Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes

Article abstract of DOI:10.3762/bjoc.13.41

Dienoic acids and pentadienyl alcohols are coupled in a decarboxylative and dehydrative manner at ambient temperature using Pd(0) catalysis to generate 1,3,6,8-tetraenes. Contrary to related decarboxylative coupling reactions, an anion-stabilizing group i

Full text of DOI:10.3762/bjoc.13.41

Decarboxylative and dehydrative coupling of dienoic acids
and pentadienyl alcohols to form 1,3,6,8-tetraenes
Ghina’a I. Abu Deiab‡1, Mohammed H. Al-Huniti‡1, I. F. Dempsey Hyatt1,§,
Emma E. Nagy1, Kristen E. Gettys1, Sommayah S. Sayed1, Christine M. Joliat1,
Paige E. Daniel1, Rupa M. Vummalaneni1, Andrew T. Morehead Jr2, Andrew L. Sargent2
and Mitchell P. Croatt*1
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2017, 13, 384–392.
1Department of Chemistry and Biochemistry, University of North
Carolina at Greensboro, Greensboro, NC 27402, USA and
2Department of Chemistry, East Carolina University, Greenville, NC
27858, USA
doi:10.3762/bjoc.13.41
Received: 17 November 2016
Accepted: 03 February 2017
Published: 28 February 2017
Email:
Mitchell P. Croatt* - mpcroatt@uncg.edu
Associate Editor: B. Stoltz
* Corresponding author ‡ Equal contributors
§ Current address: Department of Chemistry, Adelphi University,
Garden City, NY 11530, USA
© 2017 Deiab et al.; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
decarboxylation; diene; dienoate; palladium; pentadienyl; tetraene
Abstract
Dienoic acids and pentadienyl alcohols are coupled in a decarboxylative and dehydrative manner at ambient temperature using
Pd(0) catalysis to generate 1,3,6,8-tetraenes. Contrary to related decarboxylative coupling reactions, an anion-stabilizing group is
not required adjacent to the carboxyl group. Of mechanistic importance, it appears that both the diene of the acid and the diene of
the alcohol are required for this reaction. To further understand this reaction, substitutions at every unique position of both cou-
pling partners was examined and two potential mechanisms are presented.
Introduction
The construction of sp2–sp3 carbon–carbon bonds remains a Another approach to the formation of C–C bonds is through
difficult and important problem in organic synthesis. Cross-cou- decarboxylative coupling reactions (Scheme 1). This can be
pling reactions provide avenues to these otherwise difficult arrived in a one-component fashion via the removal of CO2
reactions, but often require prefunctionalization of the coupling from an ester or in a two-component manner by removal of CO2
partners [1-9]. However, recent C–H activation research has from a carboxylic acid and coupling this to a substrate with a
enabled the use of further simplified starting materials [10-18]. benzylic or allylic leaving group [19,20].
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Beilstein J. Org. Chem. 2017, 13, 384–392.
Scheme 1: Prior and current decarboxylative couplings.
Typical Pd(0)-catalyzed decarboxylative coupling reactions in our reported nine-step synthesis of clinprost [41]. A struc-
utilize an allylic or benzylic ester with either an anion-stabi- turally related compound (11) reacted similarly, however, the
lizing group adjacent to the carboxyl group (i.e., carbonyl sorbate derivative (13) was low yielding with the majority of
[19,21,22], nitrile [23-25], nitro [26,27], or alkyne [21,28-32], the material only rearranging to the linear ester. In all three of
Scheme 1), or use an aryl carboxylate [33,34] which typically these cases, we never observed the more stable, fully conju-
requires the assistance of silver or copper(I) salts for the gated tetraene. ”Skipped diene” motifs are found in various
decarboxylative step. It is rare to use a pentadienyl electrophile natural products and there are few methods available to prepare
[35], or to have a diene or simple alkene adjacent to the these dienes [42-52]. Skipped tetraene systems have even fewer
carboxyl group [20,36-39]. Despite the absence of this type of methods for their synthesis [53-55], which makes the method
reactivity, the decarboxylative coupling of a pentadienyl described herein even more valuable.
dienoate (9; Scheme 2) was desirable enough for our group’s
synthesis of clinprost that we attempted the reaction [40,41]. It was determined that modifying the dienoate motif yielded
Fortunately, this coupling reaction was successfully employed only the rearranged product under the reaction conditions, in-
Scheme 2: Esters examined in the decarboxylation reaction.
