Efficient one-to-one coupling of easily available 1,3-dienes with carbon dioxide

Article abstract of DOI:10.1021/ol2002094

An efficient one-to-one coupling reaction of atmospheric pressure carbon dioxide with 1,3-dienes is realized for the first time through PSiP-pincer type palladium-catalyzed hydrocarboxylation. The reaction is applicable to various 1,3-dienes including easily available chemical feedstock such as 1,3-butadiene and isoprene. This protocol affords a highly useful method for the synthesis of β,γ-unsaturated carboxylic acid derivatives from CO₂.

Full text of DOI:10.1021/ol2002094

ORGANIC
LETTERS
2011
Vol. 13, No. 7
1698–1701
Efficient One-to-One Coupling of Easily
Available 1,3-Dienes with Carbon Dioxide
Jun Takaya, Kota Sasano, and Nobuharu Iwasawa*
Department of Chemistry, Tokyo Institute of Technology, O-okayama, Meguro-ku,
Tokyo 152-8551, Japan
niwasawa@chem.titech.ac.jp
Received January 23, 2011
ABSTRACT
An efficient one-to-one coupling reaction of atmospheric pressure carbon dioxide with 1,3-dienes is realized for the first time through PSiP-pincer
type palladium-catalyzed hydrocarboxylation. The reaction is applicable to various 1,3-dienes including easily available chemical feedstock such
as 1,3-butadiene and isoprene. This protocol affords a highly useful method for the synthesis of β,γ-unsaturated carboxylic acid derivatives from CO2.
One-to-one coupling of CO2 with 1,3-dienes, some of
which are easily available bulk chemicals, in the transition-
metal-catalyzed CO2-fixation reaction is a formidable chal-
lenge despite its high potential as a practical method for the
preparation of carboxylic acid derivatives.1 The reason for
this scarcity is due to the facile dimerization of 1,3-dienes by
palladium(0) or nickel(0) complexes which are commonly
employed for such reactions. For example, Sasaki, Inoue,
and Hashimoto reported in 1976 the first example of the
Pd(0)-catalyzed coupling reaction of two molecules of
butadiene and CO2 to give a lactone along with butadiene
dimers.2 Since then, several research groups reported im-
provement in the yield and product selectivity by modifying
the metal complexes,3,4 and more recently, an intramole-
cular version of the reaction was developed employing a Ni
catalyst.5 All of these reactions include generation and
carboxylation of bis-allyl metallic species generated by
oxidative cyclization of two 1,3-butadiene units with low
valent metals, and there still has been no report on the
catalytic one-to-one coupling of CO2 with 1,3-butadienes.6
We previously reported the PSiP-pincer type palladium-
complex-catalyzed hydrocarboxylation reaction of allenes
(1) For reviews on transition-metal-promoted CO2-fixation reac-
tions, see: (a) Braunstein, P.; Matt, D.; Nobel, D. Chem. Rev. 1988,
88, 747. (b) Yin, X.; Moss, J. R. Coord. Chem. Rev. 1999, 181, 27. (c)
Sakakura, T.; Choi, J.-C.; Yasuda, H. Chem. Rev. 2007, 107, 2365. (d)
Zevaca, T.; Dinjus, E. Carbon Dioxide as Chemical Feedstock; Aresta, M.,
Ed.; Wiley-VCH: Weinheim, 2010; p 89. (e) Riduan, S. N.; Zhang, Y.
Dalton Trans. 2010, 39, 3347.
(2) (a) Sasaki, Y.; Inoue, Y.; Hashimoto, H. J. Chem. Soc., Chem.
Commun. 1976, 605. (b) Inoue, Y.; Sasaki, Y.; Hashimoto, H. Bull.
Chem. Soc. Jpn. 1978, 51, 2375.
(4) These reactions require high pressure CO2 and still have some
problems on the generality of substrates and product selectivity. Most of
the reported reactions employ simple 1,3-dienes such as 1,3-butadiene and
isoprene, and the products in these reactions are mainly five- or six-
membered lactones, carboxylic acids, and esters as carboxylation products
derived from the dimerized bis-allylmetallic intermediates. This diversity is
due to not only the various reactivities of reaction intermediates (bis-
allylmetal and its carboxylate complex) but also the existence of an
isomerization pathway of the lactone products under reaction conditions.
