Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)
Letter
Copper-Catalyzed Cascade Radical Addition-Cyclization-Halogen Atom Transfer between Alkynes and Unsaturated #-Halogenocarbonyls Yuzhen Gao, Pengbo Zhang, Zhe Ji, Guo Tang, and Yu-Fen Zhao ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.6b03033 • Publication Date (Web): 29 Nov 2016 Downloaded from http://pubs.acs.org on November 29, 2016
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Copper-Catalyzed Cascade Radical Addition-CyclizationHalogen Atom Transfer between Alkynes and Unsaturated αHalogenocarbonyls Yuzhen Gao, Pengbo Zhang, Zhe Ji, Guo Tang,* and Yufen Zhao Department of Chemistry, College of Chemistry and Chemical Engineering, and the Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiamen, Fujian 361005, China. Supporting Information Placeholder
ABSTRACT: A Cu-catalyzed cascade radical addition/cyclization/halogen atom transfer between alkynes and α-halogeno-γ, δunsaturated carbonyl compounds for the synthesis of various substituted-cyclopentenes is described. Since up to four Csp3-Csp2 bonds, two Csp3-Br bonds and two carbocycles can be established in a single reaction, this 100% atom efficient reaction exhibits the advantages of wide substrate scope, high functional group tolerance and step-economics and offers an entry of tandem ATRAATRC process to the synthesis of substituted-cyclopentenes. KEYWORDS: tandem ATRA-ATRC reaction, copper-catalyzed, carbon radical, cyclic systems, cyclopentenes
Practical and innovative methods to construct cyclic systems continue to be an important area in modern organic chemistry. Among all types of synthetic methods, free-radical cyclization is a powerful procedure for the formation of cyclic systems by carbon–carbon bond formation, as it provides unique routes leading to target molecules in the fewest and concise steps.1 Atom transfer radical addition (ATRA) or cyclization (ATRC) of haloalkanes and halocarbonyls to unsaturated compounds serves as an atom-economical method of simultaneously forming C-C and C-X bonds, which provide a convenient route to the construction of cyclic frameworks.2 In particular, the products of ATRA and ATRC reactions retain halogen functionality which can be used in further synthesis. ATRA and ATRC reactions have been reported with a range of metal catalysts, such as ruthenium3, iron4, nickel5, palladium6 and iridium7. However, thus far copper-based catalysts have been the most commonly employed agents, that have emerged as the mildest, most cost-effective and high yielding strategy with which to synthesize various cyclic systems. 2b, 8-12 The application of copper-catalyzed intramolecular ATRC reactions to carbon-carbon double-bond formation for the construction of γ-lactams9, γ-lactones10, cyclic-ethers11 and pyrrolidines12 are now reasonably well established. Yet, methods for the synthesis of cyclic systems through intermolecular ATRC process are lacking.7b, 13 As a result, the application scope of ATRC has been restricted. Moreover, some progress has been
also been made in the intermolecular ATRA reactions between alkyl halides and alkynes.14 Recently, Hu14a reported a Cucatalyzed cis-selective carboiodination of terminal acetylenes with functionalized alkyl iodides, which were generated by treating alkyl bromides with KI (Scheme 1a). Soon after, Scheme 1. Copper-Catalyzed Intermolecular ATRA of Alkyl Halides to Alkynes
ACS Paragon Plus Environment
ACS Catalysis Table 1. Optimization of Reaction Conditions a
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
entry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
[Cu] Cu(OAc)2·H2O CuBr2 CuBr Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O Cu(SO4)2·5H2O
ligand L1 L1 L1 L1 L2 L3 L4 L4 L4 L4 L4 L4 L4 L4 L4 L4
base K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 K2CO3 Na2CO Et3N
solvent CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN DCE DMF DMSO CH3CN CH3CN
Page 2 of 5
Table 2. Scope of Alkynes a
yield (%) 13 32 30 42 8 61 76 0 8 6 33b 67c 60 32 12 55 trace
a Reaction conditions: 1a (0.3 mmol), 2a (0.45 mmol), [Cu] (10 mol%), ligand (20 mol%) and base (0.3 mmol) in solvent (2 mL) stirring under argon for 10 h. Oil bath temperature. Yield of the isolated product. b 60 o C. c 100 oC
