-
cyclization, i.e., (2(1’)E,3(4’’)E)-isomer 5 (R3=H) and/or (2(1’)Z,3(4’’)Z)-isomer 10

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485
Fig. 4. Coupling constant 3J(H,H) of the HꢀC¼CꢀH moiety of 5f and 7f
(R3=H), or (2(4’)E,3Z)-isomer 5 (R3 ¼ H) and/or (2(4’)Z,3E)-isomer 10 (R3 ¼ H)
(Scheme 4). The obtained results indicate that these cycloadditions proceed by a
Scheme 4

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stepwise mechanism. In the cases, where the single products 5a,b were formed, the
intermediate 8 is completely transformed into intermediate 8’, while in the cases where
mixtures of two isomers were obtained, this transformation from 8 to 8’ is not complete,
and some cyclobutene intermediate 9’ is formed as well.
Contrary to 4a,b, (5Z)-5-[(dimethylamino)methylene]imidazolidine-2,4-dione (4c)
did not react with dimethyl acetylenedicarboxylate (2a) in MeCN, probably due to its
insolubility. When 4c was treated with 2a in DMF at 808, dimethyl (2E)-2-(2,5-
dioxoimidazolidin-4-ylidene)butanedioate (11) was obtained (Scheme 5). This can
easily be explained by the initial formation of dimethyl (2E,3E)-2-[(dimethylamino)-
methylene]-3-(2,5-dioxoimidazolidin-4-ylidene)butanedioate (5g) which, under the
experimental conditions, was hydrolyzed to 11 and DMF. The structure of 11 was
confirmed by X-ray-analysis (Fig. 5). The configuration of the C(2)¼C(4’) bond in
compound 11 confirms the proposed structure and consequently the mechanism of
these cycloadditions.
Scheme 5
Fig. 5. ORTEP View of compound 11 at the 50% probability level. H-Atoms are drawn as spheres of
arbitrary radii.
Conclusions. – The [2 þ 2] cycloaddition of electron-poor acetylenes 2 with (5Z)-5-
[(dimethylamino)methylene]imidazolidine-2,4-diones 4a,c or the corresponding thio-

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xo derivative 4b was established as an easy and efficient synthetic route to highly
functionalized imidazolidine-2,4-diones, which offer wide possibilities for further
transformations.
The financial support from the Slovenian Research Agency through grants P1-0179 and J1-0972 is
gratefully acknowledged. We thank the pharmaceutical companies Krka d.d., Novo mesto, Slovenia, and
Lek d.d., a Sandoz company, Ljubljana, Slovenia for the financial support. Crystallographic data were
collected on a Kappa-CCD-Nonius diffractometer in the Laboratory of Inorganic Chemistry, Faculty of
Chemistry and Chemical Technology, University of Ljubljana, Slovenia. We acknowledge with thanks the
financial contribution of the Ministry of Science and Technology, Republic of Slovenia through grant
Packet X-2000 and PS-511-102, which made the purchase of the apparatus possible.
Experimental Part
General. The acetylene derivatives 2a – 2d are commercially available (Sigma-Aldrich). (5Z)-5-
[(Dimethylamino)methylene]-3-methylimidazolidine-2,4-dione (4a) [4a], (5Z)-5-[(dimethylamino)-
methylene]-3-phenyl-2-thioxoimidazolidin-4-one (4b) [12], and (5Z)-5-[(dimethylamino)methylene]-
imidazolidine-2,4-dione (4c) [4a] were prepared according to literature procedures. Microwave
irradiations were performed in a CEM-Corporation-Discover microwave unit. Column chromatography
(CC): silica gel 60 (0.04 – 0.06 mm; Fluka). Medium-pressure liquid chromatography (MPLC): silica gel
40 (0.015 – 0.035 mm; Merck), column size 15 ꢁ 460 mm; Bꢀchi isocratic system with UV detection (UV
detector K-2001; Knauer) at 254 nm. Melting points: Kofler micro hot stage. IR Spectra: Perkin-Elmer-
Spectrum-BX-FTIR spectrophotometer; ˜n in cmꢀ1. NMR Spectra: Bruker-Avance-DPX-300 spectrom-
1
eter; at 300 MHz for H and 75.5 MHz for 13C, (D6)DMSO and CDCl3 as solvents and Me4Si as the
internal standard; d in ppm, J in Hz. MS: AutoSpecQ and Qtof-premier spectrometers; in m/z.
