An efficient synthesis of 1-acyl-3-arylimidazolidines catalyzed by montmorillonite K-10 clay under microwave irradiation

Article abstract of DOI:10.3987/COM-08-11565

The synthesis of 1-acyl-3-arylimidazolidines were performed by reaction of N-acyl-N'-arylethylenediamines with formaldehyde and Montmorillonite clay K-10 as a catalyst under microwave irradiation.

Full text of DOI:10.3987/COM-08-11565

HETEROCYCLES, Vol. 78, No. 3, 2009
771
HETEROCYCLES, Vol. 78, No. 3, 2009, pp. 771 - 781. © The Japan Institute of Heterocyclic Chemistry
Received, 1st October, 2008, Accepted, 27th October, 2008, Published online, 30th October, 2008
DOI: 10.3987/COM-08-11565
AN EFFICIENT SYNTHESIS OF 1-ACYL-3-ARYLIMIDAZOLIDINES
CATALYZED BY MONTMORILLONITE K-10 CLAY UNDER
MICROWAVE IRRADIATION
María Cristina Caterina, María Verónica Corona, Isabel Perillo, and
Alejandra Salerno*
Departament of Organic Chemistry, Faculty of Pharmacy and Biochemistry,
University of Buenos Aires, Junín 956 (1113), Buenos Aires, Argentina
E-mail: asalerno@ffyb.uba.ar
Abstract – The synthesis of 1-acyl-3-arylimidazolidines were performed by
reaction of N-acyl-N´-arylethylenediamines with formaldehyde and
Montmorillonite clay K-10 as a catalyst under microwave irradiation.
INTRODUCTION
Tetrahydroimidazoles (imidazolidines) are cyclic aminals of pharmacological interest due to the
bioactivity shown by some members which is closely related to the substitution type. The most studied
compounds are those N,N´-disubstituted ones with alkyl or aryl groups, functionalized sometimes.
Accordingly, a large number of these compounds with diverse properties such as strogenic activity1 and
mammary tumor inhibition,2 anti inflammatory and analgesic activity3 have been described in the
literature. Fungicide, bactericide and antiviral activities had also been reported.3,4 On the other hand,
due to the hydrophobic nature of imidazolidines they can be used to increase the bioavailability of
biologically active precursors in the form of a pro-drug and they had been employed as carriers of
pharmacologically active ethylenediamines5 or carbonyl compounds.6 They are also closely related to the
coenzyme N5,N10-methylenetetrahydrofolic acid, which participate in single carbon transfer at the
oxidation level of formaldehyde.7 Synthesis and study of this type of compounds present interest from a
chemical point of view, as synthetic intermediates of cyclic and acyclic compounds with the
ethylenediamine structural unit. Thus, dehydrogenation of imidazolidines leads to
4,5-dihydro-1H-imidazolium salts8 and their selective reduction to N,N,N´-trisubstituted
ethylenediamines.9 The imidazolidine system has been widely employed as protecting group of vicinal
diamines in peptide synthesis, due to its easy cleavage in mild acid medium.10 Besides, imidazolidines
were also employed as heterocyclic chiral auxiliaries in asymmetric synthesis.11 Opposite to compounds

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HETEROCYCLES, Vol. 78, No. 3, 2009
mentioned above, N-acylimidazolidines have been less studied. 1,3-Dialkanoyl imidazolidines were
reported with antimycotic activity;12 more recently 1-acetyl-2,3-dimethylimidazolidine has been reported
as a new organic reductant for aldehydes and imines.13
The classic synthesis of imidazolidines involves the condensation of adequately substituted
ethylenediamines with carbonyl compounds. Stable 1,3-disubstituted imidazolidines with alkyl or aryl
substituents are obtained from N,N´-disubstituted ethylenediamines and aldehydes, whatever substituents
are present in reactants.14 Instead, only a few reports on the preparation of N-acylimidazolidines by
cyclization of the corresponding N,N´-diacylethylenediamine and aldehydes in acid catalyzed reactions
were found.12 These were commonly prepared by acylation of the unsubstituted or N-monosubstituted
imidazolidine.15a-d Simultaneous reduction and acylation of imidazole was also reported.15e
The use of solid acid catalysts such as clays, ion-exchange resins and zeolites has received considerable
attention in different areas of organic synthesis.16 Montmorillonite clay specially, a class of inexpensive
and noncorrosive solid, exhibit high surface acidity which has been used to perform useful organic
transformations. Particularly in heterocyclic synthesis, Montmorillonite clay has been used as an efficient
catalyst in synthesis of dihydropyrimidinones,17 benzodiazepines,18 fluorined spiro heterocycles19 and
quinolines20 among others. On the other hand, microwave-assisted organic synthesis has received
increasing attention in recent years as a valuable technique for accelerating chemical reactions.21
Condensation reactions leading to heterocyclic products are particularly prone to microwave irradiation
enhancements.22 In connection with our ongoing work on synthesis and study of imidazolidines23,8a we
now report a simple and efficient method for the preparation of novel 1-acyl-3-arylimidazolidines 1.
