Chemistry of unsaturated arenetricarbonylchromium compounds 1. Reaction of (η6-arene)tricarbonylchromium complexes of nitrones with methyl phenylpropiolate

Article abstract of DOI:10.1007/s11172-014-0535-5

The reactions of nitrones of the composition (CO)₃CrC₆H₅CH=N⁺(O^-)R (R = Me, Ph, or Bu^t) with substituted acetylene were studied. The reactions proceed with high regioselectivity and give 4-

Full text of DOI:10.1007/s11172-014-0535-5

Russian Chemical Bulletin, International Edition, Vol. 63, No. 4, pp. 970—975, April, 2014
970
Chemistry of unsaturated arenetricarbonylchromium compounds
1. Reaction of (6ꢀarene)tricarbonylchromium complexes of nitrones
with methyl phenylpropiolate*
N. Yu. Zarovkina,a E. V. Sazonova,a A. N. Artemov,a and G. K. Fukinb
aN. I. Lobachevsky Nizhny Novgorod State University,
23 prosp. Gagarina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 465 8162. Eꢀmail: zarovkinan@mail.ru
bG. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 462 7497. Eꢀmail: gera@iomc.ras.ru
The reactions of nitrones of the composition (CO)3CrC6H5CH=N+(O–)R (R = Me, Ph, or
But) with substituted acetylene were studied. The reactions proceed with high regioselectivity
and give 4ꢀisoxazolines (yields 50—60%). The composition and structures of these products
6
were characterized by physicochemical methods. The reactions also afford ( ꢀbenzaldeꢀ
hyde)tricarbonylchromium, coordinated Schiff bases, and azoxy derivatives as thermal decomꢀ
position products of the starting nitrones. The reactions of uncoordinated nitrones with methyl
phenylpropiolate were also investigated. These reactions produce 4ꢀisoxazolines along with
cyclic substituted isoxazolinones.
6
Key words: nitrone, ( ꢀarene)tricarbonylchromium, isoxazoline, 1,3ꢀdipolar cycloaddition.
In recent years, studies aimed at the synthesis and charꢀ
Results and Discussion
acterization of unsaturated arenetricarbonylchromium
complexes capable of being involved in various heterolytꢀ
ic, radical, and pericyclic reactions1 have received much
attention from researchers in the field of chemistry of
organometallic compounds of transition metals. Pericyclic
reactions are of most interest. In particular, 1,3ꢀdipolar
cycloaddition reactions are widely used in organic chemꢀ
istry as an approach to the design of fiveꢀmembered heteroꢀ
cyclic structures,2—4 which are difficult to synthesize by
other methods.
Earlier, we have shown5,6 that the use of unsaturated
(6ꢀarene)tricarbonylchromium complexes as dipoles in
1,3ꢀdipolar cycloaddition reactions results in the formaꢀ
tion of isoxazolidines in good yields with high regioꢀ and
stereoselectivity. Continuing our studies, we performed
a detailed investigation of reactions of three C,Nꢀdisubstiꢀ
tuted nitrones and their arenetricarbonylchromium comꢀ
plexes with substituted alkyne, viz., methyl phenylpropiꢀ
olate. The resulting 4ꢀisoxazolines are efficient systems
for the synthesis of a large number of various organꢀ
ic derivatives (ꢀamino alcohols, ꢀhydroxy ketones,
and so on).7
We used a series of free8—10 (1a—c) and coordinated
(1d—f) C,Nꢀdisubstituted nitrones having a trans configuꢀ
ration6,9 as dipoles in the reactions under study. Comꢀ
pounds 1d—f were synthesized by the condensation of
(6ꢀbenzaldehyde)tricarbonylchromium11,12 with the corꢀ
responding hydroxylamines. Methyl phenylpropiolate (2),
which was prepared in several steps according to a known
procedure,13 served as a dipolarophile. Due to the presꢀ
ence of the ester group —CO2Me having electronꢀwithꢀ
drawing properties, alkyne is a more reactive dipolaroꢀ
phile compared with unsubstituted acetylenes. Cycloꢀ
addition reactions were carried out in degassed sealed tubes
in DMF or toluene according to Scheme 1.
The purity of 4ꢀisoxazolines 3a—f was tested by HPLC.
The composition and structures of these compounds were
established by UV, IR, and NMR spectroscopy, elemental
analysis, and, in some cases, by Xꢀray diffraction. The
characteristics of the synthesized compounds are given in
the Experimental section.
The reactions of free nitrones 1a—c with dipolaroꢀ
phile 2 afforded the expected 4ꢀisoxazolines 3a—c. The IR
spectra of these compounds show vibrational bands charꢀ
acteristic of the compounds under study (see the Experiꢀ
* According to the materials of the International Conference
"Organometallic and Coordination Chemistry: Fundamental and
Applied Aspects" (September 1—7, 2013, Nizhny Novgorod).
