1,3-Dipolar cycloaddition reaction of nitrone ?6-(arene)chromium tricarbonyl complexes with styrene and ?6-(styrene)chromium tricarbonyl

Article abstract of DOI:10.1007/s11172-013-0197-8

The products of 1,3-dipolar cycloaddition of the nitrone-type η6-(arene)chromium tri- carbonyl complexes (CO)3CrC6H5CH=N+(O-)R, where R = Me, Ph, But, with styrene and η6-(styrene)chromium tricarbonyl were obtained and characterized by a combination of physi- cochemical methods. This type of reactions proceeded with very high regio- and stereoselectiv- ity to exclusively form cis-2,3,5-tri-substituted isoxazolidines.

Full text of DOI:10.1007/s11172-013-0197-8

Russian Chemical Bulletin, International Edition, Vol. 62, No. 6, pp. 1382—1387, June, 2013
1382
1,3ꢀDipolar cycloaddition reaction
of nitrone 6ꢀ(arene)chromium tricarbonyl complexes with styrene
and 6ꢀ(styrene)chromium tricarbonyl
A. N. Artemov, E. V. Sazonova, and N. Yu. Zarovkina
N. I. Lobachevsky State University of Nizhny Novgorod,
23 korp. 5 prosp. Gagarina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 465 8162. Eꢀmail: zarovkinan@mail.ru
6
The products of 1,3ꢀdipolar cycloaddition of the nitroneꢀtype  ꢀ(arene)chromium triꢀ
carbonyl complexes (CO)3CrC6H5CH=N+(O–)R, where R = Me, Ph, But, with styrene and
6
 ꢀ(styrene)chromium tricarbonyl were obtained and characterized by a combination of physiꢀ
cochemical methods. This type of reactions proceeded with very high regioꢀ and stereoselectivꢀ
ity to exclusively form cisꢀ2,3,5ꢀtriꢀsubstituted isoxazolidines.
6
Key words: nitrone,  ꢀ(arene)chromium tricarbonyl, isoxazolidine, 1,3ꢀdipolar cycloaddition.
Lately, 6ꢀ(arene)chromium tricarbonyl complexes beꢀ
1a—c and 6ꢀ(styrene)chromium tricarbonyl11 (2a), leadꢀ
ing to the formation of isoxazolidines 3a—c, were characꢀ
terized by higher stereoselectivity as compared to the reꢀ
actions in which both components were noncoordinated
compounds (the reaction of nitrones 1a—c and styrene
(2b) with the formation of products 3d—f (Scheme 1,
Table 1)). In this case, all the products of this reacꢀ
tions (3a—f) were exclusively C(5)ꢀsubstituted derivatives.
We suggested that the introduction of the chromium triꢀ
carbonyl groups in both the dipole and the dipolarophile
would considerably influence the regioꢀ and stereoselecꢀ
tivity of 1,3ꢀdipolar cycloaddition.
To sum up, we carried out detailed studies of the reacꢀ
tions of complexed nitrones with styrene and its derivaꢀ
tives in order to prepare a number of new individual isoxꢀ
azolidine derivatives containing chromium tricarbonyl
groups and find the influence of the Cr(CO)3 group on the
selectivity of the cycloaddition process and the structure
of the products formed.
came important agents in selective organic synthesis.1—4
A pronounced electronꢀwithdrawing character of the meꢀ
tallic fragment imposes on them the reactivity unusual for
arenes: they add nucleophiles to the arene ring and faciliꢀ
tate nucleophilic addition at ꢀbenzyl position. Besides,
the bulkiness of the chromium tricarbonyl group provides
an efficient shielding of one of the arene ring sides, that
can be widely used in stereoselective synthesis.
Cycloaddition is one of the fields where arenechromꢀ
ium tricarbonyl complexes can fully exhibit their unique
abilities. 1,3ꢀDipolar cycloaddition of nitrones to funcꢀ
tional alkenes is well known as very convenient and effiꢀ
cient method for the assembling heterocyclic rings.5—7
The reaction of nitrones with different dipolarophiles is
not always regioꢀ and stereoselective, leading in most casꢀ
es to the formation of a mixture of products, the ratio of
which depends on the steric and electronic properties of
reacting compounds.
