Catalytic syntheses of polycyclic compounds based on norbornadiene in the presence of nickel catalysts

Article abstract of DOI:10.1134/S0023158410030079

Abstract-The cycloadditions of olefins containing an electron-withdrawing substituent to norbornadiene are reported. The influence of the substituent and solvent nature on the [2+2+2]-cycloadduct yield and ste- reoselectivity is elucidated. The competitive cycloaddition of pairs of olefins to norbornadiene is discussed. Hypotheses about the structure of key intermediates of the process are considered. The consistent generalized mechanism for the cycloaddition of unsaturated compounds of various classes to norbornadiene is suggested. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S0023158410030079

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2010, Vol. 51, No. 3, pp. 370–374. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © I.E. Efros, D.V. Dmitriev, V.R. Flid, 2010, published in Kinetika i Kataliz, 2010, Vol. 51, No. 3, pp. 391–395.
Catalytic Syntheses of Polycyclic Compounds Based
on Norbornadiene in the Presence of Nickel Catalysts
I. E. Efros, D. V. Dmitriev, and V. R. Flid
Lomonosov State Academy of Fine Chemical Technology, Moscow, 119571 Russia
eꢀmail: vitalyꢀflid@yandex.ru
Received April 29, 2009
Abstract—The cycloadditions of olefins containing an electronꢀwithdrawing substituent to norbornadiene
are reported. The influence of the substituent and solvent nature on the [2+2+2]ꢀcycloadduct yield and steꢀ
reoselectivity is elucidated. The competitive cycloaddition of pairs of olefins to norbornadiene is discussed.
Hypotheses about the structure of key intermediates of the process are considered. The consistent generalized
mechanism for the cycloaddition of unsaturated compounds of various classes to norbornadiene is suggested.
DOI: 10.1134/S0023158410030079
Cycloaddition
clo[2.2.1]heptadieneꢀ2,5 (norbornadiene,
reactions
involving
bicyꢀ
) and an
The reagents were distilled under reduced pressure
prior to use. Bis(η3ꢀallyl)nickel was synthesized by a
standard procedure [5].
I
activated olefin make it possible to obtain various carꢀ
bocyclic compounds. The double bond in the olefin
participating in these reactions is usually activated due
to the electronꢀwithdrawing group or is an element of
a strained cycle [1, 2]. Owing to the specific features of
the structure of norbornadiene and activated olefins,
these reactions proceed via multiple routes [3]. The
problems of isomerism are of supreme significance.
The general procedure of the cycloaddition reacꢀ
tion involving norbornadiene was as follows. Approꢀ
priate amounts of the starting compounds and the solꢀ
vent were placed in an evacuated 10ꢀml batch reactor.
Dissolved oxygen was removed by three cycles of
freezing to the liquid nitrogen temperature and thawꢀ
ing. Then a weighed sample of bis(η3ꢀallyl)nickel was
introduced into the reactor in vacuo. The reactor was
filled with highꢀpurity argon containing <10–4 vol %
oxygen and was brought to a preset temperature. The
reaction was carried out at 60°С for 8 h. After the reacꢀ
tion was complete, the reaction solution was purged
with air until the catalytic system decomposed entirely.
The decomposed catalyst was filtered from soluble
products using a silica gel bed on a porous filter. The
filtrate was concentrated on a rotary evaporator and
analyzed.
We demonstrated earlier that, in the presence of
bis(η3ꢀallyl)nickel, norbornadiene reacts with acrylic
acid esters to form the corresponding [2+2+2]ꢀ
cycloadducts with endo and exo structures and norborꢀ
nadiene homodimers [4].
