Ruthenium-catalyzed carbonylation of allene: Direct synthesis of methacrylates and methacrylamides

Article abstract of DOI:10.1039/b205817k

Carbonylation reactions of allene in alcohols and amines in the presence of a ruthenium carbonyl catalyst under mild conditions gave methacrylates and methacrylamides, respectively, in good yields with an atom economy of 100%.

Full text of DOI:10.1039/b205817k

Ruthenium-catalyzed carbonylation of allene: direct synthesis of
methacrylates and methacrylamides
Da-Yang Zhou, Eiji Yoneda, Kiyotaka Onitsuka and Shigetoshi Takahashi*
The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka 567-0047,
Japan. E-mail: takahashi@sanken.osaka-u.ac.jp
Received (in Cambridge, UK) 17th June 2002, Accepted 15th October 2002
First published as an Advance Article on the web 31st October 2002
Carbonylation reactions of allene in alcohols and amines in
the presence of a ruthenium carbonyl catalyst under mild
conditions gave methacrylates and methacrylamides, re-
spectively, in good yields with an atom economy of 100%.
to give methacrylates directly. Indeed, several efforts have been
made so far to find effective catalysts for the direct synthesis of
methacrylates from allene. The first carbonylation of allene was
reported by Jenner and Lindsey5a using a Pt–Sn binary catalyst
in 1959, however it needs extremely severe reaction conditions.
Mori and Tsuji5b in 1972 and Grigg et al.6 recently reported the
syntheses of methacrylates by Fe(CO)5- and Pd-catalyzed
carbonylations, respectively, of allene. The former system,
however, showed a low activity for the carbonylation and the
latter is limited to the synthesis of aryl methacrylates such as
phenyl and naphthyl methacrylates. Now we have successfully
applied our ruthenium system, which is active towards the
cyclocarbonylation of allenyl alcohols as mentioned above, to
intermolecular alkoxycarbonylation of allene giving directly
methacrylates. Thus, allene was reacted with carbon monoxide
(15 atm) in the presence of a catalytic amount of Ru3(CO)12 in
ethanol at 100 °C for 3 h to give ethyl methacrylate 1 (R = Et,
EMA) in 88% yield (eqn. (2)).† Polymeric products were not
detected at all.9 Reactions at higher (120 °C) or lower (80 °C)
temperature resulted in a decrease in the yield of EMA. Use of
solvents such as THF and dioxane also decreased the yield.
Co2(CO)8 and Rh6(CO)16 catalysts did not give EMA under the
same reaction conditions, but instead led to the formation of
oligo- and poly-ketones.9 RuCl3 itself showed a moderate
activity and using tertiary amine additives such as Et3N and a-
picoline improved the yield of EMA to ca. 70%, suggesting
ruthenium catalysts to exhibit a distinctive activity towards the
present alkoxycarbonylation of allene.
Carbonylations of unsaturated hydrocarbons have provided
practical methods for the production of a variety of carbonyl
compounds such as aldehydes and carboxylic acid derivatives.1
There is still continuous interest in the development of new
carbonylation systems in both academic and industrial fields.
The development is essentially dependent on finding new metal
catalysts effective for carbonylations. It is well known that
group 9 metals such as cobalt and rhodium show efficient
catalytic activities towards several types of carbonylation
reactions of alkenes and alkynes.2,3 On the other hand, few
carbonylations of 1,2-alkadienes (allenes) are known,4–6 al-
though there are many reports on transformation reactions of
allene catalyzed by group 10 metals such as nickel and
palladium.6,7 Recently we reported a new type of carbonylation
in which a ruthenium complex acts as an effective catalyst for
cyclocarbonylation of allenyl alcohols giving lactones (eqn.
(1)).8 Now we have found a new ruthenium-catalyzed alkoxy-
(1)
carbonylation of allene which gives methacrylates in a high
yield with an atom economy of 100% (eqn. (2)).
We examined the scope of the present carbonylation of allene
with respect to alcohols and the results obtained are summarized
in Table 1. Reactions in methanol, butanol and 2-ethylhexanol
afforded corresponding the methacrylates in a good yield, while
use of tert-butyl and benzyl alcohols gave a lower yield of
methacrylates (entries 4 and 6). Increase of carbon monoxide
pressure improved the efficiency of the carbonylation and the
reaction in benzyl alcohol under a CO pressure of 30 atm at 80
°C gave benzyl methacrylate in 73% yield. Phenol did not give
the corresponding methacrylate under the same reaction
conditions,6 while 1,2-addition product 2 was formed as a major
product (40% yield). Diols like ethylene glycol gave the
(2)
Poly(methacrylate)s are one of the common polymers which
have a wide range of applications. Practical syntheses of the
monomer, alkyl methacrylates, have been extensively studied,
and nowadays in industry methacrylates are produced mainly by
three methods4 consisting of several tansformation steps which
involve oxidation and condensation with undesirable formation
of wastes. One might expect the alkoxycarbonylation of allene
Table 1 Carbonylation of allene in alcohols or aminesa
Entry
Alcohol or amine
Product
Yieldc (%)
1
2
3
4
5
6
7
8
9
MeOH
EtOH
BuOH
tBuOH
CH2NC(Me)–COOMe
CH2NC(Me)–COOEt
CH2NC(Me)–COOBu
CH2NC(Me)–COOtBu
CH2NC(Me)–COOCH2CH(Et)(CH2)3Me
CH2NC(Me)–COOCH2Ph
CH2NC(Me)–COOCH2CH2OEt
CH2NC(Me)–CONEt2
CH2NC(Me)–CONBu2
CH2NC(Me)–COHN(CH2)3NMe2
84
88 (71)d
57
27 (36)e
73
27 (73)e
80
80
89 (68)d
10f
Me(CH2)3CH(Et)CH2OH
PhCH2OH
HOCH2CH2OEt
b
HNEt2
b
HNBu2
H2N(CH2)3NMe2
b
10
a Reaction conditions: allene 9 mmol; Ru3(CO)12 0.063 mmol; alcohol 15 ml; CO 15 atm; 100 °C; 3 h. b Reaction conditions: allene 3.4 mmol; Ru3(CO)12
0.014 mmol; amine 1.5 mmol; dioxane 15 ml; CO 13 atm; 100 °C; 18 h. c GC analysis. d Isolated yield. e CO 30 atm; 80 °C; 5 h. f A complex mixture of
products.
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CHEM. COMMUN., 2002, 2868–2869
This journal is © The Royal Society of Chemistry 2002