1
mental section). The H NMR spectroscopic data conꢀ
firm the compositions of the synthesized 4ꢀisoxazolines.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 0970—0975, April, 2014.
1066ꢀ5285/14/6304ꢀ0970 © 2014 Springer Science+Business Media, Inc.

(6ꢀArene)tricarbonylchromium 4ꢀisoxazolines
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 4, April, 2014
971
Scheme 1
O(5)
C(18)
C(17)
C(19)
C(12)
C(11)
O(6)
Comꢀ
pound
1, 3
Comꢀ
pound
1,3
O(4)
C(4)
C(9)
R1
R2
R1
R2
C(5)
C(10)
C(8)
a
b
c
Me
Ph
But
Ph
Ph
Ph
d
e
f
Me
Ph
But
Ph[Cr(CO)3]
Ph[Cr(CO)3]
Ph[Cr(CO)3]
N(1)
C(6)
C(7)
C(13)
Cr(1)
C(3)
For instance, the 1H NMR spectrum of 4ꢀisoxazoline 3a,
the reaction product of nitrone 1a with methyl phenylproꢀ
piolate, shows signals of protons of two methyl groups at
 3.02 (s, 3 H, NMe) and 3.67 (s, 3 H, CO2Me), of two
phenyl rings at  7.30—7.86 (m, 10 H, oꢀ, mꢀ, pꢀPh), and
a signal of the proton at the C(3) atom of the isoxazoline
ring at  5.18 (s, 1 H, C(3)H). According to the results of
earlier studies,14 the reaction of nitrone 1a with alkyne 2
affords exclusively one of the possible regioisomers, viz.,
isomer 3a, in which the ester group is attached to the
C(4) atom of the ring, and the phenyl substituent is linked
to the C(5) atom of the heterocyclic ring. We found that
the reactions of other free nitrones (1b,c) with dipolaroꢀ
phile 2 also proceed with high regioselectivity and always
give exclusively the C(5)ꢀsubstituted product.
The formation of products 3d—f with the retention of
the chromium tricarbonyl group in the reactions of areneꢀ
tricarbonylchromium complexes of nitrones 1d—f with
methyl phenylpropiolate (2) was established by IR spectroꢀ
scopy (the presence of intense bands of degenerate carbonyl
stretching vibrations in the region of 1850—2000 cm–1),
elemental analysis, 1H NMR spectroscopy (signals of proꢀ
tons of the coordinated phenyl rings, see the Experimental
section), and Xꢀray diffraction study of crystals of comꢀ
pound 3f (Fig. 1, Table 1).
C(2)
C(1)
O(2)
O(3)
O(1)
Fig. 1. Molecular structure of complex 3f (hydrogen atoms are
omitted for clarity).
the O(4)C(10)C(11)C(12) plane by 0.277 Å. The dihedral
angle between the planes of the isoxazoline and phenyl
moieties is 24.1.
The Xꢀray diffraction data also confirm that the reacꢀ
tion of the asymmetrical dipole (nitrone) with the dipoꢀ
larophile (methyl phenylpropiolate) affords a heterocycle
containing the double bond, in which the —CO2Me and
phenyl groups are attached to the fourth and fifth carbon
atoms, respectively, of the heterocyclic ring.
Therefore, the reactions of both free and coordinated
nitrones result in the regiospecific formation of the correꢀ
sponding 4ꢀisoxazolines. This is indicative of the retenꢀ
tion of high regioselectivity of the reaction in the case of
Table 1. Selected bond lengths (d) and bond angles () in comꢀ
plex 3f
According to the Xꢀray diffraction data, the carbonyl
groups in compound 3f are in a staggered orientation with
respect to the benzene ring. The Cr—6ꢀC and Cr—C(CO)
distances are 2.199(2)—2.229(2) and 1.835(2)—1.853(2) Å,
respectively. In the benzene ring, there is a significant
C—C bond alternation (see Table 1). It should be noted
that the CO groups are located under longer C—C bonds.
