Synthesis and Physical Study of Perylene and Anthracene Polynitrile

Jul 11, 2019 - Attaching electron-withdrawing nitrile groups to π-conjugated systems is an effective approach toward electron acceptors. By combining...
0 downloads 0 Views 662KB Size
Download PDF
Letter pubs.acs.org/OrgLett

Cite This: Org. Lett. XXXX, XXX, XXX−XXX

Synthesis and Physical Study of Perylene and Anthracene Polynitrile as Electron Acceptors Ting-Yu Li, Yi-Chun Lin, Yu-Huei Song, Hsiu-Feng Lu, Ito Chao,* and Chih-Hsiu Lin* Institute of Chemistry, Academia Sinica, Academia Road, Sec. 2, No. 128, Taipei, Taiwan, Republic of China

Downloaded via NOTTINGHAM TRENT UNIV on July 17, 2019 at 15:26:43 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: Attaching electron-withdrawing nitrile groups to π-conjugated systems is an effective approach toward electron acceptors. By combining various cyanation methodologies, perylene and anthracene polynitriles with up to eight nitrile substituents on one aromatic scaffold were synthesized. This strategy produces stable electron acceptors with lowest unoccupied molecular orbital (LUMO) levels comparable to benchmark acceptors. A very stable octanitrile anion was also produced serendipitously. Reactivity patterns of these acceptors were rationalized by density functional theory (DFT) calculation.

T

cyanation protocol is the direct cyanide anion attack of electron-deficient PAHs. The resulting anion can be aromatized with proper oxidants to furnish the cyanated products.11 In addition to these cyanation strategies, de novo construction of cyanated PAHs would facilitate this quest considerably. The Wittig−Knoevenagel benzannulation (Scheme 1) is an ideal candidate to fulfill this purpose.12

he development of n-type electron acceptors is crucial to the success of organic electronic materials in various applications such as field-effect transistors (OFETs),1 lightemitting diodes (OLEDs),2 magnetic materials,3 and solar cells.4 However, because of the intrinsic low electron affinity of carbon 2p orbitals, ambient stable n-type organic materials are more difficult to attain than their p-type counterparts. Therefore, the design and synthesis of new structural motifs for organic electron acceptors is a vibrant research endeavor that could greatly empower the field. The most intuitive design principle toward strong electron acceptors is to install multiple electron-withdrawing substituents to a conjugate system so that its lowest unoccupied molecular orbital (LUMO) level is sufficiently low to accommodate injected electrons. Unfortunately, to selectively synthesize multiple substituted polycyclic aromatic systems is intrinsically difficult.5 Furthermore, low LUMO levels could render electron-deficient systems susceptible to nucleophilic attacks, thereby impairing their stability.6 It is quite challenging to negotiate the delicate balance between electron-accepting capacity and stability. Recently, theoretical and synthetic studies revealed polycyclic aromatic polynitriles as a new class of electron acceptors.7 Inspired by these results, we prepared and characterized perylene and anthracene polynitriles as stable electron acceptors with tunable LUMO levels that cover the range of conventional n-type organic materials. The most reliable strategy to synthesize aryl nitrile is the century-old Rosenmund−von Braun reaction of aryl halides and copper cyanide8 or its modern palladium-catalyzed variations.9 Yet, conversion of polyhalogenated polyaromatic hydrocarbons (PAHs) to polynitrile targets can be quite challenging, since it requires the cyanation to occur multiple times on one molecule. Alternatively, nitrile groups can be introduced to electron-deficient PAHs carrying appropriate leaving groups via nucleophilic substitution.10 Another © XXXX American Chemical Society

Scheme 1. Wittig−Knoevenagel Benzannulation Protocol for the Synthesis of Aryl Nitriles