Microanalyses: Perkin-Elmer-CHN analyser 2400 II.
Imidazolidine Derivatives 5a – 5f, 6c – 6e, and 7f: General Procedure. Acetylene 2a – 2d was added to
a soln. of (5Z)-5-[(dimethylamino)methylene]imidazolidine derivative 4a,b in MeCN (4 ml), and the
mixture was stirred in a closed vessel under microwave irradiation at constant temp. The mixture was
cooled, volatile components were evaporated, and the residue was purified by CC (silica gel).
Dimethyl (2E,3E)-2-[(Dimethylamino)methylene]-3-(1-methyl-2,5-dioxoimidazolidin-4-ylidene)bu-
tanedioate (5a). Prepared from 4a (0.169 g, 1 mmol) and dimethyl but-2-ynedioate (2a; 0.250 ml,
2 mmol) at 808 for 120 min. CC (AcOEt/petroleum ether 4 :1) and crystallization (toluene) gave 0.262 g
(84%) of 5a. M.p. 165 – 1678. IR (KBr): 3213, 2953, 1771, 1720, 1711, 1674, 1632, 1562, 1453, 1441, 1291,
1229, 1106, 1097, 1046, 942, 783, 756. 1H-NMR (CDCl3): 2.99 (br. s, Me2N); 3.07 (s, MeN); 3.66 (s,
COOMe); 3.86 (s, COOMe); 6.94 (br. s, NH); 7.65 (s, CHNMe2). 13C-NMR (CDCl3): 24.4; 51.3; 52.6;
89.1; 115.3; 127.7; 153.0; 154.1; 160.9; 167.0; 168.2. Anal. calc. for C13H17N3O6 (311.29): C 50.16, H 5.50, N
13.50; found: C 50.12, H 5.73, N 13.50.
Diethyl (2E,3E)-2-[(Dimethylamino)methylene]-3-(1-methyl-2,5-dioxoimidazolidin-4-ylidene)buta-
nedioate (5b). Prepared from 4a (0.169 g, 1 mmol) and diethyl but-2-ynedioate (2b; 0.325 ml, 2 mmol) at
808 for 120 min. CC (AcOEt/petroleum ether 3 :2) and crystallization (toluene/hexane) gave 0.213 g
(63%) of 5b. M.p. 140 – 1438. IR (KBr): 3208, 2986, 1759, 1714, 1678, 1626, 1594, 1456, 1387, 1280, 1218,
1097, 1023, 724, 618. 1H-NMR (CDCl3): 1.23 (t, J ¼ 7.1, MeCH2O); 1.35 (t, J ¼ 7.1, MeCH2O); 2.98 (br. s,
Me2N); 3.07 (s, MeN); 4.14 – 4.23 (m, 1 H, MeCH2O); 4.27 – 4.36 (m, 3 H MeCH2O); 6.76 (br. s, NH);
7.65 (s, CHNMe2). Anal. calc. for C15H21N3O6 (339.34): C 53.09, H 6.24, N 12.38; found: C 53.29, H 6.47, N
12.19.
Dimethyl (2E,3E)-2-[(Dimethylamino)methylene]-3-(5-oxo-1-phenyl-2-thioxoimidazolidin-4-ylide-
ne)butanedioate (5c) and Dimethyl (2E,3Z)-2-[(Dimethylamino)methylene]-3-(5-oxo-1-phenyl-2-thio-
xoimidazolidin-4-ylidene)butanedioate (6c). Prepared from 4b (0.247 g, 1 mmol) and dimethyl but-2-
ynedioate (2a; 0.250 ml, 2 mmol) at 808 for 120 min. CC (AcOEt) and crystallization (AcOEt/heptane)
gave 0.345 g (89%) of 5c/6c 54 :46 which were not separated. M.p. 136 – 1488. IR (KBr): 3435, 2950, 1732,
1
1682, 1622, 1496, 1434, 1416, 1358, 1252, 1202, 1175, 1133, 1082, 962, 733. H-NMR (CDCl3): (2E,3E)-

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isomer 5c: 3.21 (s, 3 H, Me2N); 3.49 (s, 3 H, Me2N); 3.72 (s, COOMe); 3.76 (s, COOMe); 6.74 (s, NH);
7.11 (s, CHNMe2); 7.29 – 7.50 (m, Ph); (2E,3Z)-isomer 6c: 3.25 (s, 3 H, Me2N); 3.57 (s, 3 H, Me2N); 3.73 (s,
COOMe); 3.77 (s, COOMe); 6.28 (s, NH); 7.19 (s, CHNMe2); 7.29 – 7.50 (m, Ph). Anal. calc. for
C18H19N3O5S (389.43): C 55.52, H 4.92, N 10.79; found: C 55.77, H 5.11, N 10.63.