RESULTS AND DISCUSSION
Compounds (1a-p) were obtained from N-acyl-N´-arylethylenediamines (2) and formaldehyde. Precursors
(2) were obtained by aminolysis of N-(2-bromoethyl)amides (3) (Scheme 1).
ArNH2
ArHN
Br
NHCOR
NHCOR
2
3
MW
HCHO
Montmorillonite K-10
Ar
N
N
C
O
R
1 a-p
Scheme 1
Due to the low nucleophilicity of both aminoamide nitrogens, cyclocondensation of compounds (2) with

HETEROCYCLES, Vol. 78, No. 3, 2009
773
formaldehyde does not proceed in the absence of acid catalyst. When reactions are carried out in THF
with aqueous formaldehyde and activated Montmorillonite K-10 (1 h, 120°) as the catalyst, under
continuous stirring at rt, desired products are obtained in times varying from 3-12 hours with yields of
55-70%. Under conventional heating the reactions times can be shortened to 1-4 h with moderated yields
(45-65%). In order to decrease reaction times and improve cyclization yields, we assayed them in a
domestic microwave oven adapted for reflux heating. Reactions were conducted under intermittent
microwave irradiation24 at a lower irradiation power (180W). In such conditions, reaction times
dramatically decreased to 3-5 minutes and yields increased to 75-98%. 1-Acyl-3-arylimidazolidines
shown in Table 1 were obtained.
Table 1. Summary of reactions (2 → 1) using conventional heating and microwave irradiation.
Ar
R
Compound 1
Conventional heating Mocrowave irradiation (180 W)
Time (h)/yields (%)
Time (min)/ yields (%)
a
b
c
C6H5
4-HOC6H4
4-ClC6H4
4-MeC6H4
2-C6H5OC6H4
4-NO2C6H4
4-NO2C6H4
3,4-Cl2C6H3
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
4-NO2C6H4
C6H5
4-ClC6H4
Me
1 / 62
2 / 94
1.5/ 65
2.5 / 51
1.5 / 60
1.5 / 52
4 / 54
2 / 92
3 / 98
2 / 91
2 / 85
5 / 89
5 / 88
5 / 89
5 / 85
3 / 79
2 / 81
3 / 79
3 / 77
3 / 78
3 / 97
4 / 95
d
e
f
g
h
i
3.5 / 62
4 / 59
3.5 / 52
2 / 58
j
4-MeC6H4
4-MeOC6H4
C6H5
k
l
Me
1/ 58
Et
2.5 / 61
2.5 / 49
3 / 51
m
n
o
p
4-MeC6H4
4-ClC6H4
4-MeC6H4
4-ClC6H4
Et
Et
i-Pr
3.5 / 62
3.5 / 60
i-Pr
Results were satisfactory for N-alkanoyl and N-acyl groups. In general, longer reaction times were required
for derivatives having electron withdrawing groups on N-aryl moiety.