Finally, to secure the solubility of the polynitrile acceptors, appropriate solubilizing groups must be installed.13 A successful synthesis of PAH polynitrile requires judicious arrangements of the aforementioned methodologies. 3,4,9,10-Perylene diimide (PDI) and 1,4,5,8-naphthalene diimide (NDI) derivatives are the archetypical organic acceptors.14 Highly electron-deficient PDI and NDI polynitrile were recently synthesized by the research groups of Müllen, Wang, and Chi.6,15 Therefore, we focused on perylene polynitrile derivatives as our first class of targets. The synthetic plan is to construct the perylene skeleton through Wittig− Knoevenagel benzannulation before adopting the other cyanation strategy at a later stage. As depicted in Scheme 2, 1,5-dichloroanthraquinone (1) first underwent Ir-complexcatalyzed borylation.16 The C−H activation occurs at the leasthindered 3,7 positions with complete regioselectivity. The diboronate 1′ was oxidized (with oxone)17 to dihydroxyl 1′, Received: April 26, 2019

A

DOI: 10.1021/acs.orglett.9b01454 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Scheme 2. Synthesis of Perylene Polynitrilesa

spectrum. From the 1H NMR of 5 and 7, it can be established that the chemical shifts of bay-area protons consistently exhibit down-field shifts, compared to the peri counterparts (∼8.7 and 9.1 ppm vs 8.1 and 8.7 ppm). Since the 1H NMR of 8 possesses two aromatic signals that are rather apart (9.2 ppm vs 8.9 ppm), the most probable structure should contain two protons at peri and bay area, respectively. Furthermore, in contrast to all other perylene polynitriles studied here, the four protons signals of O−CH2 in 8 all possess distinct chemical shifts, which indicates that its structure becomes chiral upon the installation of the eighth nitrile. This observation is also consistent with an additional bay substitution, which induces a helical twist into the perylene skeleton. This reversal of regioselectivity was investigated by DFT calculation (vide infra). After the successful synthesis of polynitrile perylene series 5−9, synthesis of polynitrile anthracene derivatives was also undertaken. We have previously synthesized 2,3,6,7-tetranitrile anthracene derivatives via double Wittig−Knoevenagel benzannulation.12a However, the current investigation requires extra leaving groups on the anthracene skeleton to facilitate late-stage nucleophilic cyanation. Based on this notion, 2,3,6,7tetracyano-9,10-difluoroanthracene is designated as the entry into highly cyanated anthracene. The synthesis (Scheme 3)

a

Reagents and conditions are described as follows: (a) [Ir(COD)OMe]2 (COD = cyclooctadiene), 4,4′-di-t-butyl-2,2-dipyridyl (dtbdpy), bis(pinacolato)diboron (B2Pin2), cyclohexane. (b) Oxone, acetone, 91% over two steps. (c) K2CO3, n-C8H17I, dimethylacetamide (DMAc), (83%). (d) Vinyl tributyltin, Pd2(DBA)3, P(t-Bu)3, CsF, dioxane (84%). (e) O3, −78 °C, then Me2S (99%). (f) Fumaronitrile, PEt3, THF, then K2CO3 (40%). (g) NBS, TFA, CHCl3 (99%). (h) Pd(dppf)Cl 2 (dppf = 1,1′-di(phenylphosphino)ferrocene), Zn(CN)2, dioxane (60%). (i) TBACN, CHCl3, then 2,3-dichloro-5,6-dicyano p-benzoquinone (DDQ) (44% for 7, 47% for 8, 3% for 9).