Ethyl (2E,3E)-2-[(Dimethylamino)methylene]-4,4,4-trifluoro-3-(1-methyl-2,5-dioxoimidazolidin-4-
ylidene)butanoate (5d) and Ethyl (2E,3Z)-2-[(Dimethylamino)methylene]-4,4,4-trifluoro-3-(1-methyl-
2,5-dioxoimidazolidin-4-ylidene)butanoate (6d). Prepared from 4a (0.169 g, 1 mmol) and ethyl 4,4,4-
trifluorobut-2-ynoate (2c; 0.220 ml, 1.33 mmol) at 808 for 120 min. CC (AcOEt/petroleum ether 1:1):
0.326 g (97%) of 5d/6d 65 :35. The isomers were separated by MPLC (AcOEt/petroleum ether 1:1).
M.p. 145 – 1488 (5d), 149 – 1528 (6d). IR (KBr): (2E,3E)-isomer 5d: 3215, 2984, 1779, 1724, 1698, 1644,
1611, 1462, 1399, 1283, 1257, 1214, 1173, 1126, 1082, 991, 957, 825, 763, 711; (2E,3Z)-isomer 6d: 3237, 2983,
1767, 1725, 1699, 1648, 1614, 1457, 1398, 1329, 1271, 1245, 1215, 1193, 1109, 1048, 1027, 991, 949, 818, 764,
617. 1H-NMR (CDCl3): (2E,3E)-isomer 5d: 1.22 (t, J ¼ 7.1, MeCH2O); 2.97 (br. s, Me2N); 3.11 (s, MeN);
3.99 – 4.10 (m, 1 H, MeCH2O); 4.16 – 4.28 (m, 1 H, MeCH2O); 7.63 (s, CHNMe2); 8.45 (br. s, NH);
(2E,3Z)-isomer 6d: 1.21 (t, J ¼ 7.1, MeCH2O); 2.92 (s, Me2N); 3.08 (s, MeN); 4.01 – 4.24 (m, MeCH2O);
7.69 (s, CHNMe2); 8.47 (br. s, NH). 13C-NMR (CDCl3): (2E,3E)-isomer 5d: 14.0; 24.4; 42.6 (br. s); 60.1;
86.4 (q, J ¼ 2.2); 112.0 (q, J ¼ 37.2); 122.0 (q, J ¼ 273); 131.4 (q, J ¼ 2.2); 152.2; 153.9; 159.3; 168.0;
(2E,3Z)-isomer 6d: 14.2; 24.5; 42.8 (br. s); 59.9; 85.0 (deg. q); 109.7 (q, J ¼ 32.7); 123.0 (q, J ¼ 275); 129.3
(deg. q); 152.7; 153.8; 161.0; 168.5. EI-MS: 335 (Mþ). EI-HR-MS: 335.110030 (Mþ, C13H16F3N3O4þ ; calc.
335.109291). Anal. calc. for C13H16F3N3O4 (335.28): C 46.57, H 4.81, N 12.53; found: C 46.48, H 4.98, N
12.27.