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HETEROCYCLES, Vol. 78, No. 3, 2009
When at least one of the ortho positions of the arylamine is substituted (2-NO2, 2-Cl, 2-Me) or when aryl
group is a α-naphtyl, cyclization reaction does not occur. An exception to this is the o-phenoxy derivative
which evidently presents a minor steric hindrance and a more nucleophilic nitrogen.
1
Structure of compounds (1) was confirmed by elemental analysis and spectroscopic methods. The H
NMR spectra of compounds suggest that the molecules exist in two conformationally non-equivalent
structures (two sets of signals in different proportion) as a result of restricted rotation about the N-CO
bond. 1H NMR spectra of the preferred diastereomer are detailed in Table 2.
Table 2. Data for products (1a-p)
1H NMR (Cl3CD/TMS).δ, J (Hz)
Product mp (ºC)
IR (KBr), cm-1
* overlapped signals of both diastereomers
1a
1b
138-140 3.50-3.52* (m, CH2NAr ), 3.85 (t, CH2NCO, J= 6.3, 2 H), 5.00 2853, 1625, 1520, 1436,
(s, NCH2N, 2 H), 6.60-6.80* (m, aromatics), 7.15-7.50* (m,
1242, 748, 715
aromatics), 7.60 (d, aromatics, J= 7.3)
179-180 3.39-3.50* (m, CH2NAr ), 3.81 (t, CH2NCO, J= 6.4, 2 H), 4.90 3495, 2910, 1610, 1450,
(s, NCH2N, 2 H), 6.59 (d, aromatics, J= 8.0, 2 H), 6.70-6.82* 1377, 1244, 821, 720
(m, aromatics), 7.40-7.50* (m, aromatics), 7.51-7.53* (m,
aromatics)
1c
157-158 3.40-3.52* (m, CH2NAr), 3.92 (t, CH2NCO, J= 6.4, 2 H), 5.0 2983, 1615, 1600, 1425,
(s, NCH2N, 2 H), 6.60 (d, aromatics, J= 7.8, 2 H), 7.35-7.45* 1378, 1088, 841, 750,
(m, aromatics), 7.50-7.52* (m, aromatics)
689
1d
156-157 2.27 (s, Me, 3 H), 3.40-3.58* (m, CH2NAr), 3.71 (bs,
2848, 1630, 1525, 1447,
CH2NCO, 2 H), 4.95 (s, NCH2N, 2 H,), 6.65 (d, aromatics, J= 1244, 802, 724, 700
7.2, 2 H), 6.99-7.10* (m, aromatics), 7.40-7.51* (m,
aromatics), 7.53-7.56* (m, aromatics)
1e
1f
88-90
3.48-3.52* (m, CH2NAr), 3.65 (t, CH2NCO, J= 6.4, 2 H), 5.05 2975, 1635, 1489, 1421,
(s, NCH2N, 2 H), 6.60-6.70* (m, aromatics), 6.80-7.10* (m,
aromatics), 7.15-7.60* (m, aromatics)
1225, 750, 717, 692
225-227 3.60-3.69* (m, CH2NAr), 4.01 (bs, CH2NCO, 2H), 5.15 (s,
3056, 1599, 1308, 1113,
NCH2N, 2 H), 6.50-6.55* (m, aromatics), 6.60 (m, aromatics, 4 826, 753, 701
H), 7.40-7.50* (m, aromatics), 7.51-7.60* (m, aromatics),
8.20* (bs, aromatics)

HETEROCYCLES, Vol. 78, No. 3, 2009
775
1g
195-196 3.62-3.78* (m, CH2NAr), 3.95 (bs, CH2NCO, 2 H), 5.18 (s,
3435, 2980, 1641, 1599,
NCH2N, 2 H), 6.50-6.65* (bs, artomatics), 7.75 (dd, aromatics, 1522, 1341, 1111, 852,
1J= 7.1, 2J= 2.1), 8.15* (bs, aromatics), 8.38 (dd, aromatics,
