Efficient Synthesis of Aryl Boronates via Cobalt-Catalyzed Borylation

Apr 5, 2018 - An efficient catalytic system based on a Co(II)-NHC precursor has been developed for the cross coupling of bis(pinacolato)diboron with a...
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Efficient Synthesis of Aryl Boronates via CobaltCatalyzed Borylation of Aryl Chlorides and Bromides Piyush Kumar Verma, Souvik Mandal, and K. Geetharani ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b00536 • Publication Date (Web): 05 Apr 2018 Downloaded from http://pubs.acs.org on April 6, 2018

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ACS Catalysis

Efficient Synthesis of Aryl Boronates via Cobalt-Catalyzed Borylation of Aryl Chlorides and Bromides Piyush Kumar Verma, Souvik Mandal, K. Geetharani* Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India ABSTRACT: An efficient catalytic system based on a Co(II)-NHC precursor has been developed for the cross coupling of bis(pinacolato)diboron with aryl halides including aryl chlorides, affording the aryl boronates in good to excellent yields. A wide range of functional groups are tolerated under mild reaction conditions. The reaction shows excellent chemoselectivity for bromide over chloride. Preliminary mechanistic investigations show that the catalytic cycle relies on a cobalt(I)‒ (III) redox couple.

KEYWORDS: Boronate esters, Cobalt, C-X activation, N-heterocyclic carbenes, Suzuki–Miyaura

INTRODUCTION Aryl boronic acids and boronate esters have been recognized as indispensable building blocks in organic synthesis, particularly in transition-metal-catalyzed crosscoupling reactions for the formation of various C‒C and C-heteroatom bonds, owing to their ease of handling, bench stability, high functional group compatibility and low toxicity.1 Moreover, they have found broad applications as synthetic intermediates in pharmaceuticals, agrochemicals, liquid crystals and organic light-emitting diodes.1c Despite their versatility, the conventional methods for their synthesis involve aryl lithium compounds or Grignard reagents which are not compatible with numerous functional groups and are limited by the availability of the organometallic reagents.2 To expand the scope of arylboronates, a variety of precious metal catalyst systems, such as Rh, Re, Ru and especially Ir were developed over the past decades via direct C–H borylation of arenes.3 Complementary, highly selective metal-catalyzed borylation reactions of (sp2)C–X (X = Cl, Br, I, OTf) bonds have also been developed.4,5 However, the economic constrains, low natural abundance and environmental concerns of precious metal catalysts have demanded the investigation of earth-abundant and inexpensive base metal alternatives, such as Fe,6 Co,7 Ni,8 Cu,9 Zn,10 and even metal-free11 conditions for the borylation of aryl halides. The use of aryl iodides or bromides is often necessary, whereas, there are only few reliable methods available in the literature for the borylation of relatively inexpensive and broadly available aryl chlorides. The aryl chlorides borylation is always challenging, and there were no methods available for this transformation until 2001. The first example was reported by Ishiyama et al. using Pd as a catalyst12 and subsequently scope was expanded by others using mainly Pd13 and few Ni catalyst systems.8g-l In 2014, Bedford et al. reported iron catalyzed borylation of alkyl, allyl and aryl halides, but only chloro-

benzene could be borylated in a poor yield of 5 %.6e Metal-free photoinduced C-X and dual C-H/C-X borylation of haloarenes were reported by Larionov et al.14 and pyridine-catalyzed radical borylation of aryl halides was reported by Jiao et al.,15 but only two aryl chlorides have been described in each cases. Very recently, Nakamura and co-workers reported an iron catalyzed borylation which can effectively transform the biaryl chlorides into their corresponding boronate esters in the presence of KOtBu.6f Therefore, there remains a strong need to develop cost effective and environmentally benign base-metal catalysts, in particularly cobalt as catalyst for the borylation of aryl chlorides. The first cobalt-catalyzed borylation of aryl halides (including chloro-, bromo-, and iodoarenes) and pseudohalides was reported in 2016 by Hu, Huang and co-workers, which typically involve the use of oxazolinylferrocenylphosphine ligands and MeLi, a reactive organometallic reagent.16 Herein, we report an active catalyst composed of cobalt(II) and NHC as ligand that efficiently converts aryl chlorides to boronate esters under mild reaction conditions. RESULT AND DISCUSSION NHC supported Co(II)-complex, Co(IMes)2Cl2 (I; IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) was prepared following literature procedure in good yield.17a Reaction conditions were optimized using chloroanisole (2a) as a model substrate by using 5 mol % of I as catalyst, 1.3 equiv of B2pin2 and a variety of solvents, bases and ligands. Among several solvents screened, MTBE (tertbutylmethyl ether) was found to be superior to other solvents with 97% yield (Table 1, entries 1-5). Bases other than KOMe proved inferior (entries 6-10). Weak bases like Cs2CO3 and KOAc could not produce even trace amount of desired product (entries 9-10). There was no reaction in the absence of a base (entry 11). Further, influence of the ligand was studied using ICy (1,3-bis-cyclohexylimidazol-

