Microwave-assisted stereoselective 1,3-dipolar cycloaddition of C,N-diarylnitrone (i.e., N-(arylmethylidene)benzenamine N-oxide) and bis(arylmethylidene)acetone (=1,5-diarylpenta-1,4-dien-3-one): NMR and crystal analysis of diastereoisomeric bis(isoxazolidines)

Article abstract of DOI:10.1002/hlca.201100263

Microwave-assisted stereoselective 1,3-dipolar cycloaddition of C,N-diarylnitrones (i.e., N-(arylmethylidene)benzenamine N-oxides) 2 to substituted bis(arylmethylidene)acetones (=1,5-diarylpenta-1,4-dien-3-ones) 1 leading to diastereoisomer pairs of bis-isoxazolidines 3 and 4 in good to excellent yield is described (Scheme2 and Table2). The configuration outcome of the reaction is discussed based on the NMR and X-ray data of the products. Copyright

Full text of DOI:10.1002/hlca.201100263

Helvetica Chimica Acta – Vol. 95 (2012)
173
Microwave-Assisted Stereoselective 1,3-Dipolar Cycloaddition of C,N-
Diarylnitrone (i.e., N-(Arylmethylidene)benzenamine N-Oxide) and
Bis(arylmethylidene)acetone (¼1,5-Diarylpenta-1,4-dien-3-one): NMR and
Crystal Analysis of Diastereoisomeric Bis(isoxazolidines)
by Nidhin Paul, Selvam Kaladevi, and Shanmugam Muthusubramanian*
Department of Organic Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai-625021,
Tamil Nadu, India (phone/fax: þ 91-452-2459845; email: muthumanian2001@yahoo.com)
Microwave-assisted stereoselective 1,3-dipolar cycloaddition of C,N-diarylnitrones (i.e., N-(arylme-
thylidene)benzenamine N-oxides) 2 to substituted bis(arylmethylidene)acetones (¼1,5-diarylpenta-1,4-
dien-3-ones) 1 leading to diastereoisomer pairs of bis-isoxazolidines 3 and 4 in good to excellent yield is
described (Scheme 2 and Table 2). The configuration outcome of the reaction is discussed based on the
NMR and X-ray data of the products.
Introduction. – The 1,3-dipolar cycloaddition of nitrones to alkenes affords
isoxazolidines through a concerted CꢀC and CꢀO bond forming mechanism with
generation of as many as three new contiguous stereogenic centers in a single step [1].
Isoxazolidines exhibit antibacterial and antifungal properties [2], and the possibility of
their transformation via ring opening to open-chain derivatives [3] makes these
compounds valuable synthons for the synthesis of natural and biologically important
compounds, such as amino sugars, amino alcohols, alkaloids, b-lactams, and amino acids
[4]. The stereochemical course of the 1,3-dipolar cycloaddition reaction has been well
explained in terms of secondary orbital interactions, steric factors, H-atom bonding
and/or dipoleꢀdipole electrostatic interactions [2b][5].
The use of microwaves for carrying out organic reactions is a well established
procedure and has emerged as a promising synthetic technique, since the reactions are
clean, fast, and economical with easy workup. The technique of microwave irradiation
enables organic reactions to occur expeditiously at ambient pressure and provides
unique reaction processes with special attributes such as accelerated reaction rate and
relatively good yields [1g][2b][6] with selectivity in certain cases.
Results and Discussion. – We have already indicated that with 1:1 and 1:2 ratios of
dibenzylideneacetone (¼1,5-diphenylpenta-1,4-dien-3-one) and nitrone, the cyclo-
additon under reflux leads to a complex mixture of products, the major product being
the mono-cycloadduct indicating that the second cycloaddition seems to be difficult
under the reaction conditions studied [1b]. In the present work, in an attempt to
prepare exclusively the bis-adduct having two isoxazolidine rings connected by a C¼O
group from dibenzylideneacetone and to deliberate the stereochemical features due to
the generation of six new stereogenic centers, we carried out the cycloaddition under
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Helvetica Chimica Acta – Vol. 95 (2012)
different harsh conditions. The reaction of bis(arylmethylidene)acetone 1 with excess
nitrone 2 (1:4), even after refluxing in toluene for two days, led to a mixture of three
products; two of them, 3 and 4, were identified as the expected isomeric bis-adducts,
while the third one was the mono-isoxazolidine 5 with a free cinnamoyl moiety
(Scheme 1). Thus, this conventional procedure resulted in a nearly 90% overall yield
and a considerable amount of 5 (Table 1).
Scheme 1. Reaction of 1 and 2 at Reflux Temperature in Toluene
Table 1. Yields of 3 – 5 by the Conventional-Heating and Microwave-Irradiation Method
X
Y
Z
Yield [%] after MWa)
Yield [%] after refluxa)
3
4
3
4
5
a
b
c
d
e
f
H
H
H
H
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
48
46
47
45
48
46
43
44
45
40
44
42
24
27
27
24
29
26
21
23
24
23
26
24
44
45
45
43
41
42
Me
MeO
H
Me
MeO
a) Yield of isolated product after purification by column chromatography.