Zhu14b reported Cu-catalyzed carbohalogenation of terminal alkynes providing quaternary-carbon-containing and transselective alkenyl halides (Scheme 1b). These procedures provide an efficient process by which to generate alkenyl halides, which are important synthetic building blocks. Although sequential atom transfer reactions have been developed8f, 15, there are few reports of tandem ATRA-ATRC reactions between alkyl halides and alkynes for the construction of cyclic frameworks.7a Therefore, the development of new, efficient methods for the intermolecular and tandem ATRA-ATRC reactions between alkyl halides and alkynes would be extremely valuable. Herein, we considered that 2halogenomalonate containing unsaturated functional groups could react with alkynes via a intermolecular and tandem ATRA-ATRC process, leading to the construction of substituted cyclopentenes (Scheme 1c). To test this hypothesis, ethynylbenzene (1a) and diethyl 2allyl-2-bromomalonate (2a) were chosen as reaction partners (Table 1). Initially, the reaction between 1a and 2a was conducted in MeCN. Using 10 mol% of Cu(OAc)2·H2O as the catalyst, 20 mol% PMDTA (L1) as the ligand, and 1 equiv of K2CO3 as the base, 3a was isolated in 13% yield, after being heated at 80 oC for 10 h (entry 1). Subsequently, various copper salts were explored showing that Cu(SO4)2·5H2O was the most effective and gave 3a in 42% yield (entries 1–4). Screening other ligands, such as TMEDA (L2), 1,10-phenanthroline (L3) and bipy (L4), revealed that L4 was the best choice and gave 3a in 76% yield (entries 5–7). Although Hu group reported that the base alone was sufficient to activate certain
a
Reaction conditions: 1 (0.3 mmol), 2a (0.45 mmol), Cu(SO4)2·5H2O (10 mol%), bpy (20 mol%) and K2CO3 (0.3 mmol) in CH3CN (2 mL) stirring under argon in 80 oC for 10 h.
alkyl halide,14d the reaction was inhibited in the absence of a copper salt, ligand or base (entries 8–10). Moreover, the yield of product 3a decreased when the temperature was lowered to 60 °C or raised to 100 °C (entries 11−12) indicating that the choice of temperature is also important. Screening other solvents, such as DCE, DMF, and DMSO revealed that MeCN was the best choice (entries 13−15). The effect of base was also investigated and K2CO3 was found to be the most suitable base (entries 16−17). After a series of detailed investigations16, we established an efficient route to substituted-cyclopentenes via a Cu-catalyzed intermolecular and sequential ATRA/ATRC reactions. The optimal reaction conditions are: 1a (0.3 mmol), 2a (0.45 mmol), Cu(SO4)2·5H2O (10 mol% ), L4 (20 mol% ), K2CO3 (0.3 mmol) and CH3CN (2.0 mL) at 80 °C for 10 h under a nitrogen atmosphere. With the optimized reaction conditions in hand, we investigated the scope of this Cu-catalyzed annulation by varying the alkynes 1, and the results are summarized in Table 2. Various functional groups on the benzene were examined and most were tolerated under the optimized conditions. With methyl substitution on benzene, these compounds reacted efficiently to give the desired products (3b−3f) in 64−53% yields, indicating the position and the number of the substituent on the benzene ring exerted a small influence. It is noteworthy that when a large sterically-hindered alkyne was employed, such as 2-ethynyl-1,3,5-trimethylbenzene (1e), the product 3f was obtained in 53% yield. Some electron-donating groups such as ethyl, tert-butyl, phenyl and methoxy were investigated and gave the corresponding products 3g−3j in 82−51% yields. Halogen atoms such as fluoro, bromo, and chloro on the aromatic ring were not affected under the present reaction conditions to afford the corresponding products 3k−3n in moderate
ACS Paragon Plus Environment
Page 3 of 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Table 3. Scope of Unsaturated α-Halogenocarbonyl Compounds a
Br
EtO2C
Br
MeO2C
Br
MeO2C
MeO2C
MeO2C
EtO2C
Br
MeO2C
MeO2C S
4a 21% E : Z = 1:0.14
Br
Ph(O)C
O
O
Ph
4f 22%
4e 28%
Ac
Ph
4aab
F
EtO2C
Br EtO2C
EtO2C
EtO2C
OMe 4h 66% (dr = 1:0.7) I
4g 53% (dr = 1:0.6)
EtO2C
Cl
EtO2C EtO2C Br Ph
Ph 4i mixture
EtO2C
Br
EtO2C
Br
Ac
EtO2C
Br
Ph(O)C
4d 63%
Br
4c 61%
Ph(O)C
Ph(O)C
EtO2C
Me
4b 75%
CN