In the present work, the range of substrates was
considerably widened to reveal specific features of the
mechanism of this reaction. We studied the reactions
of norbornadiene with unsaturated compounds of varꢀ
The reaction products were analyzed by gas chroꢀ
matography (Kristall 2000 M chromatograph, flameꢀ
ionization detector, Zebron ZBꢀ5 and HPꢀ50+ capilꢀ
lary columns) and gas chromatography coupled with
mass spectrometry (Agilent Technologies 6890
GC/5973N MSD instrument, HPꢀ1 capillary colꢀ
umn). The spectral characteristics of the compounds
were compared with earlier data [4].
ious classes: acrylic esters (methyl, ethyl, nꢀbutyl, tertꢀ
butyl, and 2ꢀmethyladamantyl acrylates), acrolein,
methacrolein, methyl vinyl ketone, acrylonitrile, 2ꢀ
methylacrylonitrile, furanone, vinyl acetate, and
maleic anhydride.
EXPERIMENTAL
RESULTS AND DISCUSSION
Toluene, diethyl ether, 1,2ꢀdichloroethane, aceꢀ
tone, and methanol (all highꢀpurity grade) were puriꢀ
fied using standard methods and stored according to
the requirements imposed on these solvents.
The analysis of the reaction solutions shows that
the reactions of norbornadiene with a wide range of
activated olefins are characterized by common reguꢀ
larities and afford endo and exo isomers (IIa and IIb
,
370

CATALYTIC SYNTHESES OF POLYCYCLIC COMPOUNDS
Table 1. Reactions of norbornadiene with activated olefins
371
Yield, %
Ratio
VI
Norbornadiene
conversion, %
Olefin
norbornadiene [2+2+2]ꢀcycloadducts
jomodimers of norbornadiene and olefin
III
:
IV
:
V
:
IIa/IIb
Methyl acrylate
79.4
49.7
95.2
57.2
47.2
31.6
18.4
8.9
29
36
40
52
75
12
98
6
71
64
60
48
25
88
2
traces : 77 : 20 : 3
traces : 76 : 21 : 3
traces : 78 : 20 : 2
traces : 77 : 20 : 3
3 : 77 : 15 : 5
48 : 52
49 : 51
51 : 49
56 : 44
71 : 29
58 : 42
91 : 9
Ethyl acrylate
nꢀButyl acrylate
tertꢀButyl acrylate
2ꢀMethyladamantyl acrylate
Acrylonitrile
2 : 73 : 22 : 3
2ꢀMethylacrylonitrile
Acrolein
traces : 92 : 7 : 1
6 : 88 : 5 : traces
traces : 75 : 22 : 3
traces : 76 : 22 : 2
93
97
95
95 : 5
Methyl vinyl ketone
Furanone
4.4
3
97 : 3
22.2
5
95 : 5
Note: Reaction conditions: toluene solvent, [norbornadiene] /[Ni(C H ) ] = 20 : 1, [norbornadiene] = 2.3 mol/l, [olefin] = 1.2 mol/l.
0
3
5 2 0
0
0
respectively) of the [2+2+2]ꢀcycloadducts between an [2+2]ꢀ and [2+2+2]ꢀhomodimers of norbornadiene
olefins and norbornadiene (reaction (1)) and various
(
III–VI) (reaction (2)).
+
(1)
(2)
I
+
X
X
X
IIa
IIb
+
+
+
+
III
IV
V
VI
(Х – electronꢀwithdrawing substituent
)
Under these conditions, some olefins (vinyl aceꢀ
tate, methacrolein, maleic anhydride) undergo no
cycloaddition to norbornadiene. In these cases, highꢀ
molecularꢀweight compounds are formed as a rule.
It is well known that norbornadiene is an efficient
stabilizer of the zeroꢀvalence nickel catalysts even in
the absence of ligands traditional in metal complex
catalysis (phosphines, phosphites, amines, and othꢀ
ers). To reveal the specific features of the behavior of
the nickel systems, we attempted the homodimerizaꢀ
tion of olefins under similar conditions in the absence
of norbornadiene. However, no products were
It follows from the data in Table 1 that the reactions
involving all of the substrates proceed via various
routes, including those leading to the formation of
diverse regioꢀ and stereoisomers.
observed. Moreover, in several cases, bis(η3
ꢀ
allyl)nickel was unstable and decomposed into nickel
metal and 1,5ꢀhexadiene.