Scheme 3. Synthesis of Anthracene Polynitrilea

which was then alkylated (n-octyl iodide/K2CO3) to produce 2. The chloride groups in 2 then undergo Stille coupling with Fu’s ligand to give divinyl 3,18 which was subjected to ozonolysis to furnish dialdehyde 4. Double Wittig−Knoevenagel benzannulation (fumaryl nitrile/PEt3, then base) was then performed on the ortho-formyl ketone structural motif and furnished the perylene tetranitrile 5 with solubilizing octyloxyl groups. Further cyanation was accomplished in two stages. The fifth and sixth nitrile groups were incorporated by palladiummediated cyanation (Pd(PPh3)4, Zn(CN)2). The required dibromide perylene was synthesized by direct bromination of 5 by N-bromosuccinimide (NBS) in trifluoroacetic acid (TFA). The regioselectivity of bromination is governed by the electron-donating octyloxyl group to occur at the 4 and 10 positions. The reaction sequence furnishes hexanitrile 6 with the nitrile groups incorporated at peri sites. The seventh and eighth nitrile groups were introduced by oxidative cyanation. With six electron-withdrawing nitrile groups attached, the perylene skeleton of 6 is electron-deficient enough to undergo direct cyanide attack to produce an intermediate anion, which was aromatized to the heptanitrile 7 upon workup. X-ray crystallography confirms that the oxidative cyanation occurs overwhelmingly at the peri position (see the Supporting Information). The bay-site attack product 7′ was also produced in 1% yield. It was expected that, by simply repeating the procedure, an eighth nitrile should be installed at the other peri site to produce symmetric perylene octanitrile 9 (C2h). Yet, to our surprise, the second oxidative cyanation put the eighth nitrile group at the bay area to produce 8, while the anticipated symmetric octanitrile perylene 9 was only produced in very low yield (ca. 5%). The structural assignment for the anomalous major product 8 is based on its 1H NMR

Reagents and conditions: (a) LDA 1 eq, −78 °C, then 2,6-dimethyl4-t-butyl-benzaldehyde, then repeat; (b) PDC, CH2Cl2 (68% over two steps); (c) vinyl tributyltin, Pd(PPh3)4, toluene, reflux (94%); (d) O3, CH2Cl2, −80 °C, then Me2S (75%); (e) fumaronitrile, PEt3, toluene then KOAc (40%); (f) tetra-n-butyl ammonium cyanide (TBACN, 2.5 equiv), THF, (15-22%, 16-10%); (g) TBACN (1.2 equiv) CH2Cl2, then DDQ (24%); (h) TBACN, CH2Cl2, (99%) a

started with double lithiation of 10 (1,4-dibromo-2,5difluorobenzene) with lithium diisopropyl amide (LDA)19 to introduce the 4-tert-butyl-2,6-dimethylphenyl solubilizing groups (by quenching the lithium reagent with 4-tert-butyl2,6-dimethyl benzaldehyde, followed by pyridinium dichromate (PDC) oxidation). The bromides on 11 were then converted to aldehydes (Stille coupling, ozonolysis). Bidirectional Wittig−Knoevenagel benzannulation was performed to furnish the tetracyano difluoroanthracene 14. Further cyanation was again performed in two stages. First, the nucleophilic substitutive cyanation was performed with 2.5 equiv of tetra-n-butyl ammonium cyanide (TBACN). The two fluorides on 14 underwent smooth substitution reaction to produce anthracene hexanitrile 15 in moderate yield. The B

DOI: 10.1021/acs.orglett.9b01454 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters seventh nitrile group was installed with oxidative cyanation by treating the hexanitrile 15 with TBACN to produce the precursor anion, followed by oxidative aromatization with DDQ to furnish heptanitrile 16. Both series of the polynitrile acceptors (5−9, 14−16) thus prepared are stable to moisture, atmosphere oxygen, and flash chromatography. When stored in darkness, solution and solid samples of these compounds show no sign of decomposition for 6 weeks and six months, respectively. Since there is only one site left for oxidative cyanation on heptanitrile 16, it was anticipated that the eighth nitrile group can be introduced by repeating the oxidative cyanation protocol without the regioselectivity problem encountered in the perylene system (see Scheme 2). Unfortunately, oxidative cyanation at the last stage proved capricious again. When the cyanation was conducted with TBACN under identical conditions, a new species with three 1H NMR singlet peaks in the aromatic region (in 1:2:2 ratio) was obtained. Furthermore, 1H NMR spectrum also suggests the unexpected product contains the TBA cation. Since the TBA cation and the aromatic species are in 1:1 stoichiometry, it is proposed that compound 17 is actually a salt in which the anthracene skeleton has become an anion by direct addition of the cyanide. The regioselectivity of the cyanide attack was directed toward the more electron-deficient end of 16. Because the nucleophilic attack creates a quaternary carbon, the subsequent oxidative aromatization cannot occur. This results in a rare carbon-based anion that is stable to water, atmosphere oxygen, thin layer chromatography, and even flash chromatography. Because of the structural novelty of salt 17, several additional experiments were performed to establish its identity. First, the octanitrile anion was detected by electron spray mass spectrometry in negative mode. Second, when a titration experiment was monitored by UV-vis absorption spectrum (with Figure 1, 0.2 to 1 equiv of TBACN), an isosbestic point