The aboveꢀmentioned characteristics of the (6ꢀC6H5)ꢀ
Cr(CO)3 moiety in compound 3f are similar to those in
unsubstituted (6ꢀbenzene)tricarbonylchromium.15—17
Consequently, it can be suggested that the 2ꢀtertꢀbutylꢀ4ꢀ
methylcarboxyꢀ5ꢀphenylꢀ4ꢀisoxazoline moiety has no subꢀ
stantial electronic and steric effects on this part of the
complex. In compound 3f, the isoxazoline ring adopts an
envelope conformation. The nitrogen atom deviates from
Parameter
Value
Parameter
Bond
Value
Bond
d/Å
d/Å
N(1)—O(4)
1.483(2)
C(4)—C(5)
C(5)—C(6)
C(6)—C(7)
C(7)—C(8)
C(8)—C(9)
C(4)—C(9)
1.405(3)
1.413(3)
1.392(4)
1.420(3)
1.401(3)
1.429(3)
C(10)—C(11) 1.521(3)
C(11)—C(12) 1.350(3)
N(1)—C(10) 1.478(3)
Cr(1)—C(1)
Cr(1)—C(2)
Cr(1)—C(3)
Cr(1)—C(4)
Cr(1)—C(5)
Cr(1)—C(6)
Cr(1)—C(7)
Cr(1)—C(8)
Cr(1)—C(9)
1.853(2)
1.838(2)
1.835(2)
2.199(2)
2.208(2)
2.206(2)
2.226(2)
2.230(2)
2.229(2)
Angle
/deg
C(12)—C(11)—C(10) 107.60(17)
C(10)—N(1)—O(4) 104.32(13)
C(12)—C(11)—C(10) 107.60(17)
C(12)—O(4)—N(1) 108.51(14)
C(11)—C(12)—O(4) 112.42(17)

972
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 4, April, 2014
Zarovkina et al.
Scheme 2
R = Me, But, Ph
nitrone molecules containing the chromium tricarbonyl
group. The fact that the reactions under consideration
afford only one of the two possible regioisomers can be
explained in terms of the theory of charge distribution of
interacting molecules18 (Scheme 2).
Despite the fact that the target 4ꢀisoxazolines were the
major products in the final reaction mixtures, these comꢀ
pounds were not the only products of certain reactions
under consideration. Some characteristic features of the
cycloaddition were found with the use of both arenetricarꢀ
bonylchromium complexes of nitrones and uncoordinated
compounds. The detailed study of the reaction of each of
complex nitrones 1d—f with methyl phenylpropiolate (2)
revealed the following three byꢀproducts: (6ꢀbenzaldeꢀ
hyde)tricarbonylchromium (4), the arenetricarbonylchroꢀ
mium complex of Schiff base (5), and the corresponding
azoxy compound (6) (Scheme 3). We established that
products 4—6 are formed as a result of the thermal rearꢀ
rangement of coordinated nitrone 1d—f competitive with
the 1,3ꢀdipolar cycloaddition. The reaction of Cꢀ[triꢀ
carbonyl(6ꢀphenyl)chromium]ꢀNꢀphenylnitrone (1e) at
80 C in toluene was shown to give the following three new
compounds: (6ꢀbenzaldehyde)tricarbonylchromium,12
(6ꢀbenzylideneaniline)tricarbonylchromium,19 and azꢀ
Scheme 3
R = Me (d), Ph (e), But (f)
i. 80 C, toluene.

(6ꢀArene)tricarbonylchromium 4ꢀisoxazolines
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 4, April, 2014
973
oxybenzene.20,21 Each of the three products was isolated,
purified, and identified by HPLC, UV, IR, and NMR
spectroscopy, as well as by mass spectrometry. In addiꢀ
tion, all three compounds were prepared by the indepenꢀ
dent syntheses.11,12,19,20 We found that the synthesized
compounds are completely identical to the thermal rearꢀ
rangement products of nitrone 1e. Based on the analysis of
the resulting compounds, it can be suggested that the reꢀ
action of complex nitrones under heating proceeds via the
mechanism presented in Scheme 3: two nitrone molecules
react to form the cyclic transition state followed by the
formation of products 4 and 5 and a nitroso compound.
Under the reaction conditions, the latter gives azoxy comꢀ
pound 6.21
C(10)
N(1)
C(9)
C(8)
O(1)
C(4)
C(7)
C(6)
C(3)
O(2)
C(1)
C(2)
C(5)
Fig. 2. Molecular structure of 2ꢀtertꢀbutylꢀ3ꢀphenylꢀ3ꢀisoxazolꢀ
inꢀ5ꢀone (hydrogen atoms are omitted for clarity).
Interesting results were obtained also in the reaction of
uncoordinated nitrones with dipolarophiles 2. Thus, column
chromatography of the reaction mixture obtained in
the reaction of CꢀphenylꢀNꢀtertꢀbutylnitrone (1c) with
methyl phenylpropiolate (2) gave 4ꢀisoxazoline 3c (yield
63%) along with a colorless crystalline compound (yield
10%, m.p. 96—97 C) and a certain amount of acetoꢀ
phenone.22 As was shown by IR and NMR spectroscopy
and Xꢀray diffraction (Fig. 2, Table 2), the colorless crysꢀ
talline compound is a fiveꢀmembered heterocyclic comꢀ
pound containing the functional carbonyl group and the
double bond between the carbon atoms C(2)—C(3) of the
ring (see Fig. 2). This compound was identified as 2ꢀtertꢀ
butylꢀ3ꢀphenylꢀ3ꢀisoxazolinꢀ5ꢀone. Selected bond lengths
and bond angles in the structure of this compound are
given in Table 2.