could also react smoothly with 2a to afford the expected products 3v and 3w in 62% and 41% yields. Ethynylcyclopropane was also examined but unfortunately only trace amounts of the desired product 3x were detected. Next, we turned our attention to exploring various unsaturated α-halogenocarbonyl compounds 2 under standard conditions (Table 3). When the starting material 2b contains a terminal alkyne group, the desired vinylic bromide product 4a was obtained in lower yield. Dimethyl 2-allyl-2-bromomalonate 2c was also employed and resulted in the production of 4b–4d in 75–61% yields. By contrast, the phenacyl-substituted counterpart 2d led to the corresponding products 4e–4f in lower yields and gave 4aa as the byproduct, potentially due to the increased steric hindrance. The reaction could be applied to other activated organobromides, as exemplified by the construction of 4g and 4h. Unfortunately, an attempt to build cyclohexene ring 4i or cyclopent ring with a quaternary carbon center 4j was failed. When diethyl 2-allyl-2-chloromalonate 2h was employed instead of 2a, chlorinated product 4k was synthesized successfully in a low yield. Gratifyingly, with diethyl 2allyl-2-iodomalonate 2i acting as the carbohalogenation reagent, iodinated products 4l−4o were successfully obtained in 79−67% yields. An important extension of this protocol was achieved by simply adding 2 equiv of KI to the standard conditions, the reaction between 1 and 2a produced 4l and 4m in 62% and 68% yields, thus allowing a more simple and practical way to synthesize iodinated products.
4k 11%
4j trace I
EtO2C
EtO2C EtO2C
I EtO2C
OMe I
Scheme 2 Cu-Catalyzed Double Tandem ATRA-ATRC Reaction
EtO2C S
4l 72% (62%)c
4m 79% (68%)c
OMe
4n 67%
Br
4o 74%
a Reaction conditions: 1 (0.3 mmol), 2 (0.45 mmol), Cu(SO4)2·5H2O (10 mol%), bpy (20 mol%) and K2CO3 (0.3 mmol) in CH3CN (2 mL) stirring under argon in 80 oC for 10 h. b the byproduct when 2d was employed as the the carbohalogenation reagent. c KI (0.6 mmol, 2.0 equiv) was added to the reactions between 1 and 2a under standard conditions.
to good yields, thus providing ample opportunity for further elaboration by the transition metal-catalyzed cross-coupling reactions. Moreover, the structure of 3k was confirmed by Xray crystal structure analysis (Figure 1).17 Substrates bearing electron-withdrawing (COMe and CN) groups on the benzene ring were also investigated and smoothly converted into products 3o−3p in 56−52% yields. The process was extended to substrate 1q, bearing an amino group, providing 3q in lower yield. Gratifyingly, sterically hindered substrates with 2fluorenyl, 3,4-methylenedioxyphenyl, 2-naphthyl, 1-naphthyl
Figure 1. Crystal structure of compound 3k. also reacted with 2a efficiently to give the desired products 3r−3u in good yields. In addition, compounds with thienyl
Scheme 3 Synthetic Utility of Cu-Catalyzed Tandem ATRAATRC Reaction
Scheme 4 Radical Trapping Experiments
ACS Paragon Plus Environment
ACS Catalysis
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Scheme 5 A Tentative Mechanistic Pathway
Remarkably, the one-pot construction of dicyclopentenes 5a and 5b were achieved by reacting alkynes 1aa and 1ab with 2a, respectively (Scheme 2). Although the yield appears to be moderate, in view of the formation of four Csp3-Csp2 bonds, two Csp3-Br bonds and two new carbocycles in a single reaction, it still represents a highly attractive method for the synthesis of dicyclopentenes from readily accessible starting materials. The synthetic utility of this reaction was explored, demonstrating the practical application of this method (Scheme 3). 1a (10 mmol) was employed in a gram-scale reaction and afforded 4a in 74% yield. Epoxidation of 3a with metachloroperbenzoic acid (m-CPBA) gave 6a in 92% yield. Furthermore, the reaction between 3a and diphenylphosphinothioic S-acid gave 6b in 97% yield. We noted that dehydrohalogenation of 3a would then yield a direct route to substituted-3methylenecyclopent-1-ene 6c in 82% yield. It is noteworthy that orangoazides have been widely used in medicinal chemistry because of their versatile biological activities.18 And 6d bearing an azide group was easily obtained from 3a in 80% yield. To gain insight into the reaction mechanism, preliminary studies were carried out (Scheme 4). The reaction between 1a and 2a was inhibited by adding 1.5 equiv of 2,2,6,6-tetramethylpiperidinooxy (TEMPO). Instead, 7a was formed in 71% yield (Scheme 4a). Based on literature precedents19, we assume that the carbon radical A which is formed from 2a is trapped by TEMPO to form intermediate B. With the assistance of another molecule of TEMPO, intermediate B undergoes elimination to form product 7a. Moreover, in the presence of butylated hydroxytoluene (BHT), no detectable 3a was observed, and 7b was obtained in 55% yield (Scheme 4b).