1J= 7.1 Hz, 2J= 2.1, 2 H)
752
1h
1i
163-164 3.40-3.52* (m, CH2NAr), 3.92 (bs, CH2NCO, 2 H), 4.95 (s,
NCH2N, 2 H), 7.30-7.40* (m, aromatics), 7.49-7.54* (m,
aromatics)
2861, 1634, 1599, 1487,
1417, 1381, 1098, 715
165-167 3.49-3.59* (m, CH2NAr), 3.85 (bs, CH2NCO, 2 H), 5.02 (s,
NCH2N, 2 H), 6.60-6.69*(m, aromatics), 7.49-7.59* (m,
aromatics)
2987, 1630, 1603, 1415,
1380, 1088, 827, 751,
692
1j
1k
1l
oil
2.12 (s, Me, 3 H), 2.26 (s, Me, 3 H), 3.54 (t, CH2NAr, J= 6.6, 2 2852, 1634, 1527, 1445,
H), 3.80-3.84* (m, CH2NCO), 4.73 (s, NCH2N, 2 H),
6.58-6.64* (m, aromatics), 7.09-7.15* (m, aromatics)
1241, 809, 716, 702
oil
2.14 (s, Me, 3 H), 3.60 (t, CH2NAr, J= 6.7, 2 H), 3.78 (s, OMe, 2833, 1625, 1515, 1427,
3 H), 3.80-3.85* (m, CH2NCO), 4.73 (s, NCH2N, 2 H),
6.65-6.72* (m, aromatics), 6.90-6.95* (m, aromatics)
1246, 812, 715
118-119 1.22 (t, Me, J= 7.4, 3 H), 2.37 (q, CH2CO, J= 7.4, 2 H), 3.60 (t, 2818, 1643, 1446, 745,
CH2NAr, J= 6.5, 2 H), 3.79-3.89* (m, CH2NCO), 4.80 (s,
NCH2N, 2 H), 6.64-6.70* (m, artomatics), 6.85-6.87* (m,
aromatics), 7.23-7.33* (m, aromatics)
692
1m
1n
1o
106-108 1.19-1.23* (m, Me), 2.27(s, Me, 3 H), 2.31-2.36* (m, CH2CO), 2971, 1645, 1524, 1441,
3.54 (t, CH2NAr, J= 6.6, 2 H), 3.76-3.85* (m, CH2NCO), 4.74 800
(s,NCH2N, 2 H), 6.60* (m, aromatics), 7.07-7.13* (m,
aromatics)
118-119 1.20 (t, Me, J= 7.5, 3 H), 2.38 (q, CH2CO, J= 7.5, 2 H), 3.54 (t, 2972, 1652, 1505, 1443,
CH2NAr, J= 6.5, 2 H), 3.77-3.87* (m, CH2NCO), 4.74 (s,
NCH2N, 2 H), 6.56-6.59* (m, aromatics), 6.97-7.05* (m,
aromatics)
1259, 1025, 807
109-110 1.18 (d, Me, J= 6.9, 6 H), 2.27 (s, Me, 3 H), 2.67 (m, CH, J= 2969, 1652, 1520, 1446,
6.9, 1 H), 3.56 (t, CH2NAr, J=6.6, 2 H), 3.81-3.87*(m,
CH2NCO), 4.74 (s,NCH2N, 2 H), 6.59* (m, aromatics), 7.10*
(m, aromatics)
800
1p
91-92
1.20 (d, Me, J= 6.6, 6 H), 2.70 (m, CH, J= 6.6, 1 H), 3.60 (t, 2974, 1634, 1434, 1379,
CH2NAr, J= 6.6, 2 H), 3.85-3.93* (m, CH2NCO), 4.75 (s,
NCH2N, 2 H), 6.55-6.60* (m, aromatics), 7.20-7.30* (m,
aromatics)
1087, 822, 808, 743

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In conclusion we report a simple and efficient method for the synthesis of 1-acyl-3-arylimidazolidines
(1a-p) from N-acyl-N´-arylethylenediamines (2) and formaldehyde under microwave irradiation using
Montmorillonite K-10 activated as a solid catalyst. The coupling of microwave irradiation with the use of
Montmorillonite as efficient heterogeneous catalyst provides a clean methodology for this type of
condensations. High yields, low reaction times and easy work-up are the common advantages of this
method.