Table 2. Selected bond lengths (d) and bond angles () in 2ꢀtertꢀ
butylꢀ3ꢀphenylꢀ3ꢀisoxazolinꢀ5ꢀone
Bond
d/Å
Angle
/deg
O(1)—N(1)
O(1)—C(1)
C(1)—C(2)
C(2)—C(3)
N(1)—C(3)
C(1)—O(2)
1.4347(11)
1.3903(13)
1.4270(15)
1.3528(15)
1.3874(13)
1.2181(13)
C(1)—O(1)—N(1) 108.59(7)
C(3)—N(1)—O(1) 105.22(8)
C(2)—C(3)—N(1)
C(3)—C(2)—C(1)
O(1)—C(1)—C(2)
111.25(9)
107.83(9)
106.75(9)
Experimental
All solvents were distilled over sodium metal under atmospheric
pressure
29 NꢀPhenylꢀ and Nꢀtertꢀbutylhydroxylamines were preꢀ
.
The observed products are byꢀproducts in the synthesis
of 4ꢀisoxazolines, which are, evidently, formed as a result
of the process competitive with the cycloaddition. Acꢀ
cording to our suggestions, the acetyleneꢀallene rearrangeꢀ
ment of ester 2 (see Ref. 23) can take place in the system
followed by the reaction of the resulting compound with
nitrone according to Scheme 4. Alternative mechanisms
of the formation of byꢀproducts can involve various therꢀ
mal transformations of 4ꢀisoxazolines.14, 24—28
To conclude, in the present study we synthesized and
characterized new 4ꢀisoxazoline derivatives with high reꢀ
gioselectivity. It was shown that arenetricarbonylchromiꢀ
um complexes of nitrones can undergo thermal rearrangeꢀ
ments, and substituted isoxazolinones can be produced by
the reaction of methyl phenylpropiolate with free nitrones.
pared by the reduction of the corresponding nitro compounds.8,30
NꢀMethylhydroxylamine hydrochloride purchased from Sigmaꢀ
Aldrich was used for the synthesis of CꢀphenylꢀNꢀmethylnitrone
(1a). Benzaldehyde and triethyl formate were purified by the
distillation under reduced pressure; the reaction of these comꢀ
pounds afforded benzaldehyde diethylacetal.11 The reaction of
6
the latter with chromium hexacarbonyl gave ( ꢀbenzaldehyde
diethylacetal)tricarbonylchromium, the hydrolysis of which afꢀ
6
forded ( ꢀbenzaldehyde)tricarbonylchromium.12 C,NꢀDisubstiꢀ
tuted nitrones (1a—f) were prepared by the condensation of the
corresponding hydroxylamine derivatives with benzaldehyde8—10
6
or ( ꢀbenzaldehyde)tricarbonylchromium.6,9 Methyl phenylꢀ
propiolate (2) was synthesized from ethyl cinnamate in several
steps according to the known procedure.13
The products were isolated and purified by column chromatoꢀ
graphy on ACROS silica gel (0.035—0.070 mm) under an argon
Scheme 4

974
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 4, April, 2014
Zarovkina et al.
atmosphere. HPLC was performed on a Knauer Smartline 5000
chromatograph equipped with a S 2600 UV diode array detector
and a Diasferꢀ110ꢀC16 column (5 m, 4.6×250 mm) using
a 84 : 16 acetonitrile—water mixture as the eluent. The UV spectra
of the eluates were recorded in the 200—500 nm region. The
IR spectra were measured on an Infralum FTꢀ801 instrument in the
480—4600 cm–1 region in a suspension with KBr. The 1H NMR
spectra were recorded on an Agilent DD2 NMR 400NB spectrometꢀ
er operating at 400 MHz with the use of acetoneꢀd6 as the solvent.
1245, 1095 ((N—O, C—O)); 775, 740, 705 ((CAr—H)). 1H NMR,
: 1.18 (s, 9 H, NBut); 5.44 (s, 1 H,CHPh); 7.39—7.64 (m, 5 H,
oꢀ, mꢀ, рꢀPh).
2ꢀtertꢀButylꢀ4ꢀmethylcarboxyꢀ3,5ꢀdiphenylꢀ4ꢀisoxazoline
(3c). Yield 63%, m.p. 62—63 C. Found (%): C, 74.39; H, 6.87;
N, 4.13. C21H23NO3. Calculated (%): C, 74.78; H, 6.82; N, 4.15.
