Decarboxylative Alkynylation of α-Keto Acids and Oxamic Acids in Aqueous Media

Article abstract of DOI:10.1021/acs.orglett.5b01336

A mild K₂S₂O₈ promoted decarboxylative alkynylation of α-keto acids and oxamic acids has been developed. This process features mild reaction conditions, a broad substrate scope, and good functional-group tolerance, therefo

Full text of DOI:10.1021/acs.orglett.5b01336

Letter
pubs.acs.org/OrgLett
Decarboxylative Alkynylation of α‑Keto Acids and Oxamic Acids in
Aqueous Media
Hua Wang, Li−Na Guo, Shun Wang, and Xin-Hua Duan*
Department of Chemistry, School of Science and MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed
Matter, Xi’an Jiaotong University, Xi’an 710049, China
S
* Supporting Information
ABSTRACT: A mild K2S2O8 promoted decarboxylative alkynyla-
tion of α-keto acids and oxamic acids has been developed. This
process features mild reaction conditions, a broad substrate scope,
and good functional-group tolerance, therefore providing a new and
efficient access to a wide range of ynones and propiolamides.
Furthermore, this radical process could also be successfully applied
2
to alkynylation of the Csp −H bond in DMF with hypervalent alkynyl iodide reagents.
he decarboxylative cross-coupling reaction represents one
alkynylation of aliphatic carboxylic acids.10a However, com-
Tof the most reliable methods to construct C−C and C− pared with the above-mentioned synthetic procedures, the
heteroatom bonds in current organic synthesis.1 Compared
corresponding radical alkynylation reactions were still much
less explored.10 The above-mentioned elegant results, together
with traditional cross-coupling reactions using sensitive organo-
with our continuing interest in decarboxylative coupling of α-
keto acids,3g,4a−d prompted us to explore the direct
decarboxylative alkynylation of α-keto acids with suitable
alkynylating agents. Herein, we describe a new decarboxylative
alkynylation of α-keto acids and oxamic acids under mild
conditions for the synthesis of ynones and propiolamides,
which are an important class of compounds in synthetic and
natural product chemistry.11
metallic reagents as sources of carbon nucleophiles, the
decarboxylative reaction has proven to be a renewable and
sustainable synthetic method to achieve these goals in view of
the practical operation and easy availability of carboxylic acids.2
Over the past decades, a number of decarboxylative reactions
have been successfully developed for the synthesis of
structurally diverse carbonyl compounds using α-keto acids as
reactants.3 In 1991, Minisci described the first silver-catalyzed
homolytic acylation of heteroarenes with α-keto acids via a
decarboxylative radical process.3a Since the pioneering palla-
dium-catalyzed decarboxylative acylation reactions developed
by Goossen and co-workers,3b−d the direct oxidative acylation
Initially, the alkynyliodonium reagent 1-[(triisopropylsilyl)-
ethynyl]-1,2-benziodoxol-3(1H)-one (TIPS-EBX, 2a)6 was
chosen as a model substrate to optimize the reaction conditions
for the direct decarboxylative alkynylation of phenylglyoxylic
acid 1a. To our delight, the reaction of 1a and 2a proceeded
smoothly in the presence of 1.0 equiv of K2S2O8 in CH3CN/
H2O (1:1) at 50 °C to afford the desired product 3a in 74%
yield even in the absence of the Ag(I) catalyst3a,4,12 (Table 1,
entry 1). A much better yield of 3a was obtained by lowering
the amount of K2S2O8 to 0.7 equiv (entry 2). However, a
further decrease of the oxidant amount resulted in a lower yield
of 3a (entry 3). After extensive screening of solvents and
reaction temperatures, we found that the reaction in CH3CN/
H2O (1:1) at 50 °C gave the best result (entries 4−10). Other
oxidants, such as Na2S2O8 and (NH4)2S2O8, were also effective
for this transformation, while oxone and PhI(OAc)2 were
ineffective (entries 11−14). A control experiment revealed that
K2S2O8 was necessary for the success of this reaction (entry
15). Notably, this reaction could also be scaled up to 1 mmol,
and the desired ynone 3a was produced in 89% yield (entry 2).
