[2+4] Cycloaddition of η6-(styrene)chromium tricarbonyl and conjugated dienes

Article abstract of DOI:10.1007/s11172-011-0322-5

Cycloaddition of η⁶-(styrene)chromium tricarbonyl to hexa-2,4-diene or cyclopentadiene afford the Diels-Alder adducts with retention of the Cr(CO)₃ group, whereas cyclohexa-1,3-diene undergoes aromatization to give η⁶-(ben

Full text of DOI:10.1007/s11172-011-0322-5

Russian Chemical Bulletin, International Edition, Vol. 60, No. 10, pp. 2103—2106, October, 2011
2103
[2+4] Cycloaddition of η6ꢀ(styrene)chromium tricarbonyl
and conjugated dienes
A. N. Artemov, E. V. Sazonova, M. V. Revin, K. V. Rybkin, M. A. Lazarev, and V. I. Faerman
Research Institute of Chemistry, N. I. Lobachevsky Nizhni Novgorod State University,
Building 5, 23 prosp. Gagarina, 603950 Nizhni Novgorod, Russian Federation.
Fax: +7 (831) 465 8162, 465 7343. Eꢀmail: lazarev@ichem.unn.ru
6
Cycloaddition of η ꢀ(styrene)chromium tricarbonyl to hexaꢀ2,4ꢀdiene or cyclopentadiene
afford the Diels—Alder adducts with retention of the Cr(CO)3 group, whereas cyclohexaꢀ1,3ꢀ
6
diene undergoes aromatization to give η ꢀ(benzene)chromium tricarbonyl. The counter synꢀ
thesis of these (arene)chromium tricarbonyl derivatives from uncoordinated adducts of the
Diels—Alder reaction and chromium hexacarbonyl was carried out.
6
Key words: Diels—Alder reactions, η ꢀ(styrene)chromium tricarbonyl, chromium comꢀ
plexes.
Scheme 1
Among diverse synthetic methods of contemporary orꢀ
ganic chemistry, dieneꢀbased synthesis plays one of the
leading roles.1—4 Styrene and its derivatives are efficient
dienophiles, which in the Diels—Alder reactions with
dienes give phenylꢀsubstituted cyclohexenes or bicyclic
compounds.
The use of unsaturated (arene)chromium tricarbonyl
complexes in the reactions of diene synthesis of various
types is known5—11; however, the reactions of (styrene)ꢀ
chromium tricarbonyl with linear and cyclic dienes have
not been described to the recent time. The purpose of the
present work is to study the possibility of the Diels—Alder
reaction to occur involving hexaꢀ2,4ꢀdiene (1), cyclopenꢀ
tadiene (2) or cyclohexaꢀ1,3ꢀdiene (3), and (styrene)ꢀ
chromium tricarbonyl complex (4), which acts in this reꢀ
action as a dienophile. The reactions were carried out in
sealed glass ampules with a twofold excess of diene in the
inert solvent (octane).
i. Octane, 150 °С, 5 h; ii. hν, O2.
Diene 1 (a mixture of isomers) reacted with complex 4
at 150 °С for 5 h to yield a mixture of products from which
compound 5 was isolated in 40% yield as a dark yellow
liquid congealed on cooling (Scheme 1).
sponding data for product 6, which was obtained from the
counter synthesis by the Diels—Alder reaction between 1
and uncoordinated styrene (see below).
The IR spectrum of compound 5 contains absorption
The reaction of cyclopentadiene 2 with 4 at 120 °С
within 5 h affords η6ꢀ[(bicyclo[2.2.1]heptꢀ2ꢀenꢀ5ꢀyl)ꢀ
benzene]chromium tricarbonyl (7) as pale yellow crystals
with the melting point 50—52 °С (Scheme 2).
bands of С—Н stretches in the region of 3050—2820 cm–1
,
giving two characteristic bands at 1967 and 1886 cm–1
belonging to the CO groups of the Cr(CO)3 moiety. The
decomposition of the obtained adduct upon UV irradiaꢀ
tion of its ethyl acetate solution in air gives a mixture of
cisꢀ and transꢀisomers of hydrocarbon 6. Two substances
were found by GC/MS analysis. They have closely lying
peaks on the chromatogram and similar mass spectra with
molecular ion peaks at m/z 186. Note that the retention
times and mass spectra are entirely identical to the correꢀ
The synthesized compound was characterized by IR
1
spectroscopy and Н NMR spectroscopy. The IR specꢀ
trum of compound 7 exhibits two characteristic bands of
СО stretching vibrations at 1900 and 1878 cm–1 and bands
characteristic of bicyclic alkene.
