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Nickel-Catalyzed Oxidative Decarboxylative (Hetero)Arylation of Unactivated C-H Bonds: Ni and Ag Synergy Aaron P Honeycutt, and Jessica M Hoover ACS Catal., Just Accepted Manuscript • Publication Date (Web): 07 Jun 2017 Downloaded from http://pubs.acs.org on June 7, 2017
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ACS Catalysis
Nickel-Catalyzed Oxidative Decarboxylative (Hetero)Arylation of Unactivated C-H Bonds: Ni and Ag Synergy Aaron P. Honeycutt and Jessica M. Hoover* C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, USA
Supporting Information Placeholder ABSTRACT: Oxidative decarboxylative arylation reac-
tions are potentially attractive routes to generate biaryl structures from simple and readily available precursors, yet they are under utilized due to limitations in the carboxylic acid scope. Here we report a nickel catalyst system that enables the selective decarboxylative arylation of unactivated C-H bonds with a broad scope of (hetero)aromatic carboxylate coupling partners. Preliminary mechanistic insights suggest that the efficiency and selectivity of this protocol originate from cooperation between Ni and Ag. KEYWORDS: decarboxylation, C-H activation, nickel, silver, heteroaryl
Decarboxylative coupling reactions have gained considerable attention over the past decade as environmentally benign alternatives to traditional biaryl syntheses.1 Pioneering work from the Nilsson2 and Goossen3 groups focused on the redox-neutral formation of biaryls from aryl halides, while more recent efforts have led to oxidative variants of these coupling reactions.4-6 Oxidative decarboxylative C−H arylation strategies are particularly attractive because they eliminate the need for prefuntionalized aryl halide or pseudohalide coupling partners. The decarboxylative coupling of heteroaryl carboxylic acids would be particularly attractive as heterobiaryl structures are common motifs in biologically active compounds and the corresponding esters are the direct products of traditional heterocycle syntheses. Unfortunately, the majority of existing decarboxylative arylation protocols suffer significant substrate scope limitations, especially with respect to the carboxylic acid and the arene coupling partners, and very few systems enable the efficient decarboxylative heteroarylation of C-H bonds. For example, Pd catalysts are well-developed for oxidative decarboxylative coupling (ODC) reactions,4 yet these systems typically have a limited scope with most catalysts being limited to ortho-substituted benzoic acids
(Scheme S1). Notably the groups of Greany4c and Su4g have each reported Pd-catalyst systems for the decarboxylative arylation of heteroaromatic acids, yet these reactions are limited to arenes bearing electronically activated C-H bonds, such as thiophenes and oxazoles (Scheme 1a). More recently, copper catalyzed ODC reactions have been developed, yet these systems typically enable the coupling of only 2-nitrobenzoic acids or pentafluorobenzoic acids (Scheme 1b).5 The one exception is the recent report of a Cu-catalyzed decarboxylative arylation reaction from Shi and coworkers,5c however this reaction is limited to the couplings of 2-thiophene carboxylic acid. Finally, a silver-mediated oxidative decarboxylative C-H arylation reaction that enables the coupling of pyridine carboxylic acids has been reported by Su and coworkers (Scheme 1c).6g Unfortunately, this system shows poor regioselectivity due to the involvement of radical intermediates. Thus, each of the four systems reported to enable decarboxylative C-H heteroarylation reactions is limited to the coupling of a specific class of heteroaromatic acids. Scheme 1. Decarboxylative C-H Arylation Reactions (a) Palladium-catalyzed oxidative decarboxylative C-H arylation (ref 4c) X R1 X R1 cat. Pd O (Het)Ar + H stoich. CuCO 3 N N R (Het)Ar OH R2 2 X = S, O Limited to electronically activated C-H bonds (b) Copper-catalyzed oxidative decarboxylative C-H arylation (refs 5a, 5b) O X X cat. Cu R OH + H R stoich. Ag2CO3 or O2 N N R R X = S, O, NMe Limited to 2-nitro- and pentafluorobenzoic acids and oxazoles (c) Silver-catalyzed oxidative decarboxylative C-H arylation (ref 6g) O cat. Ag R2 R2 OH + X stoich. K2S2O8 X N R1 X = N, CH N R1 Poor regioselectivity in the arylation of (hetero)arenes (d) Nickel-catalyzed oxidative decarboxylative C-H arylation (This Work) O cat. Ni + R R stoich. Ag2CO3 (Het)Ar ONa (Het)Ar H Efficient coupling of a broad scope of (hetero)aromatic carboxylates