Since the reaction can result in the formation of regioꢀ
and stereoisomers, a lot of undertaken attempts were diꢀ
rected on the development of efficient methods for the
preparation of individual products. It was found5 that the
reactions of nitrones with electronꢀrich dipolarophiles were
fairly selective, leading, as a rule, to C(5)ꢀisomeric isoxꢀ
azolidines. This regioselectivity does not operate only in
the case of the electronꢀpoor compounds, i.e., dipolaroꢀ
philes containing strong electronꢀwithdrawing groups,
such as —COOR, —CHO, —CN, or —NO2. When elecꢀ
tronꢀdonating substituents are present, C(5)ꢀsubstituted
isoxazolidines are formed as exclusive or major products.
In our preceding work,8 we have shown that the 1,3ꢀdiꢀ
polar cycloaddition reactions between free nitrones3,9,10
Results and Discussion
A series of coordinated nitrones 1d—f were used as
dipoles in the reactions under study. Cꢀ(6ꢀPhenylchromꢀ
ium tricarbonyl)ꢀNꢀmethylnitrone (1d) was synthesized
according to the method described earlier3 from 6ꢀ(benzꢀ
aldehyde)chromium tricarbonyl12,13 and methylhydroxylꢀ
amine hydrochloride. This nitrone was found to have transꢀ
configuration.3 Nitrones 1e and 1f containing the phenyl
and the tertꢀbutyl group, respectively, at the nitrogen atom
were synthesized using the known procedure (Scheme 2).
6ꢀ(Styrene)chromium tricarbonyl (2a) and styrene
(2b) served as the dipolarophiles in the 1,3ꢀdipolar cycloꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1382—1387, June, 2013.
1066ꢀ5285/13/6206ꢀ1382 © 2013 Springer Science+Business Media, Inc.

6ꢀ(Arene)chromium tricarbonyl cycloadditions
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
1383
Scheme 1
1: R1 = Me, R2 = Ph (a); R1 = Ph, R2 = Ph (b);
2: R3 = Ph[Cr(CO)3] (a);
R3 = Ph (b)
R
1 = But, R2 = Ph (c); R1 = Me, R2 = Ph[Cr(CO)3] (d);
R1 = Ph, R2 = Ph[Cr(CO)3] (e); R1 = But, R2 = Ph[Cr(CO)3] (f)
3
a
b
c
d
e
f
R1
Me
Ph
R2
Ph
Ph
Ph
Ph
Ph
Ph
R3
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph
3
g
h
i
j
k
l
R1
Me
Ph
R2
R3
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
But
Me
Ph
But
Me
Ph
Ph
Ph
Ph
Ph
But
But
Scheme 2
addition reactions. The reactions were carried out by heatꢀ
ing of nitrone arenechromium tricarbonyl complexes (1d—f)
with alkenes (2a, b) in sealed glass tubes at 80—90 C
in vacuo during 6—40 h. The products with remained
Cr(CO)3 group 3g—l (see Table 1) were characterized by
UV, IR, and NMR spectroscopy.
All the compounds obtained are yellow crystalline subꢀ
stances, relatively stable in air. Their main physicochemiꢀ
R1 = Me, Ph, But
Table 1. Ratio of cisꢀ and transꢀisomers of isoxazolidines 3a—l in
the 1,3ꢀdipolar cycloaddition reactions
cal properties and spectroscopic characteristics are given
in Table 2.
Nitrone
(dipole)
Dipolarophile
Product
Ratio
cis : trans
The 1H NMR spectra of adducts 3j—l, obtained by the
reaction of coordinated nitrones 1d—f with styrene (2b),
show that they are exclusive cisꢀ2,3,5ꢀtriꢀsubstituted isoxꢀ
azolidines. Thus, for example, the product of the 1,3ꢀdiꢀ
polar cycloaddition of Cꢀ(6ꢀphenylchromium tricarbonꢀ
yl)ꢀNꢀphenylnitrone (1e) and styrene (2b), i.e., 6ꢀ(3ꢀpheꢀ
nylchromium tricarbonyl)ꢀ2,5ꢀdiphenylisoxazolidine (3k),
as well as analogous cisꢀisoxazolidine 3j containing the
methyl substituent at the nitrogen atom,3 has two separate
1а
1b
1c
1а
1b
1c
1d
1e
1f
2а
2a
2a
2b
2b
2b
2а
2a
2a
2b
2b
2b
3a
3b
3c
3d
3f
3e
3g
3h
3i
183 : 17a
100 : 0a
100 : 0a
167 : 33b
190 : 10b
100 : 0
100 : 0
100 : 0
100 : 0
100 : 0c
100 : 0
1
signals from the protons at atom C(4) in the H NMR
1d
1e
1f
3j
3k
3l
spectrum, while the transꢀconfiguration of this compound
should have led to the coalescence (approach) of the sigꢀ
nals for the protons at the quaternary carbon atom, that is
clearly observed in the case of noncoordinated compounds6
(Table 3). Such shapes of the spectra are due to the fact
that in the transꢀisomers, the hydrogen atoms at atom
100 : 0
aData of the work.8
bData of the work.6
cData of the work.3

1384
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
Artemov et al.