Unlike previous examples, cyclohexadiene 3 reacted
with compound 4 yielding a yellow substance readily subꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2066—2069, October, 2011.
1066ꢀ5285/11/6010ꢀ2103 © 2011 Springer Science+Business Media, Inc.

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Artemov et al.
Scheme 2
Scheme 4
i. Octane, 120 °С, 5 h.
limated in vacuo. The analysis by HPLC, IR spectroscopy,
and mass spectrometry12 showed that this substance was
η6ꢀ(benzene)chromium tricarbonyl (m.p. 160—162 °С,
cf. Ref. 13: 162 °С) (Scheme 3).
i. Hydroquinone, 160 °С, 30 h; ii. Cr(CO)6, 120—160 °С, 5—18 h.
R = Me (1, 5, 6); R + R = CH2 (2, 7, 8), (CH2)2 (3, 9, 10)
Scheme 3
transꢀstereoisomers in the same ratio that was in the subꢀ
strate subjected to complexation.
The reaction of phenylnorbornene 8 with chromium
hexacarbonyl in refluxing diglyme—octane (1 : 1) gives
complex 7 in 57% yield. Complex 7 is identical to that
obtained following Scheme 2. Decomposition of this comꢀ
plex 7 gives the product exhibiting one peak on the GC/MS
chromatogram, and its mass spectrum completely coinꢀ
cides with the spectrum of hydrocarbon 8 (see Ref. 12).
The reaction of compound 9 with chromium hexacarꢀ
bonyl proceeds similarly to form yellow crystalline subꢀ
stance 10 with m.p. 92—94 °С in 40% yield. This comꢀ
pound gives one peak on the HPLC chromatogram, whereꢀ
as its IR and NMR spectra exhibit all characteristic sigꢀ
nals, whose positions correspond to the assumed strucꢀ
ture. The decomposition of compound 10 under UV irraꢀ
diation in air affords the product, whose mass spectrum
contains the molecular ion peak with m/z 184. The mass
spectrum of the decomposition product is identical to that
of the starting hydrocarbon 9.
To conclude, [2+4] cycloaddition between the (styrene)ꢀ
chromium tricarbonyl and conjugated dienes have been
studied for the first time and can serve as an efficient route
to chromium tricarbonyl derivatives of phenylꢀsubstituted
monoꢀ and bicyclic hydrocarbons. Complexation of the
preꢀsynthesized phenylꢀcontaining Diels—Alder adducts
can be regarded as an alternative way for their preparation.
The fact of cyclohexadiene aromatization when attemptꢀ
ing to involve it into the Diels—Alder reaction with comꢀ
pound 4 was established.
i. Octane, 150 °С.
The tendency of cyclohexaꢀ1,3ꢀdiene to undergo aroꢀ
matization under the action of chromium carbonyl comꢀ
plexes is well known14,15 and, therefore, the benzene comꢀ
plex is presumably formed at the stage of an intermediate,
whose decomposition results in the aromatization of the
hexadiene ring to form η6ꢀ(benzene)chromium tricarbonꢀ
yl and ethylbenzene. The appearance of these products
and the absence of free styrene in the reaction mixture
confirm the reaction equation presented above.
Thus, our studies revealed that unsaturated (arene)ꢀ
chromium tricarbonyl complexes, such as η6ꢀ(styrene)ꢀ
chromium tricarbonyl (4), can be involved in the cycloadꢀ
dition reactions to give the corresponding adducts, alꢀ
though in low yields.
In order to additionally confirm the structure of the
(arene)chromium tricarbonyl adducts formed, we carried
out the independent synthesis, which involved prelimiꢀ
nary preparation of the Diels—Alder adducts between the
corresponding dienes 1—3 and styrene (160—200 °С, 30 h)
and subsequent complexation of the latter with chromium
hexacarbonyl (Scheme 4).