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Similar limitations exist in the scope of arene coupling partners capable of undergoing decarboxylative arylation transformations. These reactions are often specific to the couplings of electronically activated C-H bonds, such as those of oxazoles and thiazoles (Scheme 1a and 1b),4c-h,5a-b and efforts to enable reactions with unactivated C-H bonds are limited. The groups of Crabtree7 and Glorius8 reported early examples of Pd-catalyzed decarboxylative C-H arylation reactions, yet these transformations form regioisomeric product mixtures or rely on intramolecular reactions, respectively. In 2009, Yu and coworkers reported a Pd-catalyzed decarboxylative arylation of arenes bearing monodentate directing groups employing electron-deficient aryl acylperoxides.9 Although this reaction enables the installation of a broader scope of arenes, the required aryl acylperoxides are commercially limited and potentially dangerous. Similarly, two copper systems have recently been reported to enable the decarboxylative coupling with arenes bearing benzamide directing groups. The first, reported by Shi and coworkers and mentioned above, is specific to the coupling of 2-thiophene carboxylic acid and proceeds through a tandem protodecarboxylation-dehydrogenative coupling pathway resulting in the loss of regiospecificity for the acids.5c A similar Cu-mediated ODC reaction of benzamides was recently disclosed by Miura and coworkers, but again suffers from limitations in the acid Table 1. Optimization of Reaction Conditionsa
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coupling partner, and efficient coupling is achieved only with 2-nitrobenzoic acids.5d There are no examples of a catalytic decarboxylative arylation of unactivated C-H bonds capable of employing a broad scope of aromatic and heteroaromatic acid coupling partners. Herein we report a new nickel catalyst system for the oxidative decarboxylative arylation of unactivated arene C-H bonds that efficiently couples an unprecedented scope of aromatic and heteroaromatic carboxylates. Table 2. Heteroaromatic Carboxylate Scopea Ni(OAc)2•4H2O (20 mol%) Ag2CO3 (2.0 equiv) O PivOH (1.5 equiv) O + Na2CO3 (4.0 equiv) Ar NaO H DMA, 110 °C, 24 h -CO2
N HN
1a
Q N
N HN
O Ar
2
3
R
Q HN
O S
Q HN N
O S
Q HN
N
O O
Q HN N
H O S
N H
93% 3a, R = H, 89% 3b, R = Cl, 3c, R = OMe, 72% Q HN
R O N
3e, 74%
3d, 93%
Q HN
Ph O N N
N
Q HN
O X
3f, 90%
Q HN
O
N
N F
3g, R = H, 3h, R = Ph,
74% 70%
3i, 40%
3j, X = S, 70% 3k, X = O, 36%
3l, 35%
a
O
N HN
O + NaO H 1a
S
Ph
catalyst (20 mol%) oxidant (2.0 equiv) Na 2CO3 (4.0 equiv)
N
Ph HN
O S
DMA, 110 °C 24 h, N 2 -CO2
N 2a
N
3a
entry
catalyst
oxidant
additive
Yield (%)b
1
Cu(OAc)2
Ag2CO3
-
17
2
NiBr2•H2O
Ag2CO3
-
29
3
Ni(OTf)2
Ag2CO3
-
21
4
Ni(OAc)2•4H2O
Ag2CO3
-
45
5
Ni(OAc)2•4H2O
AgOAc
-
11
6
c
Ni(OAc)2•4H2O
Ag2CO3
PivOH
64
7
d
Ni(OAc)2•4H2O
Ag2CO3
AcOH
42
8
e
Ni(OAc)2•4H2O
Ag2CO3
TFA
34
9f
Ni(OAc)2•4H2O
Ag2CO3
PivOH
>95 (93)g
-
Ag2CO3
PivOH
0
Ni(OAc)2•4H2O
-
PivOH
0
10f 11
f
a
Reaction conditions: 1a (0.2 mmol), 2a (1.0 mmol) in solvent (2 mL). b1H NMR yield with 1,3,5trimethoxybenzene as an internal standard. cPivalic acid (0.3 mmol) dAcetic acid (0.3 mmol) eTrifluoroacetic acid (0.3 mmol) f2a (0.6 mmol) gIsolated yield
Isolated yields. Reaction conditions: 1a (0.2 mmol), 2 (0.6 mmol), Ni(OAc)2•4H2O (20 mol%), Ag2CO3 (2.0 equiv), Na2CO3 (4.0 equiv), and pivalic acid (1.5 equiv) in DMA (2 mL) for 24 h at 110 °C under a N2 atmosphere.