IR (KBr), /cm–1: 3065, 3035, 2973 ((C—H)); 1711 ((C=O));
1635 ((C=C)); 1577 ((C—CAr)); 1493 ((C—C)); 1245, 1095
((N—O, C—O)); 775, 740, 705 ((CAr—H)). 1H NMR, : 1.24
(s, 9 H, NBut); 3.50 (s, 3 H, CO2Me); 5.58 (s, 1 H, C(3)H);
7.21—7.91 (m, 10 H, oꢀ, mꢀ, рꢀPh).
6
( ꢀArene)tricarbonylchromium complexes of nitrones and
4ꢀisoxazolines were isolated under an argon atmosphere.
Synthesis of free 4ꢀisoxazolines 3a—c (general procedure).
According to a procedure described earlier,31 C,NꢀDisubstituted
nitrone 1a—c (2.6 mmol), methyl phenylpropiolate (2) (2.6 mmol),
and DMF (5 mL) were placed in a 10 mL glass tube. The tube
was degassed and vacuum sealed. The reaction mixture was heated
on an oil bath at 85 C. After heating, the tube was opened, and
the solvent was distilled off in vacuo. The reaction products were
isolated from the residue by column chromatography.
2ꢀMethylꢀ4ꢀmethylcarboxyꢀ3,5ꢀdiphenylꢀ4ꢀisoxazoline (3a).
The synthesis was performed according to the aboveꢀdescribed
procedure.14,31 The reaction mixture was heated for 2 h. One
fraction was isolated by column chromatography (the retention
time in the HPLC chromatogram was 6.7 min), and the recrysꢀ
tallization of this substance from hexane afforded colorless crysꢀ
tals of compound 3a. Yield 42%, m.p. 100—101 C. Found (%):
C, 73.20; H, 5.80; N, 4.57. C18H17NO3. Calculated (%): C, 73.22;
H, 5.76; N, 4.75. IR (KBr), /cm–1: 3005, 2970, 2920 ((C—H));
1714 ((C=O)); 1636 ((C=C)); 1598 ((C—CAr)); 1435 ((C—C));
1237, 1086 ((N—O, C—O)); 795, 745, 695 ((CAr—H)). 1H NMR,
: 3.02 and 3.67 (both s, 3 H each, NMe, CO2Me); 5.18 (s, 1 H,
C(3)H); 7.30—7.86 (m, 10 H, oꢀ, mꢀ, pꢀPh).
6
Synthesis of ( ꢀarene)tricarbonylchromium complexes of
4ꢀisoxazolines 3d—f (general procedure). C,NꢀDisubstituted nitrone
1d—f (0.74 mmol), dipolarophile 2 (0.74 mmol), and toluene
(5 mL) were placed in a 10 mL glass tube. The tube was degassed
and vacuum sealed. The reaction mixture was heated on an oil
bath at 80 C for 35 h. After heating, the tube was opened, and
the solvent was distilled off in vacuo. The HPLC chromatogram
of the reaction mixture showed four peaks, one of which correꢀ
sponded to 4ꢀisoxazoline; the other three, to rearrangement prodꢀ
6
ucts of the corresponding ( ꢀarene)tricarbonylchromium comꢀ
plex of nitrone. Two substances were isolated from the residue
by column chromatography. The recrystallization of these subꢀ
stances from a hexane—ethyl acetate (diethyl ether) mixture
6
afforded crystalline compounds. One of them was ( ꢀbenzꢀ
aldehyde)tricarbonylchromium,6,9 and the other was the correꢀ
6
sponding ( ꢀarene)tricarbonylchromium complex with 4ꢀisoxꢀ
azoline 3d—f.
6
3ꢀ[Tricarbonyl( ꢀphenyl)chromium]ꢀ2ꢀmethylꢀ4ꢀmethylcarbꢀ
oxyꢀ5ꢀphenylꢀ4ꢀisoxazoline (3d). Yellow crystals. Yield 50%, m.p.
125—126 C. Found (%): C, 58.12; H, 4.18; N, 3.20. C21H17CrNO6.
Calculated (%): C, 58.47; H, 3.94; N, 3.25. IR (KBr), /cm–1
:
4ꢀMethylcarboxyꢀ2,3,5ꢀtriphenylꢀ4ꢀisoxazoline (3b). The
synthesis was performed according to the aboveꢀdescribed proꢀ
cedure. The reaction mixture was heated for 10 h. Two substancꢀ
es were isolated by column chromatography (the retention times
in the HPLC chromatogram were 5.9 and 6.0 min). The subꢀ
stance with the retention time of 5.9 min was a viscous oily liquid
(acetophenone).22 The substance with the retention time of 6.0 min
was recrystallized from hexane. Yellow crystalline compound 3b
was obtained. Yield 31%, m.p. 100—101 C. Found (%): C, 76.98;
H, 5.48; N, 3.83. C23H19NO3. Calculated (%): C, 77.31; H, 5.32;
N, 3.92. IR (KBr), /cm–1: 3057, 2948, 2846 ((C—H)); 1731
((C=O)); 1686 ((C=C)); 1598 ((C—CAr)); 1484 ((C—C));
1223, 1046 ((N—O, C—O)); 870, 746, 702 ((CAr—H)). 1H NMR,
: 3.67 (s, 3 H, CO2Me); 5.96 (s, 1 H, C(3)H); 6.71—7.55 (m, 15 H,
oꢀ, mꢀ, рꢀPh).