Experimental
The reaction of hydrocarbon 6 with chromium hexaꢀ
carbonyl leads to complex 5 in 64% yield as a dark yellow
oil. The decomposition of this complex under UV irradiaꢀ
tion in air gives compound 6, being a mixture of cisꢀ and
All solvents were distilled above sodium metal under atmoꢀ
spheric pressure.16 To remove the stabilizer, styrene was washed
with 10% aqueous sodium hydroxide and then with water, dried,
and distilled (b.p. 48—49 °С (10 Torr)). Cyclopentadiene (2)

[2+4] Cycloaddition of (H2C=CHC6H5)Cr(CO)3
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 10, October, 2011
2105
was obtained from its dimer by decomposition at 180 °С and
collecting the fraction boiling at 40—42 °С (see Ref. 17). Cycloꢀ
hexaꢀ1,3ꢀdiene (3) and hexaꢀ2,4ꢀdiene (1) were distilled under
atmospheric pressure, collecting the fractions with b.p. 79—82
and 81—83 °С, respectively.
(1 : 1) mixture (70 mL). The mixture was refluxed at 160 °С for
18 h under argon. Then the mixture was filtered through a glass
filter with the Al2O3 layer, and the solvent was evaporated
in vacuo. The yield was 64%. IR (KBr), ν/cm–1: 3050 (ν(СAr—H));
2962, 2911, 2826 (ν(С—H)); 1967, 1886 (CrC=O); 1632 (С=С);
1602 (ν(C—CAr)); 1454, 1371 (ν(С—C)); 1199, 1106, 856, 741
(skeletal vibrations); 662, 621 (ω(СAr—H)).
Gas chromatographic analysis was carried out on a Tsvetꢀ
500M chromatograph with a packed column with 15% Apiezon
on Chromaton NꢀAWꢀDMCS (column length 2 m, flow rate of
helium 26 mL min–1). HPLC was carried out on a Knauer Smartꢀ
line 5000 instrument with an S 2600 PDA detector (column
Diaspherꢀ110ꢀS16, 5 μm, 4.6×250 mm, isocratic elution mode,
acetonitrile—water (84 : 16) as eluent). IR spectra were recordꢀ
ed on an InfralyumꢀFTꢀ801 instrument in the range from 480 to
6
η ꢀ[(Bicyclo[2.2.1]heptꢀ2ꢀenꢀ5ꢀyl)benzene]chromium tricarꢀ
bonyl (7). A. A solution of cyclopentadiene 2 (0.26 g, 0.004 mol)
and complex 4 (0.5 g, 0.002 mol) in octane (3 mL) was refluxed
for 5 h at 120 °С. The product was recrystallized from an ethyl
acetate—hexane mixture. The yield was 21%, m.p. 50—52 °С.
According to the NMR spectroscopy and HPLC data, the purity
of the product was 92%.
1
4600 cm–1 in a suspension with KBr. H and 13C NMR spectra
were measured on a Bruker Avance 400 spectrometer (working
frequencies 400 and 101 MHz, respectively). GC/MS studies
were carried out on an Trace GC Ultra/MS QII instrument in
the mode of positive ion detection with electron impact ionizaꢀ
tion (70 eV) in the range m/z 28—500 (capillary column TR5MS
60 000×0.25 mm, helium flow rate 1 mL min–1, temperature
programming from 60 to 300 °С at a heating rate of 15 deg min–1).