In an effort to identify a catalyst system for the efficient decarboxylative coupling of heteroaromatic acids, we focused our initial study on 4-methyl-2-phenyl-1,3thiazole-5-carboxylate (2a). We began by using Cu(OAc)2 as the catalyst because copper salts enable the decarboxylation of a broad scope of benzoic acids.10 Unfortunately, all attempts to utilize copper for this transformation were unsuccessful due to low conversion to the desired product 3a. In contrast, we found that Ni salts generated the desired ODC product 3a with high selectivity (Table 1). For example, the inclusion of 20 mol% NiBr2•H2O led to 29% yield of the desired product 3a (entry 2). The most efficient pre-catalyst is Ni(OAc)2•4H2O, which generated 3a in 45% yield (entry 4). Ag2CO3 was the best oxidant for this transformation and all other oxidants explored (AgOAc, AgNO3, and O2) gave lower yields (Table S2). Inclusion of pivalic acid led to an increase in the yield of 3a (64%, entry 6) while other acidic additives, such as AcOH and TFA, showed no improvement in yield (entries 7-8). Finally, when only 3 equivalents of 2a were used, quantitative conversion to 3a was observed (entry 9). Thus, the optimized condi-
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tions employ 20 mol% Ni(OAc)2•4H2O paired with Ag2CO3 as the oxidant with Na2CO3 and PivOH addtives in DMA at 110 °C to generate the decarboxylative arylation product 3a in quantitative yield. Although nickel salts have been shown to be effective catalysts for oxidative C−H functionalization reactions,11 their use in oxidative decarboxylative arylation reactions is limited. In fact, only two examples of such reactivity have been reported and both systems are restricted to the couplings of 2-nitro- and perfluorobenzoic acids with benzoxazoles.12 In contrast, the Ni-catalyst system reported here enables the efficient ODC coupling of a broad scope of heteroaromatic carboxylates (Table 2). Thiazoles containing electron-withdrawing groups (3b) gave higher yields than those bearing electron-donating groups (3c). The corresponding oxazole showed good reactivity resulting in 74% yield of 3e. Thiazole-5carboxylate underwent coupling with complete regioselectivity at the C-5 position to yield 90% of 3f. Other heteroaromatic carboxylates such as pyrazole (2g and 2h), triazole (2i), benzothiophene (2j) and benzofuran (2k) also underwent efficient decarboxylative coupling with 1a. The pyridine carboxylate (2l) also forms the corresponding product, though in low yields (3l, 35%). Other pyridine derivatives such as 1-isoquinoline carboxylate, picolinic carboxylate, and picolinic carboxylate N-oxide, did not undergo decarboxylative coupling under our standard conditions (Chart S1). These carboxylates underwent decarboxylation, however no coupling product was observed. Similarly, for most carboxylates shown in Tables 2 and 3, the mass balance can be accounted for by protodecarboxylation.13 Table 3. Benzoate Scope
N HN
Ni(OAc)2•4H2O (20 mol%) Ag2CO3 (2.0 equiv) O PivOH (1.5 equiv) O + Na2CO3 (4.0 equiv) Ar NaO H DMA, 110 °C, 24 h -CO2
1a Q HN
a
Q
HN
R
O
Q HN
O
F
3m, R = H, 70% 3n, R = Br, 58% 3o, R = F, 55%
O
3 Q HN
3p, 60%
MeO
O +
S
NaO
N
H R 1 Q HN
Ni(OAc)2•4H2O (20 mol%) Ag2CO3 (2.0 equiv) PivOH (1.5 equiv) Ph Na2CO3 (4.0 equiv) DMA, 110 °C, 24 h -CO2
N HN
O
Ph O S
N
3 Ph
O S
Q HN
N
Ph O S
N
Q HN
O
Ph
S
N
N 3s, 45% (26% disubst.)
R 3t, R = Me, 3u, R = OMe, 3v, R = Cl, 3w, R = Br
N
R
2a Q HN
Ph S
86% 80% 61% 55%
3x, 80%
3y, 74%
a
Isolated Yields. Reaction conditions: 1 (0.2 mmol), 2a (0.6 mmol), Ni(OAc)2•4H2O (20 mol%), Ag2CO3 (2.0 equiv), Na2CO3 (4.0 equiv), and pivalic acid (1.5 equiv) in DMA (2 mL) for 24 h at 110 °C under a N2 atmosphere.