2953, 2918, 2851 ((C—H)); 1971, 1916, 1871 ((CO)); 1693
((C=O)); 1630 ((C=C)); 1226, 1099 ((N—O, C—O)); 800,
753, 658 ((CAr—H)). 1H NMR, : 3.07 and 3.67 (both s, 3 H each,
NMe, CO2Me); 4.94 (s, 1 H, C(3)H); 5.52—5.68 (m, 3 H, mꢀ,
pꢀC(3)PhCr); 5.75—5.96 (m, 2 H, oꢀC(3)PhCr); 7.37—7.62 (m, 3 H,
mꢀ, pꢀC(5)Ph); 7.84 (dd, 2 H, oꢀC(5)Ph, J = 8.2 Hz, J =1.6 Hz).
6
3ꢀ[Tricarbonyl( ꢀphenyl)chromium]ꢀ4ꢀmethylcarboxyꢀ2,5ꢀ
diphenylꢀ4ꢀisoxazoline (3e). Yellow crystals. Yield 55%, m.p.
136—137 C. Found (%): C, 63.99; H, 4.10; N, 2.74. C26H19CrNO6.
Calculated (%): C, 63.29; H, 3.85; N, 2.84. IR (KBr), /cm–1
:
3090, 2919, 2851 ((C—H)); 1973, 1895, 1879 ((CO)); 1711
((C=O)); 1624 ((C=C)); 1269, 1155 ((N—O, C—O)); 763,
1
662, 611 ((CAr—H)). H NMR, : 3.64 (s, 3 H, CO2Me); 5.68
(m, 2 H, mꢀC(3)PhCr); 5.78—5.89 (t, 1 H, pꢀC(3)PhCr, J = 8.0 Hz);
6.16 (dd, 2 H, oꢀC(3)PhCr, J = 7.0 Hz); 6.47 (s, 1 H, C(3)H);
7.09—7.17 (t, 1 H, pꢀNPh, J = 7.4 Hz); 7.18 (d, 2 H, oꢀNPh,
J = 7.8 Hz); 7.35—7.43 (m, 2 H, mꢀNPh); 7.43—7.57 (m, 3 H,
mꢀ, pꢀC(5)Ph); 8.09 (d, 2 H, oꢀC(5)Ph, J = 7.0 Hz).
Reaction of C,Nꢀdisubstituted nitrone 1c with dipolarophile 2.
The reaction mixture was heated for 10 h. Three substances were
isolated by column chromatography (the retention times in the
HPLC chromatogram were 5.9, 6.0, and 9.6 min). The subꢀ
stance with the retention time of 5.9 min was a viscous oily liquid
(acetophenone).22 The substances with the retention times of
6.0 and 9.6 min were recrystallized from a 5 : 1 hexane—ethyl
acetate mixture. 2ꢀtertꢀButylꢀ3ꢀphenylꢀ3ꢀisoxazolinꢀ5ꢀone and
2ꢀtertꢀbutylꢀ4ꢀmethylcarboxyꢀ3,5ꢀdiphenylꢀ4ꢀisoxazoline (3c)
were isolated. Both products were colorless crystalline compounds.
2ꢀtertꢀButylꢀ3ꢀphenylꢀ3ꢀisoxazolinꢀ5ꢀone. Yield 10%, m.p.
96—97 C. Found (%): C, 71.50; H, 7.01; N, 6.47. C13H15NO2.
6
3ꢀ[Tricarbonyl( ꢀphenyl)chromium]ꢀ2ꢀtertꢀbutylꢀ4ꢀmethylꢀ
carboxyꢀ5ꢀphenylꢀ4ꢀisoxazoline (3f). Yield 58%, m.p. 109—110 C.