Helvetica Chimica Acta – Vol. 95 (2012)
175
However, the reaction of acetone derivative 1 with nitrone 2 showed remarkable
selectivity when carried out under microwave irradiation. The yield of 5 was
considerably reduced, and by optimizing the microwave parameters, only the bis-
adducts 3 and 4 with no trace of 5 were formed. The influence of microwave power,
temperature, and irradiation time on the reaction was then systematically investigated
for the reaction of 1 (X ¼ MeO) and 2 (Y¼ H, Z ¼ Cl) (Table 2). In the microwave
assisted reaction (Scheme 2), the highest yield of isomeric bis-adducts was observed
when the temperature of the reaction medium was maintained at 1258 (Table 2); a
decrease in the yield was noticed while increasing or decreasing the temperature. The
data (Tables 1 and 2) show that the reaction was stereoselective, as the yield of isomer 3
was always slightly higher than that of 4. It must be mentioned that both isomers were
successfully separated, in spite of the fact that they have close Rf values. The low
stereoselectivity observed suggests that the energies of activation for the formation of
these compounds do not differ much.
Scheme 2. Reaction of 1 and 2 under Microwave Irradiation
The cycloaddition of dibenzylideneacetones 1 with nitrones 2 proceeds regiose-
lectively through the addition of the O-atom of the nitrone to the C(b) of the
benzylidene moiety affording the two diastereoisomeric bis-isoxazolidines. The
regioselectivity is in accord with the polarization of the C¼C bond enabling the more
electron-deficient C(b) to preferentially react with the electron-rich O-atom of the

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Table 2. Optimization of the Microwave Assisted Reaction of 1 (X ¼ MeO) and 2 (Y¼ H, Z ¼ Cl)
Temp. [8]
Power [watt]
Time [min]
Yield [%]
overall
3c/4c/5c
70
80
80
100
100
120
120
120
125
130
130
140
150
150
200
12
10
15
20
10
15
15
5
25
15
10
10
36
45
48
60
72
80
92
83
90
85
54
8
43 : 40 : 17
44 : 41 : 15
47: 42 : 11
45 : 43 : 12
49 : 47: 4
50 : 48 : 2
51 : 49 : 0
50 : 47: 3
52 : 48 : 0
47: 47: 6
42 : 40 : 18
–a)
90
110
115
125
125
125
140
165
186
a) Trace amounts of all three products.
nitrone. Assigning the configuration of these two isomers is interesting. The NMR
spectra indicated that both 3 and 4 had only one set of signals for their isoxazolidine
rings showing that the bis-adducts were symmetrical with respect to the center. Based
on one- and two-dimensional NMR data, the complete assignments of the position of
the H- and C-atoms for 3 and 4 could be achieved (as detailed for 3f and 4f in Figs. 1
and 2).
Fig. 1. Selected HMBCs and 1H- and 13C-NMR chemical shifts of 3f. d in ppm, J in Hz.
The spatial arrangement of the isoxazolidine rings is again similar for both 3 and 4,
the H-atoms all being in trans relation to each other. These details restricted the
structures of the two diastereoisomeric bis-adducts to the ones shown in Schemes 1 and
2 as well as in Figs. 1 and 2. One of them is a racemate and the other a meso form. The
close similarity of the configurational features makes the energy associated with these

Helvetica Chimica Acta – Vol. 95 (2012)
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Fig. 2. Selected HMBCs and 1H- and 13C-NMR chemical shifts of 4f. d in ppm, J in Hz.
two isomers to be close accounting for the observed near-equal yield of them. Thus, out
of the twenty possible diastereoisomers due to the presence of six degenerate chiral
centers, only two diastereoisomers were selectively produced during this cycloaddition.
It should be mentioned that NMR data of 3 and 4 are not helpful to distinguish
between the racemic and meso forms. However, the single-crystal X-ray analyses of 3f
and 4f revealed unambiguously that the former is racemic and the latter is meso
(Fig. 3). The crystal structures of 3c, 3f, and 4f (Figs. 4 – 6) indicated that the
isoxazolidine rings are all in an envelope conformation. It is pertinent that the mono-
isoxazolidine has also the central ring in an envelope conformation with the O-atom
placed out-of-plane [1a][1b]. It may be highlighted that HꢀC(3) and HꢀC(3’) (and
also HꢀC(4) and HꢀC(4’) and HꢀC(5) and HꢀC(5’)) of 3 are homotopic, while in 4,
these pairs are in an enantiotopic relationship (Fig 3). Had they been diastereoisotopic,
they would have become nonequivalent in the NMR spectra, resulting in two sets of
signals for the isoxazolidine rings. The HR-MS of the compounds 3f and 4f had signals
Fig. 3. Configurations of bis-isoxazolidines 3 and 4 from crystal structures

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Fig. 4. ORTEP Diagram of 3c
Fig. 5. ORTEP Diagram of 3f
at m/z 847.12705 ([M þ 23]) and 823.13056 ([M ꢀ 1]), respectively; moreover, all
isomers 3 and 4 showed elemental analyses compatible with their structures.
A comparison of the chemical shifts and coupling constants of isomeric bis-
isoxazolidines 3 and 4 and the mono-adduct 5 is illustrated in Table 3. Thus, between the
diastereoisomers (3c and 4c, or 3f and 4f), the variations of values were not very
important. But a change in the substitution pattern of the aryl ring at C(3) of the
isoxazolidine ring altered the chemical shifts and coupling constants considerably. In
the case of the 2,4-dichloro-substituted systems (see 3f, 4f, and 5f), the isoxoazolidine-
ring H-atoms were deshielded, while the corresponding C-atoms were shielded
compared to the 4-chloro-substituted systems (see 3c, 4c, and 5c). The coupling
constant between HꢀC(3) and HꢀC(4) decreased substantially in the 2,4-dichloro-

Helvetica Chimica Acta – Vol. 95 (2012)
179
Fig. 6. ORTEP Diagram of 4f
phenyl systems, suggesting a change in the conformation, with probably more
deformation in this case due to steric hindrance. A comparison of the coupling
constants indicated a similar configuration for the isoxazolidine ring in the mono- and
bis-adducts in the respective series, with all H-atoms trans to each other at the ring. The
Ho of the 2,4-dichlorophenyl residue in 3f and 4f appeared at d(H) 7.68 (d, J ¼ 8.4 Hz)
and at d(H) 7.61 (d, J ¼ 8.7 Hz), respectively, while that for 5f appeared at d(H) 8.02 (d,
J ¼ 9.0 Hz). This deshielding in the latter can be attributed to the spatial proximity of
the C¼O group with the isoxazolidine ring in the mono-adduct as compared to the
situation in the bis-adduct.