EXPERIMENTAL
1
Melting points were taken on a Büchi capillary apparatus and are uncorrected. The H spectra were
recorded on a Bruker MSL 300 MHz in CDCl3. Standard concentration of the samples was 20 mg/mL.
Chemical shifts are quoted in parts per million (δ) downfield from an internal TMS reference. The
presence of exchangeable protons was confirmed by use of deuterium oxide. MS (EI) were performed on
a MS Shimadzu QP-1000 spectrometer operating at 70 eV. The IR spectra were recorded on a Perkin
Elmer Spectrum One FT-IR spectrometer. Reactions under MW irradiation were conducted in a domestic
MW BGH 16260. Analytical TLC was carried out on aluminum sheets Silica Gel 60 F . Reagents,
254
solvents and starting materials were purchased from standard sources and purified according to literature
procedures. Experiments performed with toxic or severely irritant substances were carried out in an
efficient cupboard.
N-Acyl-N´-arylethylenediamines (2)
Compounds (2) were prepared from N-(2-bromoethyl)amides (3) and the corresponding arylamine
following literature procedure.25 Precursor N-(2-bromoethyl)amides (3) were prepared by reaction of
N-(2-bromoethyl)amine hydrobromide with a suitable acylating agent (benzoyl chloride, acetic, propionic
or isobutiric anhydrides) under Schotten-Baumann conditions.25
Compounds (2a,f)25 (2b,c,d,g)26 and (2i)9a were previously described. The physical data and elemental
analyses of new compounds are as follows.
N-Benzoyl-N´-(2-phenoxyphenyl)ethylenediamine (2e)
Yield: 77 %. mp 190-193 °C (EtOH). 1H NMR: δ= 3.40 (t, J= 5.7 Hz, 2 H, CH2N), 3.69 (q, J= 5.7 Hz, 2
H, CH2N), 4.15 (bs, 1 H, NH), 6.50 (bs,1 H, NH), 6.71-7.70 (m, 14 H, aromatics). MS: m/z: 332 (M+). IR
(KBr): 3333, 3061, 2936, 1631, 1489, 1220, 846, 747, 739 cm-1. Anal. Calcd for C21H20N2O2: C; 75.88,
H; 6.06, N; 8.43. Found: C; 75.69, H; 6.10, N; 8.38.
N-Benzoyl-N´-(3,4-dichlorophenyl)ethylenediamine (2h)
Yield: 84%. mp 59-61 °C (EtOH). 1H NMR: δ= 3.41 (t, J= 5.6 Hz, 2 H, CH2N), 3.72 (q, J=5.6 Hz, 2 H,

HETEROCYCLES, Vol. 78, No. 3, 2009
777
CH2N), 4.35 (bs, 1 H, NH), 6.52 (bs, 1 H, NH), 6.53-6.70 (m, 3 H, aromatics), 7.48 (m, 3 H, aromatics),
7.72 (dd, J= 8.1 Hz, J= 1.7 Hz, 2 H, aromatics). MS: m/z: 308, 310 (M+). IR (KBr): 3389, 2997, 2923,
1620, 1479, 1085, 836, 747, 720 cm-1. Anal. Calcd for C15H14Cl2N2O: C; 58.27, H; 4.56, N; 9.06. Found:
C; 58.45, H; 4.50, N; 8.95.
N-Acetyl-N´-(4-methylphenyl)ethylenediamine (2j)
1
Yield: 65%; oil (column chromatography, EtOAc). H NMR: δ= 2.01 (s, 3 H, Me), 2.25 (s, 3 H, Me),
3.22 (t, J= 5.7 Hz, 2 H, CH2N), 3.47 (q, J= 5.7 Hz, 2 H, CH2N), 4.02 (bs, 1 H, NH), 6.10 (bs, 1 H, NH),
6.55 (d, J= 8.5 Hz, 2 H, aromatics), 6.98 (t, J= 8.5 Hz, 2 H, aromatics). IR (film): 3312, 2922, 1659, 1522,
1452, 1378, 807 cm-1. MS: m/z: 192 (M+). Anal. Calcd for C11H16N2O: C; 68.72, H; 8.39, N; 14.57.