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Table 1. Co(II)-Catalyzed Borylation of chloroanisole, 2a.a

entry

deviation from standard conditions

1

H NMR b yield (%) c 1 none 97 (85) d 2 THF instead of MTBE 50 d 3 DME instead of MTBE 76 d 4 toluene instead of MTBE 44 d 5 benzene instead of MTBE 41 d t 6 KO Bu instead of KOMe 63 d t 7 NaO Bu instead of KOMe 68 d 8 LiOMe instead of KOMe 38 d 9 Cs2CO3 instead of KOMe 0 d 10 KOAc instead of KOMe 0 d 11 in absence of KOMe 0 12 II instead of I 81 13 III instead of I 95 14 CoCl2 instead of I trace 15 in absence of I trace 16 2.5 mol % of I used 92 a Standard conditions: 2a (0.1 mmol), I (5 mol %), KOMe (1.3 equiv), B2pin2 (1.3 equiv), MTBE (0.5 mL) at 50 °C for 8 h (see b 1 Supporting Information (SI) for details). Determined by H c NMR using nitromethane as an internal standard. Isolated d yield. Reaction was performed at 70 °C for 20 h.

Table 2. Substrate Scope of Co(II)-Catalyzed Borylation of Aryl Chlorides.a

2b was obtained; thus, any uncatalyzed reaction is minimal (entry 15). Gratifyingly, with a reduced catalyst loading of 2.5 mol % (entry 16), we obtained a comparable yield of 92 %. Having identified the optimum conditions with chloroanisole as a standard substrate, we examined the scope of the present borylation reaction with different aryl chlorides, as depicted in Table 2. Electron-neutral (1a, 15a), electron-rich (2a-5a) and electron-deficient (6a-9a) aryl chlorides are converted to corresponding arylboronic esters in good to excellent yields. Notably, 4-fluorophenyl boronate (6b) was the sole borylated product from the reaction of 1-chloro-4-fluorobenzene, leaving the fluoro group intact. Furthermore, 1,4-dichlorobenzene with 2.5 equiv of B2pin2/KOMe gave 1,4-diborylated product (9b) in excellent yield. This protocol was also applicable to substrates having sterically hindered environment around chloro substituent. Reaction of 2-chlorotoluene (10a) under standard conditions afforded the corresponding borylated product in 92% yield. Though, sterically congested 2-chloro-m-xylene 11a, substituted at both ortho positions, afforded borylation product in only 32% yield. The system shows excellent chemoselectivity in case of chlorobenzyl chloride (12a), where the borylation was selective for (sp2)C-Cl bond, leaving the (sp3)C-Cl bond intact. Substrate having heterocyclic-arene in the system (13a) was also tolerable, affording the desired arylboronate in 88% yield. In addition, 3-chloropyridine was transformed to the desired boronate, but in lower yield (14b). Table 3. Substrate Scope of C0(II)-Catalyzed Borylation of Aryl Halides.a

a

Conditions: aryl chloride (1.0 mmol, 1 equiv), I (5 mol %), B2pin2 (1.3 equiv), KOMe (1.3 equiv), MTBE (5 mL), at 50 °C for 8 h unless otherwise stated. Isolated yield after chroma1 tographic workup. Yield determined by H NMR using nib tromethane as internal standard is given in parentheses. c The reaction was performed at 70 °C. The reaction was performed using 10 mol % of I, 2.5 equiv of B2pin2/KOMe for 20 h.

2-ylidene) supported Co-complex (Co(ICy)2Cl2, II)17b gave slightly lower yield than I (entry 12). The Co(IMes)2Br2 complex (III)17c displayed comparable reactivity to I (entry 13). Ligand is essential for this catalytic process; no borylated product was observed when the ligand was omitted (entry 14). In the absence of a Co(II) source, no

a

Conditions: aryl halide (1.0 mmol, 1 equiv), I (2.5 mol %), B2pin2 (1.3 equiv), KOMe (1.3 equiv), MTBE (5 mL), at 50 °C for 8 h unless otherwise stated. Isolated yield after chroma1 tographic workup. Yield determined by H NMR using nib tromethane as internal standard are given in parentheses. c The reaction was performed using 5 mol % of I at 70 °C. The d reaction was performed using 1.0 equiv of B2pin2 and KOMe. e 4-chlorophenyl boronate (22b) was obtained. The reaction was performed using 10 mol % of I, 2.5 equiv of B2pin2/KOMe f at 70 °C for 20 h. 1,4-bis(Bpin)benzene was obtained.

