Anhydride-Additive-Free Nickel-Catalyzed Deoxygenation of Carboxylic Acids to Olefins

Article abstract of DOI:10.1021/acs.organomet.6b00940

A nickel-catalyzed route for direct, anhydride-additive-free deoxygenation of fatty acids to the corresponding olefins has been developed. The transformation is catalyzed by simple nickel salts of the type NiX₂ (X = halide, acetate, acetylacetonate), uses PPh₃ as a stoichiometric reductant, and exhibits selectivity for generation of linear α-olefin products. The reaction was rendered cocatalytic in PPh₃ using 1,1,3,3-tetramethyldisiloxane (TMDS) as terminal reductant for the in situ reduction of OPPh₃ and catalytic Cu(OTf)₂

Full text of DOI:10.1021/acs.organomet.6b00940

Communication
pubs.acs.org/Organometallics
Anhydride-Additive-Free Nickel-Catalyzed Deoxygenation of
Carboxylic Acids to Olefins
Alex John, Marc A. Hillmyer,* and William B. Tolman*
Department of Chemistry & Center for Sustainable Polymers, University of Minnesota, 207 Pleasant Street SE, Minneapolis,
Minnesota 55455-0431, United States
*
S Supporting Information
ABSTRACT: A nickel-catalyzed route for direct, anhydride-additive-free
deoxygenation of fatty acids to the corresponding olefins has been developed.
The transformation is catalyzed by simple nickel salts of the type NiX (X =
2
halide, acetate, acetylacetonate), uses PPh as a stoichiometric reductant, and
3
exhibits selectivity for generation of linear α-olefin products. The reaction was
rendered cocatalytic in PPh using 1,1,3,3-tetramethyldisiloxane (TMDS) as
3
terminal reductant for the in situ reduction of OPPh and catalytic Cu(OTf) .
3
2
lefins are the largest volume intermediates produced in
the chemical industry and are almost exclusively obtained
Direct decarboxylation/decarbonylation of carboxylic acids
without an additive such as an anhydride is rare and is
invariably effected at high temperature (≥350 °C) in the
O
by steam cracking during petroleum and natural gas refining.
Impetus to reduce our dependence on fossil fuels has led efforts
to derive commodity chemicals such as olefins from renewable
presence of supported catalysts under a reducing atmosphere of
5
H
.
2
However, these processes result in product mixtures
1
biomass. Vegetable oils represent an abundant, renewable
comprising both saturated and unsaturated hydrocarbons, along
with cracking products. In an effort to render the deoxygena-
tion reaction more practical by using an earth-abundant
feedstock that can be converted to long-chain olefins, of which
linear α-olefins (LAOs) are of particular interest, especially as
polymerization feedstocks. The dehydrative decarbonylation
reaction catalyzed by transition-metal reagents has been
demonstrated to be effective and efficient at converting
catalyst, Ni(OAc) was recently used for the deoxygenation
2
6
of fatty acids in the absence of H and solvent at 350 °C.
2
However, almost equimolar amounts of alkene and alkane
products were obtained during the process. Enzymatic catalysis
has also been recently shown to be efficient at carrying out the
direct decarboxylation of fatty acids to the corresponding
2
biomass-derived carboxylic acids to olefins. A sacrificial
anhydride is routinely employed to activate the carboxylic
3
acid (Scheme 1a). We recently demonstrated that p-nitro-
7
alkenes. Our ultimate aim is to develop practical and efficient
phenol esters of carboxylic acids are also decarbonylated under
4
alternatives using base-metal catalysis.
Herein, we report on our findings on a nickel-catalyzed
palladium catalysis (Scheme 1b).
deoxygenation of carboxylic acids to olefins without the use of
Scheme 1. Transition-Metal-Catalyzed Deoxygenation of
Carboxylic Acids to Olefins
an activating additive, with PPh serving as both a supporting
3
ligand and terminal reductant. Use of Ni(acac) or Ni(OAc) as
2
2
catalysts yields olefins in up to 82% yield with α-selectivity as
high as 70%. Furthermore, we have demonstrated that the
deoxygenation can be rendered catalytic in PPh by using
3
1
,1,3,3-tetramethyldisiloxane (TMDS) and a copper catalyst to
effect in situ reduction of the generated OPPh (Scheme 1c).