Found: C; 68.68, H; 8.45, N; 14.50.
N-Acetyl-N´-(4-methoxyphenyl)ethylenediamine (2k)
Yield: 64%. mp 45-46 °C. 1H NMR: δ= 1.97 (s, 3 H, Me), 3.22 (t, J= 5.7 Hz, 2 H, CH2N), 3.46 (q, J= 5.7
Hz, 2 H, CH2N), 3.73 (s, 3 H, Me), 4.01 (bs, 1 H, NH), 5.95 (bs, 1 H, NH), 6.59 (d, J=8.9 Hz, 2 H,
aromatics), 6.77 (d, J= 8.9 Hz, 2 H, aromatics). MS: m/z : 208 (M+). IR (film): 3301, 2938, 1651, 1514,
1463, 1237, 824 cm-1. Anal. Calcd. for C11H16N2O2: C; 63.44, H; 7.74, N; 13.45. Found: C; 63.54, H;
7.67, 13.51.
N-Phenyl-N´-propionylethylenediamine (2l)
Yield: 78%; oil (column chromatography, EtOAc). 1H NMR: δ= 1.13 (t, J= 7.5 Hz, 3 H, Me), 2.20 (q, J=
7.5 Hz, 2 H, CH2), 3.24 (t, J= 5.6 Hz, 2 H, CH2N), 3.48 (q, J= 5.6 Hz, 2 H, CH2N), 4.30 (bs, 1 H, NH),
6.30 (bs, 1 H, NH), 6.59 (dd, J= 8.7, J= 1.03 Hz, 2 H, aromatics), 6.68 (tt, J= 7.4, J= 1.03 Hz, 1 H,
aromatic), 7.15 (dd, J= 8.7, J= 7.4 Hz, 2 H, aromatics). MS: m/z: 192 (M+). IR (film): 3300, 2978, 1649,
1463, 1182, 750, 694 cm-1. Anal. Calcd. for C11H16N2O: C; 68.72, H; 8.39, N; 14.57. Found: C; 68.69, H;
8.46, N; 14.67.
N-(4-Methylphenyl)-N´-propionylethylenediamine (2m)
Yield: 78%; oil (column chromatography, EtOAc). 1H NMR: δ= 1.15 (t, J= 7.4 Hz, 3 H, Me), 2.17 (q, J=
7.4 Hz, 2 H, CH2), 2.23 (s, 3 H, Me), 3.22 (t, J= 5.8 Hz, 2 H, CH2NH), 3.45 (q, J= 5.8 Hz, 2 H, CH2H),
4.15 (bs, 1 H, NH), 6.14 (bs, 1 H, NH), 6.52 (d, J= 8.3 Hz, 2 H, aromatics), 6.98 (d, J= 8.3 Hz, 2 H,
aromatics). MS: m/z: 206 (M+). IR (film): 3307, 2939, 1645, 1519, 1463, 1254, 810 cm-1. Anal. Calcd. for
C12H18N2O: C; 69.87, H; 8.79, N; 13.58. Found: C; 69.74, H; 8.89, N; 13.47.