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ACS Catalysis The reaction conditions optimized for aryl chlorides were found to be compatible with both aryl bromides and iodides, and they even need less catalyst loading of 2.5 mol % (Table 3). Bromobenzene (16a) gave the desired boronate ester in 95 % yield. Aryl bromides with electron donating (17a-19a) and withdrawing (20a-22a) substituents were borylated in moderate to high yield. Reaction of 1-bromo-4-chlorobenzene (22a) with 1.3 equiv of B2pin2/KOMe gave mixture of mono and diborylated products, in ca. 80:20 ratio. To achieve chemoselective CBr bond activation over C-Cl bond, reaction was performed using 1.0 equiv of B2pin2/KOMe, yielded solely monoborylated product (4-chlorophenyl boronate), verified by 1H NMR spectroscopy and GC-MS analysis. Using 2.5 equiv of B2pin2/KOMe at elevated temperature (70 ºC) and longer reaction time (20 h) gave exclusively 1,4bis(Bpin)benzene in good yield. To study the steric effect of substituents, we investigated the borylation of 2bromo-1,3-dimethylbenzene (23a), which gave moderate yield of arylboronate. 4-Bromo-3-methylaniline (24a) gave the desired product in 49% yield. Biaryl system (25a) worked well to afford excellent yield of arylboronic ester. A variety of heteroaryl bromides, such as thiophene, pyridine, quinoline and indole systems (26a-29a) produced the corresponding boronate esters in moderate to high yield. Furthermore, aryl iodides (30a and 31a) produced good yields of the corresponding arylboronic esters. The method enables convenient gram scale synthesis (6 mmol) with the same efficiency, as demonstrated for 2a (2b: 1.07 g, 75%), 7a (7b: 1.15 g, 70 %), 15a (15b: 1.3 g, 84 %) and 19a (19b: 1.16 g, 78 %). To gain insight into the mechanism, first we conducted the reactions in the presence of radical scavenger. When the reaction of 2a with B2pin2 was performed in the presence of radical scavenger 9,10-dihydroanthracene (1.3 equiv), the borylation product was obtained without any significant decrease in the yield (85%), indicating that the borylation does not appear to be a radical process (see SI for details). In addition, no detected amount of expected borylated as well as radical cyclization product was observed by NMR and GC-MS analysis, when a radical-clock experiment was performed using 1-(allyloxy)-2iodoobenzene as a substrate under the standard reaction conditions. Given the propensity of cobalt complexes to undergo redox reaction via Co(I)-Co(III) catalytic cycle, as observed in Co-catalysed (sp2)C–H functionalization,18 we speculated that this borylation reaction might have involvement of Co(I) species as the active catalyst. Thus, adopting a modified procedure,19 we synthesized Co(IMes)2Cl (IV) by the reaction of Co(IMes)2Cl2 (I) using Mg dust as a reducing agent. To our delight, using IV as a catalyst also produced 92% of the borylated product from 2a under standard conditions. The involvement of Co(I) complex in this borylation process was further confirmed by a series of NMR monitoring experiments. Treatment of equimolar amount of I with KOMe and B2pin2 in C6D6 shows the formation of IV, determined by 1H NMR spectroscopy (δ = 107.27 ppm).19 To provide further evidence

that IV is the active catalyst in catalytic cycle, EPR experiments were performed (see SI). The EPR active IV could be produced by the reaction of I with the preformed diboron ate complex, but not with diboron itself (see SI for details). A similar EPR signal was observed for the pure IV as well as for the borylation reaction mixture. These results further supports that Co(I) species is involved as an active catalyst in this borylation process. Based on the experimental results and related reports on Co-catalyzed borylation reactions,18 a possible mechanism for this C-X activation is depicted in Figure 1. The active catalyst IV generated from the reduction of I by K+[B2pin2OMe]¯ (generated via reaction between B2pin2 and KOMe),11f which undergo ligand exchange reaction with KOMe to produce a cobalt-OMe complex A. Reaction of A with B2pin2 may produce Co-boryl intermediate B together with formation of MeO-Bpin. Oxidative addition of aryl halide to B followed by reductive elimination gives the product Ar-Bpin and regenerates the Co(I) active species IV.

Figure 1. A plausible mechanism of Co-catalyzed borylation of aryl halides with B2pin2. CONCLUSIONS In summary, we have demonstrated an efficient Cocatalyzed borylation of aryl halides, including aryl chlorides with B2pin2. The reaction proceeds under mild conditions, displays broad scope and functional group tolerance, and furnishes arylboranates in good to excellent yields. From a mechanistic standpoint, based on preliminary experimental results it show that the catalytic cycle operates via a Co(I)−Co(III) redox couple. Current investigations are aimed to explore the reactivity of NHC supported cobalt systems toward more diverse set of substrates.

ASSOCIATED CONTENT AUTHOR INFORMATION Corresponding Author * E-mail: [email protected]

Notes The authors declare no competing financial interest. Supporting Information

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Experimental and spectroscopic data, copies of H, C and B NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org.

ACKNOWLEDGMENT K.G. thanks AllyChem Co. Ltd., China for a gift of B2pin2, and the SERB (EMR/2016/000367) and Indian Institute of Science (IISc) start-up research grant, for funding. P.K.V. thanks IISc Bangalore for a research fellowship. S.M. thanks Kishore Vaigyanik Protsahan Yojana (KVPY) for fellowship. We also thank Prof. S. Ramakrishnan, IISc Bangalore for the GC-MS analysis and Prof. S. Maheswaran, IIT Bombay for his help in obtaining the EPR Spectra.