Selective formation of δ-lactone has been well investigated by Behr, and
Ni-catalyzed selective formation of cyclopentanecarboxylic acid derivative
was reported by Hoberg; see refs 1a, 3d, and 3m.
(5) (a) Takimoto, M.; Nakamura, Y.; Kimura, K.; Mori, M. J. Am.
Chem. Soc. 2004, 126, 5956. (b) Takimoto, M.; Mori, M. J. Am. Chem.
Soc. 2002, 124, 10008.
(6) There have been reported several examples of stoichiometric one-
to-one coupling of 1,3-dienes with CO2 using transition-metal com-
(3) (a) Musco, A.; Perego, C.; Tartiari, V. Inorg. Chim. Acta 1978, 28,
L147. (b) Musco, A. J. Chem. Soc., Perkin Trans. 1 1980, 693. (c) Behr,
A.; Juszak, K.; Keim, W. Synthesis1983, 574. (d) Behr, A.; Juszak, K.-D.
J. Organomet. Chem. 1983, 255, 263. (e) Behr, A.; He, R. J. Organomet.
Chem. 1984, 276, C69. (f) Behr, A. Bull. Soc. Chim. Belg. 1985, 94, 671.
€
(g) Behr, A.; He, R.; Juszak, K.-D.; Kruger, C.; Tsay, Y.-H. Chem. Ber.
1986, 119, 991. (h) Behr, A.; Kanne, U. J. Organomet. Chem. 1986, 309,
215. (i) Behr, A.; Heite, M. Chem. Eng. Technol. 2000, 23, 952. (j) Behr,
A.; Becker, M. Dalton Trans. 2006, 4607. (k) Behr, A.; Bahke, P.;
Klinger, B.; Becker, M. J. Mol. Catal. A: Chem. 2007, 267, 149. (l)
Braunstein, P.; Matt, D.; Nobel, D. J. Am. Chem. Soc. 1988, 110, 3207.
(m) Hoberg, H.; Gross, S.; Milchereit, A. Angew. Chem., Int. Ed. 1987,
26, 571. (n) Hoberg, H.; Peres, Y.; Milchereit, A.; Gross, S. J. Organo-
met. Chem. 1988, 345, C17. (o) Pitter, S.; Dinjus, E. J. Mol. Catal. A:
Chem. 1997, 125, 39. (p) Holzhey, N.; Pitter, S.; Dinjus, E. J. Organomet.
Chem. 1997, 541, 243. (q) Holzhey, N.; Pitter, S. J. Mol. Catal. A: Chem.
1999, 146, 25.
€
plexes. For examples, see: (a) Braunlich, G.; Walther, D.; Eibisch, H.;
€
Schonecker, B. J. Organomet. Chem. 1993, 453, 295. (b) Takimoto, M.;
Mori, M. J. Am. Chem. Soc. 2001, 123, 2895. (c) Hoberg, H.; Jenni, K. J.
Organomet. Chem. 1987, 322, 193. (d) Gao, Y.; Iijima, S.; Urabe, H.;
Sato, F. Inorg. Chim. Acta 1994, 222, 145 and references cited therein.
r
10.1021/ol2002094
Published on Web 03/03/2011
2011 American Chemical Society

to give β,γ-unsaturated carboxylic acids through nucleo-
philic carboxylation of the σ-allyl palladium intermediates
generated by hydropalladation of allenes.7,8 We expected
that such catalysis with palladium(II) bearing an anionic
tridentate ligand would avoid the formation of the bis-
allylmetal species from 1,3-dienes. In this paper, we report
the first example of a catalytic one-to-one coupling reac-
tion of CO2 with easily available 1,3-dienes including 1,3-
butadiene and isoprene as a useful CO2-fixation by the
palladium-catalyzed hydrocarboxylation reaction.9,10
We first examined the hydrocarboxylation reaction
employing 1,3-butadiene. When the reaction was carried
out byusing10μmol of PSiP-pincertypepalladium triflate
complex1 and 0.5 mmol of AlEt3 (50 molar amounts based
on 1) at ambient temperature in DMF in the presence of
excess 1,3-butadiene under 1 atm of CO2 in a closed
system,11 2-methyl-3-butenoic acid 2 was obtained selec-
tively in a TON of 100 (200% yield based on one mole of
AlEt3, Table 1, entry 1). The high efficiency of this reaction
was demonstrated by the reaction in THF, where all three
ethyls on aluminum were utilized as a reductant although
isomerization of the initial product 2 to R,β-unsaturated
carboxylic acid 3 occurred to some extent (entry 2).