3
During our recent investigation of a NiI /PPh -catalyzed
2
3
3k
decarbonylation of nonanoic acid, we observed that octene(s)
were generated even in the absence of the pivalic anhydride
additive. Subsequent experiments showed that the yield of
octene(s) under these conditions (NiI (10 mol %)/PPh , 190
2
3
°
C, under distillation conditions) scaled proportionately with
the loading of PPh (Table 1, entries 1−4). At 100 mol % of
PPh with respect to the acid, an 82% yield of octene(s) was
3
3
Received: December 18, 2016
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00940
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Communication
a
a
Table 1. Nickel-Catalyzed Deoxygenation of Nonanoic Acid
Table 2. Nickel-Catalyzed Deoxygenation of Fatty Acids
b
yield /
entry
fatty acid
olefin
[Ni]
NiI2
α-olefin (%)
1
2
undecylenic
(C )
11
85/nd
65/71
decadiene (C )
10
b
Ni(OAc)2
entry
[cat.] (mol %)
PPh (mol %) yield (%) α-olefin (%)
3
1
2
NiI (10)
25
40
27
15
9.5
2
3
Ni(OAc)2
77/63
63/nd
NiI (10)
33
lauric (C12)
undecene (C11)
2
c
c
4
Ni(OAc)
2
3
NiI (10)
100
100
100
100
0
57
9.3
6.3
7.2
2
4
5
6
NiI (10)
83
2
d
5
NiI2
88/17
56/41
NiI (6)
85
2
myristic (C14
)
tridecene (C13
pentadecene
)
6
Ni(OAc)2
Ni(OAc)2
NiCl (10)
86
14
2
d
7
NiI (10)
trace
34
2
d
7
palmitic (C )
51/38
80
1
6
8
NiI (0.1)
100
40
40
66
70
55
70
76
2
(
C )
15
9
Ni(PPh ) (10)
31
3
4
e
10
11
12
13
14
(PPh ) Ni(CO) (10)
40
25
3
2
2
8
cyclohexane
(C6)
cyclohexene
NiI2
Ni(acac) (10)
100
100
100
100
73
2
Ni(OAc) (10)
82
a
2
Reaction conditions: Fatty acid (1 equiv), PPh (100 mol %), and
[Ni] (10 mol %) were heated in distillation mode for 16 h at 190 °C.
The distillate was analyzed by GC-MS and H NMR spectroscopy.
Yield and α-olefin selectivity are an average of 2 to 3 runs. From the
distillate. Using PPh (40%) and KI (100%). Reaction performed
under weak vacuum (∼500 mTorr). nd = not determined.
3
FeI (10)
∼5
trace
2
1
CoBr (10)
2
b
a
Reaction conditions unless specified otherwise: nonanoic acid (1
equiv), PPh , and [catalyst] were heated in a distillation mode for 16 h
at 190 °C. The distillate was analyzed by GC-MS and H NMR
spectroscopy. Determined by GC-MS and confirmed by H NMR
spectroscopy (1-octene selectivity). Yield and α-olefin selectivity are
an average of two to three runs. Reaction stopped after 4 h. Reaction
carried out using OPPh (100 mol %) instead of PPh . Reaction
carried out using P(Ph-p-OMe)3.
c
d
3
3
1
b
1
While PPh has been used as terminal reductant in a variety
of synthetically useful transformations, separation of the
OPPh coproduct is problematic and could be avoided if
OPPh could be recycled. Among the known methods for
efficient reduction of phosphine oxides to phosphine, we
focused on the use of 1,1,3,3-tetramethyldisiloxane (TMDS),
which has been demonstrated to be effective under Cu or Ti
3
c
d
9
e
3
3
3
3
10
obtained in the distillate (Table 1, entry 4). 31P NMR analysis
of the residue revealed that PPh was quantitatively converted
to OPPh , suggesting that PPh served as a reductant in the
reaction. A control experiment involving nonanoic acid and
PPh under similar conditions in the absence of nickel catalyst
did not generate any octene(s) or OPPh . Similarly, octenes
were not generated under nickel-catalyzed conditions when the
reaction was carried out using OPPh instead of PPh (Table 1,
entry 7). The reducing capability of PPh has been employed
by others, including recent reports on deoxydehydration
reactions that convert biomass-derived glycols and polyols to
olefins. NiI and NiCl were found to be equally efficient.
Transitioning to the Ni(0) catalyst precursor Ni(PPh3)4
resulted in a higher α selectivity but lower overall yield.
3
10b,c,e,11
3
3
catalysis.