385

Beilstein J. Org. Chem. 2017, 13, 384–392.
cluding the dihydro (14), cinnamate (15), benzoate (16), and for a slow reaction and incomplete conversion, 1–2 equivalents
acrylate (17) analogues (Scheme 2). Moreover, allylic dienoates was optimal with yields around 70% and more water was not
18 and 19 gave no reaction with Pd(0) catalysis. These results beneficial (Table 1, entries 2–8). The use of equimolar amounts
led us to the determination that there was a unique reactivity of methanol and water as a proton source allowed for decarbox-
imbued to the molecule by having both the dienoate and penta- ylation to take place but with a low yield (Table 1, entry 9) and
dienyl moieties. Herein, are presented more details for this reac- the reaction run in TFE as a solvent did not result in any
tion, including the substrate scope for the intermolecular case.
decarboxylation (Table 1, entry 10).
Results and Discussion
In addition to the requirement for water, it was determined that
In addition to determining the requisite nature of both the penta- phosphine ligands were necessary (Table 1, entry 11), either as
dienyl and dienoate groups, it was found that trace amounts of ligands or as participants in the reaction as discussed later. The
water were required for decarboxylative coupling (Table 1). For typical catalyst used, Pd(PPh3)4, worked well, however, it was
example, careful exclusion of water from reagents and solvent found that a more ideal ratio of palladium metal to ligand was
and performing the reaction in the glovebox led to formation of 1:1 or 1:2, with greater amounts of triphenylphosphine lowering
rearranged product and no decarboxylative coupling reaction the reaction yield when using the Pd2dba3 catalyst (Table 1,
(22, Table 1, entry 1). Less than 1 equivalent of water allowed entries 12–14). It was determined that reactions performed in
Table 1: Optimization of the one-component decarboxylation reaction.a
Entry
Catalyst
Solvent
Additives
Yield of 10
(Yield of 22)b
1
2
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd(OAc)2
Pd(OAc)2
none
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2/H2O
CH2Cl2
TFE
anhydrous
0.5 equiv H2O
0% (99%)
27%
3
1.1 equiv H2O
77%
4
1.3 equiv H2O
72%
5
silylated glass, 1 equiv H2O
dry glass balls
55% (15%)
37% (24%)
51%
6
7
wet glass balls
8
biphasic
49%
9
1 equiv MeOH, 1 equiv H2O
trace CH2Cl2
33% (26%)
0%
10
11
12
13
14
15
16
17
18
19
20
21
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
0 mol % PPh3, 1 equiv H2O
10 mol % PPh3, 1 equiv H2O
20 mol % PPh3, 1 equiv H2O
30 mol % PPh3, 1 equiv H2O
10 mol % L1, 1 equiv H2O
10 mol % L2, 1 equiv H2O
10 mol % L4, 1 equiv H2O
10 mol % L5, 1 equiv H2O
1 equiv H2O
0%
64%
61%
12%
70%
70%
18%
10%
0%
40 mol % PPh3, 1 equiv H2O
1 equiv PPh3, 1 equiv H2O
10%
0%
aReaction Conditions: Pd metal (10 mol %) and the indicated solvent and additives for 24 hours. bIsolated yields.
386

Beilstein J. Org. Chem. 2017, 13, 384–392.
the presence of electron-rich ligands had both quicker kinetics Despite the low yield for decarboxylation with sorbate 13, the
and more efficient yields compared to electron-deficient ligands initial attempt used inexpensive sorbic acid as the dienoic acid.