Importantly, the carboxylation occurred at the 2-position
of 1,3-butadiene in good selectivity.12 Use of ZnEt2 instead
of AlEt3 afforded a complex mixture containing a small
amount of 2 (entry 3).13 The highest TON of 446 was
realized by the reaction using 5 μmol of 1 and 5.0 mmol of
AlEt3 in DMF (entry 4).
Table 1. Hydrocarboxylation of 1,3-Butadiene
2 þ 3/
ratio of
entry
MEtn
solvent
time
mmol
2:3
TON
1
AlEt3
AlEt3
ZnEt2
AlEt3
DMF
THF
DMF
DMF
39 h
40 h
3 d
1.0a
>95:<5
82:18
-
100
150
-
2
1.5a
3
4b
<0.05
2.23
3 d
48:52
446
a NMR yield. b Reaction was carried out using 5 μmol of 1 and 5.0
mmol of AlEt3.
As summarizedin Table 2, the reaction was applicable to
other commercially available 1,3-dienes such as isoprene,
myrcene, piperylene, 1,3-cyclohexadiene, and 3-methyl-
1,3-pentadiene to afford corresponding β,γ-unsaturated
carboxylic acids 4-8 in high regioselectivityand high TON
(over 200) without being accompanied by isomerization of
the double bond in most cases under similar reaction
conditions. It should be noted that, in contrast to the
Table 2. Reaction of Commercially Available 1,3-Dienesa
(7) Takaya, J.; Iwasawa, N. J. Am. Chem. Soc. 2008, 130, 15254.
(8) Hydrocarboxylation of styrene derivatives were reported using
Ni-catalyst, see: Williams, C. M.; Johnson, J. B.; Rovis, T. J. Am. Chem.
Soc. 2008, 130, 14936.
(9) Sequential reactions of allylmetal species generated by hydro-
zincation or -magnesation of 1,3-diene with electrophiles including CO2
were reported; see: (a) Gao, Y.; Urabe, H.; Sato, F. J. Org. Chem. 1994,
59, 5521. (b) Viktorov, N.; Zubritskii, L. Russ. J. Gen. Chem. 2001, 71,
1773.
(10) There are numerous reports on the catalytic intermolecular
reductive coupling of 1,3-dienes with carbonyl compounds such as
aldehyde. For examples of Ni-catalyzed reaction with aldehyde, see:
(a) Kimura, M.; Tamaru, Y. Top. Curr. Chem. 2007, 279, 173 and
references cited therein. (b) Yang, Y.; Zhu, S.-F.; Duan, H.-F.; Zhou, C.-
Y.; Wang, L.-X.; Zhou, Q.-L. J. Am. Chem. Soc. 2007, 129, 2248. (c)
Sato, Y.; Hinata, Y.; Seki, R.; Oonishi, Y.; Saito, N. Org. Lett. 2007, 9,
5597. For examples of Rh and Ir-catalyzed reactions, see:(d) Jang, H.-
Y.; Huddleston, R. R.; Krische, M. J. Angew. Chem., Int. Ed. 2003, 42,
4074. (e) Bower, J. F.; Patman, R. L.; Krische, M. J. Org. Lett. 2008, 10,
1033. (f) Kimura, M.; Nojiri, D.; Fukushima, M.; Oi, S.; Sonoda, Y.;
Inoue, Y. Org. Lett. 2009, 11, 3794. (g) Zbieg, J. R.; Fukuzumi, T.;
Krische, M. J. Adv. Synth. Catal. 2010, 352, 2416. For examples of Ru-
catalyzed reactions, see:(h) Shibahara, F.; Bower, J. F.; Krische, M. J. J.