To evaluate the generality of this decarboxylative alkynyla-
tion reaction, a wide range of α-keto acids 1 and hypervalent
2
of unactivated Csp −H bonds has been particularly investigated
in recent years.3e−m Subsequently, our group4a−d and
others4e−g developed the radical-mediated tandem decarbox-
ylative difunctionalization of unsaturated substrates with α-keto
acids for the synthesis of various heterocycles and organo-
fluorine compounds. Despite significant progress made in the
2
2
2
3
formation of Csp −Csp and Csp −Csp bonds, the construction
2
of the Csp −Csp bond via transition-metal-free decarboxylative
alkynylation of α-keto acids has not yet been reported and
remains a challenging topic.5
In recent years, the hypervalent alkynyl iodide reagent has
emerged as an efficient alkynylating reagent in organic
synthesis.6−10 In this field, Waser and co-workers have reported
a series of the direct alkynylations of diverse substrates under
transition-metal catalysis or metal-free conditions.7 More
recently, Rh(III)-catalyzed directed C−H alkynylation reactions
have also been developed successfully by different research
groups.8 In addition, some excellent results using the
alkynylated cyclic hypervalent iodine reagent as the reactant
have also been described.9 Recently, Li and co-workers
developed an efficient Ag-catalyzed radical decarboxylative
Received: May 7, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.5b01336
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Organic Letters
Letter
Table 1. Optimization of the Decarboxylative Alkynylation
of Phenylglyoxylic Acid
Scheme 1. Scope of α-Keto Acids and Alkynylating Agents
a
b
entry
oxidant (equiv)
solvent
yield (%)
74
1
2
3
4
5
6
7
8
K2S2O8 (1.0)
K2S2O8 (0.7)
K2S2O8 (0.5)
K2S2O8 (0.7)
K2S2O8 (0.7)
K2S2O8 (0.7)
K2S2O8 (0.7)
K2S2O8 (0.7)
K2S2O8 (0.7)
K2S2O8 (0.7)
Na2S2O8 (0.7)
(NH4)2S2O8 (0.7)
oxone (0.7)
PhI(OAc)2 (0.7)
−
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
acetone/H2O (1:1)
AcOH/H2O (1:1)
DMF/H2O (1:1)
CH2Cl2/H2O (1:1)
H2O
c
86 (89)
59
80
39
trace
trace
32
d
9
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
CH3CN/H2O (1:1)
11
e
10
78
11
12
13
14
15
83
80
trace
f
n.r.
0
a
Reaction conditions: 1a (0.24 mmol, 1.2 equiv), 2a (0.20 mmol, 1.0
b
equiv), solvent (2 mL), oxidant, 50 °C, 24 h under N2. Yield of
c
isolated product. Yield on a 1 mmol scale is given in parentheses.
d
e
f
Room temperature. At 80 °C. n.r. = no reaction.
iodine reagents 2 were examined under the optimized reaction
conditions (Scheme 1). In general, phenylglyoxylic acids having
different substituents on the aromatic ring were all efficiently
engaged in this reaction. As shown in Scheme 1, both electron-
rich and -poor p-substituents on the phenylglyoxylic acid were
compatible with the reaction conditions to give the desired
products 3b−h in good to excellent yields. Satisfactorily,
phenylglyoxylic acids bearing an ortho-substituent, such as o-
methyl, o-halo, and o-trifluoromethyl, also afforded the desired
ynones 3i−l in good yields, which indicated that the steric
hindrance had little effect on this transformation. Furthermore,
the meta-substituted phenylglyoxylic acids also worked well and
gave the desired products 3m−o in moderate to good yields. It
is noteworthy that several functional groups such as ether, halo,
and trifluoromethyl groups were tolerated well under the
standard reaction conditions. In addition to the monosub-
stituted phenylglyoxylic acids, the sterically congested 2,4-
disubstituted α-keto acids 1p and 1q also smoothly furnished
the desired ynones 3p and 3q in 78% and 82% yields,
respectively. The α- and β-naphthyloxoacetic acids 1r and 1s
also produced the desired products 3r and 3s, albeit in
somewhat low yields. The 2-thienylglyoxylic acid could also
afford the corresponding product 3t in 45% yield when 10%
AgNO3 was used as a catalyst. Furthermore, aliphatic α-keto
acids, such as pyruvic acid, also provided the corresponding
ynone 3u in 68% yield. The silyl-substituted hypervalent
alkynyl iodine reagent 2b also afforded good yields of ynones
3v and 3w. Finally, aryl-EBXs and alkyl-EBX also worked with
1a to afford the corresponding products 3x−z in moderate
yields. It should be noted that the phenyl phenylethynyl sulfone
was less effective under this reaction system to furnish the
desired product 3x only in 8% yield. Moreover, the phenyl-
ethynyl phenyliodonium tosylate failed to produce the product
3x.
