A novel non-metathetic behavior of Grubbs catalyst: Ruthenium-mediated intramolecular [3 + 2] cycloaddition of bis-1,3-dienes

Article abstract of DOI:10.1016/j.jorganchem.2012.09.004

A ruthenium-mediated intramolecular [3 + 2] cycloaddition of bis-1,3-dienes to give bicyclic products, which is a novel non-metathetic behavior of Grubbs catalyst, is reported. The formation of a ruthenium-olefin complex is proposed to be a key step for the success of the reaction.

Full text of DOI:10.1016/j.jorganchem.2012.09.004

Journal of Organometallic Chemistry 723 (2013) 171e175
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Journal of Organometallic Chemistry
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A novel non-metathetic behavior of Grubbs catalyst: Ruthenium-mediated
intramolecular [3 þ 2] cycloaddition of bis-1,3-dienes
*
Ryukichi Takagi , Koumei Yamamoto, Yoshikazu Hiraga, Satoshi Kojima, Manabu Abe
Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A ruthenium-mediated intramolecular [3 þ 2] cycloaddition of bis-1,3-dienes to give bicyclic products, which
is a novel non-metathetic behavior of Grubbs catalyst, is reported. The formation of a rutheniumeolefin
complex is proposed to be a key step for the success of the reaction.
Received 10 August 2012
Received in revised form
5 September 2012
Ó 2012 Elsevier B.V. All rights reserved.
Accepted 13 September 2012
Keywords:
Grubbs catalyst
Non-metathetic reaction
Ruthenium-mediated reaction
Intramolecular [3 þ 2] cycloaddition
Bis-1,3-dienes
1. Introduction
On the basis of this hypothesis, we examined the reaction of
diene 1a with rutheniumecarbene complex I (Scheme 2, entry 1).
The stable and highly active rutheniumecarbene complexes
developed by Grubbs and others as catalysts for olefin metathesis
are a series of innovative reagents for carbonecarbon bond
formation reactions in organic synthesis (Fig. 1) [1]. Nowadays,
ruthenium-catalyzed olefin metathesis has become an important
tool in many fields of chemistry, including organic synthesis [2,3],
biochemistry [4], and green chemistry [5]. Furthermore,
rutheniumecarbene complexes have been reported to catalyze
non-metathetic reactions [6].
Several tandem processes involving olefin metathesis have been
developed by taking advantage of both the potential reactivity of
olefins and the tolerance of rutheniumecarbene complexes to
various functional groups. Many successful tandem processes
involve combinations of olefin metathesis reactions with
ruthenium-catalyzed non-metathetic reactions that proceed under
the same conditions [7].
In this reaction, a stoichiometric amount of complex I was required
to ensure complete consumption of diene 1a. Although the
compounds 3 and 4, which are the products of an RCM or a tandem
RCM/6p-electrocyclization process of diene 1a, respectively, were
not obtained, an unexpected bicyclic compound 2a was obtained in
29% yield, together with styrene (ca. 35% yield) and benzaldehyde
(ca. 10% yield) (Fig. 2) [9,10]. When diene 1a was treated with
complex II or III, which are more reactive olefin metathesis cata-
lysts than complex I, a stoichiometric amount of complex was not
required to ensure complete consumption of diene 1a (Scheme 2,
entries 2 and 3). However, no improvement on the chemical yield of
2a was observed. In this article, we wish to report the detail of the
novel non-metathetic behavior of Grubbs catalyst in the reaction of
diene 1.
2. Results and discussion
The 6p-electrocyclization is also a suitable reaction for the
development of tandem process [8]. We hypothesized that
a combination of an RCM between terminal bis-1,3-diene to
A plausible reaction pathway for the reaction of diene 1a with
complex I is outlined in Scheme 3. The reaction pathway can be
rationalized by a ruthenium-mediated intramolecular [3 þ 2]
cycloaddition. Thus, cross metathesis reaction of diene 1a with
complex I produce ruthenium-alkenyl carbene complex 5, followed
by an intramolecular [3 þ 2] cycloaddition to afford bicyclic
compound 2a. The reaction pathway accords with the formation of
styrene and the requirement for a stoichiometric amount of
complex I. Benzaldehyde may be formed in the reaction of complex
generate
a 1,3,5-hexatriene with the subsequent 6p-electro-
cyclization would provide a useful tandem process for building
polycyclic molecules in a one-pot process (Scheme 1).
* Corresponding author. Tel.: þ81 82 424 7434; fax: þ81 82 424 0727.
E-mail address: rtakagi@hiroshima-u.ac.jp (R. Takagi).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.09.004