When TMDS and Cu(OTf) were incorporated into the
NiI -catalyzed deoxygenation conditions with catalytic PPh ,
octene(s) were generated from nonanoic acid (94%, Table 3,
entry 3). In the absence of Cu(OTf) /TMDS only
stoichiometric amounts of olefin corresponding to PPh3
loadings were produced; no olefin was obtained in the absence
of PPh . The reaction was equally efficient with NiCl as the
2
3
2
3
3
12
2
3
3
3
3
2
8
2
2
Table 3. Ni/PPh -Catalyzed Deoxygenation using TMDS as
Terminal Reductant
3
a
Alternative Ni(II) precursors such as Ni(acac) and Ni(OAc)2
2
gave high yields while maintaining moderate α selectivity (55−
70%) (Figure S1 in the Supporting Information). Other first-
row transition-metal catalysts (Fe and Co) were found to be
inefficient under similar conditions. A screen of various ligands
using Ni(acac) or Ni(OAc) (10 mol %) did not uncover any
marked improvements (Table S1 in the Supporting Informa-
tion). The addition of KI to the reaction mixture was found to
enhance yields; although the reason for this effect is unclear, we
b
entry
fatty acid
TMDS (mol %) PPh (mol %) yield (%)
3
1
2
3
4
5
nonanoic (C9)
nonanoic (C9)
nonanoic (C9)
nonanoic (C9)
nonanoic (C9)
nonanoic (C9)
nonanoic (C9)
nonanoic (C9)
myristic (C )
14
14
14
17
53
94
50
0
2
2
40
80
80
80
80
80
80
80
80
7.5
0
14
14
5
presume that iodide acts as a reductant (Table S1, entries 5 and
c
7
6
81
78
61
77
66
6).
d
7
e
Using optimized conditions for deoxygenating nonanoic acid
directly to 1-octene with good selectivity (Ni(OAc) (10 mol
8
2
9
14
14
1
4
%
), PPh (1 equiv) at 190 °C for 16 h), fatty acids with varying
3
1
0
stearic (C )
18
chain lengths (C −C ) were examined (Table 2, 51−88%
1
1
16
yield; Figures S2−S6 in the Supporting Information). For the
heavier fatty acids the reactions had to be performed under
reduced pressure (∼500 mTorr) to assist distillation of the
a
Reaction conditions unless specified otherwise: fatty acid (2.84
mmol), TMDS, PPh , NiI (2.8 mol %), and Cu(OTf) (2.8 mol %),
6 h, 190 °C. Analysis by H NMR spectroscopy. α-Olefin selectivities
were <5% in all cases. Versus 1,3,5-trimethoxybenzene internal
3
2
2
1
1
b
olefin from the reaction mixture. NiI was consistently found to
2
c
d
be more efficient than Ni(OAc) . The 2° cyclohexanecarboxylic
standard. Reaction stopped after 4 h. NiCl (2.8 mol %) used as
2
2
e
acid was converted to cyclohexene in 80% yield (entry 8).
catalyst. Using NiI (1 mol %) and Cu(OTf) (1 mol %).
2
2
B
DOI: 10.1021/acs.organomet.6b00940
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Organometallics
Communication
catalyst. Finally, extending the conditions to longer chain fatty
acids, myristic acid (C ) and stearic acid (C ), produced
2015, 8, 1585−1592. (c) Maetani, S.; Fukuyuma, T.; Suzuki, N.;
Ishihara, D.; Ryu, I. Organometallics 2011, 30, 1389−1394. (d) Liu, Y.;
Kim, K. E.; Herbert, M. B.; Fedorov, A.; Grubbs, R. H.; Stoltz, B. M.
Adv. Synth. Catal. 2014, 356, 130−136. (e) Miranda, M. O.;
Pieterangelo, A.; Hillmyer, M. A.; Tolman, W. B. Green Chem. 2012,
1
4
18
tridecene(s) and heptadecene(s) in 77% and 66% yields,
respectively. Given the high volatility of TMDS relative to the
other components of the mixture, these reactions were
performed in a closed Schlenk tube and as a result gave
relatively low α selectivity (<5%) since the olefin was not
removed from the reaction mixture; isomerization to the more
thermodynamically favored internal alkenes was implicated.
Analysis of the headspace volume in NiI /PPh deoxygena-
1
4, 490−494. (f) Kraus, G. A.; Riley, S. Synthesis 2012, 44, 3003−
3
005. (g) Le Notre, J.; Scott, E. L.; Franssen, M. C. R.; Sanders, J. P.