a
b
10 mol % AgNO3 was used. Phenyl phenylethynyl sulfone was used
as an alkynylating agent.
Encouraged by the above results, we wished to apply this
effective decarboxylative alkynylation reaction to the synthesis
of other functionalized alkynes. To our delight, various oxamic
acids could also undergo a similar process to give propiolamides
in moderate yields under modified reaction conditions (Scheme
2). Treatment of N-phenyloxamic acid 4a with 2a in the
presence of 1.0 equiv of K2S2O8 in CH3CN/H2O (1:1) at 50
°C for 24 h afforded the desired N-phenylpropiolamide 5a in
51% yield.13 Yet, oxamic acids with electron-donating and
-withdrawing groups at the para or ortho positions of the aryl
ring just led to the corresponding N-arylpropiolamides 5b−g in
poor yields, together with some unreacted starting materials
recovered. We were delight to find that the yields of 5a−g
could be further improved to 51−74% by using 10% AgNO3 as
a catalyst. However, the meta-substituted oxamic acid 4h
resulted in only 29% yield. Oxamic acid 4i bearing a bulky
group also provided the desired amide 5i, but in low yield.
Moreover, N,N-disubstituted oxamic acids were also suitable
substrates for this alkynylation reaction, the corresponding
propiolamides 5j and 5k were isolated in 60% and 65% yields in
the presence of catalyst, respectively. Unfortunately, when
alkoxycarbonyl ketoacids such as monoethyl oxalate was used,
no reaction occurred with 2a. Interestingly, switching N,N-
dimethyloxamic acid to N,N-dimethylformamide (DMF) as the
−CONMe2 source4h,i,14 also led to the corresponding
alkynylation products in moderate yields at 100 °C in the
presence of Ag(I)/K2S2O8 (eq 1).
To further explore the potential utilities of the alkynylation
products, some transformations were conducted (for details see
B
DOI: 10.1021/acs.orglett.5b01336
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a
Scheme 2. Scope of Oxamic Acids with 2
Scheme 4. Proposed Mechanism
acids, we presumed that the benziodoxolonyl radical III might
also be participating in the generation of acyl radical I to fulfill
the product formation.
In summary, we have developed a new K2S2O8-promoted
oxidative decarboxylative alkynylation of α-keto acids under
mild conditions. This process allows for the efficient
preparation of functionalized ynones, which are important
synthetic intermediates with diverse utilities in organic
synthesis. Furthermore, the concept of this radical alkynylation
could also be extended to oxamic acids and DMF, thus
affording an alternative approach for the synthesis of
propiolamides.
a
Reaction conditions: 4 (0.24 mmol, 1.2 equiv), 2 (0.20 mmol, 1.0
equiv), CH3CN/H2O (1:1, 2 mL), K2S2O8 (0.20 mmol, 1.0 equiv), 50
°C, 24 h under N2. 10 mol % AgNO3 was used. Yield on a 1 mmol
scale is given in parentheses.
b
c
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures and spectroscopic data of new
compounds. The Supporting Information is available free of
charge on the ACS Publications website at DOI: 10.1021/
acs.orglett.5b01336.
the Supporting Information). As shown in Scheme 3, the
product 3a could be easily converted to triazole 7a via
Scheme 3. Derivatization of the Products 3a and 5a
AUTHOR INFORMATION
Corresponding Author
■
*E-mail: duanxh@mail.xjtu.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from Natural Science Basic Research Plan in
Shaanxi Province of China (No. 2014JQ2071) and the
Fundamental Research Funds of the Central Universities
(No. 2015qngz17) is greatly appreciated.
sequential desilylation and cycloaddition with benzyl azide.