In all cases, no formation of olefin homodimers
was observed, although the possibility of this process in
the presence of norbornadiene was established by carꢀ
rying out the reaction involving methyl vinyl ketone
on a heterogeneous nickel catalyst [6].
The homodimerization of norbornadiene under
the same conditions, but without an olefin, affords
exo
and endo
ꢀ
trans
ꢀ
ꢀ
exo
endo
(
III), exo
ꢀ
trans
ꢀ
ꢀ
endo
endo
(
IV) pentacyclic
(
V
) and exo
(VI) hexacyclic
KINETICS AND CATALYSIS Vol. 51
No. 3
2010

372
EFROS et al.
Table 2. Codimerization of norbornadiene with acrylic acid esters
Composition
of the olefin mixture
Yield, %
Ratio
Norbornaꢀ
diene conꢀ
version, %
[2+2+2]ꢀcycloadducts
of norbornadiene and acrylates
IIa : IIb
norbornaꢀ
diene
olefin1
olefin2
III : IV : V : VI
dimers
olefin1
olefin2
olefin1 olefin2
Ethyl
acrylate
nꢀButyl acrylate
95
96
38.5
38.5
31.5
30.0
1 : 76 : 20 : 3
49 : 51 51 : 49
Methyl
acrylate
tertꢀButyl acrylate
36.0
25.5
traces : 77 : 20 : 3 48 : 52 56 : 44
Note: Reaction conditions: toluene solvent, [norbornadiene] /[Ni(C H ) ] = 20 : 1, [norbornadiene] = 2.3 mol/l, [olefin
] = [olefin ] =
1 0 2 0
0
3
5 2 0
0
0.6 mol/l.
dimers as the reaction products. In addition, the prodꢀ
ucts of norbornadiene allylation form in stoichiometꢀ
ric amounts. In this case, the major reaction product is
To elucidate the character of the coordination of
the molecules in the key intermediates of the catalytic
process, we carried out experiments in which norborꢀ
nadiene competitively interacted simultaneously with
the exo
ꢀ
trans
ꢀ
exo dimer of norbornadiene (III) (up to
90%), and the hexacyclic isomers (
formed in small amounts (<2% in aggregate) [7–9].
V
and VI) are
two olefins (with ethyl and nꢀbutyl acrylates or with
methyl and tertꢀbutyl acrylates) (Table 2). An analysis
of the reaction products shows that the reaction
affords norbornadiene homodimers and the [2+2+2]ꢀ
cycloaddition products of each olefin. No products of
olefin crossꢀcoupling were found. The stereoselectivꢀ
ity of [2+2+2]ꢀcycloadduct formation and the ratio of
the norbornadiene homodimers remain the same as in
individual reactions (Table 1). These results indicate
In the presence of activated olefins, the composiꢀ
tion of the norbornadiene dimers becomes different:
the exo
is almost absent and the major product is the exo
trans
endo
ꢀ
trans
ꢀ
exo homodimer of norbornadiene (III
)
ꢀ
ꢀ
ꢀ
endo isomer (IV). In addition, the hexacyclic
endo ) and endo exo VI) isomers are formed.
(
V
ꢀ
(
It is important that the ratio between the norbornaꢀ that the key intermediate should contain only one oleꢀ
diene homodimers remains almost unchanged in the
reactions involving all substrates except 2ꢀmethylacryꢀ
lonitrile and acrolein. With these two substrates, the
ratios of the norbornadiene dimers also differ insignifꢀ
icantly (Table 1).
fin molecule, because the mutual influence of olefins
is absent for the hypothetical intermediate and all proꢀ
cesses proceed via independent parallel routes.
The constant ratio of the norbornadiene
homodimers also indicates their formation from interꢀ
mediates containing only norbornadiene molecules—
another route (scheme).