Table 2. Some characteristics* of isoxazolidines 3g—l
cisꢀIsoxazolidine
R1
R2
R3
M.p./C
Yield (%)
(CO)/cm–1
3g
3h
3i
3j
3k
3l
Me
Ph
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
155—156
132—133
136—137
Oil
121 —122
40—41
20
38
36
—
62
30
1967, 1880
1964, 1875
1964, 1875
1970, 1890
1962, 1886
1965, 1884
But
Me
Ph
Ph
Ph
Ph
But
* The data for isoxazolidine cisꢀ3j are taken from the work.3
C(4) are equidistant from the protons at atoms C(3) and
C(5) and, consequently, equally interact with them. In
the case of cisꢀcomplexes, this interaction of one of the
protons at atom C(4) predominates because of its proximꢀ
ity to the protons at atoms C(3) and C(5), that finally
leads to the greater difference in the chemical shift values.
The reaction of coordinated nitrones 1d—f with
6ꢀ(styrene)chromium tricarbonyl (2a) in toluene at 80 C
also leads to the selective preparation of 2,3,5ꢀtriꢀsubstiꢀ
tuted isoxazolidines with the cisꢀstructure (3g—i). The
NMR spectroscopic and mass spectrometric data indicate
the presence in the molecules of two Cr(CO)3 groups.
Xꢀray diffraction analysis of complex 3h confirms the
cisꢀstructure of the compound and shows that the phenylꢀ
chromium tricarbonyl groups are on the same side of the
plane of the isoxazolidine ring (Fig. 1, Table 4).
It is possible that the formation of the transition state
A in the reaction of nitrones 1d—f with styrene (2b) is
more preferable as compared to the complex B because of
the possibility of the —ꢀinteraction of the dipolarophile
benzene ring with the coordinated ring of the nitrone. The
arising of the stable enough charge transfer complex beꢀ
tween benzene and 6ꢀ(benzene)chromium tricarbonyl has
been reported earlier.16 The electronꢀwithdrawing effect
of the chromium tricarbonyl group in the dipole signifiꢀ
cantly stabilizes the —ꢀinteraction between the arene
rings (the transition step A), whereas complex B has no
such a stabilizing influence. Similarly, the reactions of
complexed nitrones 1d—f with 6ꢀ(styrene)chromium triꢀ
carbonyl (2a) are also very selective and form products
3g—i with the cisꢀstructure, possibly due to the existing
possibility of stabilization of state C.
The chemical shift of the signals for two protons at
atom C(4) of compound 3h are different (see Table 3),
that confirms the cisꢀstructure of the complex. Similar
results are also observed in the case of isoxazolidines cisꢀ3g
and cisꢀ3i (see Experimental).
The exclusive formation of one of the possible regioiꢀ
somers in the reactions of complexed nitrones 1d—f with
different dipolarophiles (2a, 2b) can be explained in terms
of both the frontier orbital theory and the charge distribuꢀ
tion in the reacting molecules theory.14,15 The mechanism
of the high stereoselectivity is not yet completely clear.
However, it can be suggested that the reason is the stabiliꢀ
zation of the transition states due to the stacking interacꢀ
tions (Scheme 3).
O(5A)
C(25A)
O(7A)
C(27A)
O(6A)
N(1A)
C(12A)
C(19A)
C(11A)
Cr(2A)
C(26A)
C(13A)
O(4A)
C(10A)
C(9A)
Table 3. Chemical shifts and shapes of 1H NMR signals of
the protons at carbon atom C(4) of isoxazolidines 3b,e,h,k*
O(2A)
C(2A)
Cr(1A)
C(1A)
Compound

H
cisꢀ3b
cisꢀ3e
transꢀ3e
cisꢀ3h
cisꢀ3k
2.37 (td), 3.37 (td)
2.36 (td), 2.88 (td)
2.52—2.68 (м)
2.41 (ddd), 3.40 (ddd)
2.25—2.51 (m), 3.15—3.53 (m)
C(3A)
O(1A)
O(3A)
* The data for compound cisꢀ3b are taken from the work,8
for compounds cisꢀ3e and transꢀ3e, from the work.6
Fig. 1. Molecular structure of complex cisꢀ3h (hydrogen atoms
are not shown).