allene (9 mmol, 360 mg) and CO (15 atm). Reaction at 100 °C for 3 h gave
ethyl methacrylate in 88% yield (GC). The reaction mixture was poured into
water (60 ml) and extracted with diethyl ether. The fractional distillation
gave 730 mg (71% yield) of ethyl methacrylate.
corresponding methacrylate, in which one of two hydroxyl
groups remained free, in 8% yield along with uncarbonylated 3
as the major product (52% yield) (eqn. (3)).
1 H. M. Colquhoun, D. J. Thompson and M. V. Twigg, Carbonylation:
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(3)
Interestingly, the present catalytic system is also active for
the aminocarbonylation of allene yielding methacrylamides
(eqn. (4)). Secondary amines gave methacrylamides in a good
yield, but use of primary amines gave methacrylamides in a low
yield along with several unidentified products (Table 1, entries
8–10).
4 E. Drent, W. W. Jager, J. J. Keijsper and F. G. M. Niele, Applied
Homogeneous Catalysis with Organometallic Compounds, ed. B.
Cornils and W. A. Herrmann, VHC, Weinheim, Germany, 1996, vol. 1,
cp. 2.
(4)
5 E. L. Jenner and R. V. Lindsey, Jr., US Pat., 2 876 254, 1959; Chem.
Abstr., 1959, 53, 17906f; (b) Y. Mori and J. Tsuji, Jpn. Pat., 4 703 7931,
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Methylacetylene, which is an isomer of allene and is
carbonylated by the catalysis of palladium and platinum,4,10 did
not undergo carbonylation in the present catalytic system.
In summary, we have shown that ruthenium carbonyl
effectively catalyzes intermolecular alkoxy- and amino-carbo-
nylation of allene under mild conditions, which may provide a
new simple and effective method for the production of a variety
of methacrylates and methacrylamides directly from allene with
an atom economy 100%.
9 J.-c. Choi, I. Yamaguchi, K. Osakada and T. Yamamoto, Macromole-
cules, 1998, 31, 8731.
Notes and references
† Carbonylation reactions were performed in a 100 ml stainless steel
autoclave equipped with a stirrer bar and the following were placed in the
autoclave in the order, Ru3(CO)12 (0.063 mmol, 40 mg), EtOH (15 ml),
10 Y. Kushino, K. Itoh, M. Miura and M. Nomura, J. Mol. Catal., 1994, 89,
151; Daicel Chem. Ind. Ltd., Jpn. Pat., 08/84933, 1996; Daicel Chem.
Ind. Ltd., JP Pat., 09/173 860 (1997).
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