Page 4 of 5
BHT could produce phenoxyl radical C which abstracts a hydrogen atom through an intramolecular transfer to afford intermediate D.20 Subsequently, intermediate D would react with carbon radical A to afford product 7b. These results indicated that the Cu-catalyzed cascade reaction might proceed via a radical mechanism. On the basis of the above-mentioned experiments, we propose a tentative pathway for this transformation (Scheme 5). Initially, the carbon radical A is formed by a SET process from 2a, which then adds to 1a to give the alkenyl radical E. The resulting alkenyl radical E participates in an intramolecular radical substitution reaction to generate the intermediate F. Subsequently, cationic intermediate G was formed through a second SET between F and Cu(II) which ultimately was attacked by Br- to afford product 3a (path a). Alternatively, the carbon radical F directly react with [Cu]Br species to form the desired product 3a (path b). In conclusion, we have successfully developed a facile method for the preparation of a broad spectrum of substitutedcyclopentenes via Cu-catalyzed tandem ATRA-ATRC reaction between alkynes and α-halogeno-γ, δ-unsaturated carbonyl compounds. Importantly, this transformation would provide a new pathway for the formation of two Csp3-Csp2 bonds and one Csp3-X bond in one step, highlighting the step-economics of this protocol. This method is highly efficient and a wide range of functional groups are well tolerated under mild reaction conditions. Moreover, the use of an inexpensive CuSO4·5H2O catalyst and readily available alkynes means that this facile protocol will be attractive for academia and industry.
ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1039/x0xx00000x. Experimental procedures for the synthesis, spectral data and copies of 1H and 13C NMR spectra of all the products. (PDF) Crystallographic data. ( CIF)
AUTHOR INFORMATION Corresponding Author *E-mail:
[email protected] .
Notes The authors declare no competing financial interest.
ACKNOWLEDGMENT We thank NSFC (21232005, 21375113) and the National Basic Research Program of China (2013CB910700), and the Fundamental Research Funds for the Central Universities (20720160030). We are grateful to Prof. Dr D. M. J. Lilley from University of Dundee for valuable discussions on this paper.
REFERENCES (1) (a) Bowman, W. R.; Bridge, C. F.; Brookes, P. J. Chem. Soc. Perkin Trans. 1, 2000, 1–14. (b) Manoj, M.; Bora, U. RSC Adv. 2013, 3, 18716–18754. (c) Bowman, W. R.; Cloonan, M. O.; Krintel, S. L. J. Chem. Soc. Perkin Trans. 1, 2001, 2885–2902. (d) Bowman, W. R.; Fletcher, A. J.; Potts, G. B. S. J. Chem. Soc. Perkin Trans. 1, 2002, 2747–2762. (2) For selected reviews on ATRC and ATRA reactions, see: (a) Clark, A. J. Chem. Soc. Rev. 2002, 31, 1–11. (b) Clark, A. J. Eur. J. Org. Chem. 2016, 2231–2243. (c) Studer, A.; Curran, D. P. Angew.