(Table 1, entries 15–18 and Supporting Information File 1 for Gratifyingly, this reaction was successful and it was again de-
kinetic information). Although not as efficient, it was found that termined that no isomerization to the fully conjugated system
a palladium(II) catalyst functioned in this reaction, presumably was observed (Table 2, entry 1). Other bis-allylic leaving
functioning as a pre-catalyst and being reduced in situ to the groups were studied and, unexpectedly, it was determined that
palladium(0) catalyst (Table 1, entries 19 and 20). As a control divinylcarbinol was superior (Table 2, entries 1–6). In fact, the
reaction, it was found that no reaction occurred in the absence better leaving groups were either slow or ineffective. This could
of palladium catalyst (Table 1, entry 21).
be due to the less basic leaving groups not sufficiently deproto-
nating sorbic acid, which may be required for this reaction as is
As shown earlier, bis-allylic sorbate 13 (Scheme 2) was found discussed mechanistically later (Scheme 3). Similar to the
to be low yielding for the decarboxylative coupling reaction. single component reaction, more than two equivalents of phos-
Reactions of sorbate 13 monitored by 1H NMR showed nearly phine, relative to palladium metal, was detrimental (compare
quantitative isomerization of the bis-allylic group into a linear entries 12–14 of Table 1 with entries 6–8 of Table 2), however,
pentadienyl system. Increasing the reaction time did not result the reaction was successful using Pd(PPh3)4 (Table 1, entry 9).
in greater conversion to tetraene 8a, which indicates that the
products may be competitively ligating and poisoning the Pd(0) To further understand this interesting decarboxylative coupling
catalyst (see Supporting Information File 1 for additional evi- reaction, a handful of different pentadienyl electrophiles and
dence of product inhibition). The isomerization reaction to form dienoic acids were examined (Table 3). Typically, the pentadi-
22 was presumably occurring via ionization of the allylic enyl alcohol was used; however, in some cases the acetate was
system using Pd(0), followed by recombination of the carboxyl- superior. It was found that both a methyl or phenyl substituent
ate at the terminal position of the pentadienyl system. Based on on the alcohol derivative would result in branched product 8b or
these data, we hypothesized that a two-component reaction 8d as a major product with a product ratio of 6:1 or 4:1, respec-
using a dienoic acid and bis-allylic acetate might be possible, tively (Table 3, entries 2–4). The yields for these reactions were
however, the presence of both water and a carboxylic acid low, but the remaining material was typically starting material
would increase the possibility for isomerization of the 1,3,6,8- and the ester where the acid and alcohol are coupled together.
tetraenes into the fully conjugated 1,3,5,7-tetraenes, or possibly There was no effect on the yields upon leaving the reactions
polymerization.
longer than 48 hours and it was found that the addition of
Table 2: Optimization of the two-component decarboxylation reaction.a
Entry
Pentadienyl group
Additive
Yieldb
1
2
6a, X = OAc
6b, X = OCO2Me
6c, X = OBz
PPh3 (20 mol %)
PPh3 (20 mol %)
PPh3 (20 mol %)
PPh3 (20 mol %)
PPh3 (20 mol %)
PPh3 (20 mol %)
PPh3 (10 mol %)
PPh3 (30 mol %)
NA
12%
35%
11%
6%
3
4
6d, X = O2C(4-CF3Ph)
7a, X = Br
5
0%
6
6e, X = OH
40%
18%
24%
28%
7
6e, X = OH
8
6e, X = OH
9c
6e, X = OH
aReaction conditions: Sorbic acid (5a, 1 equiv), pentadienyl group (6 or 7, 1 equiv), Pd2(dba)3·CHCl3 (5 mol %) unless indicated otherwise, H2O
(1 equiv), in CDCl3 for 48 hours. bNMR yields. cPd(PPh3)4 (10 mol %).
387

Beilstein J. Org. Chem. 2017, 13, 384–392.
Table 3: Substrate scope for the two-component decarboxylation reaction.a
Entry
Dienoic acid
Pentadienyl group
Yield (product)b
1
6e
40%b (8a)
5a
2
7b
5a
8%c (8b/8c)
3
6f
5a
21%b, 17%c (8d/8e)
4
6g
5a
13%b, 6%c (8d/8e)
5
7c
5a
16%c (8f)
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Beilstein J. Org. Chem. 2017, 13, 384–392.