Table 3. Comparison of NMR Chemical Shifts and Coupling Constants of Isomeric Bis-isoxazolidines
and Mono-isoxazolidines. d in ppm, J in Hz.
d(H)
d(C)
HꢀC(3)
HꢀC(4)
HꢀC(5)
C(3)
C(4)
C(5)
3c
3f
4c
4f
5c
5f
5.20 (J ¼ 7.5)
5.84 (J ¼ 4.5)
4.95 (J ¼ 9.3)
5.61 (J ¼ 5.1)
5.37 (J ¼ 7.2)
5.85 (J ¼ 4.5)
3.12 (J ¼ 9.6, 7.5)
3.15 (J ¼ 9.0, 4.5)
3.22 (J ¼ 9.3, 8.1)
3.45 (J ¼ 9.0, 5.1)
3.97 (J ¼ 9.3, 7.2)
3.86 (J ¼ 8.7, 4.5)
4.56 (J ¼ 9.6)
4.79 (J ¼ 9.0)
4.73 (J ¼ 8.1)
4.91 (J ¼ 9.0)
5.22 (J ¼ 9.3)
5.16 (J ¼ 8.7)
71.4
67.4
72.7
68.0
72.4
70.1
73.6
72.5
73.7
72.4
73.1
71.9
83.5
83.9
82.2
82.9
83.9
84.9
Conclusions. – We optimized a method for the preparation of diastereoisomeric bis-
isoxazolidines exclusively achieving the selectivity through microwave irradiation. The
1
diastereoisomers were separated and well characterized by H-, 13C-, and 2D-NMR,
MS, and single-crystal X-ray analyses.
The authors thank DST, New Delhi, for funds under the IRHPA program towards high-resolution
NMR spectrometer, and UGC, New Delhi, for the financial support to one of the authors, N. P. Prof. J.

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Helvetica Chimica Acta – Vol. 95 (2012)
Jeyakanthan of the Alagappa University, Karaikudi, Tamil Nadu, India, and Prof. J. C. Menendez of the
´
´
Departamento de Quꢂmꢂca Organica y Farmaceutica, Facultad de Farmacia, Universidad Complutense,
28040 Madrid, Spain, are acknowledged for the X-ray diffraction and MS analyses, respectively.
Experimental Part
General. A CEM-Discover microwave synthesizer (model No. 908010) operating at 180/264 V and
50/60 Hz with a microwave-power maximum level of 300 W and microwave frequency of 2455 MHz was
employed for the microwave-assisted experiments. TLC: silica gel G plates (SiO2; Merck), petroleum
ether (60 – 808) and AcOEt as eluents. M.p.: open capillary tubes; uncorrected. IR Spectra: Jasco FT-IR
instrument; in KBr; ˜n in cmꢀ1.1H-, 13C-, and 2D-NMR: Bruker-Avance-300 NMR instrument; in CDCl3; d
in ppm rel. to Me4Si as internal standard, J in Hz. Elemental analyses: PerkinꢀElmer-2400 series II
elemental CHNS analyzer.
Conventional-Heating Method. A mixture of dibenzylideneacetone 1 (1 mmol) and nitrone 2
(4 mmol) in toluene (7 ml) was heated under reflux for 48 h. Then the mixture was concentrated under
vacuum and the crude residue subjected to NMR analysis before separation. The separation by column
chromatography (CC; SiO2 petroleum ether/AcOEt 9 :1) afforded the pure diastereoisomers 3 and 4 and
the mono-adduct 5.
Microwave-Irradiation Method. A mixture of dibenzylideneacetone 1 (1 mmol) and nitrone 2
(4 mmol) in toluene (3 ml) in a 10-ml microwave tube was placed in the microwave synthesizer and
irradiated at 1258 with 130 watts for 15 min. After completion of the reaction (TLC monitoring), the
mixture was concentrated under vacuum, and the residue was subjected to CC (SiO2 petroleum ether/
AcOEt 9 :1): pure diastereoisomers 3 and 4. Spectroscopic data for all the compounds are given below.
(ꢁ)-rel-Bis[(3R,4S,5S)-3-(4-chlorophenyl)-2,5-diphenylisoxazolidin-4-yl]methanone (3a). Colorless
solid. M.p. 1928. IR: 2931 (arom. H), 1705 (C¼O). 1H-NMR: 3.11 (dd, J ¼ 9.6, 7.5, 2 H, HꢀC(4)); 4.66 (d,
J ¼ 9.6, 2 H, HꢀC(5)); 5.14 (d, J ¼ 7.5, 2 H, HꢀC(3)); 6.70 (d, J ¼ 7.5, 4 arom. H); 6.84 (d, J ¼ 7.8, 4 arom.