̂
M. Tetrahedron Lett. 2010, 51, 3712−3715. (h) Gooβen, L. J.;
Rodríguez, N. Chem. Commun. 2004, 724−725. (i) Miller, J. A.;
Nelson, J. A.; Byrne, M. P. J. Org. Chem. 1993, 58, 18−20. (k) John, A.;
2
3
̃
Miranda, M. O.; Ding, K.; Dereli, B.; Ortuno, M. A.; LaPointe, A. M.;
tion of nonanoic acid under standard reaction conditions tested
Coates, G. W.; Cramer, C. J.; Tolman, W. B. Organometallics 2016, 35,
2391−2400. (l) Maetani, S.; Fukuyuma, T.; Suzuki, N.; Ishihara, D.;
1
5,13
positive for CO but not for CO2,
a decarbonylation pathway.
suggesting that it follows
̂
Ryu, I. Chem. Commun. 2012, 48, 2552−2554. (m) Le Notre, J.; Scott,
E. L.; Franssen, M. C. R.; Sanders, J. P. M. Green Chem. 2011, 13,
07−809.
4) John, A.; Hogan, L. T.; Hillmyer, M. A.; Tolman, W. B. Chem.
Commun. 2015, 51, 2731−2733.
5) (a) Han, J.; Sun, H.; Ding, Y.; Lou, H.; Zheng, X. Green Chem.
010, 12, 463−467. (b) Gosselink, R. W.; Stellwagen, D. R.; Bitter, J.
H. Angew. Chem., Int. Ed. 2013, 52, 5089−5092. (c) Peng, B.; Zhao,
C.; Kasakov, S.; Foraita, S.; Lercher, J. A. Chem. - Eur. J. 2013, 19,
4732−4741. (d) Wang, C.; Tian, Z.; Wang, L.; Xu, R.; Liu, Q.; Qu, W.;
Ma, H.; Wang, B. ChemSusChem 2012, 5, 1974−1983. (e) Peng, B.;
Yuan, X.; Zhao, C.; Lercher, J. A. J. Am. Chem. Soc. 2012, 134, 9400−
In conclusion, we have identified a method for deoxygenating
8
(
fatty acids to alkenes where PPh serves as a terminal reductant
3
and no exogenous acid-activating species is needed. The
reaction is catalyzed by simple nickel salts under solvent-free
conditions. Ni(II) precatalysts were found to be superior to
(
2
Ni(0) counterparts, and by using Ni(OAc) high yields (up to
2
8
2%) and α selectivity (up to 70%) could be achieved. The
reaction can be run at a low loading of NiI (0.1 mol %),
2
achieving a high turnover number (TON) of 340. The
deoxygenation reaction can be rendered catalytic in PPh by
3
9
405. (f) Sun, K. Y.; Wilson, A. R.; Thompson, S. T.; Lamb, H. H.
ACS Catal. 2015, 5, 1939−1948.
6) Li, W.; Gao, Y.; Yao, S.; Ma, D.; Yan, N. Green Chem. 2015, 17,
198−4205.
7) (a) Zachos, I.; Gabmeyer, S. K.; Bauer, D.; Sieber, V.; Hollmann,
using TMDS and Cu(OTf) , albeit to form a mixture of olefin
2
products under the reaction conditions used.
(
4
(
ASSOCIATED CONTENT
Supporting Information
■
*
S
F.; Kourist, R. Chem. Commun. 2015, 51, 1918−1921. (b) Grant, J. L.;
Hsieh, C. H.; Makris, T. M. J. Am. Chem. Soc. 2015, 137, 4940−4943.
(c) Dennig, A.; Kuhn, M.; Tassoti, S.; Thiessenhusen, A.; Gilch, S.;
Butler, T.; Haas, T.; Hall, M.; Faber, K. Angew. Chem., Int. Ed. 2015,
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00940.
5
4, 8819−8822. (d) Rude, M. A.; Baron, T. S.; Brubaker, S.; Alibhai,
M.; Del Cardayre, S. B.; Schirmer, A. Appl. Environ. Microbio. 2011, 77,
718−1727.
8) (a) Handbook of Reagents for Organic Synthesis, Oxidizing and
Experimental details, including characterization data for
the compounds (PDF)
1
(
AUTHOR INFORMATION
Corresponding Authors
E-mail for M.A.H.: hillmyer@umn.edu.
E-mail for W.B.T.: wtolman@umn.edu.
Reducing Agent; Burke, S. D., Danheiser, R. L., Eds.; Wiley: Hoboken,
NJ, 1999. (b) Raju, S.; van Slagmaat, C. A. M. R.; Li, J.; Lutz, M.;
Jastrzebski, J. T. B. H.; Moret, M. − E.; Klein Gebbink, R. J. M.
Organometallics 2016, 35, 2178−2187. (c) Sousa, S. C. A.; Fernandes,
A. C. Coord. Chem. Rev. 2015, 284, 67−92. (d) Boucher-Jacobs, C.;
Nicholas, K. M. Top. Curr. Chem. 2014, 353, 163−184.