6ꢀ(Arene)chromium tricarbonyl cycloadditions
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
1385
Table 4. Principal bond distances and bond angles in the structure of complex cisꢀ3h
Bond
d/Å
Angle
/deg
N(1A)—C(12A)
N(1A)—O(4A)
O(4A)—C(10A)
C(10A)—C(11A)
C(11A)—C(12A)
C(9A)—C(10A)
C(12A)—C(19A)
N(1A)—C(13A)
Cr(1A)—C(1A)
Cr(1A)—C(2A)
Cr(1A)—C(3A)
Cr(2A)—C(25A)
Cr(2A)—C(26A)
Cr(2A)—C(27A)
1.474(6)
1.423(5)
1.469(6)
1.523(7)
1.554(7)
1.533(7)
1.514(8)
1.441(7)
1.844(6)
1.852(6)
1.844(6)
1.848(7)
1.844(6)
1.842(6)
O(4A)—N(1A)—C(12A)
N(1A)—O(4A)—C(10A)
O(4A)—C(10A)—C(11A)
C(10A)—C(11A)—C(12A)
N(1A)—C(12A)—C(11A)
C(1A)—Cr(1A)—C(2A)
C(3A)—Cr(1A)—C(1A)
C(3A)—Cr(1A)—C(2A)
C(26A)—Cr(2A)—C(25A)
C(27A)—Cr(2A)—C(25A)
C(27A)—Cr(2A)—C(26A)
105.0(4)
107.2(3)
105.1(4)
104.0(4)
105.2(4)
89.3(2)
88.7(2)
86.9(2)
87.2(3)
91.6(3)
90.4(3)
Scheme 3
R1 = Me, Ph, But
To sum up, the analysis of the cisꢀ and transꢀisomer
ratios of isoxazolidines 3a—l in the 1,3ꢀdipolar cycloaddiꢀ
tion reactions shows that the stereoselectivity of the proꢀ
cess for the complexed nitrones is 100% and, therefore,
higher than in the case when coordinated dipolarophiles
are used:8 the reaction of free nitrone 1a and styrene
(arene)chromium tricarbonyl complex 2a leads to a mixꢀ
ture of isomers in the ratio 83 : 17, while the reaction of
Cꢀ(6ꢀphenylchromium tricarbonyl)ꢀNꢀphenylnitrone (1d)
with styrene (2b) gives cisꢀisoxazolidine 3j as the only
product (see Table 1). In the case of the phenyl and the
tertꢀbutyl substituents at the nitrogen atom of the nitrone
molecule, both reactions, involving the complexed nitrones
and that using the coordinated styrene, proceed with 100%
stereoselectivity.
intramolecular interaction of the Cr(CO)3 group with the
oxygen atom,8,17 complexes 3j—l have only two bands of
such vibrations, that is explained by the impossibility of
the intramolecular contact of the Cr(CO)3 group with the
oxygen atom, since they are remote from each other.
In conclusion, based on the experimental data obꢀ
tained, the following conclusions can be drawn:
— the high regioselectivity still persists in the reaction
of nitrones containing the Cr(CO)3 group at the carbon
atom with styrene and 6ꢀ(styrene)chromium tricarbonyl,
that leads to the exclusive formation of C(5)ꢀsubstituted
products;
— the formed isoxazolidines are cisꢀisomers, that reꢀ
sulted from the stronger —ꢀinteraction of the phenyl
rings in the transition state.
Interesting features were found while analyzing the IR
spectra of the obtained isoxazolidines 3j—l. In contrast to
the C(5)ꢀ(arene)chromium tricarbonyl complexes, which
are characterized by the presence of three bands of the
carbonyl stretching vibrations (CO)8 resulted from the
Experimental
All the solvents were distilled over metallic sodium at atmoꢀ
spheric pressure.18 To remove the stabilizer, styrene (2b) was

1386
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
Artemov et al.