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R. Takagi et al. / Journal of Organometallic Chemistry 723 (2013) 171e175
I with adventitious traces of H2O in the solvent and/or atmosphere
[11]. There was no improvement in the chemical yield of 2a when
we used complex II or III. This may be as a result that complex II or
III more catalyze oligomerization of diene 1a by cross metathesis
than complex I. Therefore, we considered complex I to be a suitable
reagent for the ruthenium-mediated intramolecular [3 þ 2] cyclo-
addition. Complex I was used for the further investigations to
explore the scope of the cycloaddition.
Fig. 1. Rutheniumecarbene complexes IeIII.
Next, we examined the effects of the substituents on the diene
moieties to the novel non-metathetic reaction (Table 1). The
chemical yields of compounds 2 formed in the reactions of the C30-
demethylated diene 1b and the C2-methylated diene 1c were
superior to that of 2a. The reaction of diene 1c proceeded with
a satisfactory yield. This improvement in reaction yield may be due
to inhibition of cross metathesis oligomerization of diene 1c as
a result of the introduction of the methyl groups at the C2- and the
C30-position.
Scheme 1. Hypothesized tandem process of bis-dienes.
The formation of other bicyclic systems (5-5 and 5-7 ring
systems) by the ruthenium-mediated intramolecular [3 þ 2]
cycloaddition of dienes 1d and 1e were examined (Table 2). The
bicyclic product 2d was formed by treating diene 1d with complex I
in refluxing CH2Cl2 for 3 h [10]. In the case of diene 1e, the
ruthenium-mediated intramolecular [3 þ 2] cycloaddition of the
initially generated rutheniumealkenyl carbene complex 5 did not
proceed. Instead, the rutheniumealkenyl carbene complex 5 reac-
ted with styrene to give the cross metathesis product 6.
The ruthenium-mediated intramolecular [3 þ 2] cycloaddition
of dienes 1f-h, which are geometric isomers of dienes 1c,d at the
C3eC4 or the C30eC40 double bonds, was also examined (Table 3).
The reaction of diene 1f with complex I did not afford a [3 þ 2]
cycloaddition product but the cross metathesis product 7. When
dienes 1g and 1h were treated with complex I, a high reaction
temperature was required to ensure consumption of the dienes. In
the reactions, the trace amounts of corresponding [3 þ 2] cyclo-
addition products 2g and 2h were obtained, respectively (Table 3,
entries 2 and 3). These experimental results suggest that the
substituents and geometry of the diene moieties and the ring sizes
Scheme 2. Reaction of diene 1a with complexes IeIII.
Fig. 2. RCM product 3 and RCM/6p-electrocyclization product 4.
Scheme 3. Plausible reaction pathway for the reaction of diene 1a with complex I to bicyclic compound 2a.
Table 1
Reaction of dienes 1b,c with complex I.
Entry
Diene
Conditions
Producta
1
2
Complex I (0.7 equiv.), 4 h
Complex I (1.6 equiv.), 12 h
a
Isolated yield.