H); 6.95 (t, J ¼ 7.2, 2 arom. H); 7.10 – 7.38 (m, 18 arom. H). 13C-NMR: 71.6; 74.0; 83.4; 114.0; 122.1; 127.1;
127.6; 128.9; 129.0; 129.2; 129.4; 133.7; 134.5; 139.3; 151.2; 200.9. Anal. calc. for C43H34Cl2N2O3: C 74.03,
H 4.91, N 4.02; found: C 74.00, H 4.87, N 4.07.
(ꢁ)-rel-Bis[(3R,4S,5S)-3-(4-chlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]metha-
1
none (3b): Colorless solid. M.p. 1878. IR: 2931 (arom. H), 1703 (C¼O). H-NMR: 2.38 (s, 2 Me); 3.15
(dd, J ¼ 9.6, 7.5, 2 H, HꢀC(4)); 4.60 (d, J ¼ 9.6, 2 H, HꢀC(5)); 5.15 (d, J ¼ 7.5, 2 H, HꢀC(3)); 6.61 (d, J ¼
7.8, 4 arom. H); 6.84 (d, J ¼ 7.8, 4 arom. H); 6.97 (d, J ¼ 7.8, 4 arom. H); 7.13 (d, J ¼ 8.4, 4 arom. H); 7.21
(d, J ¼ 8.4, 4 arom. H); 7.25 – 7.28 (m, 6 arom. H). 13C-NMR: 21.3; 71.5; 73.6; 83.6; 113.9; 114.4; 121.9;
127.2; 127.6; 129.0; 129.1; 129.6; 131.0; 133.6; 139.5; 151.3; 201.1. Anal. calc. for C45H38Cl2N2O3: C 74.48, H
5.28, N 3.86; found: C 74.44, H 5.25, N 3.92.
(ꢁ)-rel-Bis[(3R,4S,5S)-3-(4-chlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl]metha-
none (3c): Colorless solid. M.p. 1848. IR: 2930 (arom. H), 1702 (C¼O). 1H-NMR: 3.12 (dd, J ¼ 9.6, 7.5,
2 H, HꢀC(4)); 3.84 (s, 2 MeO); 4.56 (d, J ¼ 9.6, 2 H, HꢀC(5)); 5.20 (d, J ¼ 7.5, 2 H, HꢀC(3)); 6.63 (d, J ¼
8.4, 4 arom. H); 6.68 (d, J ¼ 9.0, 4 arom. H); 6.84 (d, J ¼ 8.4, 4 arom. H); 6.94 (t, J ¼ 7.2, 2 arom. H); 7.15 –
7.30 (m, 12 arom. H). 13C-NMR: 55.3; 71.4; 73.6; 83.5; 113.8; 114.2; 121.8; 125.7; 127.6; 128.6; 129.0; 129.1;
133.5; 139.7; 151.4; 160.4; 201.0. Anal. calc. for C45H38Cl2N2O5: C 71.33, H 5.06, N 3.70; found: C 71.27, H
5.01, N 3.73.
(ꢁ)-rel-Bis[(3R,4S,5S)-3-(2,4-dichlorophenyl)-2,5-diphenylisoxazolidin-4-yl]methanone (3d): Col-
orless solid. M.p. 1618. IR: 2934 (arom. H), 1705 (C¼O). 1H-NMR: 3.18 (dd, J ¼ 8.7, 4.5, 2 H, HꢀC(4));
4.84 (d, J ¼ 8.7, 2 H, HꢀC(5)); 5.83 (d, J ¼ 4.5, 2 H, HꢀC(3)); 6.66 (d, J ¼ 7.5, 4 arom. H); 6.97 – 7.05 (m, 10
arom. H); 7.19 – 7.31 (m, 8 arom. H); 7.40 (s, 2 arom. H); 7.66 (d, J ¼ 8.4, 2 arom. H). 13C-NMR: 67.4; 72.7;
84.0; 113.9; 122.1; 127.3; 127.9; 128.9; 129.1; 129.2; 129.3; 129.8; 132.3; 133.9; 134.5; 138.3; 149.6; 198.5.
Anal. calc. for C43H32Cl4N2O3: C 67.38, H 4.21, N 3.65; found: C 67.35, H 4.17, N 3.70.
(ꢁ)-rel-Bis[(3R,4S,5S)-3-(2,4-dichlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]me-
thanone (3e): Colorless solid. M.p. 1888. IR: 2928 (arom. H), 1704 (C¼O). 1H-NMR: 2.30 (s, 2 Me); 3.19
(dd, J ¼ 9.0, 4.5, 2 H, HꢀC(4)); 4.79 (d, J ¼ 9.0, 2 H, HꢀC(5)); 5.82 (d, J ¼ 4.5, 2 H, HꢀC(3)); 6.56 (d,

Helvetica Chimica Acta – Vol. 95 (2012)
181
J ¼ 8.1, 4 arom. H); 6.82 (d, J ¼ 7.8, 4 arom. H); 6.95 – 6.98 (m, 6 arom. H); 7.23 – 7.30 (m, 6 arom. H); 7.40
(d, J ¼ 2.1, 2 arom. H); 7.65 (d, J ¼ 8.7, 2 arom. H). 13C-NMR: 21.2; 67.4; 72.5; 84.0; 113.9; 122.0; 127.3;
127.8; 129.0; 129.2; 129.4; 129.8; 131.2; 133.3; 133.8; 138.4; 139.2; 149.8; 198.6. Anal. calc. for
C45H36Cl4N2O3: C 68.02, H 4.57, N 3.53; found: C 67.99, H 4.54, N 3.56.