N-(4-Chlorophenyl)-N´-propionylethylenediamine (2n)
Yield: 72 %; oil (column chromatography, EtOAc). 1H NMR: δ= 1.10 (t, J= 7.6 Hz, 3 H, Me), 2.20 (q, J=
7.6 Hz, 2 H, CH2), 3.22 (t, J= 5.6 Hz, 2 H, CH2N), 3.56 (q, J= 5.6 Hz, 2 H, CH2N), 4.20 (bs, 1 H, NH),
5.90 (bs, 1 H, NH), 6.50 (d, J= 8.9 Hz, 2 H, aromatics), 7.05 (d, J= 8.9 Hz, 2 H, aromatics). MS: m/z :

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HETEROCYCLES, Vol. 78, No. 3, 2009
226, 228 (M+). IR (film): 2981, 1662, 1510, 1440, 1241, 1025, 806 cm-1. Anal. Calcd. for C11H15ClN2O:
C; 58.28, H; 6.67, N; 12.36. Found: C; 58.15, H; 6.73, N; 12.42.
N-(4-Methylphenyl)-N´-(2-methylpropionyl)ethylenediamine (2o)
Yield: 75%; oil (column chromatography, EtOAc). 1H NMR: δ= 1.10 (d, J= 6.9 Hz, 6 H, Me), 2.20 (s, 3
H, Me), 2.31 (m, 1 H, CH), 3.25 (t, J= 5.9 Hz, 2 H, CH2N), 3.50 (q, J= 5.9 Hz, 2 H, CH2N), 4.42 (bs, 1 H,
NH), 5.85 (bs, 1 H, NH), 6.55 (d, J= 8.4 Hz, 2 H, aromatics), 7.00 (d, J= 8.4 Hz, 2 H, aromatics). MS:
m/z: 220 (M+). IR (film): 3306, 2970, 1645, 1548, 1249, 813 cm-1. Anal. Calcd. for C13H20N2O: C; 70.87,
H; 9.15, N; 12.72. Found: C; 70.74, H; 9.23, N; 12.65.
N-(4-Chlorophenyl)-N´-(2-methylpropionyl)ethylenediamine (2p)
Yield: 79%. mp 69-70 °C (EtOH). 1H NMR: δ= 1.10 (d, J=7.0 Hz, 6 H, Me), 2.30 (sep, J= 7.0 Hz, 1 H,
CH), 3.20 (t, J= 6.4 Hz, 2 H, CH2N), 3.50 (q, J= 6.4 Hz, 2 H, CH2N), 4.06 (bs, 1 H, NH), 5.90 (bs, 1 H,
NH), 6.64 (d, J=8.8 Hz, 2 H, aromatics), 7.10 (d, J= 8.8 Hz, 2 H, aromatics). MS: m/z: 240, 242 (M+). IR
(KBr): 3334, 2971, 1660, 1470, 1434, 1252, 1137, 816 cm-1. Anal. Calcd. for C12H17ClN2O: C; 59.87, H;
7.12, N; 11.64. Found: C; 59.76, H; 7.20, N; 11.55.
Imidazolidines (1a-p): General Procedure
To a solution of N-acyl-N´-arylethylenediamine (2) (1 mmol) in anhydrous THF (5 mL) was added
Montmorillonite K-10 actived 1 h/ 120 °C (500 mg) followed by aqueous 37% formaldehyde (3 mmol). To
the reaction mixture , a 30 s of irradiation at 180 W and a 20 s without irradiation were repeated alternately
until the starting material disappeared as monitored by TLC. After filtration, the solvent was removed in
vacuo and the residue was crystallized from EtOH except compounds (1j,k) which were purified by column
chromatography (EtOAc).
Melting points, 1H-NMR and IR data are given in table 2. Elemental analyses and MS data are as follows.
1-Benzoyl-3-phenylimidazolidine (1a)
MS: m/z: 252 (M+). Anal. Calcd for C16H16N2O: C; 76.16, H; 6.39, N; 11.10. Found: C; 76.22, H; 6.28, N;
11.15.
1-Benzoyl-3-(4-hidroxyphenyl)imidazolidine (1b)
MS (EI, 70eV): m/z: 268 (M+). Anal. Calcd for C16H16N2O2: C; 71.62, H; 6.01, N, 10.44. Found: C; 71.50,
H; 5.91, N; 10.51.
1-Benzoyl-3-(4-chlorophenyl)imidazolidine (1c)
MS: m/z : 286, 288 (M+). Anal. Calcd for C16H15ClN2O: C; 67.02, H; 5.27, N; 9.77. Found: C; 67.13, H;
5.31, N; 9.65.