R. Takagi et al. / Journal of Organometallic Chemistry 723 (2013) 171e175
173
Table 2
Reaction of dienes 1d,e with complex I.
Entry
Diene
Conditions
Producta
1
Complex I (1.2 equiv.), 3 h
2
Complex I (2.2 equiv.), 9 h
a
Isolated yield.
b
Compound 6 could not be completely purified due to instability.
Table 3
Reaction of dienes 1f-h with complex I.
Entry Diene
Conditions
Producta
1
Complex I (1.6 equiv.), 5 h
2
Complex I (1.0 equiv.), PhCl, 100 ꢀC, 20 h
3
Complex I (1.6 equiv.), PhCl, 100 ꢀC, 18 h
a
Isolated yield.
b
Compound 7 could not be completely purified due to instability.
of the products are important factors for the formation of the
ruthenium-mediated intramolecular [3 þ 2] cycloadducts.
result suggests that the coordination of the C1eC2 double bond to
Ru metal in rutheniumealkenyl carbene complex 5 is essential for
the success of the intramolecular [3 þ 2] cycloaddition as is the case
in olefin metathesis [12]. When dienes 1a,b were treated with
complex I, other bicyclic product, which was formed by the
ruthenium-mediated intramolecular [3 þ 2] cycloaddition between
the C2eC4 moiety and the C30eC40 double bond, was not observed.
The fact may indicate that the coordination of the C10eC20 double
bond to Ru metal in rutheniumealkenyl carbene complex, which is
generated by cross metathesis between the C1eC2 double bond
and complex I, is relatively unstable and the ruthenium-alkenyl
carbene complex lead to oligomerization.
In the ruthenium-mediated intramolecular [3 þ 2] cycloaddi-
tion, new CeC bonds are formed between the C3eC4 double bond
and the C20eC40 moiety. At the same time, the C1eC2 double bond
does not formally participate in the CeC bond formation. To
elucidate the role of the C1eC2 double bond, we examined the
reaction of complex I with diene 1i, in which the C1eC4 diene
moiety was replaced by one double bond (Scheme 4). In this case,
the ruthenium-mediated intramolecular [3 þ 2] cycloaddition did
not proceed and the cross metathesis product 8 was obtained. The
A proposed mechanism for the ruthenium-mediated intra-
molecular [3 þ 2] cycloaddition is outlined in Scheme 5. This
mechanism, which is based on that of a metal-mediated [3 þ 2]
cycloaddition of Fischer alkenyl carbene complexes [13], involves
the formation of ruthenacycle A by an intramolecular metalla-
Diels-Alder reaction of rutheniumealkenyl carbene complex 5.
This is followed by the reductive elimination to generate the [3 þ 2]
Scheme 4. Reaction of diene 1i with complex I.