(ꢁ)-rel-Bis[(3R,4S,5S)-3-(2,4-dichlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl]me-
1
thanone (3f): Colorless solid. M.p. 1658. IR: 2932 (arom. H), 1702 (C¼O). H-NMR: 3.15 (dd, J ¼ 9.0,
4.5, 2 H); 3.78 (s, 2 MeO); 4.79 (d, J ¼ 9.0, 2 H); 5.84 (d, J ¼ 4.5, 2 H); 6.54 (d, J ¼ 8.7, 4 H); 6.60 (d, J ¼
8.7, 4 H); 6.95 – 7.00 (m, 6 arom. H); 7.25 – 7.31 (m, 6 arom. H); 7.41 (d, J ¼ 2.1, 2 arom. H); 7.68 (d, J ¼ 8.4,
2 arom. H). 13C-NMR: 55.2; 67.4; 72.5; 83.9; 113.9; 114.2; 122.0; 126.2; 127.8; 128.8; 129.1; 129.2; 129.9;
132.4; 133.8; 138.6; 149.8; 160.3; 198.6. HR-MS: 847.12705 ([M þ 23]; calc. 847.13783). Anal. calc. for
C45H36Cl4N2O5: C 65.39, H 4.39, N, 3.39; found: C 65.34, H 4.35, N 3.43.
meso-Bis[3-(4-chlorophenyl)-2,5-diphenylisoxazolidin-4-yl]methanone (¼ [(3R,4S,5S)-3-(4-Chloro-
phenyl)-2,5-diphenylisoxazolidin-4-yl][(3S,4R,5R)-3-(4-chlorophenyl)-2,5-diphenylisoxazolidin-4-yl]-
methanone; 4a): Colorless solid. M.p. 1618. IR: 2933 (arom. H), 1714 (C¼O). 1H-NMR: 3.19 (dd, J ¼ 9.3,
8.1, 2 H, HꢀC(4)); 4.72 (d, J ¼ 8.1, 2 H, HꢀC(5)); 5.00 (d, J ¼ 9.3, 2 H, HꢀC(3)); 6.83 (d, J ¼ 8.4, 4 arom.
H); 6.89 (d, J ¼ 7.5, 4 arom. H); 6.96 (t, J ¼ 7.2, 2 arom. H); 7.02 (d, J ¼ 8.4, 4 arom. H); 7.19 – 7.30 (m, 14
arom. H). 13C-NMR: 72.8; 74.0; 82.2; 114.6; 122.5; 126.7; 128.0; 128.8; 128.9; 129.0; 129.4; 134.1; 135.7;
139.1; 150.9; 201.7. Anal. calc. for C43H34Cl2N2O3: C 74.03, H 4.91, N 4.02; found: C 74.01, H 4.89, N 4.07.
meso-Bis[3-(4-chlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]methanone (¼ [(3R,4S,
5S)-3-(4-Chlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl][(3S,4R,5R)-3-(4-chlorophenyl)-
5-(4-methylphenyl)-2-phenyl)-2-phenylisoxazolidin-4-yl]methanone; 4b): Colorless solid. M.p. 1858. IR:
2931 (arom. H), 1716 (C¼O). 1H-NMR: 2.37 (s, 2 Me); 3.23 (dd, J ¼ 9.3, 8.1, 2 H, HꢀC(4)); 4.73 (d, J ¼
8.1, 2 H, HꢀC(5)); 4.50 (d, J ¼ 9.3, 2 H, HꢀC(3)); 6.81 (t, J ¼ 7.5, 4 arom. H); 6.96 – 7.10 (m, 6 arom. H);
7.18 – 7.30 (m, 10 arom. H); 7.36 (d, J ¼ 8.4, 4 arom. H); 7.52 (d, J ¼ 8.4, 2 arom. H). 13C-NMR: 21.2; 71.5;
72.7; 82.3; 114.2; 122.3; 126.7; 127.9; 129.0; 129.1; 129.3; 129.5; 132.2; 133.9; 138.9; 151.0; 201.9. Anal. calc.
for C45H38Cl2N2O3: C 74.48, H 5.28, N 3.86; found: C 74.45, H 5.26, N 3.90.
meso-Bis[3-(4-chlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl]methanone (¼ [(3R,
4S,5S)-3-(4-Chlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl][(3S,4R,5R)-3-(4-chloro-
phenyl)-5-(4-methoxyphenyl)-2-phenyl)-2-phenylisoxazolidin-4-yl]methanone; 4c). Colorless solid. M.p.
1828. IR: 2929 (arom. H), 1714 (C¼O). 1H-NMR: 3.22 (dd, J ¼ 9.3, 8.1, 2 H, HꢀC(4)); 3.84 (s, 2 MeO);
4.73 (d, J ¼ 8.1, 2 H, HꢀC(5)); 4.95 (d, J ¼ 9.3, 2 H, HꢀC(3)); 6.74 (d, J ¼ 8.7, 4 arom. H); 6.81 – 6.85 (m, 6
arom. H); 6.90 – 6.97 (m, 4 arom. H); 7.06 (d, J ¼ 8.4, 4 arom. H); 7.18 – 7.25 (m, 4 arom. H); 7.30 (d, J ¼
8.4, 4 arom. H). 13C-NMR: 55.3; 72.7; 73.7; 82.2; 114.2; 114.4; 122.3; 125.5; 128.0; 128.2; 129.0; 129.3;
134.0; 139.4; 151.0; 160.2; 202.0. Anal. calc. for C45H38Cl2N2O5: C 71.33, H 5.06, N 3.70; found: C 71.28, H
5.01, N 3.75.