REFERENCES (1) (a) Miyaura, N.; Suzuki, A. Palladium-Catalyzed CrossCoupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457-2483. (b) Miyaura, N. In Metal-Catalyzed CrossCoupling Reactions, 2nd ed.; Meijere, A. D., Diederich, F., Eds.; Wiley-VCH: Weinheim, Germany, 2004; Vol. 1, p 41. (c) Boronic Acids-Preparation and Applications in Organic Synthesis, Medicine and Materials; 2nd ed.; Hall, D. G., Ed.; Wiley-VCH: Weinheim, 2011. (d) Jana, R.; Pathak, T. P.; Sigman, M. S. Advances in Transition Metal (Pd, Ni, Fe)-Catalyzed Cross-Coupling Reactions Using Alkyl-organometallics as Reaction Partners. Chem. Rev. 2011, 111, 1417-1492. (e) Rudolph, A.; Lautens, M. Secondary Alkyl Halides in Transition-Metal-Catalyzed Cross-Coupling Reactions. Angew. Chem. Int. Ed. 2009, 48, 2656-2670. (f) Imao, D.; Glasspoole, B. W.; Laberge, V. S.; Crudden, C. M. Cross Coupling Reactions of Chiral Secondary Organoboronic Esters With Retention of Configuration. J. Am. Chem. Soc. 2009, 131, 50245025. (g) Frisch, A. C.; Beller, M. Catalysts for Cross-Coupling Reactions with Non-Activated Alkyl Halides. Angew. Chem. Int. Ed. 2005, 44, 674-688. (h) Beenen, M. A.; An, C.; Ellman, J. A. Asymmetric Copper-Catalyzed Synthesis of α-Amino Boronate Esters from N-tert-Butanesulfinyl Aldimines. J. Am. Chem. Soc. 2008, 130, 6910-6911. (2) (a) Khotinsky, E.; Melamed, M. Die Wirkung der Magnesiumorganischen Verbindungen auf die Borsäureester. Ber. Dtsch. Chem. Ges. 1909, 42, 3090-3096. (b) Bean, F. R.; Johnson, J. R. Derivatives of Phenylboric Acid, Their Preparation and Action Upon Bacteria. II. Hydroxyphenylboric Acids. J. Am. Chem. Soc. 1932, 54, 4415-4425. (c) Letsinger, R. L.; Skoog, I. H. The Preparation and Some Properties of 2-Methyl-1-Propene-1-Boronic acid. J. Org. Chem. 1953, 18, 895-897. (d) Brown, H. C. Organic Syntheses via Boranes, Wiley, New York, 1975. (3) (a) Ishiyama, T.; Miyaura, N. Transition Metal-Catalyzed Borylation of Alkanes and Arenes via C-H Activation. J. Organomet. Chem. 2003, 680, 3-11. (b) Miyaura, N. Metal-Catalyzed Reactions of Organoboronic Acids and Esters. Bull. Chem. Soc. Jpn. 2008, 81, 1535-1553. (c) Mkhalid, I. A. I.; Barnard, J. H.; Marder, T. B.; Murphy, J. M.; Hartwig, J. F. C-H Activation for the Construction of C-B Bonds. Chem. Rev. 2010, 110, 890-931. (d) Hartwig, J. F. Regioselectivity of the Borylation of Alkanes and Arenes. Chem. Soc. Rev. 2011, 40, 1992-2002. (e) Hartwig, J. F. Borylation and Silylation of C–H Bonds: A Platform for Diverse C–H Bond Functionalizations. Acc. Chem. Res. 2012, 45, 864-873. (f) Dewhurst, R. D.; Neeve, E. C.; Braunschweig, H.; Marder, T. B. sp2–sp3 Diboranes: Astounding Structural Variability and Mild Sources of Nucleophilic Boron for Organic Synthesis. Chem. Commun. 2015, 51, 9594-9607. (g) Hartwig, J. F. Evolution of C–H Bond Functionalization from Methane to Methodology. J. Am. Chem. Soc. 2016, 138, 2-24. (h) Neeve, E. C.; Geier, S. J.; Mkhalid, I. A. I.; Westcott, S. A.; Marder, T. B. Diboron(4) Compounds:

From Structural Curiosity to Synthetic Workhorse. Chem. Rev. 2016, 116, 9091-9161. (4) (a) Ishiyama, T.; Miyaura, N. Metal-Catalyzed Reactions of Diborons for Synthesis of Organoboron Compounds. Chem. Rec. 2004, 3, 271-280. (b) Chow, W. K.; Yuen, O. Y.; Choy, P. Y.; So, C. M.; Lau, C. P.; Wong, W. T.; Kwong, F. Y. A Decade Advancement of Transition Metal-Catalyzed Borylation of Aryl Halides and Sulfonates. RSC Adv. 2013, 3, 12518-12539. (c) Murata, M. Transition-Metal-Catalyzed Borylation of Organic Halides with Hydroboranes. Heterocycles 2012, 85, 1795-1819. (d) Kubota, K.; Iwamoto, H.; Ito, H. Formal Nucleophilic Borylation and Borylative Cyclization of Organic Halides. Org. Biomol. Chem. 2017, 15, 285-300. (5) (a) Ishiyama, T.; Murata, M.; Miyaura, N. Palladium(0)Catalyzed Cross-Coupling Reaction of Alkoxydiboron with Haloarenes: A Direct Procedure for Arylboronic Esters. J. Org. Chem. 1995, 60, 7508-7510. (b) Murata, M.; Oyama, T.; Watanabe, S.; Masuda, Y. Palladium-Catalyzed Borylation of Aryl Halides or Triflates with Dialkoxyborane:  A Novel and Facile Synthetic Route to Arylboronates. J. Org. Chem. 2000, 65, 164168. (c) Baudoin, O.; Guénard, D.; Guéritte, F. PalladiumCatalyzed Borylation of Ortho-Substituted Phenyl Halides and Application to the One-Pot Synthesis of 2,2‘-Disubstituted Biphenyls. J. Org. Chem. 2000, 65, 9268-9271. (d) Zhu, L.; Duquette, J.; Zhang, M. An Improved Preparation of Arylboronates:  Application in One-Pot Suzuki Biaryl Synthesis. J. Org. Chem. 2003, 68, 3729-3732. (e) Wolan, A.; Zaidlewicz, M. Synthesis of Arylboronates by the Palladium Catalysed CrossCoupling Reaction in Ionic Liquids. Org. Biomol. Chem. 2003, 1, 3274-3276. (f) Murata, M.; Oda, T.; Watanabe, S.; Masuda, Y. 4,4,6-Trimethyl-1,3,2-dioxaborinane: A Practical Reagent for Palladium-Catalyzed Borylation of Aryl Halides. Synthesis 2007, 3, 351-354. (g) PraveenGanesh, N.; Chavant, P. Y. Improved Preparation of 4,6,6-Trimethyl-1,3,2-dioxaborinane and Its Use in a Simple [PdCl2(TPP)2]-Catalyzed Borylation of Aryl Bromides and Iodides. Eur. J. Org. Chem. 2008, 27 4690-4696. (h) Tang, W.; Keshipeddy, S.; Zhang, Y.; Wei, X.; Savoie, J.; Patel, N. D.; Yee, N. K.; Senanayake, C. H. Efficient Monophosphorus Ligands for Palladium-Catalyzed Miyaura Borylation. Org. Lett. 2011, 13, 1366-1369. (i) Lu, J.; Guan, Z.-Z.; Gao, J.-W.; Zhang, Z.-H. An Improved Procedure for the Synthesis of Arylboronates by Palladium-Catalyzed Coupling Reaction of Aryl Halides and Bis(pinacolato)Diboron in Polyethylene Glycol. Appl. Organometal. Chem. 2011, 25, 537-541. (j) Molander, G. A.; Trice, S. L. J.; Kennedy, S. M.; Dreher, S. D.; Tudge, M. T. Scope of the Palladium-Catalyzed Aryl Borylation Utilizing Bis-Boronic Acid. J. Am. Chem. Soc. 2012, 134, 11667-11673. (k) Guerrand, H. D. S.; Vaultier, M.; Pinet, S.; Pucheault, M. Amine–Borane Complexes: Air- and Moisture-Stable Partners for Palladium-Catalyzed Borylation of Aryl Bromides and Chlorides. Adv. Synth. Catal. 2015, 357, 11671174. (l) Iwai, T.; Harada, T.; Tanaka, R.; Sawamura, M. SilicaSupported Tripod Triarylphosphines: Application to PalladiumCatalyzed Borylation of Chloroarenes. Chem. Lett. 2014, 43, 584586. (6) (a) Marciasini, L. D.; Richy, N.; Vaultier, M.; Pucheault, M. Iron-Catalysed Borylation of Arenediazonium Salts to Give Access to Arylboron Derivatives via Aryl(amino)boranes at Room Temperature. Adv. Synth. Catal. 2013, 355, 1083-1088. (b) Bedford, R. B.; Brenner, P. B.; Carter, E.; Clifton, J.; Cogswell, P. M.; Gower, N. J.; Haddow, M. F.; Harvey, J. N.; Kehl, J. A.; Murphy, D. M.; Neeve, E. C.; Neidig, M.; Nunn, J.; Snyder, B. E. R.; Taylor, J. Iron Phosphine Catalyzed Cross-Coupling of Tetraorganoborates and Related Group 13 Nucleophiles with Alkyl Halides. Organometallics 2014, 33, 5767-5780. (c) Atack, T.; Lecker, R. M.; Cook, S. P. Iron-Catalyzed Borylation of Alkyl Electrophiles. J. Am. Chem. Soc. 2014, 136, 9521-9523. (d) Bedford, R. B. How Low Does Iron Go? Chasing the Active Species in Fe-Catalyzed Cross-Coupling