Found (%): C, 60.07; H, 5.02; N, 2.96. C24H23CrNO6. Calcuꢀ
lated (%): C, 60.89; H, 4.86; N, 2.96. IR (KBr), /cm–1: 2978,
2943, 2900 ((C—H)); 1961, 1882 ((CO)); 1688 ((C=O));
1635 ((C=C)); 1235, 1100 ((N—O, C—O)); 690, 659, 625
1
((CAr—H)). H NMR, : 1.31 (s, 9 H, NBut); 3.67 (s, 3 H,
CO2Me); 5.28 (s, 1 H, C(3)H); 5.36—5.48 (m, 2 H, mꢀC(3)PhCr);
5.80 (t, 1 H, pꢀC(3)PhCr, J = 6.26 Hz); 6.02 (d, 1 H, oꢀC(3)PhCr,
J = 6.7 Hz); 6.11 (d, 1 H, oꢀC(3)PhCr, J = 6.7 Hz); 7.44—7.61
(m, 3 H, mꢀ, pꢀC(5)Ph); 7.85—7.96 (m, 2 H, oꢀC(5)Ph).
Calculated (%): C, 71.89; H, 6.91; N, 6.45. IR (KBr), /cm–1
1729 ((C=O)); 1635 ((C=C)); 1560 ((C—CAr)); 1493 ((C—C));
:

(6ꢀArene)tricarbonylchromium 4ꢀisoxazolines
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 4, April, 2014
975
Thermal rearrangement of nitrones 1d—f. C,NꢀDisubstituted
nitrone 1d—f (0.74 mmol) and toluene (5 mL) were placed in
a 10 mL glass tube. The tube was degassed and vacuum sealed.
The reaction mixture was heated on an oil bath at 80 C for 35 h.
After heating, the solvent was distilled off in vacuo. The HPLC
chromatogram of the reaction mixture showed three peaks corꢀ
responding to reaction products. In the case of nitrone 1e, three
substances were isolated by column chromatography from the
residue, which was obtained after the distillation of the solvent.
The recrystallization of these substances from a 4 : 1 hexane—ethyl
2. R. Huisgen, Angew. Chem., Int. Ed. Engl., 1968, 7, 321.
3. R. Huisgen, J. Org. Chem., 1968, 33, 2291.
4. 3. R. Huisgen, Helv. Chim. Acta, 1967, 50, 2421.
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Zarovkina, Russ. Chem. Bull., Int. Ed., 2012, 61, 2076 [Izv.
Akad. Nauk, Ser. Khim., 2012, 2059].
6. A. N. Artemov, E. V. Sazonova, N. Yu. Zarovkina, Russ.
Chem. Bull., Int. Ed., 2013, 62, 1382 [Izv. Akad. Nauk, Ser.
Khim., 2013, 1382].
7. A. P. Kozikowski, Acc. Chem. Res., 1984, 17, 410.
8. K. Heusler, P. Wieland, Ch. Meystre, Org. Synth., 1973,
5, 1124.
9. C. Mukai, I. J. Kim, W. J. Cho, M. Kido, M. Hanaoka,
J. Chem. Soc., Perkin Trans. 1, 1993, 2495.
6
acetate mixture afforded red crystals of ( ꢀbenzaldehyde)ꢀ
6
tricarbonylchromium,6,9 orange crystals of ( ꢀbenzylideneꢀ
aniline)tricarbonylchromium,19 and colorless crystals of azoxyꢀ
benzene.20,21
Xꢀray diffraction study. Complex 3f. Crystals (C24–H23CrNO6•
•0.5Et2O, M = 510.49), triclinic, space group P1, at 100 K:
a = 9.4167(9) Å, b = 9.6938(10) Å, c = 13.9258(14) Å,  =
= 89.030(2),  =86.830(2),  = 78.077(2), V = 1241.9(2) Å3,
Z = 2, dcalc = 1.365 g cm–3,  = 5.04 cm–1, F(000) 534,
2.15 <  < 26.00; were prepared by the crystallization from
a 5 : 1 : 0.5 hexane—ethyl acetate—diethyl ether mixture. The inꢀ
10. W. D. Emmons, J. Am. Chem. Soc., 1957, 79, 5739.
11. H. W. Post, J. Org. Chem., 1940, 5, 244.
12. G. Drehfahl, H. H. Horhold, K. Kuhne, Chem. Ber., 1965,
98, 1826.
13. Organic Syntheses, 2, Ed. A. Blatt, New York, 1943, 654 p.
14. J. P. Freeman, Chem. Rev., 1983, 63, 241.
15. B. Rees, P. Coppens, Acta Crystallogr., Sect. B., 1973, 9, 2515.
16. L. J. Farrugia, C. Evans, D. Lentz, M. Roemer, J. Am. Chem.
Soc., 2009, 131, 1251.
tensities of 7473 reflections (4846 unique reflections, Rint
=
= 0.0177) were measured on a Smart Apex diffractometer (graphꢀ
ite monochromator, (MoꢀK) = 0.71073 Å). The final R facꢀ
tors are R1 = 0.0656 (I > 2(I)), wR2 = 0.1846 (the refinement
17. Y. Wang, K. Angermund, R. Goddard, C. Kruger, J. Am.
Chem. Soc., 1987, 109, 587.
based on F 2
for all unique reflections), S(F 2) = 1.092,
18. K. V. Gothelf, K. A. Jorgensen, Chem. Rev., 1998, 98, 863.
19. N. Eberhard, S. Afr. J. Chem., 1975, 28, 365.
20. Organanic Syntheses, 3, Ed. A. Blatt, New York, 1943, 590 p.
21. D. Barton, W. D. Ollis, Comprehensive Organic Chemistry.
The Synthesis and Reaction of Organic Compounds, 3, Ed. I.