ACS Paragon Plus Environment
Page 5 of 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Chem. Int. Ed. 2016, 55, 58–102. (d) Matyjaszewski, K.; Xia, J. Chem. Rev. 2001, 101, 2921–2990. (e) Pintauer, T.; Matyjaszewski, K. Chem. Soc. Rev. 2008, 37, 1087–1097. (3) (a) Severin, K. Chimia 2012, 66, 386–388. (b) Severin, K. Curr. Org. Chem. 2006, 10, 217–224. (c) Nagashima, H.; Seji, K.; Ozaki, N.; Wakamatsu, H.; Itoh, K.; Tomo, Y.; Tsuji, J. J. Org. Chem. 1990, 55, 985–990. (4) (a) Dneprovskii, A. S.; Kasatochkin, A. N.; Boyarskii, V. P.; Ermoshkin, A. A.; Yakovlev, A. A. Russ. J. Org. Chem. 2006, 42, 1120–1130. (b) De Campo, F.; Lastécouères, D.; Verlhac, J. B. J. Chem. Soc. Perkin Trans. 1, 2000, 575–580. (5) Boivin, J.; Yousfi, M.; Zard, S. Z. Tetrahedron Lett. 1994, 35, 5629–5632. (6) (a) Liu, Q.; Chen, C.; Tong, X. Tetrahedron Lett. 2015, 56, 4483–4485. (b) Monks, B. M.; Cook, S. P. Angew. Chem. Int. Ed. 2013, 52, 14214–14218. (7) (a) Gu, X.; Li, X.; Qu, Y.; Yang, Q.; Li, P.; Yao, Y. Chem. Eur. J. 2013, 19, 11878–11882. (b) Nguyen, J. D.; Tucker, J. W.; Konieczynska, M. D.; Stephenson, C. R. J. J. Am. Chem. Soc. 2011, 133, 4160–4163. (8) For recent reports on the Cu-catalyzed intramolecular ATRA of alkyl halides to C=C bonds, see: (a) Isse, A. A.; Vison, G.; Ghelfi, F.; Roncaglia, F.; Gennaro, A. Adv. Synth. Catal. 2015, 357, 782–792. (b) Bull, J. A.; Hutchings, M. G.; Quayle, P. Angew. Chem. Int. Ed. 2007, 46, 1869–1872. (c) De Paoli, P.; Isse, A. A.; Bortolamei, N.; Gennaro, A. Chem. Commun. 2011, 47, 3580–3582. (d) Clark, A. J.; Collis, A. E. C.; Fox, D. J.; Halliwell, L. L.; James, N.; O’ Reilly, R. K.; Parekh, H.; Ross, A.; Sellars, A. B.; Willcock, H.; Wilson, P. J. Org. Chem. 2012, 77, 6778–6788. (e) Sebren, L. J.; Devery III, J. J.; Stephenson, C. R. J. ACS Catal. 2014, 4, 703–716. (f) Yang, D.; Yan, Y.-L.; Zheng, B.-F.; Gao, Q.; Zhu, N.-Y. Org. Lett. 2006, 8, 5757– 5760. (9) (a) Ram, R. N.; Kumar, N.; Singh, N. J. Org. Chem. 2010, 75, 7408–7411. (b) Motoyama, Y.; Kamo, K.; Yuasa, A.; Nagashima, H. Chem. Commun. 2010, 46, 2256–2258. (c) Clark, A. J.; Battle, G. M.; Bridge, A. Tetrahedron Lett. 2001, 42, 1999–2001. (10) (a) De Campo, F.; Lastécouères, D.; Vinccent, J.-M.; Verlhac, J.-B. J. Org. Chem. 1999, 64, 4969–4971. (b) Felluga, F.; Forzato, C.; Ghelfi, F.; Nitti, P.; Pitacco, G.; Pagnoni, U. M.; Roncaglia, F. Tetrahedron: Asymmetry 2007, 18, 527–536. (c) Chen, V. X.; Boyer, F.-D.; Rameau, C.; Pillot, J.-P.; Vors, J.-P.; Beau, J.-M. Chem. Eur. J. 2013, 19, 4849–4857. (11) (a) Udding, J. H.; Hiemstra, H.; Van Zanden, M. N. A.; Speckamp, W. N. Tetrahedron Lett. 1991, 32, 3123–3126. (b) Ram, R. N.; Charles, I. Chem. Commun. 1999, 2267–2268.