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ACS Catalysis Reactions. Acc. Chem. Res. 2015, 48, 1485-1493. (e) Bedford, R. B.; Brenner, P. B.; Carter, E.; Gallagher, T.; Murphy, D. M.; Pye, D. R. Iron-Catalyzed Borylation of Alkyl, Allyl, and Aryl Halides: Isolation of an Iron(I) Boryl Complex. Organometallics 2014, 33, 5940-5943. (f) Yoshida, T.; Ilies, L.; Nakamura, E. Iron-Catalyzed Borylation of Aryl Chlorides in the Presence of Potassium tButoxide. ACS Catal. 2017, 7, 3199-3203. (7) Co-mediated stoichiometric borylation of aryl halides: (a) Adams, C. J.; Baber, R. A.; Batsanov, A. S.; Bramham, G.; Charmant, J. P. H.; Haddow, M. F.; Howard, J. A. K.; Lam, W. H.; Lin, Z.; Marder, T. B.; Norman, N. C.; Orpen, A. G. Synthesis and Reactivity of Cobalt Boryl Complexes. Dalton. Trans. 2006, 11, 1370-1373. (b) Dai, C.; Stringer, G.; Corrigan, J. F.; Taylor, N. J.; Marder, T. B.; Norman, N. C. Synthesis and Molecular Structure of the Paramagnetic Co(II) Bis(boryl) Complex [Co(PMe3)3(Bcat)2 (cat = 1,2,-O2C6H4). J. Organomet. Chem. 1996, 513, 273-275. (c) Frank, R.; Howell, J.; Campos, J.; Tirfoin, R.; Phillips, N.; Zahn, S.; Mingos, D. M. P.; Aldridge, S. Cobalt Boryl Complexes: Enabling and Exploiting Migratory Insertion in BaseMetal-Mediated Borylation. Angew. Chem., Int. Ed. 2015, 54, 9586-9590. (d) Komeyama, K.; Kiguchi, S.; Takaki, K. The Drastic Effect of Cobalt and Chromium Catalysts in the Borylation of Arylzinc Reagents. Chem. Commun., 2016, 52, 7009-7012. (8) (a) Rosen, B. M.; Huang, C.; Percec, V. Sequential NiCatalyzed Borylation and Cross-Coupling of Aryl Halides via in Situ Prepared Neopentylglycolborane. Org. Lett. 2008, 10, 25972600. (b) Wilson, V.; Wilson, C. J.; Moldoveanu, C.; Resmerita, A. M.; Corcoran, P.; Hoang, L. M.; Rosen, B. M.; Percec, V. Neopentylglycolborylation of Aryl Mesylates and Tosylates Catalyzed by Ni-Based Mixed-Ligand Systems Activated with Zn. J. Am. Chem. Soc. 2010, 132, 1800-1801. (c) Huang, K.; Yu, D.-G.; Zheng, S.-F.; Wu, Z.- H.; Shi, Z.-J. Borylation of Aryl and Alkenyl Carbamates through Ni-Catalyzed C-O Activation. Chem. Eur. J. 2011, 17, 786791. (d) Sogabe, Y.; Namikoshi, T.; Watanabe, S.; Murata, M. Synthesis of Aryl Triolborates via Nickel-Catalyzed Borylation of Aryl Halides with 5-(tert-Butyldimethylsiloxymethyl)-5-methyl1,3,2-dioxaborinane. Synthesis 2012, 44, 1233-1236. (e) Liu, X. W.; Echavarren, J.; Zarate, C.; Martin, R. Ni-Catalyzed Borylation of Aryl Fluorides via C–F Cleavage. J. Am. Chem. Soc. 2015, 137, 12470-12473. (f) Hu, J.; Sun, H.; Cai, W.; Pu, X.; Zhang, Y.; Shi, Z. Nickel-Catalyzed Borylation of Aryl- and Benzyltrimethylammonium Salts via C–N Bond Cleavage. J. Org. Chem. 2016, 81, 14-24. (g) Moldoveanu, C.; Wilson, D. A.; Wilson, C. J.; Corcoran, P.; Rosen, B. M.; Percec, V. Neopentylglycolborylation of Aryl Chlorides Catalyzed by the Mixed Ligand System NiCl2(dppp)/dppf. Org. Lett. 2009, 11, 4974-4977. (h) Moldoveanu, C.; Wilson, D. A.; Wilson, C. J.; Leowanawat, P.; Resmerita, A.-M.; Liu, C.; Rosen, B. M.; Percec, V. Neopentylglycolborylation of OrthoSubstituted Aryl Halides Catalyzed by NiCl2-Based Mixed-Ligand Systems. J. Org. Chem. 2010, 75, 5438-5452. (i) Leowanawat, P.; Resmerita, A.-M.; Moldoveanu, C.; Liu, C.; Zhang, N.; Wilson, D. A.; Hoang, L. M.; Rosen, B. M.; Percec, V. Zero-Valent Metals Accelerate the Neopentylglycolborylation of Aryl Halides Catalyzed by NiCl2-Based Mixed-Ligand Systems. J. Org. Chem. 2010, 75, 7822-7828. (j) Murata, M.; Sambommatsu, T.; Oda, T.; Watanabe, S.; Masuda, Y. Palladium- or Nickel-Catalyzed Coupling Reaction of Dialkoxyboranes with Chloroarenes: Arylation of 1,3,2-Dioxaborolanes or 1,3,2-Dioxaborinanes. Heterocycles 2010, 80, 213-218. (k) Yamamoto, T.; Morita, T.; Takagi, J.; Yamakawa, T. NiCl2(PMe3)2-Catalyzed Borylation of Aryl Chlorides. Org. Lett. 2011, 13, 5766-5769. (l) Molander, G. A.; Cavalcanti, L. N.; García-García, C. Nickel-Catalyzed Borylation of Halides and Pseudohalides with Tetrahydroxydiboron [B2(OH)4]. J. Org. Chem. 2013, 78, 6427-6439. (9) (a) Zhu, W.; Ma, D. Formation of Arylboronates by a CuICatalyzed Coupling Reaction of Pinacolborane with Aryl Iodides at Room Temperature. Org. Lett. 2006, 8, 261-263. (b) Kleeberg,