Table 1. Optical and Electrochemical Properties of Aromatic Polynitrile Acceptors 5 6 7 7′ 8 9 14 15 16 PDICN4 PDICN4Cl4 NDICN4

λmax (nm)

Eg (eV)

LUMOEXP (eV)

LUMODFT (eV)

458 490 510 497 517 522 421 437 452 518 524 376

2.47 2.38 2.26 2.30 2.20 2.23 2.63 2.02 1.89

−3.46 −4.00 −4.26 −4.27 −4.51 −4.44 −3.47 −4.17 −4.49 −4.42 −4.64 −4.70

−3.01 −3.73 −4.03 −4.08 −4.30 −4.37 −3.07 −3.87 −4.20

the charge-transfer band between the electron-deficient anthracene core and the trialkyl phenyl groups. The fluorescent wavelengths of the polynitrile perylene series exhibit red shifts (from 500 nm to 565 nm) as the number of nitrile groups increases, while the quantum efficiencies diminish (49% to 8%). Anthracene hexanitrile 15 and heptanitrile 16 exhibit no fluorescence, presumably due to charge separation quenching. The LUMO levels of these acceptors were probed with cyclic voltammetry (Table 1). Since the nitrile groups were gradually incorporated, the LUMO energies can be tuned progressively from −3.5 eV to −4.5 eV, covering the energetic range of classical acceptors such as naphthalene bisimide (−3.67 eV), perylene bisimide (−3.9 eV), fullerene (−3.86 eV), tetracyanoethylene (TCNE, −4.48 eV), and 7,7,8,8tetracyanoquinodimethane (TCNQ, −4.55 eV). For the perylene series, each additional nitrile substitution suppresses the LUMO level by ∼0.2 eV, while those of the anthracene series are stabilized by 0.3 eV per additional nitrile. Because anthracene is a smaller conjugated system than perylene (14 versus 20 sp2 carbons), each additional nitrile group stabilizes the LUMO of anthracene more than that of perylene. Heptanitrile and octanitrile acceptors (7, 8, 9, 15, and 16) all display two reversible reductions. For perylene acceptors, the difference between the first and second reductions is 0.5 eV. Again, because of their smaller size, this difference for anthracene acceptors increase to 0.7 eV. LUMO energies of these acceptors were computed by DFT calculation (M06-2X/ 6-31+G*; see Table 1). The computed LUMOs are consistently higher than the empirical values. Nevertheless, the trend of stabilization is qualitatively reproduced, even down to the subtle differences between regioisomers 8 and 9. Several recently reported acceptors with exceedingly low LUMO levels are listed for comparison (PDICN4,15b PDICl4CN4,15a NDICN414g). The LUMO levels for the strongest polynitrile acceptors in the present study (8) are ∼0.2 eV higher than the current record holder, NDICN4, despite both contain eight electron-withdrawing groups. Apparently, for a smaller chromophore such as naphthalene, each electron-withdrawing group lowers the LUMO level more than it would do to a bigger chromophore such as perylene. The peculiar regioselectivity of oxidative cyanation (6 to 7 vs 7 to 8) was also studied computationally by examining the initial cyanide addition to the acceptors (see the Supporting Information). The reactants were simplified to dimethoxy perylene polynitriles (mimicking 6 and 7) and tetramethyl ammonium cyanide (TMACN, mimicking TBACN). Surpris-