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R. Takagi et al. / Journal of Organometallic Chemistry 723 (2013) 171e175
Scheme 5. Proposed mechanism for the ruthenium-mediated intramolecular [3 þ 2] cycloaddition and relative energies for the model system.
cycloaddition product 2a. The computations on the model reaction,
116.0, 59.9, 56.0, 52.7, 52.6, 50.7, 49.0, 33.0, 28.7, 27.4,12.9; HR-EIMS
using the density functional theory (BP86), support the reaction
m/z [Mþ] calcd. for C16H22O4 278.1518, found 278.1508.
mechanism [14]. Thus, the Gibbs energy of activation (D
Gz) at 298 K
was computed to be 28.7 kcal molꢁ1, which is relative to complex 5
4.4. 5,5-Dimethoxycarbonyl-3,7a-dimethyl-1-(prop-1-en-2-yl)-
3a,4,5,6,7,7a-hexahydro-1H-indene (2c)
(Scheme 5) [15].
1H NMR (500 MHz, C6D6)
d
5.39 (dq, J ¼ 4.7, 1.6 Hz, 1H), 4.92 (dq,
3. Conclusion
J ¼ 2.1, 1.5 Hz, 1H), 4.87 (dq, J ¼ 2.1, 1.0 Hz, 1H), 3.40 (s, 3H), 3.31 (s,
3H), 2.72e2.68 (m, 1H), 2.71 (dt, J ¼ 13.1, 2.5 Hz, 1H), 2.58 (ddt,
J ¼ 13.3, 3.8, 2.5 Hz, 1H), 2.28 (ddq, J ¼ 14.1, 2.5, 1.6 Hz, 1H), 2.15 (dd,
J ¼ 14.1, 13.1 Hz, 1H), 2.02 (td, J ¼ 13.3, 4.6 Hz, 1H), 1.94 (td, J ¼ 13.3,
3.8 Hz, 1H), 1.70 (ddd, J ¼ 13.3, 4.6, 2.5 Hz, 1H), 1.62 (s, 3H), 1.57 (dt,
In conclusion, a ruthenium-mediated intramolecular [3 þ 2]
cycloaddition of bis-1,3-dienes to give bicyclic products, which is
a novel non-metathetic behavior of Grubbs catalyst, is discovered.
It is suggested that the coordination of the C1eC2 double bond to
Ru metal in rutheniumealkenyl carbene complex 5 is a key step
for the success of the intramolecular [3 þ 2] cycloaddition.
Although the ruthenium-mediated intramolecular [3 þ 2] cyclo-
addition is very narrow scope at present stage, the mechanistically
and synthetically fascinated reaction would stimulate further
investigation on the novel type of ruthenium-mediated non-
metathetic reactions.
J ¼ 2.7, 1.6 Hz, 3H), 0.75 (s, 3H); 13C NMR (125 MHz, C6D6)
d 172.7,
171.7, 144.5, 141.2, 127.2, 111.7, 62.0, 56.2, 53.4, 52.2 (ꢂ2), 48.7, 35.1,
28.1, 28.0, 24.0, 14.4, 13.2; HR-EIMS m/z [Mþ] calcd. for C18H26O4
306.1831, found 306.1844.
4.5. 2,2-Dimethoxycarbonyl-3a,6-dimethyl-4-(prop-1-en-2-yl)-
1,2,3,3a,4,6a-hexahydropentalene (2d)
1H NMR (500 MHz, C6D6)
d 5.52 (s, 1H), 4.88 (s, 1H), 4.87 (s, 1H),
4. Experimental section
3.37 (s, 3H), 3.33 (s, 3H), 2.95e2.87 (m, 1H), 2.68 (d, J ¼ 12.3 Hz, 1H),
2.67 (bs, 1H), 2.59 (dd, J ¼ 12.1, 6.0 Hz, 1H), 2.38 (d, J ¼ 12.3 Hz, 1H),
2.24 (dd, J ¼ 13.9,12.2 Hz,1H),1.57 (bs, 3H),1.54 (s, 3H), 0.82 (s, 3H);
4.1. General procedure for the reaction of diene 1 with rutheniume
carbene complexes IeIII
13C NMR (125 MHz, C6D6)
d 173.2, 172.5, 144.2, 139.9, 130.8, 110.9,
65.2, 62.4, 58.4, 57.5, 52.4 (ꢂ2), 43.4, 31.7, 23.0, 15.5, 15.0; HR-EIMS
Diene 1 and rutheniumecarbene complex I were dissolved in
CH2Cl2 (10 mM). The mixture was refluxed until diene was dis-
appeared. The solvent was evaporated. The residue was purified by
preparative TLC on silica gel (hexane/AcOEt).
m/z [Mþ] calcd. for C17H24O4 292.1675, found 292.1679.
Acknowledgments
NMR and MS measurements were made using JEOL JMN-LA500
and JEOL SX-102A, respectively, at the Natural Science Center for
Basic Research and Development (N-BARD), Hiroshima University.
This work was supported by a Grant-in-Aid for Scientific Research
(No. 20550045) from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan.
4.2. 5,5-Dimethoxycatbonyl-3,7a-dimethyl-1-vinyl-3a,4,5,6,7,7a-
hexahydro-1H-indene (2a)
1H NMR (500 MHz, C6D6)
d
5.76 (ddd, J ¼ 18.2, 10.4, 7.8 Hz, 1H),
5.29 (bs,1H), 5.07 (d, J ¼ 7.8 Hz,1H), 5.04 (s,1H), 3.39 (s, 3H), 3.30 (s,
3H), 2.74e2.71 (m, 1H), 2.70 (dt, J ¼ 12.7, 1.8 Hz, 1H), 2.57 (d,
J ¼ 13.7 Hz, 1H), 2.23 (d, J ¼ 13.7 Hz, 1H), 2.13 (dd, J ¼ 13.7, 12.5 Hz,
1H), 1.99 (td, J ¼ 13.7, 4.6 Hz, 1H), 1.81 (td, J ¼ 13.7, 4.2 Hz, 1H), 1.61e
1.54 (m, 1H), 1.55 (bs, 3H), 0.77 (s, 3H); 13C NMR (125 MHz, C6D6)
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2012.09.004.
d
172.8, 171.8, 142.0, 137.5, 126.7, 115.8, 59.6, 56.4, 52.8, 52.2 (ꢂ2),
49.2, 33.7, 28.0, 27.7, 14.3, 13.4; HR-EIMS m/z [Mþ] calcd. for
C17H24O4 292.1675, found 292.1680.
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