C.; Dang, L.; Lin, Z.; Marder, T. B. A Facile Route to Aryl Boronates: Room-Temperature, Copper-Catalyzed Borylation of Aryl Halides with Alkoxy Diboron Reagents. Angew. Chem., Int. Ed. 2009, 48, 5350-5354. (c) Grigg, R. D.; Van Hoveln, R.; Schomaker, J. M. Copper-Catalyzed Recycling of Halogen Activating Groups via 1,3-Halogen Migration. J. Am. Chem. Soc. 2012, 134, 16131-16134. d a e, im e t, annwa th, P live o, S u a h, Chavant, P Application of Cooperative Iron/Copper Catalysis to a Palladium-Free Borylation of Aryl Bromides with Pinacolborane. Org. Lett. 2014, 16, 2366-2369. (e) Ando, S.; Matsunaga, H.; Ishizuka, T. A Bicyclic N-Heterocyclic Carbene as a Bulky but Accessible Ligand: Application to the Copper-Catalyzed Borylations of Aryl Halides. J. Org. Chem. 2015, 80, 9671-9681. (f) Niwa, T.; Ochiai, H.; Watanabe, Y.; Hosoya, T. Ni/Cu-Catalyzed Defluoroborylation of Fluoroarenes for Diverse C–F Bond Functionalizations. J. Am. Chem. Soc. 2015, 137, 14313-14318. (g) Schmid, S. C.; Van Hoveln, R.; Rigoli, J. W.; Schomaker, J. M. Development of N-Heterocyclic Carbene–Copper Complexes for 1,3-Halogen Migration. Organometallics 2015, 34, 4164-4173. (10) (a) Nagashima, Y.; Takita, R.; Yoshida, K.; Hirano, K.; Uchiyama, M. Design, Generation, and Synthetic Application of Borylzincate: Borylation of Aryl Halides and Borylzincation of Benzynes/Terminal Alkyne. J. Am. Chem. Soc. 2013, 135, 1873018733. (b) Bose, S. K.; Marder, T. B. Efficient Synthesis of Aryl Boronates via Zinc-Catalyzed Cross-Coupling of Alkoxy Diboron Reagents with Aryl Halides at Room Temperature. Org. Lett. 2014, 16, 4562-4565. (c) Bose, S. K.; Deiβenberger, A.; Eichhorn, A.; Steel, P. G.; Lin, Z. Y.; Marder, T. B. Zinc-Catalyzed Dual C–X and C–H Borylation of Aryl Halides. Angew. Chem., Int. Ed. 2015, 54, 11843-11847. (11) (a) Yamamoto, E.; Izumi, K.; Horita, Y.; Ito, H. Anomalous Reactivity of Silylborane: Transition-Metal-Free Boryl Substitution of Aryl, Alkenyl, and Alkyl Halides with Silylborane/Alkoxy Base Systems. J. Am. Chem. Soc. 2012, 134, 19997-20000. (b) Zhu, C.; Yamane, M. Transition-Metal-Free Borylation of Aryltriazene Mediated by BF3·OEt2. Org. Lett. 2012, 14, 4560-4563. (c) Zhang, J.; Wu, H.-H.; Zhang, J. Cesium Carbonate Mediated Borylation of Aryl Iodides with Diboron in Methanol. Eur. J. Org. Chem. 2013, 28, 6263-6266. (d) Yamamoto, E.; Izumi, K.; Horita, Y.; Ukigai, S.; Ito, H. Formal Nucleophilic Boryl Substitution of Organic Halides with Silylborane/Alkoxy Base System. Top. Catal. 2014, 57, 940-945. (e) Yamamoto, E.; Ukigai, S.; Ito, H. Boryl Substitution of Functionalized Aryl-, Heteroaryl- and Alkenyl Halides with Silylborane and an Alkoxy Base: Expanded Scope and Mechanistic Studies. Chem. Sci. 2015, 6, 2943-2951. (f) Pietsch, S.; Neeve, E. C.; Apperley, D. C.; Bertermann, R.; Mo, F.; Cheung, M. S.; Dang, L.; Wang, J.; Radius, U.; Lin, Z.; Kleeberg, C.; Marder, T. B. Synthesis, Structure, and Reactivity of Anionic sp2–sp3 Diboron Compounds: Readily Accessible Boryl Nucleophiles. Chem. Eur. J. 2015, 21, 7082-7098. (g) Chen, K.; Cheung, M. S.; Lin, Z.; Li, P. Metal-Free Borylation of Electron-Rich Aryl (pseudo)Halides Under Continuous-Flow Photolytic Conditions. Org. Chem. Front. 2016, 3, 875-879. (12) Ishiyama, T.; Ishida, K.; Miyaura, N. Synthesis of Pinacol Arylboronates via Cross-Coupling Reaction of Bis(pinacolato)Diboron with Chloroarenes Catalyzed by Palladium(0)–Tricyclohexylphosphine Complexes. Tetrahedron 2001, 57, 9813-9816. (13) (a) Fürstner, A.; Seidel, G. Org. Lett. 2002, 4, 541-543. (b) Murata, M.; Sambommatsu, T.; Watanabe, S.; Masuda, Y. An Efficient Catalyst System for Palladium-Catalyzed Borylation of Aryl Halides with Pinacolborane. Synlett 2006, 12, 1867-1870. (c) Broutin, P.- Če ňa, I Campaniello, M e oux, Colo e t, Palladium-Catalyzed Borylation of Phenyl Bromides and Application in One-Pot Suzuki−Miyau a iphenyl Synthesis Org. Lett. 2004, 6, 4419-4422. (d) Billingsley, K. L.; Barder, T. E.;