Figure 1. Titration of 16 by TBACN to produce 17 monitored via UV-vis absorption spectroscopy.

near 450 nm suggests that the cyanation reaction produces a single species, which is also evident from NMR spectrum. A broad absorption extending to 700 nm indicates the chargetransfer characteristic and an anionic nature. Finally, Job plot confirms the 1:1 stoichiometry of the cyanation adduct. The photophysical properties of these polynitrile acceptors were investigated by UV-vis spectroscopy (Table 1). The λmax of both series exhibit 10−20 nm bathochromic shifts on each additional nitrile. Featureless broad bands at 500−600 nm are observed for 15 and 16, which can be reasonably attributed to C

DOI: 10.1021/acs.orglett.9b01454 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters

Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

ingly, the gas-phase model indicates that the more-crowded bay position is preferentially attacked by TMACN in both reactions, because of its more positive electrostatic potential. Yet, this preference is smaller for 6 to 7 than 7 to 8 (0.24 kcal/ mol vs 1.34 kcal/mol). The empirical peri selectivity leading to 7 emerges only after the solvation effect was included (IEFPCM model in chloroform). Because of the more open steric environment near the peri sites, the transition states leading to peri products are better solvated than its bayresulting counterpart. This difference in solvation is sufficient to selectively stabilize the transition state leading to peri attack in 6 to 7 transformation over that of bay attack by 1.37 kcal/ mol. In contrast, the difference in peri vs bay solvation energy in 7 to 8 reaction does not overturn the electrostatic-directed preference for bay-site attack. Even with solvation, the transition state for bay-site attack remains slightly more stable than that of peri attack by 0.04 kcal/mol. Finally, the structure of octanitrile anion in salt 17 was also examined with DFT calculation.19 Given the reversible nature of the nucleophilic attack, it is assumed this transformation should produce the most stable anion. Between the two anionic products, it was determined that cyanide attack at the 2 position yields a much softer anion than the regioisomer produced via 1 position attack (computed aqueous pKa 0.86 vs pKa 3.10). The DFT result, combined with experimental data, strongly suggests the cyanide group attacks 16 exclusively at the 2 position to produce the extraordinary soft organic anion in 17. In summary, we have devised a synthetic strategy toward polynitrile perylene and anthracene combining Wittig− Knoevenagel benzannulation, Pd-catalyzed cyanation, nucleophilic substitutive cyanation, and oxidative cyanation. These organic acceptors are stable with LUMO levels comparable to benchmark compounds such as TCNQ and TCNE. The stepwise cyanation scheme allows the LUMO levels to be tuned progressively for various applications. In addition, a persistent octanitrile carbanion was synthesized by the direct nucleophilic attack of cyanide to anthracene heptanitrile. DFT calculation reasonably reproduced the trends of LUMO levels in these acceptors. The computational study also suggests that both electrostatic potential and solvation contribute to the peri vs bay selectivity during cyanide addition. This new class of organic acceptors possesses great potential as air-stable n-type semiconductors or n-type dopants in various devices. Application in building charge-transfer salts or supramolecular assemblies can also be explored.

■

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Chih-Hsiu Lin: 0000-0003-0492-4705 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors are grateful to the financial supports from Academia Sinica and Ministry of Science and Technology (MOST) of Taiwan.