Table 3: Substrate scope for the two-component decarboxylation reaction.a (continued)
6
7d
18%c (8g)
5a
7
6e
14%b (8h/8i/8j)
5b
8
6e
24%c (8k)
5c
9
6e
36%b (8l)
5d
10
decomposition
6e
5e
11
decomposition
6e
5f
12
6e
5g
74%c (8m)
aReaction conditions: Dienoic acid (5, 1 equiv), pentadienyl group (6 or 7, 1 equiv), H2O (1 equiv), Pd2(dba)3·CHCl3 (5 mol %), PPh3 (20 mol %), in
CDCl3 for 48 h. bNMR yields due to volatility of product. cIsolated yields.
tetraene product inhibited the reaction (see Supporting Informa- With respect to the dienoic acid, it was determined that the un-
tion File 1 for details). With these highly unsubstituted tetraene substituted compound, pentadienoic acid, underwent decarbox-
products, it is hypothesized that the product may be seques- ylative coupling, although as a mixture of E/E, E/Z, and Z/Z
tering the palladium catalyst. Two cyclic dienyl acetates were isomers (Table 3, entry 7). Alkyl and aryl substituents were
also studied (Table 3, entries 5 and 6) and they yielded tetraenes possible on the dienoate with the exception of an aryl group at
8f and 8g. The dienes of entries 5 and 6 could have formed ad- the gamma position (Table 3, entries 8–10). Two cyclic dienoic
ditional isomers by coupling to the other end of the pentadienyl acids were synthesized [56,57] and while the cyclohexadienoic
group, but only one regioisomer was observed.
acid did not decarboxylate (Table 3, entry 11), the vinylcy-
389

Beilstein J. Org. Chem. 2017, 13, 384–392.
clopentenoic acid had a good yield of a complex tetraene and π-complex (E) to a different allyl/π-complex (F). Finally,
(Table 3, entry 12).
decarboxylative reduction of the palladium would release the
product while regenerating the catalyst. Preliminary computa-
Based on the information obtained during optimization and tional calculations using NEB [59] support pathway A and the
screening of compounds, two potential mechanisms are pro- HOMO of the transition state between E and F (Figure 1) calcu-
posed (Scheme 3). Both options allow for the one (13) or two (5 lated using the Gaussian 09 implementation of DFT with a
and 6) component process to be used while also allowing for the B3LYP functional, 6-31g* basis, and polarized continuum
reversible formation of linear ester 23. Pathway B involves a model of solvation for DCM, shows close proximity of two
Morita–Baylis–Hillman type process. The role of water would in-phase orbitals for the requisite C–C bond, whereas removal
be to hydrogen bond to the carboxylate to make the system
more electrophilic (B). This would accelerate the addition of the
phosphine to generate zwitterion C [58]. Preliminary modeling
for this ion indicates that both the electrophilic terminal vinyl
group of the pentadienyl ligand and the nucleophilic α-carbon
are in close proximity to one another. Formation of the
carbon–carbon bond would then regenerate the Pd(0) catalyst
and phosphonium carboxylate D. Decarboxylative elimination
of the phosphine results in formation the 1,3,6,8-tetraene. It is
proposed for pathway B that the dienoate is required so that the
α-carbon is not blocked by the bulky phosphine group since it
can add in a 1,6- or 1,4-manner, both reversibly.
Alternatively, pathway A has the palladium catalyst coordinate
to one of the alkenes of the dienoate instead of the carboxylate
(E). It is proposed that a water cluster around the carboxylate
would enable this process by hydrogen bonding to the carboxyl-
ate. The conversion of E to F would form the C–C bond by
Figure 1: Calculated HOMO of transition state between E and F.
having the palladium catalyst convert from one type of η3-allyl
Scheme 3: Possible mechanistic pathways.
390

Beilstein J. Org. Chem. 2017, 13, 384–392.