6
washed with 10% aqueous sodium hydroxide and water, dried,
and distilled (b.p. 48—49 C (10 Torr)). NꢀPhenylꢀ and Nꢀtertꢀ
butylhydroxylamines were obtained by the reduction of the corꢀ
responding nitro compounds.9,19 NꢀMethylhydroxylamine hyꢀ
drochloride from SigmaꢀAldrich was used for the synthesis of
CꢀphenylꢀNꢀmethylnitrone (1a). Benzaldehyde and triethyl
orthoformate were purified by distillation at reduced pressure,
the reaction of these compounds led to the formation of benzalꢀ
dehyde diethyl acetal.12 The reaction of benzaldehyde diethyl
3,5ꢀDiꢀ ꢀ(phenylchromium tricarbonyl)ꢀ2ꢀmethylisoxazoliꢀ
dine (cisꢀ3g). The yield was 20%, m.p. 155—156 C. Found (%):
Cr, 19.70. C22H17NO7Cr2. Calculated (%): Cr, 20.35. MS
(MALDI MS), m/z (Irel (%)): 549.6 [M + K]+ (41), 429.1
[M + K – C6H6 – CH3 – H]+ (36), 291.0 [M + K – Cr(CO)3 –
– Ph – CH3]+ (100). IR (KBr), /cm–1: 2356 ((C—H)); 1967,
1880 ((CO)); 1632 ((C—CAr)); 1147, 1099 ((N—O, C—O));
1011 ((C—N)); 660, 633 ((CAr—H)). 1H NMR (400 MHz),
: 2.08 (s, 3 H, CH3N); 2.31 (ddd, 1 H, HC(4), J = 14.4 Hz,
J = 12.8 Hz, J = 7.2 Hz); 3.43 (ddd, 1 H, HC(4), J = 12.8 Hz,
J = 7.6 Hz, J = 7.2 Hz); 3.83 (t, 1 H, HC(3), J = 7.6 Hz); 5.07
(t, 1 H, HC(5), J = 7.5 Hz); 5.64 (m, 10 H, C(3)PhCr, C(5)PhCr).
6
acetal and chromium hexacarbonyl led to  ꢀ(benzaldehyde
diethyl acetal)chromium tricarbonyl, which was hydrolyzed to
6
 ꢀ(benzaldehyde)chromium tricarbonyl.13 C,NꢀDiꢀsubstituted
6
nitrones (1a—f) were obtained by the condensation of the correꢀ
3,5ꢀDiꢀ ꢀ(phenylchromium tricarbonyl)ꢀ2ꢀphenylisoxazolꢀ
sponding hydroxylamine derivatives with benzaldehyde,3,9,10 or
idine (cisꢀ3h). The yield was 38%, m.p. 132—133 C. Found (%):
Cr, 18.03. C27H19NO7Cr2. Calculated (%): Cr, 18.15. MS
(MALDI MS), m/z (Irel (%)): 611.6 [M + K]+ (35), 475.2 [M +
+ K – Cr(CO)3]+ (69), 429.1 [M + K – 2 Ph – CO]+ (57), 340.0
[M + K – 2 Cr(CO)3 + H]+ (38), 301.0 [M – 2 Cr(CO)3]+ (18),
108.0 [Cr(CO)2]+ (100). IR (KBr), /cm–1: 2967, 2928, 2877
((C—H)); 1964, 1875 ((CO); 1643 ((C—CAr)); 1384 ((C—C));
1015 ((C—O)); 660, 632, 533 ((CAr—H)). 1H NMR (200 MHz),
: 2.41 (ddd, 1 H, HC(4), J = 12.9 Hz, J = 8.7 Hz, J = 4.2 Hz);
3.40 (ddd, 1 H, HC(4), J = 12.1 Hz, J = 8.5 Hz, J = 7.8 Hz);
4.82—5.19 (m, 2 H, HC(3), HC(5)); 5.50—5.76 (m, 7 H,
C(3)PhCr, C(5)PhCr); 5.83 (br.d, 1 H, C(3)PhCr/C(5)PhCr,
J = 5.9 Hz); 5.92 (d, 1 H, C(3)PhCr/C(5)PhCr, J = 5.3 Hz);
6.10 (d, 1 H, C(3)PhCr/C(5)PhCr, J = 2.91 Hz); 6.88—7.09
(m, 1 H, PhN); 7.09—7.46 (m, 4 H, PhN).
6
6
with  ꢀ(benzaldehyde)chromium tricarbonyl.3  ꢀ(Styrene)ꢀ
chromium tricarbonyl (2a) was synthesized according to the
method described in the literature.11
The products were isolated and purified by column chromaꢀ
tography on Acros silica gel (0.035—0.070 mm). HPLC was carꢀ
ried out on a Knauer Smartline 5000 chromatograph with
a PDA detector S 2600, a Diasferꢀ110ꢀC16, 5 m, 4.6×250 mm
column, eluent acetonitrile—water (84 : 16). UV spectra of eluꢀ
ates were recorded in the range 200—500 nm. IR spectra (susꢀ
pension with KBr) were recorded on a Infralyum FTꢀ801 specꢀ
trometer in the range 480—4600 cm–1 1H NMR spectra were
.
recorded on Bruker DPX 200 and Bruker Avance DPX 400
spectrometers (200 and 400 MHz, respectively), solvent acetꢀ
oneꢀd6. Mass spectrometric studies were carried out on a Bruker
Microflex LT instrument using timeꢀofꢀflight mass spectroꢀ
metry with the matrixꢀactivated laser desorbtion/ionization
(MALDI MS).