meso-Bis[3-(2,4-dichlorophenyl)-2,5-diphenylisoxazolidin-4-yl]methanone (¼ [(3R,4S,5S)-3-(4-Di-
chlorophenyl)-2,5-diphenylisoxazolidin-4-yl][(3S,4R,5R)-3-(2,4-dichlorophenyl)-2,5-diphenylisoxazoli-
1
din-4-yl]methanone; 4d): Colorless solid. M.p. 1808. IR: 2931 (arom. H), 1713 (C¼O). H-NMR: 3.35
(dd, J ¼ 8.7, 5.1, 2 H, HꢀC(4)); 4.96 (d, J ¼ 8.7, 2 H, HꢀC(5)); 5.62 (d, J ¼ 5.1, 2 H, HꢀC(3)); 6.86 (d, J ¼
8.4, 4 arom. H); 6.94 (d, J ¼ 8.4, 4 arom. H); 7.16 – 7.40 (m, 16 arom. H); 7.57 (d, J ¼ 8.4, 2 arom. H).
13C-NMR: 68.0; 72.7; 82.9; 114.1 (2C); 122.3; 126.9; 128.2; 128.9; 129.1; 129.2; 129.9; 132.4; 134.1; 135.4;
137.7; 149.5; 200.5. Anal. calc. for C43H32Cl4N2O3: C 67.38, H 4.21, N 3.65; found: C 67.34, H 4.16, N 3.71.
meso-Bis[3-(2,4-dichlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]methanone (¼ [(3R,
4S,5S)-3-(4-Dichlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl][(3S,4R,5R)-3-(2,4-dichloro-
phenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]methanone; 4e): Colorless solid. M.p. 1758. IR:
2931 (arom. H), 1715 (C¼O). 1H-NMR: 2.36 (s, 2 Me); 3.45 (dd, J ¼ 9.0, 5.1, 2 H, HꢀC(4)); 4.93 (d, J ¼
9.0, 2 H, HꢀC(5)); 5.62 (d, J ¼ 5.1, 2 H, HꢀC(3)); 6.79 (d, J ¼ 8.1, 4 arom. H); 6.93 (d, J ¼ 7.8, 4 arom. H);
7.00 (d, J ¼ 8.1, 4 arom. H); 7.18 (dd, J ¼ 8.7, 1.8, 2 arom. H); 7.22 – 7.28 (m, 6 arom. H); 7.30 (d, J ¼ 1.8, 2
arom. H); 7.58 (d, J ¼ 8.7, 2 arom. H). 13C-NMR: 21.2; 68.0; 72.6; 83.0; 114.2; 122.2; 127.0; 128.0; 129.0;
129.1; 129.5; 130.1; 132.3; 132.5; 134.1; 138.1; 139.1; 149.7; 200.7. Anal. calc. for C45H36Cl4N2O3: C 68.02, H
4.57, N 3.53; found: C 67.97, H 4.52, N 3.58.
meso-Bis[3-(2,4-dichlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl]methanone (¼ [(3R,
4S,5S)-3-(2,4-Dichlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl][(3S,4R,5R)-3-(2,4-di-

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Helvetica Chimica Acta – Vol. 95 (2012)
chlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl]methanone; 4f). Colorless solid. M.p.
1
1788. IR: 2930 (arom. H), 1714 (C¼O). H-NMR: 3.45 (dd, J ¼ 9.0, 5.1, 2 H); 3.82 (s, 2 MeO); 4.91 (d,
J ¼ 9.0, 2 H); 5.61 (d, J ¼ 5.1, 2 H); 6.71 (d, J ¼ 8.7, 4 H); 6.82 (d, J ¼ 8.7, 4 H); 6.91 – 6.98 (m, 6 arom. H);
7.20 (dd, J ¼ 8.7, 2.1, 2 arom. H); 7.23 – 7.28 (m, 4 arom. H); 7.31 (d, J ¼ 2.1, 2 arom. H); 7.61 (d, J ¼ 8.7,
2 H). 13C-NMR: 55.3; 68.0; 72.4; 82.9; 114.0; 114.1; 122.1; 126.8; 128.0; 128.4; 128.9; 129.1; 129.9; 132.4;
134.0; 138.0; 149.6; 160.1; 200.8. MS: 823.13056 ([M ꢀ 1]; calc. 823.13783). Anal. calc. for C45H36Cl4N2O5:
C 65.39, H 4.39, N 3.39; found: C 65.35, H 4.36, N 3.42.
(ꢁ)-rel-(2E)-1-[(3R,4S,5S)-3-(4-Chlorophenyl)-2,5-diphenylisoxazolidin-4-yl]-3-phenylprop-2-en-
1-one (5a): Colorless solid. M.p. 1728. IR: 2931 (arom. H), 1687 (C¼O). 1H-NMR: 4.03 (dd, J ¼ 9.3, 6.9,
1 H); 5.29 (d, J ¼ 9.3, 1 H); 5.36 (d, J ¼ 6.9, 1 H); 6.35 (d, J ¼ 16.2, 1 H); 6.86 (d, J ¼ 8.4, 2 arom. H); 6.95
(d, J ¼ 8.4, 2 arom. H); 7.03 (t, J ¼ 6.9, 3 arom. H); 7.13 – 7.28 (m, 6 arom. H); 7.33 – 7.45 (m, 7 arom. H).
13C-NMR: 72.6; 73.1; 83.9; 114.5; 124.9; 125.3; 126.9; 127.7; 127.8; 128.1; 128.9; 129.1; 129.3; 129.8; 130.4;
130.9; 134.7; 139.2; 140.3; 145.1; 151.1; 194.6. Anal. calc. for C30H24ClNO2: C 77.33, H 5.19, N 3.01; found:
C 77.29, H 5.16, N 3.06.