Ni(OAc)2 •4H2O (20 mol%) Q Ag2CO3 (2.0 equiv) HN PivOH (1.5 equiv)
Ph O S
Na2CO3 (4.0 equiv) DMA, 110 °C, 24 h
N
O
+ HO
S N
H Ph
+
S
Ph
N
O
Cl
3q, 42%
HN
1a + 2a
Q HN
O
F
O N
Ar
2 Me
Table 4. Benzamide Scopea
Scheme 2. Control Reactions
N
N
est yields (3m, 3n, 3o, and 3p). To our delight, this catalyst system tolerates aryl bromides and chlorides, suggesting potential for further functionalization. These data illustrate the ability of this catalyst system to couple both heteroaromatic carboxylates and ortho-substituted benzoates. Finally, we explored the scope of substituted benzamides (Table 4). Reaction of the unsubstituted benzamide 1s formed both the mono- and diarylation products. Reactions of the meta-substituted benzamides (1t1w) showed selective arylation at the less hindered ortho-C-H bond, and again illustrated the tolerance of this catalyst system toward aryl halides (3v and 3w) and aryl ethers (3u). Similarly, the naphthyl (1x) and Nmethypyrrole (1y) derived amides also underwent efficient arylation under the standard reaction conditions.
Cl
3r, 40%
a
Isolated yields. Reaction conditions: 1a (0.2 mmol), 2 (0.6 mmol), Ni(OAc)2•4H2O (20 mol%), Ag2CO3 (2.0 equiv), Na2CO3 (4.0 equiv), and pivalic acid (1.5 equiv) in DMA (2 mL) for 24 h at 110 °C under a N2 atmosphere.
To demonstrate that this catalyst system is not limited to the coupling of heteroaromatic carboxylates, we also explored the reactivity of benzoates under the standard reaction conditions (Table 3). The decarboxylative arylation of ortho-fluoro and -chloro benzoates proceeded cleanly, with the 2-fluoro-benzoates providing the high-
[Ni] (20 mol%), [Ag] (2 equiv) (standard conditions) No Ni(OAc)2 •4H2O No Ag2CO3
>95%
ND
ND
ND ND
ND >95%
85% ND
In order to gain insight into the reaction pathway, we conducted a series of preliminary mechanistic experiments. We began with a pair of control reactions. When the standard reaction was performed in the absence of nickel, no product 3a was formed, and instead 2-phenyl4-methyl-thiazole, the protodecarboxylation product was formed in 85% yield (Scheme 2). In the complementary experiment performed in the absence of silver oxidant, neither the coupling product 3a nor the protodecarboxylation product was observed, and instead the heteroaromatic acid was recovered in quantitative yield. These
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data indicate that decarboxylation is occurring only at Ag, while Ni is required for the C-C coupling to occur. Silver salts are known to promote the decarboxylation of aromatic acids through both oxidative decarboxylation pathways generating radical intermediates14 and alternative pathways involving organometallic silveraryl intermediates.15 To probe the possible formation of free radical intermediates under our reaction conditions, radical trapping experiments were carried out utilizing TEMPO and DHA. When the standard reaction is conducted in the presence of 1 equivalent of either trapping agent, no decrease in the yield of 3a was observed (>95% yield in all cases, Table S6), consistent with a decarboxylation step that generates a well-defined silver-aryl intermediate. To explore the C-H activation step, the kinetic isotope effect was obtained from the intermolecular competition experiment (Scheme 3). When an equimolar mixture of 1a and 1a-d7 was treated with 2a under the standard reaction conditions for 2 h, the product isotopologues 3a and 3a-d6 were formed in 17% and 4% yields respectively, giving a KIE of 4.3. When the reaction of 1a-d7 was conducted under the standard conditions, no proton incorporation was observed in the recovered starting material or the product (Scheme S2). This irreversible C-H activation step is consistent with the primary isotope effect observed in the competition experiment.16 Scheme 3. Kinetic Isotope Effect Q HN
Q HN
O
H D3C + H D
H3C H H 1a
Q HN
O
D 1a-d7
D 2a (3 equiv) H C 3 standard D conditions H 2h
Q HN
Ph O S
N +
Ph O S
D3C
N
D
D D 3a-d6, 4%
H H 3a, 17%
Intermolecular KIE = 4.3
HN
O
Ph
S
N H
N
HX + AgIX Ph O
S
O
N NiIIX
N NiI
N
O N NiII
N
N NiIII
N
B
S
S N
Ph
C
Ag0
Ph
AUTHOR INFORMATION Corresponding Author
REFERENCES
A
D
O
Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. Experimental details, spectral data, 1H and 13C NMR spectra (PDF)
We are grateful to West Virginia University for financial support of this work. NMR spectroscopy facilities (CHE1228336) and APH (CHE-1453879) were supported in part by the NSF. We thank Prof. Stephen Valentine and Mahdiar Kahkinejad of WVU for HRMS analyses.