The total yield of the [2+2+2]ꢀcycloadducts
increases and the yield of the norbornadiene
homodimers decreases with the enhancement of the
electronꢀacceptor strength of the substituent in the
olefin (in the 2ꢀmethyladamantyl acrylate < tertꢀbutyl
The data obtained confirm the earlier suggested
mechanism of [2+2+2]ꢀcycloaddition of acrylates to
norbornadiene [4]. The homodimers of norbornaꢀ
diene and cycloadducts are formed via parallel routes
from the common intermediate Ni(norbornadiene)2
[7–9]. The intermediates Ni(norbornadiene)3 and
Ni(norbornadiene)2(olefin) are formed in the initial
complex after the change in the coordination mode of
one of the norbornadiene molecules. The subsequent
successive formation of the metallocycles and reducꢀ
tive elimination yield the reaction products.
acrylate < nꢀbutyl acrylate < ethyl acrylate < methyl
acrylate < acrylonitrile <acrolein < furanone < methyl
vinyl ketone order). It is likely that 2ꢀmethylacryloniꢀ
trile falls out of this series.
The reactions of norbornadiene with acrylic acid
esters and acrylonitrile differ insignificantly in stereoꢀ
selectivity. The reactions involving methyl and ethyl
acrylates afford exo and endo cycloadducts with norꢀ
bornadiene in equal amounts, and the exo isomers are
formed in the other cases. The reaction of norbornaꢀ
diene with the olefin having the most bulky substituꢀ
ent, namely, 2ꢀmethyladamantyl acrylate, affords 71%
exo isomer. The other olefins containing a strong elecꢀ
tronꢀwithdrawing group give more exo isomers (up to
95–97%).
The ratio between the rates of the parallel reactions
determines the selectivity of the process. Olefins with
a stronger electronꢀwithdrawing substituent are more
easily coordinated, increasing the fraction of heteroliꢀ
gand complexes, and, accordingly, the yield of the
[2+2+2]ꢀcycloadducts increases. Evidently, the stereoꢀ
KINETICS AND CATALYSIS Vol. 51
No. 3
2010

CATALYTIC SYNTHESES OF POLYCYCLIC COMPOUNDS
373
VI
IV
V
Ni
Ni
X
Ni
X
X
X
IIa
IIb
(Х, electronꢀwithdrawing substituent
)
Scheme. Mechanism of the interaction between norbornadiene and olefins in the presence of nickel (0) complexes.
selectivity of the process depends on the spatial strucꢀ mediates. The polarity of the medium affects considꢀ
ture of the intermediates.
erably the ratio of the heteroligand nickel complexes,
which results in a change in the stereoselectivity of forꢀ
mation of the cycloadducts of norbornadiene and oleꢀ
fin [10]. The ratios between various norbornadiene
homodimers remain almost unchanged. This influꢀ
ence of the solvent confirms that the exo and endo
products form from the intermediates with different
spatial orientations of the molecules and indirectly
indicates that these intermediates contain a single oleꢀ
fin molecule.
The role of the stabilization of the key intermediꢀ
ates by the solvent molecules should be taken into
account at each stage of the reaction. The influence of
the medium was studied for the reaction of norbornaꢀ
diene with tertꢀbutyl acrylate (TBA). The reaction was
carried out in toluene, diethyl ether, 1,2ꢀdichloroetꢀ
hane, acetone, and methanol. A linear dependence of
the logarithm of the ratio of the exo to endo cycloadꢀ
ducts of norbornadiene and TBA on the molar polarꢀ
izability of the solvent was observed (figure).
A tendency to lower reactant conversions is
The solvent effect on the cycloaddition reaction observed as the polarity of the medium is increased
can be explained by the stabilization of the key interꢀ (Table 3). This can be due to the stabilization of the
KINETICS AND CATALYSIS Vol. 51
No. 3
2010

374
EFROS et al.
Table 3. Reaction of norbornadiene and TBA in various media
Yield, %
Ratio
VI IIa : IIb
Norbornaꢀ
Dielectric
constant*
Solvent
diene conꢀ
version, %
norbornadiene [2+2+2]ꢀcycloadducts
homodimers of norbornadiene and TBA
III
:
IV
:
V
:
Toluene
2.38
4.34
10.4
20.7
32.6
52.2
40.5
21.2
19.5
26.3
52
39
52
61
38
48
61
48
39
62
traces : 77 : 20 : 3
1 : 76 : 20 : 3
57/43
53/47
48/52
46/54
36/64
Diethyl ether
1,2ꢀDichloroethane
Acetone
2 : 75 : 21 : 2
traces : 80 : 15 : 5
traces : 82 : 15 : 3
Methanol
Note: Reaction conditions: toluene solvent, [norbornadiene] /[Ni(C H ) ] = 20 : 1, [norbornadiene] = [TBA] = 0.8 mol/l.