Furthermore, propiolamide 9a was obtained in 56% yield
through a one-pot desilylation/Sonogashira coupling of 5a with
methyl 4-iodobenzoate 8a.
REFERENCES
■
Finally, when radical scavengers, such as TEMPO and BHT,
were added to the reaction system of 1a and 2a, only a trace
amount of 3a was detected (for details see the Supporting
Information). These results indicated that the reaction probably
proceeded via a free radical process. Based on our under-
standing of the oxidative decarboxylation of α-keto acids3a,4 and
previous investigations,10 a plausible mechanism was illustrated
in Scheme 4. First, the oxidative decarboxylation of 1a
generates nucleophilic acyl radical I in the presence of
K2S2O8. Then, the radical I attacks the triple bond of
hypervalent iodine reagent 2a to produce the radical
intermediate II.10 Finally, the radical II undergoes β-elimination
to afford the desired product 3a along with the formation of 2-
iodobenzoic acid, which was generated by a reduction−
protonation of the benziodoxolonyl radical III. Given that
only 0.7 equiv of K2S2O8 was required in the cases of α-keto
(1) For recent reviews, see: (a) Baudoin, O. Angew. Chem., Int. Ed.
2007, 46, 1373. (b) Goossen, L. J.; Rodríguez, N.; Goossen, K. Angew.
Chem., Int. Ed. 2008, 47, 3100. (c) Satoh, T.; Miura, M. Synthesis 2010,
3395. (d) Rodríguez, N.; Goossen, L. J. Chem. Soc. Rev. 2011, 40, 5030.
(e) Shang, R.; Liu, L. Sci. China Chem. 2011, 54, 1670. (f) Dzik, W. I.;
Lange, P. P.; Goossen, L. J. Chem. Sci. 2012, 3, 2671. (g) Cornella, J.;
Larrosa, I. Synthesis 2012, 653.
(2) For selected examples, see: (a) Myers, A. G.; Tanaka, D.;
Mannion, M. R. J. Am. Chem. Soc. 2002, 124, 11250. (b) Goossen, L.
J.; Deng, G.; Levy, L. M. Science 2006, 313, 662. (c) Forgione, P.;
Brochu, M.-C.; St-Onge, M.; Thesen, K. H.; Bailey, M. D.; Bilodeau, F.
J. Am. Chem. Soc. 2006, 128, 11350. (d) Miyasaka, M.; Fukushima, A.;
Satoh, T.; Hirano, K.; Miura, M. Chem.Eur. J. 2009, 15, 3674.
(e) Zhang, F.; Greaney, M. F. Org. Lett. 2010, 12, 4745. (f) Dai, J.-J.;
Liu, J.-H.; Luo, D.-F.; Liu, L. Chem. Commun. 2011, 47, 677.
(g) Messaoudi, S.; Brion, J.-D.; Alami, M. Org. Lett. 2012, 14, 1496.
(h) Zhang, Y.; Patel, S.; Mainolfi, N. Chem. Sci. 2012, 3, 3196. (i) Hu,
C
DOI: 10.1021/acs.orglett.5b01336
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Letter
P.; Shang, Y.; Su, W. Angew. Chem., Int. Ed. 2012, 51, 5945. (j) Zuo, Z.;
Ahneman, D. T.; Chu, L.; Terrett, J. A.; Doyle, A. G.; MacMillan, D.