6
3,5ꢀDiꢀ ꢀ(phenylchromium tricarbonyl)ꢀ2ꢀtertꢀbutylisoxazolꢀ
idine (cisꢀ3i). The yield was 36%, m.p. 136—137 C. Found (%):
Cr, 18.60. C25H23NO7Cr2. Calculated (%): Cr, 18.80. MS
(MALDI MS), m/z (Irel (%)): 591.8 [M + K]+ (100), 507.9
[M – But]+ (30). IR (KBr), /cm–1: 2967, 2928, 2877 ((C—H));
1964, 1875 ((CO); 1643 ((C—CAr)); 1384 ((C–C)); 1015
((C—O)); 660, 632, 533 ((CAr—H)). 1H NMR (200 MHz),
: 1.20 (s, 9 H, ButN); 2.37 (ddd, 1 H, HC(4), J = 12.8 Hz,
J = 6.8 Hz, J = 5.9 Hz); 3.14—3.70 (m, 1 H, HC(4)); 4.51 (dd,
1 H, HC(3), J = 7.3 Hz, J = 7.0 Hz); 4.99 (t, 1 H, HC(5),
J = 7.3 Hz); 5.39—5.73 (m, 7 H, C(3)PhCr, C(5)PhCr); 5.79
(d, 1 H, C(3)PhCr/C(5)PhCr, J = 6.7 Hz); 5.95 (d, 1 H, C(3)PhCr/
C(5)PhCr, J = 7.0 Hz); 6.09 (d, 1 H, C(3)PhCr/C(5)PhCr,
J = 6.6 Hz).
6
Cꢀ( ꢀPhenylchromium tricarbonyl)ꢀNꢀphenylnitrone (1e).
The yield was 75%, m.p. 118—119 C. Found (%): C, 58.06;
H, 3.54; N, 4.20; Cr, 15.71. C16H11NO4Cr. Calculated (%):
C, 57.67; H, 3.33; N, 4.20; Cr, 15.60. IR (KBr), /cm–1: 2956,
2924, 2867 ((C—H)); 1979, 1891, 1866 ((CO)); 1644
(C—CAr); 1547((C=N)); 1197 ((Ph—N)); 1068 ((N—O));
887, 771, 689 ((CAr—H)). 1H NMR (200 MHz), : 5.56—5.90
(m, 3 H, m,pꢀPhCr); 6.88 (d, 2 H, oꢀPhCr, J= 6.3 Hz); 7.54 (m, 3 H,
o,pꢀPh); 7.72—7.98 (m, 2 H, mꢀPh); 8.18 (s, 1 H, =C—H).
6
Cꢀ( ꢀPhenylchromium tricarbonyl)ꢀNꢀtertꢀbutylnitrone (1f).
The yield was 90%. m.p. 102—103 C. Found (%): C, 54.03;
H, 4.81; N, 4.50; Cr, 16.43. C14H15NO4Cr. Calculated (%):
C, 53.68; H, 4.83; N, 4.47; Cr, 16.60. IR (KBr), /cm–1: 2963,
2922, 2850 ((C—H)); 1976, 1893, 1871 ((CO)); 1650 (C—CAr);
1557((C=N)); 1118 ((N—O)); 803, 680, 628 ((CAr—H)).
1H NMR (200 MHz), : 1.54 (s, 9 H, But—N); 5.68 (m, 3 H,
p,mꢀPhCr); 6.71 (dd, 2 H, oꢀPhCr, J = 6.5 Hz, J = 1.7 Hz); 7.59
(s, 1 H, =C—H).
6
Synthesis of  ꢀ(3ꢀphenylchromium tricarbonyl)ꢀsubstituted
isoxazolidines 3j—l (general procedure). The corresponding
nitrone 1d—f (0.65 mmol) and freshly distilled styrene (2b) (3 mL,
0.0261 mol) were placed in a 5ꢀmL glass tube. The tube was
degassed and sealed in vacuo. The reaction mixture was heated
for 6 h at 90 C. The tube was unsealed, the solution in the tube
was diluted with isopropyl alcohol to make the formed polystyꢀ
rene to precipitate. Then, the solution was decanted, toluene
and isopropyl alcohol were evaporated in vacuo. Column chroꢀ
matography was used to isolate the reaction products from a dense
residue, which were recrystallized from a mixture of hexꢀ
ane—ethyl acetate (15 : 2) to obtain the target products.