B. Compound 7 was also obtained by the complexation of
hydrocarbon 8 (4.6 g, 0.027 mol) with chromium hexacarbonyl
(6 g, 0.027 mol) in diglyme—octane (1 : 1) similarly to the synꢀ
thesis of compound 5, method B. The yield was 57%. 1Н NMR
(acetoneꢀd6), δ: 6.34 (dd, 1 H, =CH, J = 5.3 Hz, J = 3.1 Hz);
5.84 (dd, 1 H, =CH, J = 5.4 Hz, J = 2.6 Hz); 5.77—5.53 (m, 4 H,
ArCr(CO)3); 5.21 (d, 1 H, oꢀArCr(CO)3, J = 6.4 Hz); 3.26—3.08
(m, 1 H, CH—Ar); 3.02 (s, 1 H, CH—CH2); 2.92 (s, 1 H,
CH—CH2), 2.14 (td, 1 H, СH2—CHAr, J = 12.6 Hz, J = 9.4
Hz, J = 3.6 Hz); 1.46 (td, 2 H, CH2, J = 19.8 Hz, J = 8.5 Hz);
1.11 (d, 1 H, CH2—CHAr, J = 10.5 Hz). 13С NMR (101 MHz,
acetoneꢀd6), δ: 138.17, 131.78 (=CH); 95.43, 95.03, 92.26, 92.42
(ArCr(CO)3); 43.16 (CH—Ar); 49.56, 43.14 (CH—CH2); 31.71
(CH2—CHAr); 50.35 (CH2); 31.73 (CH2—CHAr). 1Нꢀ1Н COSY
(400 MHz, acetoneꢀd6), δ: 1.11 (1.46, 2.14, 3.17); 1.46 (1.11,
2.92, 3.02); 2.14 (1.11, 2.92, 3.17); 2.92 (1.46, 2.14, 6.33); 3.02
(1.44, 5.83); 3.17 (1.46, 2.14, 3.02); 5.21 (5.60); 5.60 (5.21); 5.83
6
η ꢀ(Styrene)chromium tricarbonyl (4) was synthesized by the
Rausch method.18
Synthesis of the Diels—Alder adducts of diene hydrocarbons
with styrene 6, 8, and 9 (general procedure). A 100ꢀmL glass
ampule was filled with the corresponding diene (0.25 mol), styꢀ
rene (0.25 mol), and hydroquinone (0.25 g). The ampule was
freezed with liquid nitrogen, deaerated in vacuo, and sealed. The
reaction mixture was heated in a thermostat for 30 h at 160 °С,
then the ampule was opened, and the products were twice disꢀ
tilled in vacuo.
1
3,6ꢀDimethylꢀ4ꢀphenylcyclohexene (6). The yield was 65%,
b.p. 121—125 °С (3 Torr) (cf. Ref. 19: b.p. 124—128 °С (3 Torr)),
(3.02; 6.34); 6.34 (2.92, 5.83). Нꢀ13C COSY NMR (400—101
MHz, acetoneꢀd6), δ: 1.10—31.73; 1.47—50.35; 2.14—31.72;
2.92—43.14; 3.02—49.56; 3.17—43.16; 5.22—92.42; 5.45—92.26;
5.61—95.03; 5.83—131.78; 6.34—138.17. IR (KBr), ν/cm–1: 3064
(ν(СAr—H)); 2966, 2921, 2852 (ν(С—H)); 1970, 1878 (CrC=O);
1632 (С=С); 1608 (ν(C—CAr)); 1458, 1335 (ν(С—С)); 1152,
1106, 882, 725 (skeletal vibrations); 691, 630 (ω(СAr—H)).
20
20
nD 1.5093 (cf. Ref. 19: nD 1.50916). GC/MS (EI, 70 eV),
τ/min: 16.4, 16.8; m/z (Irel (%)): 186 [M]+ (37), 118 [M – C5H8]+
(21), 104 [M — C6H10]+ (12), 82 [M – C8H8]+ (100), 68 [M –
– C9H10]+ (24).
5ꢀPhenylbicyclo[2.2.1]hepꢀ2ꢀene (8).20,21 The yield was 72%,
b.p. 82—95 °С (3 Torr) (cf. Ref. 20: b.p. 114—116 °С (14 Torr)),
6
η ꢀ[(Bicyclo[2.2.2]octꢀ2ꢀenꢀ5ꢀyl)benzene]chromium tricarꢀ
20
20
nD 1.5504 (cf. Ref. 20: nD 1.5510). MS (EI, 70 eV), m/z
(Irel (%)): 170 [M]+ (21), 115 [M – C2H4]+ (9), 104 [M – C5H6]+
(100), 91 [C6H5CH2]+, 78 [C6H6]+ (26).