4. Terao, J.; Kambe, N. Acc. Chem. Res. 2008, 41, 1545.
of any one of the alkenes from this structure would lead to anti-
bonding relationships to bond to the alpha carbon.
doi:10.1021/ar800138a
5. Martin, R.; Buchwald, S. L. Acc. Chem. Res. 2008, 41, 1461.
doi:10.1021/ar800036s
Conclusion
6. Marion, N.; Nolan, S. P. Acc. Chem. Res. 2008, 41, 1440.
doi:10.1021/ar800020y
In summary, we present information that is of value to
advancing the area of metal-catalyzed decarboxylative coupling
reactions, specifically those of pentadienyl dienoates that do not
require an anion-stabilizing group, are run at ambient tempera-
ture, and can utilize the more accessible alcohol for a leaving
group. This reaction was advanced to be possible in a two-com-
ponent fashion, allowing for the conversion of dienoic acids and
pentadienyl alcohols into 1,3,6,8-tetraenes with the only stoi-
chiometric byproducts being water and carbon dioxide. These
reactions currently require a diene motif with each coupling
partner, but the product maintains the independent reactivity op-
portunities of these isolated dienes as opposed to forming the
fully conjugated 1,3,5,7-tetraene. A variety of substrates were
explored where each of the unique positions on the coupling
partners was modified and two different mechanistic pathways
are presented. A more in-depth mechanistic analysis to improve
the yields and to explore other reactivity possibilities based on
this process are currently being studied and will be published in
due time.
7. Denmark, S. E.; Regens, C. S. Acc. Chem. Res. 2008, 41, 1486.
doi:10.1021/ar800037p
8. Kantchev, E. A. B.; O'Brien, C. J.; Organ, M. G. Angew. Chem., Int. Ed.
2007, 46, 2768. doi:10.1002/anie.200601663
9. Corbet, J.-P.; Mignani, G. Chem. Rev. 2006, 106, 2651.
doi:10.1021/cr0505268
10.Schaub, T. A.; Kivala, M. Cross-Coupling Reactions to sp Carbon
Atoms. Metal-Catalyzed Cross-Coupling Reactions and More;
Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2014; pp 665 ff.
11.Davies, H. M. L.; Morton, D. J. Org. Chem. 2016, 81, 343.
doi:10.1021/acs.joc.5b02818
12.Brückl, T.; Baxter, R. D.; Ishihara, Y.; Baran, P. S. Acc. Chem. Res.
2012, 45, 826. doi:10.1021/ar200194b
13.Stuart, D. R.; Fagnou, K. The Discovery and Development of a
Palladium(II)-Catalyzed Oxidative Cross-Coupling of Two Unactivated
Arenes. In Inventing Reactions; Gooßen, L. J., Ed.; Springer: Berlin,
Heidelberg, 2013; pp 91 ff.
14.Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. Rev. 2010, 110,
624. doi:10.1021/cr900005n
15.Campeau, L.-C.; Rousseaux, S.; Fagnou, K. J. Am. Chem. Soc. 2005,
127, 18020. doi:10.1021/ja056800x
16.Stuart, D. R.; Alsabeh, P.; Kuhn, M.; Fagnou, K. J. Am. Chem. Soc.
2010, 132, 18326. doi:10.1021/ja1082624
17.Gorelsky, S. I.; Lapointe, D.; Fagnou, K. J. Org. Chem. 2012, 77, 658.
doi:10.1021/jo202342q
Supporting Information
18.Lafrance, M.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 16496.
doi:10.1021/ja067144j
Supporting Information File 1
Experimental procedures and analytical data for all
substrates and products, product inhibition study,
computational calculation information, and relevant
energies and Cartesian coordinates.
19.Jana, R.; Trivedi, R.; Tunge, J. A. Org. Lett. 2009, 11, 3434.
doi:10.1021/ol901288r
20.Tokoroyama, T.; Nakamura, M. Chem. Lett. 1977, 6, 659.
doi:10.1246/cl.1977.659
21.Tsuda, T.; Chujo, Y.; Nishi, S.; Tawara, K.; Saegusa, T.