1-Benzoyl-3-(4-methylphenyl)imidazolidine (1d)

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MS: m/z: 266 (M+). Anal. Calcd for C17H18N2O: C; 76.66, H; 6.81, N; 10.52. Found: C; 76.54, H; 6.70,
N; 10.65.
1-Benzoyl-3-(2-phenoxyphenyl)imidazolidine (1e)
MS: m/z: 344 (M+). Anal. Calcd for C22H20N2O2: C; 76.72, H; 5.85, N; 8.13. Found: C; 76.65, H; 5.91, N;
8.07.
1-Benzoyl-3-(4-nitrophenyl)imidazolidine (1f)
MS: m/z: 297 (M+). Anal. Calcd for C16H15N3O3: C; 64.64, H; 5.09, N; 14.13. Found: C; 64.72, H; 5.20,
N; 14.25.
1-(4-Nitrobenzoyl)-3-(4-nitrophenyl)imidazolidine (1g)
MS: m/z: 342 (M+). Anal. Calcd for C16H14N4O5: C; 56.14, H; 4.12, N; 16.37. Found: C; 56.23, H; 4.05,
N; 16.29.
1-Benzoyl-3-(3,4-dichlorophenyl)imidazolidine (1h)
MS: m/z : 320, 322 (M+). Anal. Calcd for C16H14Cl2N2O: C; 59.83, H; 4.39, N; 8.72. Found: C; 59.96, H;
4.42, N; 8.68.
1-(4-Chlorobenzoyl)-3-phenylimidazolidine (1i)
MS: m/z: 286, 288 (M+). Anal. Calcd for C16H15ClN2O: C; 67.02, H; 5.27, N; 9.77. Found: C; 67.10, H;
5.29, N; 9.69.
1-Acetyl-3-(4-methylphenyl)imidazolidine (1j)
MS: m/z : 204 (M+). Anal. Calcd for C12H16N2O: C; 70.56, H; 7.89, N; 13.71. Found: C; 70.47, H; 7.95,
N; 13.65.
1-Acetyl-3-(4-methoxyphenyl)imidazolidine (1k)
MS: m/z: 220 (M+). Anal. Calcd for C12H16N2O2: C; 65.43, H; 7.32, N; 12.72. Found: C; 65.32, H; 7.39,
N; 12.68.
1-Phenyl-3-propionylimidazolidine (1l)
MS: m/z: 204 (M+). Anal. Calcd for C12H16N2O: C; 70.56, H; 7.89, N; 13.71. Found: C; 70.48, H; 7.95,
N; 13.65.
1-(4-Methylphenyl)-3-propionylimidazolidine (1m)
MS: m/z: 218 (M+). Anal. Calcd for C13H18N2O: C; 71.53, H; 8.31, N; 12.83. Found: C; 71.67, H; 8.39,
N; 12.72.
1-(4-Chlorophenyl)-3-propionylimidazolidine (1n)
MS: m/z: 238, 240 (M+). Anal. Calcd for C12H15ClN2O: C; 60.38, H; 6.33, N; 11.73. Found: C; 60.45, H;
6.28, N; 11.79.
1-(4-Methylphenyl)-3-(2-methylpropionyl)imidazolidine (1o)
MS: m/z : 232 (M+). Anal. Calcd for C14H20N2O: C; 72.38, H; 8.68, N; 12.06. Found: C; 72.27, H; 8.75,

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N; 12.13.
1-(4-Chlorophenyl)- 3-(2-methylpropionyl)imidazolidine (1p)
MS: m/z: 252, 254 (M+). Anal. Calcd for C13H17ClN2O: C; 61.78, H; 6.78, N; 11.08. Found: C; 61.67, H;
6.59, N; 11.13.
ACKNOWLEDGEMENTS
This work is supported by Universidad de Buenos Aires and Agencia Nacional de Promoción Científica y
Tecnológica.
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