0
3
5 2 0
0
0
* According to [11].
intermediates by solvent molecules. According to the
mechanism proposed, the starting intermediate in
both reaction routes is lowꢀpolarity Ni(norbornaꢀ
diene)2, which is more stable in nonpolar media.
ACKNOWLEDGMENTS
This work was supported by the Russian Foundaꢀ
tion for Basic Research (project no. 08ꢀ03ꢀ00743ꢀa)
and by the President of the Russian Federation (grant
no. MKꢀ1809.2007.3).
It should be mentioned that the solvent effect is
weaker than the influence of the nature of the olefin
involved in the reaction.
REFERENCES
Thus, the cycloadditions of the olefins to norborꢀ
nadiene are of the same character. This study revealed
specific features of the mechanism of the process and
established the factors affecting the regioꢀ and stereoꢀ
selectivity.
1. Lautens, M., Klute, W., and Tam, W., Chem. Rev.
1996, vol. 96, p. 42.
2. Noyori, R., Umeda, I., Kawauchi, H., and Takaya, H.,
J. Am. Chem. Soc., 1975, vol. 97, p. 812.
3. Lautens, M., Edwards, L., Tam, W., and Lough, A.,
,
J. Am. Chem. Soc., 1995, vol. 117, p. 10 276.
4. Dmitriev, D.V., Manulik, O.S., and Flid, V.R., Kinet.
Katal., 2004, vol. 45, no. 2, p. 181 [Kinet. Catal. (Engl.
Transl.), vol. 45, no. 2, p. 165].
5. Wilke, G., Bogdanovich, B., Hardt, P., et al., Angew.
Chem., Int. Ed. Engl., 1966, vol. 5, p. 151.
log(Cexo/Cendo)
0.15
1
0.10
0.05
0
2
6. Vetrova, O.B., Katsman, E.A., Zhavoronkov, I.P., et al.,
Zh. Org. Khim., 1991, vol. 27, p. 2624.
−
−
−
−
−
−
0.05
0.10
0.15
0.20
0.25
0.30
7. Flid, V.R., Manulik, O.S., Grigor’ev, A.A., and
3
Belov, A.P., Kinet. Katal., 2000, vol. 41, no. 5, p. 658
4
[Kinet. Catal. (Engl. Transl.), vol. 41, no. 5, p. 597].
8. Flid, V.R., Manulik, O.S., Grigor’ev, A.A., and
5
Belov, A.P., Kinet. Katal., 2000, vol. 41, no. 5, p. 666
[Kinet. Catal. (Engl. Transl.), vol. 41, no. 5, p. 604].
2
4
6
8
10
ε – 1 ρ
2ε + 1M
12
9. Evstigneeva, E.M. and Flid, V.R., Izv. Akad. Nauk, Ser.
Khim., 2008, no. 4, p. 823.
10. Yoshikawa, S., Kiji, J., and Furukawa, J., Bull. Chem.
Soc. Jpn., 1975, vol. 48, no. 11, p. 3239.
11. Gordon, A.J. and Ford, R.A., The Chemist’s Companꢀ
ion: A Handbook of Practical Data, Techniques, and Refꢀ
erences, New York: Wiley, 1972.
3
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ × 10
Influence of the molar polarizability of the solvent on the
ratio of stereoisomers (exo endo) in the cycloaddition of
TBA to norbornadiene: ( ) toluene, ( ) diethyl ether;
) 1,2ꢀdichloroethane, ( ) acetone, and ( ) methanol.
/
1
2
(3
4
5
KINETICS AND CATALYSIS Vol. 51
No. 3
2010