J. Am. Chem. Soc. 1980, 102, 6381. doi:10.1021/ja00540a053
22.Tsuda, T.; Okada, M.; Nishi, S.; Saegusa, T. J. Org. Chem. 1986, 51,
421. doi:10.1021/jo00354a001
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-13-41-S1.pdf]
23.Trost, B. M.; Bunt, R. C. J. Am. Chem. Soc. 1998, 120, 70.
doi:10.1021/ja9726522
Acknowledgements
Funding for this project from the North Carolina Biotech-
nology Center (BRG-1205) and University of North Carolina at
Greensboro is gratefully acknowledged. The authors thank Dr.
Franklin J. Moy for assisting with analysis of NMR data and
Dr. Daniel A. Todd for acquisition of the high resolution mass
spectrometry data at the Triad Mass Spectrometry Laboratory at
the University of North Carolina at Greensboro.
24.Corey, E. J.; Fraenkel, G. J. Am. Chem. Soc. 1953, 75, 1168.
doi:10.1021/ja01101a047
25.Waetzig, S. R.; Rayabarapu, D. K.; Weaver, J. D.; Tunge, J. A.
Angew. Chem., Int. Ed. 2006, 45, 4977. doi:10.1002/anie.200600721
26.Waetzig, S. R.; Tunge, J. A. J. Am. Chem. Soc. 2007, 129, 14860.
doi:10.1021/ja077070r
27.Grenning, A. J.; Tunge, J. A. Org. Lett. 2010, 12, 740.
doi:10.1021/ol902828p
28.Rayabarapu, D. K.; Tunge, J. A. J. Am. Chem. Soc. 2005, 127, 13510.
doi:10.1021/ja0542688
References
29.Sim, S. H.; Park, H.-J.; Lee, S. I.; Chung, Y. K. Org. Lett. 2008, 10,
433. doi:10.1021/ol702577g
1. Torborg, C.; Beller, M. Adv. Synth. Catal. 2009, 351, 3027.
doi:10.1002/adsc.200900587
30.Pi, S.-F.; Tang, B.-X.; Li, J.-H.; Liu, Y.-L.; Liang, Y. Org. Lett. 2009, 11,
2309. doi:10.1021/ol900643r
2. McGlacken, G. P.; Fairlamb, I. J. S. Eur. J. Org. Chem. 2009, 4011.
doi:10.1002/ejoc.200900139
31.Torregrosa, R. R. P.; Ariyarathna, Y.; Chattopadhyay, K.; Tunge, J. A.
J. Am. Chem. Soc. 2010, 132, 9280. doi:10.1021/ja1035557
3. Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem., Int. Ed. 2005,
44, 4442. doi:10.1002/anie.200500368
391

Beilstein J. Org. Chem. 2017, 13, 384–392.
32.Zhang, W.-W.; Zhang, X.-G.; Li, J.-H. J. Org. Chem. 2010, 75, 5259.
doi:10.1021/jo1010284
License and Terms
33.Rodriguez, N.; Goossen, L. J. Chem. Soc. Rev. 2011, 40, 5030.
doi:10.1039/c1cs15093f
This is an Open Access article under the terms of the
Creative Commons Attribution License
34.Gooßen, L. J.; Deng, G.; Levy, L. M. Science 2006, 313, 662.
doi:10.1126/science.1128684
(http://creativecommons.org/licenses/by/4.0), which
permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
35.Gruber, S.; Zaitsev, A. B.; Wörle, M.; Pregosin, P. S.; Veiros, L. F.
Organometallics 2008, 27, 3796. doi:10.1021/om800295z
36.Yamashita, M.; Hirano, K.; Satoh, T.; Miura, M. Org. Lett. 2010, 12,
592. doi:10.1021/ol9027896
37.Patel, B. A.; Dickerson, J. E.; Heck, R. F. J. Org. Chem. 1978, 43,
5018. doi:10.1021/jo00420a029
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
38.Yamashita, M.; Hirano, K.; Satoh, T.; Miura, M. Adv. Synth. Catal.