Am. Chem. Soc. 2008, 130, 6338. (i) Smejkal, T.; Han, H.; Breit, B.;
Krische, M. J. J. Am. Chem. Soc. 2009, 131, 10366. (j) Han, H.; Krische,
M. J. Org. Lett. 2010, 12, 2844. For an example of a Ti-catalyzed
reaction, see:(k) Bareille, L.; Gendre, P. L.; Moıse, C. Chem. Commun.
2005, 775.
(11) Gaseous 1,3-butadiene (ca. 30 mmol) was bubbled into a DMF
solution containing 1 under 1 atm of CO2 in a 30 mL two-necked flask
equipped with a three-way stopcock with a balloon. After AlEt3 was
added to a mixture, the system was cut off from the balloon to keep the
flask closed.
(12) A very small amount of 3-pentenoic acid, which is the regioi-
somer of the carboxylation step, was detected by 1H NMR (less than 3%
of the carboxylation product).
a Reactions were carried out using 20 mmol of 1,3-dienes, 5.0 mmol
of AlEt3, and 5.0 μmol 1 in DMF. b Very small amounts of 2,3-dimethyl-
2-butenoic acid (isomerization product) and 3-methyl-3-pentenoic acid
(regioisomer of the carboxylation step) were included as judged by 1H
NMR (less than 3% of the carboxylation product). c 6.0 mmol of
myrcene were used. d E/Z = 67:33. e E/Z = 93:7. f E/Z = 70:30. g E/
Z = 67:33.
(13) Use of common palladium catalysts such as Pd(PPh3)4 or PdCl2-
(PPh3)2 instead of 1 resulted in no formation of the desired one-to-one
adduct.
Org. Lett., Vol. 13, No. 7, 2011
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previously reported CO2-fixation reactions with 1,3-
dienes,14 this reaction proceeded successfully with 1,3-dienes
with several substitution patterns including 1- or 2-mono-
substituted, 1,2-disubstituted, and cyclic ones.15 These results
demonstrate the first example of a one-to-one coupling
reaction of 1 atm of CO2 with 1,3-butadiene and other easily
available 1,3-dienes, providing a useful method for the syn-
thesis of β,γ-unsaturated carboxylic acids by CO2-fixation.
Table 3. Generality of 1,3-Dienes
Scheme 1. Proposed Reaction Mechanism
The reaction is thought to proceed with generation of
PSiP-pincer type palladium hydride complex A by β-
hydride elimination after transmetalation of AlEt3 to 1
(Scheme 1). Hydrometalation of 1,3-dienes occurs at the
less hindered alkene moiety to give σ-allylpalladium inter-
mediates B, which isomerize to the other, less sterically
crowded σ-allylpalladium intermediates C.16 Then, nu-
cleophilic addition of σ-allylpalladium intermediates C to
CO2 occurs at the γ-position of the palladium regioselec-
tively to give palladium carboxylate complexes D,17 which
are reconverted to the catalytically active palladium hy-
dride A by subsequent transmetalation with AlEt3 fol-
lowed by β-hydride elimination.
a E/Z = 9:1. b E/Z = 7:3. c E/Z = 9:1. d E/Z = 8:2. e Isolated as a
carboxylic acid without esterification. f dr = 78:22. g In THF at rt for 2
i
j
days. h AlEt2(OEt) was employed instead of AlEt3. E/Z = 95:5. 105
mol % of AlEt(OEt)2. k NMR yield. In THF. m 105 mol % of AlEt2-
l
(OEt). n The reaction was carried out for 40 h.