(ꢁ)-rel-(2E)-1-[(3R,4S,5S)-3-(4-Chlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]-3-
(4-methylphenyl)prop-2-en-1-one (5b): Colorless solid. M.p. 1858. IR: 2930 (arom. H), 1686 (C¼O).
1H-NMR: 2.28 (s, Me); 2.33 (s, Me); 4.01 (dd, J ¼ 9.3, 7.2, 1 H); 5.25 (d, J ¼ 9.3, 1 H); 5.36 (d, J ¼ 7.2, 1 H);
6.32 (d, J ¼ 15.9, 1 H); 6.83 (d, J ¼ 8.1, 2 arom. H); 6.98 – 7.09 (m, 5 arom. H); 7.17 – 7.24 (m, 7 arom. H);
7.34 (d, J ¼ 8.1, 2 arom. H); 7.49 (d, J ¼ 8.1, 2 arom. H). 13C-NMR: 21.1; 21.2; 72.5; 73.1; 83.9; 114.0; 124.0;
124.4; 127.0; 128.2; 128.5; 128.9; 129.1; 129.4; 129.5; 129.9; 130.0; 130.9; 133.3; 138.8; 140.5; 145.1; 151.2;
194.6. Anal. calc. for C32H28ClNO2: C 77.80, H 5.71, N 2.84; found: C 77.76, H 5.68, N 2.88.
(ꢁ)-rel-(2E)-1-[(3R,4S,5S)-3-(4-Chlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-yl]-3-
(4-methoxyphenyl)prop-2-en-1-one (5c): Colorless solid. M.p. 1788. IR: 2930 (arom. H), 1687 (C¼O).
1H-NMR: 3.79 (s, MeO); 3.85 (s, MeO); 3.97 (dd, J ¼ 9.3, 7.2, 1 H); 5.22 (d, J ¼ 9.3, 1 H); 5.37 (d, J ¼ 7.2,
1 H); 6.25 (d, J ¼ 16.2, 1 H); 6.81 (d, J ¼ 8.7, 2 arom. H); 6.96 – 7.09 (m, 5 arom. H); 7.13 (d, J ¼ 6.9, 2
arom. H); 7.19 (d, J ¼ 6.9, 2 arom. H); 7.25 – 7.30 (m, 2 arom. H); 7.38 (t, J ¼ 8.7, 3 arom. H); 7.52 (d, J ¼ 8.7,
2 arom. H). 13C-NMR: 55.2 (2 C); 72.4; 73.1; 83.9; 113.9; 114.3 (2 C); 122.7; 123.4; 127.7; 128.5; 128.6;
128.9; 129.0; 129.9; 130.2; 133.3; 140.6; 144.9; 151.5; 160.1; 161.4; 194.5. Anal. calc. for C32H28ClNO4: C
73.07, H 5.37, N 2.66; found: C 73.04, H 5.33, N 2.70.
(ꢁ)-rel-(2E)-1-[(3R,4S,5S)-3-(2,4-Dichlorophenyl)-2,5-diphenylisoxazolidin-4-yl]-3-phenylprop-2-
1
en-1-one (5d): Colorless solid. M.p. 1788. IR: 2932 (arom. H), 1687 (C¼O). H-NMR: 3.92 (dd, J ¼ 8.7,
4.2, 1 H); 5.22 (d, J ¼ 8.7, 1 H); 5.84 (d, J ¼ 4.2, 1 H); 6.49 (d, J ¼ 15.9, 1 H); 7.06 (d, J ¼ 8.1, 2 arom. H);
7.13 (d, J ¼ 8.1, 2 arom. H); 7.18 – 7.25 (m, 4 arom. H); 7.29 – 7.46 (m, 10 arom. H); 8.03 (d, J ¼ 9.0, 1 arom.
H). 13C-NMR: 70.1; 72.0; 85.0; 113.9; 121.0; 122.3; 126.5; 127.6; 128.3; 128.6; 128.7; 128.9; 129.2; 129.5;
129.6; 130.0; 130.8; 131.8; 133.9; 136.4; 138.8; 145.2; 150.2; 194.9. Anal. calc. for C30H23Cl2NO2: C 72.00,
H 4.63, N 2.80; found: C 71.97, H 4.60, N 2.84.
(ꢁ)-rel-(2E)-1-[(3R,4S,5S)-3-(2,4-Dichlorophenyl)-5-(4-methylphenyl)-2-phenylisoxazolidin-4-yl]-
3-(4-methylphenyl)prop-2-en-1-one (5e): Colorless solid. M.p. 1888. IR: 2927 (arom. H), 1686 (C¼O).
1H-NMR: 2.26 (s, 3 H); 2.30 (s, 3 H); 3.90 (dd, J ¼ 8.7, 4.5, 1 H); 5.20 (d, J ¼ 8.7, 1 H); 5.86 (d, J ¼ 4.5,
1 H); 6.44 (d, J ¼ 15.9, 1 H); 6.80 (d, J ¼ 8.4, 2 arom. H); 6.97 (d, J ¼ 8.4, 2 arom. H); 7.02 – 7.14 (m, 4
arom. H); 7.19 – 7.32 (m, 5 arom. H); 7.34 (d, J ¼ 1.8, 1 arom. H); 7.45 (d, J ¼ 7.8, 2 arom. H); 8.02 (d, J ¼
9.0, 1 arom. H). 13C-NMR: 21.1; 21.3; 69.9; 71.8; 84.9; 113.9; 121.5; 123.7; 126.4; 126.8; 127.6; 128.0; 128.9;
129.1; 129.2; 129.3; 129.5; 132.6; 133.2; 133.6; 138.7; 138.9; 141.3; 145.1; 150.2; 194.8. Anal. calc. for
C32H27Cl2NO2: C 72.73, H 5.15, N 2.65; found: C 72.70, H 5.11, N 2.68.