2011, 353, 631. doi:10.1002/adsc.201000897
(http://www.beilstein-journals.org/bjoc)
39.Yamashita, M.; Hirano, K.; Satoh, T.; Miura, M. Chem. Lett. 2010, 39,
68. doi:10.1246/cl.2010.68
The definitive version of this article is the electronic one
which can be found at:
40.Abu Deiab, G. I.; Croatt, M. P. Chapter 3 - Step-Economical Synthesis
of Clinprost and Analogs Utilizing a Novel Decarboxylation Reaction. In
Strategies and Tactics in Organic Synthesis; Michael, H., Ed.;
Academic Press, 2017; Vol. 12, pp 95 ff.
doi:10.3762/bjoc.13.41
41.Nagy, E. E.; Hyatt, I. F. D.; Gettys, K. E.; Yeazell, S. T.;
Frempong, S. K., Jr.; Croatt, M. P. Org. Lett. 2013, 15, 586.
doi:10.1021/ol303402e
42.Thadani, A. N.; Rawal, V. H. Org. Lett. 2002, 4, 4317.
doi:10.1021/ol0269594
43.Wilson, S. R.; Zucker, P. A. J. Org. Chem. 1988, 53, 4682.
doi:10.1021/jo00255a007
44.Tang, W.; Prusov, E. V. Org. Lett. 2012, 14, 4690.
doi:10.1021/ol302219x
45.Gagnepain, J.; Moulin, E.; Fürstner, A. Chem. – Eur. J. 2011, 17, 6964.
doi:10.1002/chem.201100178
46.Jeso, V.; Micalizio, G. C. J. Am. Chem. Soc. 2010, 132, 11422.
doi:10.1021/ja104782u
47.Schnermann, M. J.; Romero, F. A.; Hwang, I.; Nakamaru-Ogiso, E.;
Yagi, T.; Boger, D. L. J. Am. Chem. Soc. 2006, 128, 11799.
doi:10.1021/ja0632862
48.McCammant, M. S.; Shigeta, T.; Sigman, M. S. Org. Lett. 2016, 18,
1792. doi:10.1021/acs.orglett.6b00517
49.Todd, D. P.; Thompson, B. B.; Nett, A. J.; Montgomery, J.
J. Am. Chem. Soc. 2015, 137, 12788. doi:10.1021/jacs.5b08448
50.Kong, W.; Che, C.; Kong, L.; Zhu, G. Tetrahedron Lett. 2015, 56, 2780.
doi:10.1016/j.tetlet.2015.04.036
51.Xu, S.; Zhu, S.; Shang, J.; Zhang, J.; Tang, Y.; Dou, J. J. Org. Chem.
2014, 79, 3696. doi:10.1021/jo500375q
52.Huang, Y.; Fañanás-Mastral, M.; Minnaard, A. J.; Feringa, B. L.
Chem. Commun. 2013, 49, 3309. doi:10.1039/c3cc41021h
53.Schmidt, A.; Hilt, G. Org. Lett. 2013, 15, 2708. doi:10.1021/ol401015e
54.Lim, H. N.; Parker, K. A. J. Am. Chem. Soc. 2011, 133, 20149.
doi:10.1021/ja209459f
55.Kennard, O.; Watson, D. G.; Fawcett, J. K.; Kerr, K. A. Tetrahedron
1970, 26, 607. doi:10.1016/S0040-4020(01)97853-6
56.Hettrick, C. M.; Kling, J. K.; Scott, W. J. J. Org. Chem. 1991, 56, 1489.
doi:10.1021/jo00004a028
57.Gradén, H.; Hallberg, J.; Kann, N.; Olsson, T. J. Comb. Chem. 2004, 6,
783. doi:10.1021/cc049929w
58.Surovtseva, D. A.; Orlov, D. A.; Morozova, T. A.; Krylov, A. V.;
Belov, A. P. Kinet. Catal. 2006, 47, 855.
doi:10.1134/s0023158406060073
59.Alfonso, D. R.; Jordan, K. D. J. Comput. Chem. 2003, 24, 990.
doi:10.1002/jcc.10233
392