(12) (a) Udding, J. H.; Tuijp, C. K. J. M.; Hiemstra, H.; Speckamp, W. N. Tetrahedron 1994, 50, 1907–1918. (b) Balili, M. N. C.; Pintauer, T. Dalton Trans. 2011, 40, 3060–3066. (c) Ricardo, C.; Pintauer, T. Chem. Commun. 2009, 3029–3031. (13) (a) Iwamatsu, S.-I.; Kondo, H.; Matsubara, K.; Nagashima, H. Tetrahedron 1999, 55, 1687–1760. (b) Knorn, M.; Rawner, T.; Czerwieniec, R.; Reiser, O. ACS Catal. 2015, 5, 5186–5193. (c) Nishikata, T.; Noda, Y.; Fujimoto, R.; Sakashita, T. J. Am. Chem. Soc. 2013, 135, 16372–16375. (d) Arceo, E.; Montroni, E.; Melchiorre, P. Angew. Chem. Int. Ed. 2014, 53, 12064–12068. (14) For Cu-catalyzed ATRA of alkyl halides to alkynes, see: (a) Xu, T.; Hu, X. Angew. Chem. Int. Ed. 2015, 54, 1307–1311. (b) Che, C.; Zheng, H.; Zhu, G. Org. Lett. 2015, 17, 1617–1620. (c) Tang, Y.; Li, C. Org. Lett. 2004, 6, 3229–3231. (d) Xu, T.; Cheung, C. W.; Hu, X. Angew. Chem. Int. Ed. 2014, 53, 4910–4914. (e) Wallentin, C.-J.; Nguyen, J. D.; Finkbeiner, P.; Stephenson, C. R. J. J. Am. Chem. Soc. 2012, 134, 8875–8884. (f) Li, Z.; García-Domínguez, A.; Nevado, C. Angew. Chem. Int. Ed. 2016, 55, 6938–6941. (g) Belhomme, M.-C.; Dru, D.; Xiong, H.-Y.; Cahard, D.; Besset, T.; Poisson, T.; Pannecoucke, X. Synthesis 2014, 46, 1859–1870. (h) Lai, J.; Tian, L.; Liang, Y.; Zhang, Y.; Xie, X.; Fang, B.; Tang, S. Chem. Eur. J. 2015, 21, 14328–14331. (15) (a) Muñoz-Molina, J. M.; Belderraín, T. R.; Pérez, P. J. Adv. Synth. Catal. 2008, 350, 2365–2372. (b) Stevens, C. V.; Van Meenen, E.; Masschelein, K. G. R.; Eeckhout, Y.; Hooghe, W.; D’hondt, B.; Nemykin, V. N.; Zhdankin, V. V. Tetrahedron Lett. 2007, 48, 7108– 7111. (c) Helliwell, M.; Fengas, D.; Knight, C. K.; Parker, J.; Quayle, P.; Raftery, J.; Richards, S. N. Tetrahedron Lett. 2005, 46, 7129–7134. (16) See the Supporting Information for detailed data. (17) CCDC 1505770 (3k) contains the supplementary crystallographic data for this paper. See the Supporting Information for details. (18) (a) Hennessy, E. T.; Betley, T. A. Science 2013, 340, 591–595. (b) Sun, X.; Li, X.; Song, S.; Zhu, Y.; Liang, Y. F.; Jiao, N. J. Am. Chem. Soc. 2015, 137, 6059–6066. (c) Huryn, D. M.; Okabe, M. Chem. Rev. 1992, 92, 1745–1768. (19) (a) Jie, X.; Shang, Y.; Zhang, X.; Su, W. J. Am. Chem. Soc. 2016, 138, 5623–5633. (b) Maity, S.; Naveen, T.; Sharma, U.; Maiti, D. Org. Lett. 2013, 15, 3384–3387. (c) Gui, Q.; Hu, L.; Chen, X.; Liu, J.; Tan, Z. Chem. Commun. 2015, 51, 13922–13924. (20) (a) Egami, H.; Ide, T.; Kawato, Y.; Hamashima, Y. Chem. Commun. 2015, 51, 16675–16678. (b) Gao, Y.; Lu, G.; Zhang, P.; Zhang, L.; Tang, G.; Zhao, Y. Org. Lett. 2016, 18, 1242–1245.
ACS Paragon Plus Environment