■

REFERENCES

(1) (a) Quinn, J. T. E.; Zhu, J.; Li, X.; Wang, J.; Li, Y. J. Mater. Chem. C 2017, 5, 8654. (b) Wurthner, F.; Stolte, M. Chem. Commun. 2011, 47, 5109. (c) Jones, B. A.; Ahrens, M. J.; Yoon, M.-H.; Facchetti, A.; Marks, T. J.; Wasielewski, M. R. Angew. Chem., Int. Ed. 2004, 43, 6363. (d) Naibi Lakshminarayana, A.; Ong, A.; Chi, C. J. Mater. Chem. C 2018, 6, 3551. (2) Kulkarni, A. P.; Tonzola, C. J.; Babel, A.; Jenekhe, S. A. Chem. Mater. 2004, 16, 4556. (3) (a) Manriquez, J. M.; Yee, G. T.; McLean, R. S.; Epstein, A. J.; Miller, J. S. Science 1991, 252, 1415. (b) Miller, J. S.; Epstein, A. J. Angew. Chem., Int. Ed. Engl. 1994, 33, 385. (4) (a) Nielsen, C. B.; Holliday, S.; Chen, H.-Y.; Cryer, S. J.; McCulloch, I. Acc. Chem. Res. 2015, 48, 2803. (b) Zhang, G.; Zhao, J.; Chow, P. C. Y.; Jiang, K.; Zhang, J.; Zhu, Z.; Zhang, J.; Huang, F.; Yan, H. Chem. Rev. 2018, 118, 3447. (5) (a) Suzuki, S.; Segawa, Y.; Itami, K.; Yamaguchi, J. Nat. Chem. 2015, 7, 227. (b) Suzuki, S.; Itami, K.; Yamaguchi, J. Angew. Chem., Int. Ed. 2017, 56, 15010. (6) (a) Chang, J.; Ye, Q.; Huang, K.-W.; Zhang, J.; Chen, Z.-K.; Wu, J.; Chi, C. Org. Lett. 2012, 14, 2964. (b) Ye, Q.; Chang, J.; Huang, K.W.; Shi, X.; Wu, J.; Chi, C. Org. Lett. 2013, 15, 1194. (7) (a) Zhang, X.; Li, Q.; Ingels, J. B.; Simmonett, A. C.; Wheeler, S. E.; Xie, Y.; King, R. B.; Schaefer, H. F.; Cotton, F. A. Chem. Commun. 2006, 758. (b) Kuo, M.-Y.; Chen, H.-Y.; Chao, I. Chem. - Eur. J. 2007, 13, 4750. (c) Zhong, M.; Zhou, J.; Jena, P. ChemPhysChem 2017, 18, 1937. (d) Swartz, C. R.; Parkin, C. R.; Bullock, J. E.; Anthony, J. E.; Mayer, A. C.; Malliaras, G. G. Org. Lett. 2005, 7, 3163. (e) Glocklhofer, F.; Petritz, A.; Karner, E.; Bojdys, M. J.; Stadlober, B.; Frohlich, J.; Unterlass, M. M. J. Mater. Chem. C 2017, 5, 2603. (8) Ellis, G. P.; Romney-Alexander, T. M. Cyanation of Aromatic Halides. Chem. Rev. 1987, 87, 779. (9) (a) Maligres, P. E.; Waters, M. S.; Fleitz, F.; Askin, D. Tetrahedron Lett. 1999, 40, 8193. (b) Sundermeier, M.; Zapf, A.; Beller, M. Angew. Chem., Int. Ed. 2003, 42, 1661. (c) Yeung, P. Y.; Tsang, C. P.; Kwong, F. Y. Tetrahedron Lett. 2011, 52, 7038. (d) Pawar, A. B.; Chang, S. Chem. Commun. 2014, 50, 448. (e) Anbarasan, P.; Schareina, T.; Beller, M. Chem. Soc. Rev. 2011, 40, 5049. (10) (a) Xia, W.; Scheffer, J. R.; Botoshansky, M.; Kaftory, M. Org. Lett. 2005, 7, 1315. (b) Poutiainen, P. K.; Oravilahti, T.; Peräkylä, M.; Palvimo, J. J.; Ihalainen, J. A.; Laatikainen, R.; Pulkkinen, J. T. J. Med. Chem. 2012, 55, 6316. (11) Schmitt, S.; Baumgarten, M.; Simon, J.; Hafner, K. Angew. Chem., Int. Ed. 1998, 37, 1077. (12) (a) Lin, C.-H.; Lin, K.-H.; Pal, B.; Tsou, L.-D. Chem. Commun. 2009, 45, 803. (b) Hsu, D. T.; Lin, C.-H. J. Org. Chem. 2009, 74, 9180. (13) Both 2,3,6,7-tetracyanoanthracene and 1,2,7,8-tetracyanoperylene are barely soluble in DMSO. See: (a) Lin, Y.-C.; Lin, C.-H.;