Ethyl (2E,3E)-2-[(Dimethylamino)methylene]-4,4,4-trifluoro-3-(5-oxo-1-phenyl-2-thioxoimidazoli-
din-4-ylidene)butanoate (5e) and Ethyl (2E,3Z)-2-[(Dimethylamino)methylene]-4,4,4-trifluoro-3-(5-
oxo-1-phenyl-2-thioxoimidazolidin-4-ylidene)butanoate (6e). Prepared from 4b (0.247 g, 1 mmol) and
ethyl 4,4,4-trifluorobut-2-ynoate (2c; 0.246 ml, 1.48 mmol) at 808 for 60 min. CC (AcOEt): 0.394 g (95%)
of 5b/6e 54 :46 which were not separated. Oil. IR (KBr): 3443, 2984, 2934, 1731, 1681, 1620, 1497, 1418,
1358 1264, 1178, 1141, 1084, 1027, 962, 733. 1H-NMR (CDCl3): (2E,3E)-isomer 5e: 1.27 (t, J ¼ 7.1,
MeCH2O); 3.23 (s, 3 H, Me2N); 3.53 (s, 3 H, Me2N); 4.20 (q, J ¼ 7.1, MeCH2O); 6.49 (s, NH); 7.17 (s,
CHNMe2); 7.28 – 7.49 (m, Ph); (2E,3Z)-isomer 6e: 1.29 (t, J ¼ 7.1, MeCH2O); 3.26 (s, 3 H, Me2N); 3.59 (s,
3 H, Me2N); 4.23 (q, J ¼ 7.1, CH2O); 6.72 (s, NH); 7.23 (s, CHNMe2); 7.28 – 7.49 (m, Ph). EI-MS: 413
(Mþ). EI-HR-MS: 413.103250 (Mþ, C18H18F3N3O3Sþ; calc. 413.102098). Anal. calc. for C18H18F3N3O3S
(413.41): C 52.08, H 4.55, N 9.94; found: C 52.29, H 4.39, N 10.16.
Ethyl (2E,3Z)-4-(Dimethylamino)-2-(5-oxo-1-phenyl-2-thioxoimidazolidin-4-ylidene)but-3-enoate
(5f) and Ethyl (2E,3E)-4-(Dimethylamino)-2-(5-oxo-1-phenyl-2-thioxoimidazolidin-4-ylidene)but-3-
enoate (7f). Prepared from 4b (0.247 g, 1 mmol) and ethyl prop-2-ynoate (2d; 0.410 ml, 4 mmol) at
1008 for 210 min. CC (AcOEt) and crystallization (AcOEt/petroleum ether) gave 0.326 g (94%) of 5f/7f
61:39 which were not separated. M.p. 136 – 1488. IR (KBr): 3447, 3039, 2975, 2927, 1695, 1685, 1629, 1583,
1498, 1413, 1360, 1313, 1223, 1170, 1127, 1071, 1026, 963, 735. 1H-NMR (CDCl3): (2E,3Z)-isomer 5f: 1.27
(t, J ¼ 7.1, MeCH2O); 3.24 (s, 3 H, Me2N); 3.63 (s, 3 H, Me2N); 4.19 (q, J ¼ 7.1, MeCH2O); 6.10 (d, J ¼
10.1, HꢀC(3)); 7.12 (s, NH); 7.28 – 7.50 (m, Ph); 8.29 (d, J ¼ 10.1, HꢀC(4)); (2E,3E)-isomer 7f: 1.28
(t, J ¼ 7.1, MeCH2O); 3.23 (br. s, 3 H, Me2N); 3.62 (br. s, 3 H, Me2N); 4.20 (q, J ¼ 7.1, MeCH2O); 6.08 (d,
J ¼ 15.9, HꢀC(3)); 7.14 (s, NH); 7.28 – 7.50 (m, Ph); 8.34 (d, J ¼ 15.9, HꢀC(4)). 13C-NMR (CDCl3): 14.0;
39.5; 46.2; 46.3; 60.3; 60.4; 114.5; 114.9; 115.2; 118.6; 127.0; 127.2; 128.3; 128.4; 129.1; 129.2; 133.0; 133.1;
139.2; 139.5; 140.2; 140.7; 140.8; 143.8; 164.5; 166.3; 168.3; 168.7. Anal. calc. for C17H19N3O3S (345.42): C
59.11, H 5.54, N 12.17; found: C 59.27, H 5.64, N 11.99.
Dimethyl (2E)-2-(2,5-Dioxoimidazolidin-4-ylidene)butanedioate (11). Dimethyl but-2-ynedioate
(2a; 0.250 ml, 2 mmol) was added to a soln. of 4c (0.156 g, 1 mmol) in DMF (4 ml), and the mixture was
stirred in a closed vessel under microwave irradiation at 808 for 180 min. The mixture was cooled, volatile
components were evaporated, and the residue was purified by CC (silica gel, AcOEt/petroleum ether
1:1). The product was crystallized from AcOEt/petroleum ether: 0.112 g (46%) of 11. M.p. 160 – 1638. IR
(KBr): 3184, 3075, 1773, 1744, 1725, 1670, 1439, 1402, 1384, 1367, 1339, 1208, 1170, 1118, 1035, 868, 781,
757. EI-MS: 242 (Mþ). 1H-NMR (D6)(DMSO): 3.45 (s, CH2); 3.62 (s, COOMe); 3.66 (s, COOMe); 10.54
(br. s, NH); 11.32 (br. s, NH). 13C-NMR ((D6)DMSO): 34.4; 51.9; 52.0; 108.0; 132.9; 154.2; 162.2; 166.9;

Helvetica Chimica Acta – Vol. 92 (2009)
489
168.8. EI-MS: 242 (Mþ). EI-HR-MS 242.052544 (Mþ, C9H10N2O6þ ; calc. 242.053886). Anal. calc. for
C9H10N2O6 (242.19): C 44.63, H 4.16, N 11.57; found: C 44.83, H 4.27, N 11.53.