W. C. Science 2014, 345, 437. (k) Kan, J.; Huang, S.; Lin, J.; Zhang, M.;
Su, W. Angew. Chem., Int. Ed. 2015, 54, 2199. (l) Noble, A.; McCarver,
S. J.; MacMillan, D. W. C. J. Am. Chem. Soc. 2015, 137, 624.
(3) For selected examples, see: (a) Fontana, F.; Minisci, F.; Barbosa,
M. C. N.; Vismara, E. J. Org. Chem. 1991, 56, 2866. (b) Goossen, L. J.;
Rudolphi, F.; Oppel, C.; Rodríguez, N. Angew. Chem., Int. Ed. 2008, 47,
3043. (c) Goossen, L. J.; Zimmermann, B.; Knauber, T. Angew. Chem.,
Int. Ed. 2008, 47, 7103. (d) Goossen, L. J.; Zimmermann, B.; Linder,
C.; Rodríguez, N.; Lange, P. P.; Hartung, J. Adv. Synth. Catal. 2009,
351, 2667. (e) Fang, P.; Li, M.; Ge, H. J. Am. Chem. Soc. 2010, 132,
11898. (f) Li, M.; Ge, H. Org. Lett. 2010, 12, 3464. (g) Wang, H.; Guo,
L.-N.; Duan, X.-H. Org. Lett. 2012, 14, 4358. (h) Yang, Z.; Chen, X.;
Liu, J.; Gui, Q.; Xie, K.; Li, M.; Tan, Z. Chem. Commun. 2013, 49,
1560. (i) Park, J.; Kim, M.; Sharma, S.; Park, E.; Kim, A.; Lee, S. H.;
Kwak, J. H.; Jung, Y. H.; Kim, I. S. Chem. Commun. 2013, 49, 1654.
(j) Li, H.; Li, P.; Zhao, Q.; Wang, L. Chem. Commun. 2013, 49, 9170.
(k) Yao, J.; Feng, R.; Wu, Z.; Liu, Z.; Zhang, Y. Adv. Synth. Catal.
2013, 355, 1517. (l) Li, Z.-Y.; Li, D.-D.; Wang, G.-W. J. Org. Chem.
2013, 78, 10414. (m) Ma, Y.-N.; Tian, Q.-P.; Zhang, H.-Y.; Zhou, A.-
X.; Yang, S.-D. Org. Chem. Front. 2014, 1, 284.
(4) (a) Wang, H.; Guo, L.-N.; Duan, X.-H. Adv. Synth. Catal. 2013,
355, 2222. (b) Wang, H.; Guo, L.-N.; Duan, X.-H. Chem. Commun.
2014, 50, 7382. (c) Yang, H.; Guo, L.-N.; Duan, X.-H. RSC Adv. 2014,
4, 52986. (d) Wang, H.; Zhou, S.-L.; Guo, L.-N.; Duan, X.-H.
Tetrahedron 2015, 71, 630. (e) Liu, J.; Fan, C.; Yin, H.; Qin, C.; Zhang,
G.; Zhang, X.; Yi, H.; Lei, A. Chem. Commun. 2014, 50, 2145. (f) Mai,
W.-P.; Sun, G.-C.; Wang, J.-T.; Song, G.; Mao, P.; Yang, L.-R.; Yuan,
J.-W.; Xiao, Y.-M.; Qu, L.-B. J. Org. Chem. 2014, 79, 8094. (g) Yan, K.;
Yang, D.; Wei, W.; Wang, F.; Shuai, Y.; Li, Q.; Wang, H. J. Org. Chem.
2015, 80, 1550. For other related examples reported in our group, see:
(h) Zhang, S.; Guo, L.-N.; Wang, H.; Duan, X.-H. Org. Biomol. Chem.
2013, 11, 4308. (i) Wang, H.; Guo, L.-N.; Duan, X.-H. Org. Biomol.
Chem. 2013, 11, 4573. (j) Wang, H.; Yang, H.; Li, Y.; Duan, X.-H. RSC
Adv. 2014, 4, 8720.
(5) For transition-metal-free decarboxylative coupling of α-
oxocarboxylates and oxamic acids with other reactants, see: (a) He,
Z.; Qi, X.; Li, S.; Zhao, Y.; Gao, G.; Lan, Y.; Wu, Y.; Lan, J.; You, J.
Angew. Chem., Int. Ed. 2015, 54, 855. (b) Yuan, M.; Chen, L.; Wang, J.;
Chen, S.; Wang, K.; Xue, Y.; Yao, G.; Luo, Z.; Zhang, Y. Org. Lett.
2015, 17, 346.