bonyl (10) was synthesized from hydrocarbon 9 (5 g, 0.027 mol)
and chromium hexacarbonyl (6 g, 0.027 mol) in a diglyme—
octane (1 : 1) mixture similarly to the synthesis of compound 5,
method B. The yield was 40%, m.p. 92—94 °С. IR (KBr), ν/cm–1
:
5ꢀPhenylbicyclo[2.2.2]octꢀ2ꢀene (9).22,23 The yield was 83%,
b.p. 105—111 °С (3 Torr) (cf. Ref. 22: 94—97 °С (1—2 Torr)),
3064 (ν(СAr—H)); 2963, 2923, 2851 (ν(С—H)); 1965, 1857
(CrC=O); 1631 (С=С); 1601 (ν(C—CAr)); 1445, 1335 (ν(С—С));
1152, 1106, 882, 725 (skeletal vibrations); 691, 635 (ω(СAr—H)).
1Н NMR (acetoneꢀd6), δ: 6.41 (t, 1 Н, =СН, J = 7.3 Hz); 6.13
(t, 1 Н, =СН, J = 7.3 Hz); 5.76—5.33 (m, 4 H, ArCr(CO)3);
5.24 (d, 1 H, oꢀArCr(CO)3, J = 6.4 Hz); 2.63 (s, 1 H, C=C—CH);
2.03 (dd, 1 H, ≡C—H, J = 15.9 Hz, J = 6.9 Hz); 1.86—1.61
(m, 1 H, ArC—H); 1.67—1.45 (m, 2 H, ArCHCH2), 1.45—1.12
(m, 4 H, СН2—СН2).
20
20
nD 1.5432 (cf. Ref. 22: nD 1.5430). MS (EI, 70 eV), m/z
(Irel (%)): 184 [M]+ (100), 154 [M – C2H6]+ (19), 142 [M – C3H6]+
(23), 115 [M – C5H10 – H]+ (73), 104 [M – C6H8]+ (100), 91
[C6H5CH2]+ (88), 80 [M – C8H8]+ (100).
6
η ꢀ[(3,6ꢀDimethylcyclohexenꢀ4ꢀyl)benzene]chromium triꢀ
carbonyl (5). A. A 10ꢀmL glass ampule was filled with complex 4
(0.24 g, 0.001 mol), diene 1 (0.32 g, 0.004 mol), and octane
(3 mL). The ampule was heated in a thermostat for 5 h at 150 °С.
Then the ampule was cooled down and centrifuged, and yellow
solution was decanted, the solvent from which was evaporated
in vacuo, and the products were extracted with hot hexane. The
target product was isolated as a yellow viscous liquid congealed
in a refrigerator. The yield was 40%.
B. A glass ampule with an allꢀsealed reflux condenser and
a device for mechanical return of sublimed chromium hexacarbꢀ
onyl was filled with hydrocarbon 6 (1.8 g, 0.0096 mol), chromiꢀ
um hexacarbonyl (2.6 g, 0.0115 mol), and a diglyme—octane
6
η ꢀ(Benzene)chromium tricarbonyl was obtained by the reacꢀ
tion of compounds 4 and 5. The yield was 85%, m.p. 160—162 °С
(cf. Ref. 13: 162 °С). IR (KBr), ν/cm–1: 3056 (ν(СAr—H)); 2987,
2916, 2848 (ν(С—H)); 1975, 1858 (CrC=O); 1599 (ν(C—CAr));
1018, 787. MS (EI, 70 eV), m/z (Irel (%)): 214 [M]+ (16); 186
[M – CO]+ (2); 158 [M – 2 CO]+ (3); 130 [M – 3 CO]+ (35),
77 [C6H5]+ (14), 52 [Cr]+ (100), 28 [CO]+ (27).
Decomposition of (arene)chromium tricarbonyl compounds was
carried out in a quartz beaker equipped with a magnetic stirrer in

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Artemov et al.
an ethyl acetate solution under UV irradiation with a highꢀpresꢀ
sure mercury lamp in air for 10 h. The precipitate of chromium
oxide that formed was filtered off. The reaction products were
analyzed using physicochemical methods.
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341, 137.
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Received August 9, 2010;
in revised form April 28, 2011