 ꢀ(3ꢀPhenylchromium tricarbonyl)ꢀ2,5ꢀdiphenylisoxazolidine
(cisꢀ3k). The yield was 62%, m.p. 121—122 C. Found (%):
C, 65.73; H, 4.21; N, 3.06; Cr, 12.01. C24H19NO4Cr. Calculatꢀ
ed (%): C, 65.90; H, 4.38; N, 3.20; Cr, 11.89. IR (KBr), /cm–1
2920, 2954, 2853 ((C—H)); 1962, 1886 ((CO)); 1594
((C—CAr)); 1488 ((C—C)); 1230, 1110 (N—O, C—O)); 1031
((C—N)); 762, 657, 631 ((CAr—H)). 1H NMR (400 MHz),
6
Synthesis of 3,5ꢀdiꢀ ꢀ(phenylchromium tricarbonyl)ꢀsubstiꢀ
tuted isoxazolidines 3g—i (general procedure). The correspondꢀ
6
ing nitrone 1d—f (0.8 mmol),  ꢀ(styrene)chromium tricarbonyl
(2a) (0.8 mmol), and toluene (3 mL) were placed in a 5ꢀmL glass
tube. The tube was degassed and sealed in vacuo. The reaction
mixture was heated for 40 h at 80 C. The tube was unsealed, the
content was filtered through a Shotte filter, the precipitate was
washed on the filter with toluene, and the solvent was evaporatꢀ
ed in vacuo. Column chromatography was used to isolate the
reaction products from a dense residue, which were recrystalꢀ
lized from a mixture of hexane—ethyl acetate (3 : 1) to obtain
the target products.
6
:

6ꢀ(Arene)chromium tricarbonyl cycloadditions
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
1387
: 2.25—2.51 (m, 1 H, HC(4)); 3.15—3.53 (m, 1 H, HC(4)); 5.04
(dd, 1 H, J = 8.7 Hz, J = 5.0 Hz, HC(3)); 5.13—5.33 (m, 1 H,
HC(5)); 5.69 (d, 3 H, m,pꢀC(3)PhCr, J = 3.9 Hz); 5.91 (d, 1 H,
oꢀC(3)PhCr, J = 5.5 Hz); 6.12 (d, 1 H, oꢀC(3)PhCr, J = 3.6 Hz);
6.99 (t, 1 H, pꢀPhN, J = 7.0 Hz); 7.11—7.58 (m, 9 H, PhN,
PhC(5)).
2. C. Mukai, I. J. Kim, W. J. Cho, M. Hanaoka, Tetrahedron
Lett., 1990, 31, 6893.
3. C. Mukai, I. J Kim., W. J. Cho, M. Kido, M. Hanaoka,
J. Chem. Soc. Perkin Trans., 1, 1993, 2495.
4. C. Baldoli, S. Maiorana, E. Licandro, G. Zinzalla, M. Lanꢀ
franchi, A. Tiripicchio, Tetrahedron Asymmetry, 2001,
12, 2159.
6
 ꢀ(3ꢀPhenylchromium tricarbonyl)ꢀ2ꢀtertꢀbutylꢀ5ꢀphenylꢀ
isoxazolidine (cisꢀ3l). The yield was 30%, m.p. 40—41 C.
Found (%): C, 63.05; H, 5.69; N, 3.17; Cr, 12.63. C22H23NO4Cr.
Calculated (%): C, 63.30; H, 5.55; N, 3.35; Cr, 12.46. IR (KBr),
/cm–1: 2960, 2924, 2853 ((C—H)); 1965, 1884 ((CO)); 1643
((C—CAr)); 1454 ((C—C)); 1261, 1138 (N—O, C—O)); 1023
((C—N)); 803, 663, 632 ((CAr—H)). 1H NMR (400 MHz),
: 1.21 (s, 9 H, ButN); 2.18—2.52 (m, 1 H, HC(4)); 3.32 (ddd, 1 H,
J = 12.6 Hz, J =7.4 Hz, J = 6.0 Hz, HC(4)); 4.53 (dd, 1 H,
HC(3), J = 8.3 Hz, J = 6.2 Hz); 5.26 (t, 1 H, HC(5), J = 7.6 Hz);
5.51 (dd, 2 H, mꢀC(3)PhCr, J = 9.6 Hz, J = 5.9 Hz); 5.66 (t, 1 H,
pꢀC(3)PhCr, J = 6.3 Hz); 5.91 (d, 1 H, oꢀC(3)PhCr, J = 6.4 Hz);
6.10 (d, 1 H, oꢀC(3)PhCr, J = 6.9 Hz); 7.04—7.66 (m, 5 H,
C(5)Ph).