■
*
*
ORCID
(
9) (a) Mitsunobu, O.; Yamada, M.; Mukaiyama, T. Bull. Chem. Soc.
Marc A. Hillmyer: 0000-0001-8255-3853
William B. Tolman: 0000-0002-2243-6409
Notes
Jpn. 1967, 40, 935−939. (b) Mitsunobu, O.; Yamada, M. Bull. Chem.
Soc. Jpn. 1967, 40, 2380−2382. (c) Appel, R. Angew. Chem., Int. Ed.
Engl. 1975, 14, 801−811. (d) Staudinger, H.; Meyer, J. Helv. Chim.
The authors declare no competing financial interest.
Acta 1919, 2, 635−646. (e) Wittig, G.; Scho
7, 1318−1330. (f) Wittig, G.; Haag, W. Chem. Ber. 1955, 88, 1654−
1666.
́
10) (a) Herault, D.; Nguyen, D. H.; Nuel, D.; Buono, G. Chem. Soc.
̈
llkopf, U. Chem. Ber. 1954,
8
ACKNOWLEDGMENTS
■
(
Funding for this work was provided by the Center for
Sustainable Polymers at the University of Minnesota, a
National Science Foundation (NSF) supported Center for
Chemical Innovation (CHE-1413862).
Rev. 2015, 44, 2508−2528. (b) Li, Y.; Lu, L. − Q.; Das, S.; Pisiewicz,
S.; Junge, K.; Beller, M. J. Am. Chem. Soc. 2012, 134, 18325−18329.
(c) Li, Y.; Das, S.; Zhou, S.; Junge, K.; Beller, M. J. Am. Chem. Soc.
2
012, 134, 9727−9732. (d) Busacca, C. A.; Raju, R.; Grinberg, N.;
Haddad, N.; James-Johns, P.; Lee, H.; Lorenz, J. C.; Saha, A.;
Senanyake, C. H. J. Org. Chem. 2008, 73, 1524−1531. (e) Berthod, M.;
Favre-Reguillon, A.; Mohamad, J.; Mignani, G.; Docherty, G.; Lemaire,
M. Synlett 2007, 2007, 1545−1548. (f) Wu, H. − C.; Yu, J. − Q.;
Spencer, J. B. Org. Lett. 2004, 6, 4675−4678.
(11) For a recent example see: Wang, L.; Xie, Y. − B.; Huang, N. −
Y.; Yan, J. − Y.; Hu, W. − M.; Liu, M. − G.; Ding, M. − W. ACS Catal.
2016, 6, 4010−4016.
(12) On the basis of the results of GC-MS analysis, TMDS is
converted to a mixture of cyclic silyl ethers.
REFERENCES
1) (a) Dapsens, P. Y.; Mondelli, C.; Per
■
(
2
́
ez-Ramírez, J. ACS Catal.
012, 2, 1487−1499. (b) Corma, A.; Iborra, S.; Velty, A. Chem. Rev.
2
007, 107, 2411−2502. (c) Ragauskas, A. J.; Williams, C. K.; Davison,
B. H.; Britovsek, G.; Cairney, J.; Eckert, C. A.; Frederick, W. J., Jr.;
Hallett, J. P.; Leak, D. J.; Liotta, C. L.; Mielenz, J. R.; Murphy, R.;
Templer, R.; Tschaplinski, T. Science 2006, 311, 484−489.
(
2) (a) Dawes, G. J. S.; Scott, E. L.; No
̂
tre, J. L.; Sanders, J. P. M.;
Bitter, J. H. Green Chem. 2015, 17, 3231−3250. (b) Santillan-Jimenez,
E.; Crocker, M. J. J. Chem. Technol. Biotechnol. 2012, 87, 1041−1050.
(13) (a) CO test: the headspace was analyzed by passing through a
2
(
7
3) (a) Foglia, T. A.; Barr, P. A. J. Am. Oil Chem. Soc. 1976, 53, 737−
solution of Ba(OH) . No precipitation indicative of the formation of
2
41. (b) Ternel, J.; Lebarbe,
́
T.; Monflier, E.; Hapiot, F. ChemSusChem
BaCO was observed. (b) CO test: the gas in the headspace was
3
C
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transferred to a solution of Ni(PPh ) in dry toluene. When the
3
4
mixture was stirred for 10 min, the solution changed from deep red-
31
orange to light yellow. Analysis of the solution by P NMR
spectroscopy showed the formation of (CO) Ni(PPh ) .
2
3 2
D
DOI: 10.1021/acs.organomet.6b00940
Organometallics XXXX, XXX, XXX−XXX