(6) (a) Zhdankin, V. V.; Kuehl, C. J.; Krasutsky, A. P.; Bolz, J. T.;
Simonsen, A. J. J. Org. Chem. 1996, 61, 6547. (b) Brand, J. P.; Waser, J.
Synthesis 2012, 44, 1155. (c) Bouma, M. J.; Olofsson, B. Chem.Eur. J.
2012, 18, 14242. (d) Zhdankin, V. V. Hypervalent Iodine Chemistry:
Preparation, Structure, and Synthetic Applications of Polyvalent Iodine
Compounds; Wiley-VCH: Weinheim, 2013. (e) Singh, F. V.; Wirth, T.
Oxidative Functionalization with Hypervalent Halides. In Comprehen-
sive Organic Synthesis, 2nd ed.; Knochel, P., Molander, G. A., Eds.;
Elsevier: Oxford, 2014.
(9) (a) Ohta, Y.; Tokimizu, Y.; Oishi, S.; Fujii, N.; Ohno, H. Org.
Lett. 2010, 12, 3963. (b) Wang, Z.; Li, X.; Huang, Y. Angew. Chem., Int.
Ed. 2013, 52, 14219. (c) Lu, B.; Wu, J.; Yoshikai, N. J. Am. Chem. Soc.
2014, 136, 11598. (d) Wang, Z.; Li, L.; Huang, Y. J. Am. Chem. Soc.
2014, 136, 12233. (e) Finkbeiner, P.; Weckenmann, N. M.;
Nachtsheim, B. J. Org. Lett. 2014, 16, 1326. (f) Utaka, A.;
Cavalcanti, L. N.; Silva, L. F., Jr. Chem. Commun. 2014, 50, 3810.
(g) Kamlar, M.; Císaro
2884.
̌ ́
́
va, I.; Vesely, J. Org. Biomol. Chem. 2015, 13,
(10) (a) Liu, X.; Wang, Z.; Cheng, X.; Li, C. J. Am. Chem. Soc. 2012,
134, 14330. (b) Huang, H.; Zhang, G.; Gong, L.; Zhang, S.; Chen, Y. J.
Am. Chem. Soc. 2014, 136, 2280. (c) Zhang, R.-Y.; Xi, L.-Y.; Zhang, L.;
Liang, S.; Chen, S.-Y.; Yu, X.-Q. RSC Adv. 2014, 4, 54349. For the
radical alkynylation reactions using alkynyl sulfones and iodoalkynes as
alkynylating reagents, see: (d) Schaffner, A.-P.; Darmency, V.; Renaud,
P. Angew. Chem., Int. Ed. 2006, 45, 5847. (e) Liautard, V.; Robert, F.;
Landais, Y. Org. Lett. 2011, 13, 2658. (f) Yang, J.; Zhang, J.; Qi, L.; Hu,
C.; Chen, Y. Chem. Commun. 2015, 51, 5275. (g) Xie, J.; Shi, S.;
Zhang, T.; Mehrkens, N.; Rudolph, M.; Hashmi, A. S. K. Angew.
Chem., Int. Ed. 2015, 54, 6046. (h) Liu, X.; Yu, L.; Luo, M.; Zhu, J.;
Wei, W. Chem.Eur. J. 2015, 21, 8745.
(11) For selected examples of ynones, see: (a) Aiguade, J.; Hao, J.;
Forsyth, C. J. Org. Lett. 2001, 3, 979. (b) Wender, P. A.; Bi, F. C.;
Brodney, M. A.; Gosselin, F. Org. Lett. 2001, 3, 2105. (c) Gaunt, M. J.;
Jessiman, A. S.; Orsini, P.; Tanner, H. R.; Hook, D. F.; Ley, S. V. Org.
Lett. 2003, 5, 4819. (d) Pattenden, G.; Stoker, D. A.; Thomson, N. M.
Org. Biomol. Chem. 2007, 5, 1776. (e) Kirkham, J. D.; Edeson, S. J.;
Stokes, S.; Harrity, J. P. A. Org. Lett. 2012, 14, 5354. (f) Unsworth, W.
P.; Cuthbertson, J. D.; Taylor, R. J. K. Org. Lett. 2013, 15, 3306.