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b01454. Synthetic procedures, UV spectroscopy data, and CV analysis data (PDF) NMR spectra (PDF) DFT results (PDF) Accession Codes

CCDC 1909595 and 1909596 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The D

DOI: 10.1021/acs.orglett.9b01454 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Chen, C.-Y.; Sun, S.-S.; Pal, B. Org. Biomol. Chem. 2011, 9, 4507. (b) Bhargava Rao, B.; Wei, J.-R.; Lin, C.-H. Org. Lett. 2012, 14, 3640. (14) (a) Bhosale, S. V.; Jani, C. H.; Langford, S. J. Chem. Soc. Rev. 2008, 37, 331. (b) Al Kobaisi, M.; Bhosale, S. V.; Latham, K.; Raynor, A. M.; Bhosale, S. V. Chem. Rev. 2016, 116, 11685. (c) Sakai, N.; Mareda, J.; Vauthey, E.; Matile, S. Chem. Commun. 2010, 46, 4225. (d) Huang, C.; Barlow, S.; Marder, S. R. J. Org. Chem. 2011, 76, 2386. (e) Wurthner, F.; Saha-Moller, C. R.; Fimmel, B.; Ogi, S.; Leowanawat, P.; Schmidt, D. Chem. Rev. 2016, 116, 962. (f) Kumar, S.; Shukla, J.; Kumar, Y.; Mukhopadhyay, P. Org. Chem. Front. 2018, 5, 2254. (g) Kumar, Y.; Kumar, S.; Mandal, K.; Mukhopadhyay, P. Angew. Chem., Int. Ed. 2018, 57, 16318. (15) (a) Gao, J.; Xiao, C.; Jiang, W.; Wang, Z. Org. Lett. 2014, 16, 394. (b) Battagliarin, G.; Zhao, Y.; Li, C.; Müllen, K. Org. Lett. 2011, 13, 3399. (c) Kerisit, N.; Gawel, P.; Levandowski, B.; Yang, Y.-F.; Garcia-Lopez, V.; Trapp, N.; Ruhlmann, L.; Boudon, D.; Houk, K. N.; Diederich, F. Chem. - Eur. J. 2018, 24, 159 and ref 6a. . (16) (a) Ishiyama, T.; Takagi, J.; Ishida, K.; Miyaura, N.; Anastasi, N. R.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 390. (b) Mkhalid, I. A. I.; Barnard, J. H.; Marder, T. B.; Murphy, J. M.; Hartwig, J. F. Chem. Rev. 2010, 110, 890. (17) Maleczka, R. E.; Shi, F.; Holmes, D.; Smith, M. R., III J. Am. Chem. Soc. 2003, 125, 7792. (18) Littke, A. F.; Schwarz, L.; Fu, G. C. J. Am. Chem. Soc. 2002, 124, 6343. (19) Kongprakaiwoot, N.; Luck, R. L.; Urnezius, E. J. Organomet. Chem. 2004, 689, 3350.

E

DOI: 10.1021/acs.orglett.9b01454 Org. Lett. XXXX, XXX, XXX−XXX