5. P. N. Confalone, E. M. Huie, Org. React., 1988, 36, 1.
6. R. Huisgen, R. Grashey, H. Hauk, H. Seidl, Chem. Ber.,
1968, 101, 2548.
7. R. Huisgen, H. Hauk, R. Grashey, H. Seidl, Chem. Ber.,
1968, 101, 2568.
8. A. N. Artemov, E. V. Sazonova, E. A. Mavrina, N. Yu.
Zarovkina, Russ. Chem. Bull. (Int. Ed.), 2012, 61, 2076 [Izv.
Akad. Nauk, Ser. Khim., 2012, 11, 2059].
9. K. Heusler, P. Wieland, Ch. Meystre, Org. Synth., 1973,
5, 1124.
10. W. D. Emmons, J. Am. Chem. Soc., 1957, 79, 5739.
11. M. D. Raush, G. A. Moser, E. S. Zaiko, A. L. Lipman,
J. Organomet. Chem., 1970, 23, 185.
Xꢀray diffraction studies of complex cisꢀ3h. Crystals
(C27H19NO7Cr2, M = 573.43), triclinic, space group Рꢀ1, at 100 К:
a = 7.9506(9), b = 13.9545(16), c = 22.393(3) Å,  = 80.218(2),
12. H. W. Post, J. Org. Chem., 1940, 5, 244.
13. G. Drehfahl, H. H. Horhold, K. Kuhne, Chem. Ber., 1965,
98, 1826.
14. K. N. Houk, J. Am. Chem. Soc., 1972, 94, 8953.
15. K. N. Houk, A. Bimanand, D. Mukherjee, J. Sims, Y.ꢀM.
Chang, D. C. Kaufman, N. L. Domelsmith, Heterocycles,
1977, 7, 293.
3
 = 83.792(2),  = 89.219(2), V = 2433.9(5) Å , Z = 4,
dcalc = 1.565 g cm–3,  = 9.42 cm–1, were obtained by crystalliꢀ
zation from a mixture of hexane—ethyl acetate (10 : 1). Intensiꢀ
ties of 20067 reflections (9429 independent reflections,
Rint = 0.0532) were measured on a Smart Apex diffractometer
(graphite monochromator, (MoꢀK) = 0.71073 Å, temperature
100 К). Allowance for absorption was made using the SADABS
program.20 The structure was solved by direct method and reꢀ
fined by the fullꢀmatrix least squares method on F2hkl with anisoꢀ
tropic thermal parameters for all the nonhydrogen atoms. The
hydrogen atoms were placed in the geometrically calculated
positions and refined using the riding model. The final divergent facꢀ
16. W. J. Bland, R. Davis, J. L. A. Durrant, J. Organomet. Chem.,
1982, 234, C20.
17. I. V. Bodrikov, I. I. Grinval´d, A. N. Artemov, L. I. Bazhan,
I. Yu. Kalagaev, Zh. Obshch. Khim., 2010, 80, 24 [Russ.
J. Gen. Chem. (Engl. Transl.), 2010, 80, 20].
18. Organic solvents; Physical Properties and Methods of Purificaꢀ
tion, Intersci. Publ. Inc., New York—London, 1955, 552 pp.
19. OrganischꢀChemische Experimentierkunst, 2 Auflage, Johann
Ambrosius Barth, Leipzig, 1948, 824 S.
tors: R1 = 0.0744 (I > 2(I)), wR2 = 0.1632 (refinement on F2 for
hkl
all the independent reflections). All the calculations were perꢀ
formed on a personal computer using the SHELXTL software.21
20. G. M. Sheldrick, SADABS, 1997, Bruker AXS, Inc., Madiꢀ
son (WI), USA.
21. G. M. Sheldrick, Acta Crystallogr., Sect. A, Found. Crystalꢀ
logr., 2008, 64, 112.
The authors are grateful to G. K. Fukin for performing
the Xꢀray diffraction analysis.
References
1. M. Rosillo, G. Dominguez, J. PerezꢀCastells, Chem. Soc.
Rev., 2007, 36, 1589.
Received February 7, 2013;
in revised form April 24, 2013