(ꢁ)-rel-(2E)-1-[(3R,4S,5S)-3-(2,4-Dichlorophenyl)-5-(4-methoxyphenyl)-2-phenylisoxazolidin-4-
yl]-3-(4-methoxyphenyl)prop-2-en-1-one (5f): Colorless solid. M.p. 1788. IR: 2931 (arom. H), 1684
1
(C¼O). H-NMR: 3.79 (s, MeO, 6 H); 3.86 (dd, J ¼ 8.7, 4.5, 1 H); 5.16 (d, J ¼ 8.7, 1 H); 5.85 (d, J ¼ 4.5,
1 H); 6.36 (d, J ¼ 16.2, 1 H); 6.81 (d, J ¼ 8.7, 2 arom. H); 6.88 (d, J ¼ 8.7, 2 arom. H); 6.96 – 7.02 (m, 2 arom.
H); 7.08 – 7.17 (m, 4 arom. H); 7.21 – 7.40 (m, 6 arom. H); 8.02 (d, J ¼ 9.0, 1 arom. H). 13C-NMR: 55.3
(2C); 70.1; 71.9; 84.9; 113.9; 114.4 (2 C); 121.8; 122.6; 126.7; 127.8; 128.3; 128.7; 129.2; 129.3; 129.6; 130.2;
132.9; 133.8; 139.1; 144.9; 150.4; 160.2; 161.9; 194.8. Anal. calc. for C32H27Cl2NO4: C 68.58, H 4.86, N 2.50;
found: C 68.54, H 4.83, N 2.55.

Helvetica Chimica Acta – Vol. 95 (2012)
183
Crystallographic Investigations1). Single crystals for crystallographic studies were prepared in a
AcOEt/CH2Cl2. Crystallographic data for compounds 3c, 3f, and 4f are given in Table 4.
Table 4. Crystallographic Data for 3c, 3f, and 4f
3f
3c
4f
Empirical formula
Mr
C45H36Cl4N2O5
826.56
C45H38Cl2N2O5
757.67
C45H36Cl4N2O5
826.56
Temperature [K]
293(2)
295(2)
293(2)
Wavelength [ꢃ]
0.71073
0.71073
0.71073
Crystal system
Space group
monoclinic
P2 1/n
monoclinic
P2 1/n
triclinic
P1
¯
Unit cell dimensions:
a [ꢃ]
b [ꢃ]
c [ꢃ]
a [8]
b [8]
g [8]
V [ꢃ3]
17.857(5)
10.882(5)
21.663(5)
90.000(5)
118.364(5)
90.000(5)
3995(2)
4
14.7972(4)
12.3197(4)
21.7046(6)
90.00
96.314(2)
90.00
3932.7(2)
4
1.280
10.919(5)
11.831(5)
16.135(5)
78.632(5)
81.595(5)
80.473(5)
2001.3(14)
2
1.372
0.345
856
0.4 ꢂ 0.4 ꢂ 0.15
2.78 – 25.00
ꢀ 12 ꢃ h ꢃ 12,
ꢀ 14 ꢃ k ꢃ 14,
ꢀ 19 ꢃ l ꢃ 19
22935
Z
Density (calc.) [Mg/m3]
Absorption coefficient [mmꢀ1
F(000)
]
0.346
1712
0.213
1584
Crystal size [mm3]
0.4 ꢂ 0.4 ꢂ 0.15
2.72 – 25.00
ꢀ 21 ꢃ h ꢃ 21,
ꢀ 7 ꢃ k ꢃ 12,
ꢀ 17 ꢃ l ꢃ 25
17018
0.28 ꢂ 0.19 ꢂ 0.15
1.90 – 24.31
ꢀ 17 ꢃ h ꢃ 17,
ꢀ 14 ꢃ k ꢃ 14,
ꢀ 25 ꢃ l ꢃ 25
74589
q Range for data collection [8]
Index ranges
Reflections collected
Independent reflections
Completeness to q ¼ 60.008
Max. and min. transmission
Data, restraints, parameters
Goodness-of-fit on F2
7021 (Rint ¼ 0.0475) 6390 (Rint ¼ 0.0335) 7038 (Rint ¼ 0.0385)
99.8%
99.8%
99.9%
1.00000; 0.69497
7021, 0, 507
0.840
0.97; 0.95
6390, 0, 487
1.019
1.00000; 0.71113
7038, 0, 507
0.995
Final R indices (I > 2s(I))
R1 ¼ 0.0505,
wR2 ¼ 0.1322
R1 ¼ 0.0983,
wR2 ¼ 0.1738
0.189; ꢀ 0.290
R1 ¼ 0.0455,
wR2 ¼ 0.1130
R1 ¼ 0.0684,
wR2 ¼ 0.1305
0.272; ꢀ 0.378
R1 ¼ 0.0465,
wR2 ¼ 0.1342
R1 ¼ 0.0671,
wR2 ¼ 0.1508
0.219; ꢀ 0.342
R Indices (all data)
Largest diff. peak and hole [e · ꢃꢀ3
]
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Helvetica Chimica Acta – Vol. 95 (2012)
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Received June 22, 2011