NiIIX2
N
ASSOCIATED CONTENT
ACKNOWLEDGMENT
O
Ni(OAc)2•4H2O
N
Ag0 +
Based on the results above, we propose a pathway for this transformation involving the decarboxylation by silver to generate a AgI-aryl species15 and initial C-H activation by Ni to generate the NiII metallacycle B (Scheme 4).11,17 Transmetallation of the aryl fragment from Ag to Ni could occur with concomitant oxidation of the nickel center from NiII to NiIII to form intermediate C. Finally, reductive elimination from intermediate D would generate the coupled product. We believe that the key to the remarkable efficiency and selectivity of this catalyst system involves the cooperation of Ag and Ni in the formation of the high-valent Ni intermediate C. In this transmetallation step, the silver-aryl species enables the controlled delivery of an aryl radical equivalent while avoiding the formation of radical intermediates and the corresponding byproducts. In conclusion, we have disclosed the first nickelcatalyzed oxidative decarboxylative (hetero)arylation of unactivated C−H bonds. This catalyst system enables the efficient coupling of an unprecedented substrate scope of heteroaromatic carboxylates in addition to orthosubstituted benzoates and tolerates a wide array of functional groups. Current work is focused on exploring the mechanism of this transformation, in particular, as it relates to the remarkable substrate scope of this system.
*E-mail:
[email protected] Notes The authors declare no competing financial interest.
Scheme 4. Plausible Reaction Mechanism N
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O
AgI Ph
S N
N NaX + CO2
ONa + AgX
(1) (a) Goossen, L. J.; Rodríguez, N.; Goossen, K. Angew. Chem. Int. Ed. 2008, 47, 3100-3120. (b) Rodríguez, N.; Goossen, L. J. Chem. Soc. Rev. 2011, 40, 5030-5048. (c) Cornella, J.; Larrosa, I. Synthesis 2012, 44, 653-676. (2) Nilsson, M. Acta. Chem. Scand. 1966, 20, 423-426. (3) (a) Goossen, L. J.; Deng, G. J.; Levy, L. M. Science 2006, 313, 662-664. (b) Goossen, L. J.; Rodríguez, N.; Melzer, B.; Linder, C.; Deng, G.; Levy, L. M. J. Am. Chem. Soc. 2007, 129, 4824-4833. (4) Pd-catalyzed decarboxylative arylation: (a) Wang, C.; Piel, I.; Glorius, F. J. Am. Chem. Soc., 2009, 131, 4194-4195. (b) Cornella, J.;
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Lu, P.; Larrosa, I. Org. Lett., 2009, 11, 5506-5509. (c) Zhang, F.; Greaney, M. F. Angew. Chem. Int. Ed. 2010, 49, 2768-2771. (d) Xie, K.; Yang, Z.; Zhou, X.; Li, X.; Wang, S.; Tan, Z.; An, X.; Guo, C.-C. Org. Lett., 2010, 12, 1564-1567. (e) Zhou, J.; Hu, P.; Zhang, M.; Huang, S.; Wang, M.; Su, W. Chem. Eur. J., 2010, 16, 5876-5881. (f) Zhao, H.; Wei, Y.; Xu, J.; Kan, J.; Su, W.; Hong, M. J. Org. Chem., 2011, 76, 882-893. (g) Hu, P.; Zhang, M.; Jie, X.; Su, W. Angew. Chem. Int. Ed. 2012, 51, 227-231. (h) Pei, K.; Jie, X.; Zhao, H.; Su, W. Eur. J. Org. Chem. 2014, 4230-4233. (5) Cu-catalyzed decarboxylative arylation: (a) Chen, L.; Ju, L.; Bustin, K. A.; Hoover, J. M. Chem. Commun. 