We next applied this hydrocarboxylation reaction to
variously substituted and functionalized 1,3-dienes. Treat-
ment of 1-methyl-1-phenyl-1,3-butadiene 9a and AlEt3
with 0.5 mol % of 1 in DMF at 40 °C afforded R-
quaternary (E)-β,γ-unsaturated ester 10a in 91% yield
regio- and stereoselectively after esterification of the crude
product by TMSCHN2 (Table 3, entry 1). The catalyst
loading could be reduced to 0.1 mol % and the TON
reached 610 (entry 2). Furthermore this reaction showed
wide compatibility with functional groups such as silyl
ether (9d), alkene moiety (9c), carbamate (11b), and ketal
(11c) without affecting these functionalities. Importantly,
this carboxylation is highly stereoselective to give (E)-β,γ-
unsaturatedestersevenby usinga mixture of stereoisomers
of the starting dienes 9a-d (E/Z = 9:1-7:3). Carboxyla-
tion products bearing synthetically useful alkenylsilane
and allylsilane moieties (17 and 18) were obtained selec-
tively depending on the choice of solvent and aluminum
reagent when dienylsilane 16 was used as the substrate
(entries 10 and 11). The reaction is highly regioselective
except for the reaction of 1-monosubstituted diene 13
probably because the regioisomeric σ-allylpalladium inter-
mediates existed in equal amounts by equilibration (entry
9). Interestingly, the reaction of dienamide 19 was found to
give R-amino (E)-β,γ-unsaturated acid 20 as a single
(14) Some examples of a Pd-catalyzed reaction of CO2 with isoprene
were reported to give several CO2-incorporated products in low selec-
tivity. See: (a) Hoberg, H.; Minato, M. J. Organomet. Chem. 1991, 406,
C25. (b) Dinjus, E.; Leitner, W. Appl. Organomet. Chem. 1995, 9, 43. See
also refs 1a, 3f, and 3g.
(15) At present, the reaction is limited to terminal dienes (vinyl-
substituted olefins) except for 1,3-cyclohexadiene.
(16) σ-Allylpalladium complexes bearing a PSiP-pincer backbone
have been prepared. See: (a) Takaya, J.; Iwasawa, N. Organometallics
2009, 28, 6636. (b) Mitton, S., J.; McDonald, R.; Turculet, L. Angew.
Chem., Int. Ed. 2009, 48, 8568.
(17) For examples of allylation of CO2 by σ-allyl palladium com-
plexes, see: (a) Hung, T.; Jolly, P.; Wilke, G. J. Organomet. Chem. 1980,
190, C5. (b) Shi, M.; Nicholas, K. M. J. Am. Chem. Soc. 1997, 119, 5057.
(c) Johansson, R.; Wendt, O. F. Dalton Trans. 2007, 36, 488. (d)
Johnson, M. T.; Johansson, R.; Kondrashov, M. V.; Steyl, G.; Ahlquist,
M. S. G.; Roodt, A.; Wendt, O. F. Organometallics 2010, 29, 3521. (e)
Wu, J.; Green, J. C.; Hazari, N.; Hruszkewycz, D. P.; Incarvito, C. D.;
Schmeier, T. J. Organometallics 2010, 29, 6369. See also ref 16a.
1700
Org. Lett., Vol. 13, No. 7, 2011

regioisomer, and this reaction would be a useful method
for R-amino acid synthesis by CO2-fixation (entry 12).
Inconclusion, we have developed an efficient one-to-one
coupling reaction of atmospheric pressure CO2 with 1,3-
butadiene and other easily available 1,3-dienes by the PSiP-
pincer type palladium-catalyzed hydrocarboxylation. This
protocol affords a highly useful method for the synthesis of
β,γ-unsaturated carboxylic acid derivatives from CO2.
“Molecular Activation Directed toward Straightforward
Synthesis” (No. 22105006), a Grant-in-Aid for Scientific
Research (A) (No. 21245024), and a Grant-in-Aid for
Scientific Research on Innovative Areas (No. 20200049)
from the Ministry of Education, Culture, Sports, Science,
and Technology of Japan.
Supporting Information Available. Preparative meth-
ods and spectral and analytical data of compounds 2-20.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. This research was supported by a
Grant-in-Aid for Scientific Research on Innovative Areas
Org. Lett., Vol. 13, No. 7, 2011
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