X-Ray Crystal Structures of 5d, 6d, and 111). Single crystal X-ray diffraction data of compounds 5d,
6d, and 11 were collected at r.t. with a Nonius-Kappa-CCD diffractometer and the Nonius Collect
Software [13]. DENZO and SCALEPACK [14] were used for indexing and scaling of the data, and the
structures were solved by means of SIR97 [15]. Refinement was done with the Xtal3.4 [16] program
package. Crystal structures were refined on F values by the full-matrix least-squares procedure. The non-
H atoms were refined anisotropically in all cases, while the positions of H-atoms were geometrically
calculated, and their positional and isotropic atomic displacement parameters were not refined.
Absorption correction was not necessary. Regina [17] weighting scheme was used in all cases. Difference
Fourier maps for compounds 5d, 6d, and 11 do not show any significant features. The crystal data and
details concerning data collection and refinement for 5d, 6d, and 11 are given in Table 2. The ORTEP III
[18] drawing of the content of the asymmetric unit of 5d, 6d, and 11 showing the atom-labeling scheme
are presented in Figs. 2, 3, and 5.
Table 2. Crystal Data, Data Collection, and Structure Refinement for Compounds 5d, 6d, and 11
5d
6d
11
Formula
Mr
(C13H16F3N3O4)2 · CHCl3
721.8
C13H16F3N3O4
335.3
C9H10N2O6
242.2
Crystal system
Space group
a [ꢄ]
b [ꢄ]
c [ꢄ]
triclinic
P1
monoclinic
P21/a
monoclinic
P21/a
¯
10.2964(2)
12.3965(3)
15.7860(3)
88.4712(13)
71.6915(12)
78.3911(14)
1872.34(7)
2
8.6660(3)
12.8666(6)
14.0048(5)
90.00000
99.467(2)
90.00000
1540.29(11)
4
9.63630(10)
12.2444(2)
10.2366(2)
90.00000
116.0526(9)
90.00000
1085.10(3)
4
a [ꢄ]
b [8]
g [8]
V [ꢄ3]
Z
1 [Mg mꢀ3
]
1.401
0.326
1.446
0.131
1.482
0.127
m [mmꢀ1
]
Color of crystal
Shape of crystal
Dimensions [mm]
Temperature [K]
Wavelength [ꢄ]
qmax [8]
yellow
block
yellow
block
colorless
block
0.14 ꢁ 0.10 ꢁ 0.08
0.22 ꢁ 0.18 ꢁ 0.14
0.20 ꢁ 0.20 ꢁ 0.12
293(1)
293(1)
293(1)
0.71073
27.49
0.71073
27.46
0.71073
27.44
No. of integrated refl.
No. of independent refl.
Rint
32306
8462
0.032
20278
3500
0.035
15073
2467
0.032
No. of observed reflections
Threshold criterion
No. of refined parameters
Final R and Rw
5491
I > 2.0s(I)
479
0.078, 0.082
0.55
ꢀ 0.55, 0.60
2372
I > 2.0s(I)
208
0.052, 0.053
0.0002
ꢀ 0.31, 0.33
2076
I > 2.0s(I)
154
0.044, 0.007
0.0004
ꢀ 0.26, 0.30
(D/s)max
D1max, D1min [e ꢄꢀ3
]
1
)
CCDC-691932, -691933, and -695011 contain the supplementary crystallographic data for the
structures 5d, 6d, and 11, resp., described in this work. These data can be obtained, free of charge,
via www.ccdc.cam.ac.uk/data_request/cif.).

490
Helvetica Chimica Acta – Vol. 92 (2009)
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Received July 29, 2008