O. Sutherland, University of Liverrpool, 1979, 1344 p.
22. A. N. Nesmeyanov, N. A. Nesmeyanov, Nachala organiꢀ
cheskoi khimii [Fundamentals of Organic Chemistry], 2,
Khimiya, Moscow, 1970, p. 150 (in Russian).
23. D. I. Mikhailovskii, Izomerizatsiya i peregruppirovki atsetileꢀ
nov [Isomerization and Rearrangements of Acetylenes], Izdꢀvo
ZAO NRL, Nizhny Novgorod, 2012, 320 pp. (in Russian).
24. I. Adachi, R. Miyazaki, H. Kano, Chem. Pharm. Bull., 1974,
22, 61.
25. I. Adachi, R. Miyazaki, H. Kano, Chem. Pharm. Bull., 1974,
22, 70.
26. J. E. Baldwin, R. G. Pudussery, A. K. Qureshi, B. Sklarz,
J. Am. Chem. Soc., 1968, 90, 5325.
27. R. Huisgen, H. Seidl, J. Wulff, Chem. Ber., 1969, 102, 915.
28. R. A. Abramovitch, I. Shinkai, J. Am. Chem. Soc., 1974,
96, 5265.
nkl
 (max/min) = 1.920 / –0.772 e Å–3
2ꢀtertꢀButylꢀ3ꢀphenylꢀ3ꢀisoxazolinꢀ5ꢀone.
.
Crystals
–
(C13H15NO2, M = 217.26), triclinic, space group P1, at 100 K:
a = 7.55264(12) Å, b = 8.32849(14) Å, c = 10.43754(15) Å,
 = 67.5411(15),  = 69.9071(14),  = 81.5091(14), V =
= 569.717(15) Å3, Z = 2, dcalc = 1.266 g cm–3,  = 0.85 cm–1
,
F(000) 232, 3.45 <  < 26.00; were prepared by the crystallizaꢀ
tion from a 5 : 1 hexane—ethyl acetate mixture. The intensities
of 8304 reflections (2232 unique reflections, Rint = 0.0142) were
measured on a Smart Apex diffractometer (graphite monoꢀ
chromator, (MoꢀK) = 0.71073 Å). The final R factors are
R1 = 0.0333 (I > 2(I)), wR2 = 0.0819 (the refinement based on
F2 for all unique reflections), S(F2) = 1.071,  (max/min) =
nkl
= 0.231/ –0.200 e Å–3
.
Both structures were solved by direct methods and refined by
the fullꢀmatrix leastꢀsquares method based on F2 with anisoꢀ
hkl
tropic displacement parameters for all nonhydrogen atoms. The
hydrogen atoms were geometrically positioned and refined using
a riding model. The absorption corrections were applied using
the SADABS program.32 All calculations were carried out using
the SHELXTL program package.33 The structures were depositꢀ
ed in the Cambridge Crystallographic Data Centre (CCDC
965364 and 965365).
29. A. Weissberger, E. Proskauer, J. A. Riddick, E. E. Toops, Jr.,
Organic Solvents; Physical Properties and Methods of Purificaꢀ
tion, Intersci. Publ. Inc., New York—London, 1955, 552 pp.
30. C. Weygand, Organisch Chemische Experimentierkunst, 2 Aufꢀ
lage, Johann Ambrosius Barth, Leipzig, 1948, 824.
31. H. Seidl, R. Huisgen, R. Grashey, Chem. Ber., 1969, 102, 915.
32. G. M. Sheldrick, SADABS, 1997, Bruker AXS, Inc., Madiꢀ
son (WI), USA.
We thank Yu. B. Malysheva (N. I. Lobachevsky Nizhny
Novgorod State University) for performing the NMR
analysis.
This work was financially supported by the Ministry of
Education and Science of the Russian Federation.
33. G. M. Sheldrick, Acta Crystallogr., Sect. A, Found. Crystalꢀ
logr., 2008, 64, 112.
References
1. L. L. Semenycheva, A. N. Artemov, I. S. Ilichev, D. F.
Grishin, Russ. Chem. Bull., Int. Ed., 2002, 51, 581 [Izv. Akad.
Nauk, Ser. Khim., 2002, 540].
Received October 22, 2013;
in revised form January 22, 2014