2015, 51, 15059-15062. (b) Patra, T.; Nandi, S.; Sahoo, S. K.; Maiti, D. Chem. Commun. 2016, 52, 1432-1435. (c) Zhao, S.; Liu, Y.-J.; Yan, S.-Y.; Chen, F.-J.; Zhang, Z.-Z.; Shi, B.-F. Org. Lett. 2015, 17, 3338-3341. (d) Takamatsu, K.; Hirano, K.; Miura, M. Angew. Chem. Int. Ed. 2017, 56, 53535357. (6) For select examples of ODC reactions of benzoic acids see: (a) Hu, P.; Shang, Y.; Su, W. Angew. Chem. Int. Ed., 2012, 51, 59455949. (b) Zhang, Y.; Patel, S.; Mainolfi, N. Chem. Sci., 2012, 3, 31963199. (c) Cornella, C.; Lahlali, H.; Larrosa, I. Chem. Commun. 2010, 46, 8276-8278. (d) Bhadra, S.; Dzik, W. I.; Goossen,L. J. J. Am. Chem. Soc., 2012, 134, 9938-9941. (e) Seo, S.; Slater, M.; Greaney, M. F. Org. Lett. 2012, 14, 2650-2653. (f) Bhadra, S.; Dzik, W. I.; Goossen, L. J. Angew. Chem. Int. Ed. 2013, 52, 2959-2962. (g) Kan, J.; Huang, S.; Lin, J.; Zhang, M.; Su, W. Angew. Chem. Int. Ed. 2015, 54, 2199-2203. (h) Zhang, Y.; Zhao, H.; Zhang, M.; Su, W. Angew. Chem. Int. Ed., 2015, 54, 3817-3821. (i) Fu, Z. Li, Z.; Xiong, Q.; Cai, H. RSC Adv. 2015, 5, 52101-52104. (j) Li, M.; Hoover, J. M. Chem. Commun. 2016, 52, 8733-8736. (7) Voutchkova, A.; Coplin, A.; Leadbeater, N. E.; Crabtree, R. H. Chem. Commu. 2008, 6312-6314. (8) Wang, C.; Piel, I.; Glorius, F. J. Am. Chem. Soc. 2009, 131, 4194-4195. (9) Yu, W. Y.; Sit, W. N.; Zhou, Z. Y.; Chan, A. S. C. Org. Lett. 2009, 11, 3174-3177. (10) Goossen, L. J.; Thiel, W. R.; Rodriguez, N.; Linder, C.; Melzer, B. Adv. Synth. Catal. 2007, 349, 2241-2246. (11) (a) Castro, L. C. M.; Chatani, N. Chem. Lett. 2015, 44, 410421. (b) Williams, A. C. Nickel Catalyzed C-H Activation. In C-H Bond Activation in Organic Synthesis Li, J. J.; CRC: Boca, Raton, Fl, 2015; pp 113-144. (c) Zhao, S.; Liu, B.; Zhan, B.-B.; Zhang, W.-D.; Shi, B.-F. Org. Lett. 2016, 18, 4586-4589. (d) Chatani, N. Top. Organomet. Chem. 2016, 56, 19-46. (12) (a) Yang, K.; Wang, P.; Zhang, C.; Kadi, A. A. ; Fun, H.-K.; Zhang, Y.; Lu, H. Eur. J. Org. Chem. 2014, 7586-7589. (b) Crawford, J. M.; Shelton, K. E.; Reeves, E. K.; Sadarananda, B. K.; Kalyani, D. Org. Chem. Front. 2015, 2, 726-729. (13) Carboxylates 1i and 1r undergo incomplete decarboxylation. (14) See refs 6e, 6g and Seo, S.; Taylor, J. B.; Greaney, M. F. Chem. Commun. 2012, 48, 8270-8272. (15) (a) Goossen, L. J.; Rodríguez, N.; Linder, C.; Lange, P. P.; Fromm, A. Chem. Cat. Chem. 2010, 2, 430-442. (b) Xue, L.; Su, W.; Lin, Z. Dalton Trans. 2011, 40, 11926-11936. (16) Simmons, E. M.; Hartwig, J. F. Angew. Chem. Int. Ed. 2012, 51, 2-9. (17) (a) Yokota, A.; Aihara, Y.; Chatani, N. J. Org. Chem. 2014, 79, 11922-11932. (b) Shiota, H.; Ano, Y.; Aihara, Y.; Fukumoto, Y.; Chatani, N. J. Am. Chem. Soc. 2011, 133, 14952-14955.
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Table of Contents Graphic Q HN
O
Q HN
Nickel'
H
O Ar
+ O
Silver'
25 examples up to 93% yield
Ar
NaO
Selected Arenes
Selected Carboxylates O
O NaO
X
N X = O, S
R NaO
X
X = O, S
O NaO
N N R
Q HN O
Q
R
Q HN O
HN O H
N
H
H
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