(g) Nguyen, K. H.; Tomasi, S.; Roch, M. L.; Toupet, L.; Renault, J.;
Uriac, P.; Gouault, N. J. Org. Chem. 2013, 78, 7809. (h) Boukouvalas,
J.; Thibault, C. J. Org. Chem. 2015, 80, 681. For propiolamides, see:
(i) Pinto, A.; Neuville, L.; Retailleau, P.; Zhu, J. Org. Lett. 2006, 8,
4927. (j) Pinto, A.; Neuville, L.; Zhu, J. Angew. Chem., Int. Ed. 2007,
46, 3291. (k) Tang, S.; Peng, P.; Wang, Z.-Q.; Tang, B.-X.; Deng, C.-
L.; Li, J.-H.; Zhong, P.; Wang, N.-X. Org. Lett. 2008, 10, 1875.
(l) Qian, D.; Zhang, J. Chem. Commun. 2012, 48, 7082. (m) Wei, W.-
T.; Song, R.-J.; Ouyang, X.-H.; Li, Y.; Li, H.-B.; Li, J.-H. Org. Chem.
Front. 2014, 1, 484. (n) Mantovani, A. C.; Goulart, T. A. C.; Back, D.
F.; Menezes, P. H.; Zeni, G. J. Org. Chem. 2014, 79, 10526.
(12) For pioneering work on the decarboxylation of carboxylic acids
under Ag(I)/persulfates, see: (a) Anderson, J. M.; Kochi, J. K. J. Am.
Chem. Soc. 1970, 92, 1651. (b) Anderson, J. M.; Kochi, J. K. J. Org.
Chem. 1970, 35, 986.
(13) In order to improve the conversion of this reaction, some
conditions have been studied. Unfortunately, no satisfying results have
been achieved at present. For details, see the Supporting Information.
(14) For recent reviews using DMF as a reactant, see: (a) Muzart, J.
Tetrahedron 2009, 65, 8313. (b) Ding, S.; Jiao, N. Angew. Chem., Int.
Ed. 2012, 51, 9226 and references cited therein.
(7) For selected examples, see: (a) Brand, J. P.; Charpentier, J.;
Waser, J. Angew. Chem., Int. Ed. 2009, 48, 9346. (b) Brand, J. P.;
Waser, J. Angew. Chem., Int. Ed. 2010, 49, 7304. (c) Nicolai, S.;
Piemontesi, C.; Waser, J. Angew. Chem., Int. Ed. 2011, 50, 4680.
(d) Brand, J. P.; Waser, J. Org. Lett. 2012, 14, 744. (e) Tolnai, G. L.;
Ganss, S.; Brand, J. P.; Waser, J. Org. Lett. 2013, 15, 112. (f) Frei, R.;
Waser, J. J. Am. Chem. Soc. 2013, 135, 9620. (g) Chen, C. C.; Waser, J.
Chem. Commun. 2014, 50, 12923. (h) Chen, C. C.; Waser, J. Org. Lett.
2015, 17, 736.
(8) For selected examples, see: (a) Xie, F.; Qi, Z.; Yu, S.; Li, X. J. Am.
Chem. Soc. 2014, 136, 4780. (b) Feng, C.; Loh, T.-P. Angew. Chem., Int.
Ed. 2014, 53, 2722. (c) Collins, K. D.; Lied, F.; Glorius, F. Chem.
Commun. 2014, 50, 4459. (d) Feng, C.; Feng, D.; Loh, T.-P. Chem.
Commun. 2014, 50, 9865. (e) Jeong, J.; Patel, P.; Hwang, H.; Chang, S.
Org. Lett. 2014, 16, 4598. (f) Zhang, X.; Qi, Z.; Gao, J.; Li, X. Org.
Biomol. Chem. 2014, 12, 9329. (g) Feng, C.; Feng, D.; Luo, Y.; Loh,
T.-P. Org. Lett. 2014, 16, 5956. (h) Wang, H.; Xie, F.; Qi, Z.; Li, X.
Org. Lett. 2015, 17, 920.
D
DOI: 10.1021/acs.orglett.5b01336
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