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Buchwald, S. L. Palladium-Catalyzed Borylation of Aryl Chlorides: Scope, Applications, and Computational Studies. Angew. Chem. Int. Ed. 2007, 46, 5359-5363. (e) Billingsley, K. L.; Buchwald, S. L. An Improved System for the PalladiumCatalyzed Borylation of Aryl Halides with Pinacol Borane. J. Org. Chem. 2008, 73, 5589-5591. (f) Praveenganesh, N.; Demory, E.; Gamon, C.; Blandin, V.; Chavant, P. Y. Efficient Borylation of Reactive Aryl Halides with MPBH (4,4,6-Trimethyl-1,3,2dioxaborinane). Synlett 2010, 16, 2403-2406. (g) Ma, N.; Zhu, Z.; Wu, Y. Cyclopalladated Ferrocenylimine: A Highly Effective Catalyst for the Borylation/Suzuki Coupling Reaction. Tetrahedron 2007, 63, 4625-4629. (h) Xu, C.; Gong, J.-F.; Song, M.-P.; Wu, Y.-J. Catalysis of the Coupling Reaction of Aryl Chlorides with Bis(pinacolato)Diboron by Tricyclohexylphosphine-cyclopalladated Ferrocenylimine Complexes. Transition Met. Chem. 2009, 34, 175-179. (i) Wang, L.; Li, J.; Cui, X.; Wu, Y.; Zhu, Z.; Wu, Y. Cyclopalladated Ferrocenylimine as Efficient Catalyst for the Syntheses of Arylboronate Esters (pages 2002–2010). Adv. Synth. Catal. 2010, 352, 2002-2010. (j) Leng, Y.; Yang, F.; Zhu, W.; Zou, D.; Wu, Y.; Cai, R. Facile Synthesis of Arylboronic Esters by PalladacycleCatalyzed Bromination of 2-Arylbenzoxazoles and Subsequent Borylation of the Brominated Products. Tetrahedron 2011, 67, 6191-6196. (k) Wang, L.; Cui, X.; Li, J.; Wu, Y.; Zhu, Z.; Wu, Y. Synthesis of Biaryls through a One-Pot Tandem Borylation/Suzuki–Miyaura Cross-Coupling Reaction Catalyzed by a Palladacycle. Eur. J. Org. Chem. 2012, 595-603. (l) Molander, G. A.; Trice, S. L. J.; Kennedy, S. M. Palladium-Catalyzed Borylation of Aryl and Heteroaryl Halides Utilizing Tetrakis(dimethylamino)diboron: One Step Greener. Org. Lett. 2012, 14, 4814-4817. (m) Kawamorita, S.; Ohmiya, H.; Iwai, T.; Sawamura, M. Palladium-Catalyzed Borylation of Sterically Demanding Aryl Halides with a Silica-Supported Compact Phosphane Ligand. Angew. Chem., Int. Ed. 2011, 50, 8363-8366. (n) Chow, W. K.; Yuen, O. Y.; So, C. M.; Wong, W. T.; Kwong, F. Y. Carbon–Boron Bond Cross-Coupling Reaction Catalyzed by −PPh2 Containing Palladium–Indolylphosphine Complexes. J. Org. Chem. 2012, 77, 3543-3548. (o) Guerrand, H. D. S.; Marciasini, L. D.; Jousseaume, M.; Vaultier, M.; Pucheault, M. Borylation of Unactivated Aryl Chlorides under Mild Conditions by Using Diisopropylaminoborane as a Borylating Reagent. Chem. Eur. J. 2014, 20, 5573-5579. (p) Li, P.; Fu, C.; Ma, S. GorlosPhos for Palladium-Catalyzed Borylation of Aryl Chlorides. Org. Biomol. Chem. 2014, 12, 3604-3610. (q) Xu, L.; Li, P. Direct Introduction of a Naphthalene-1,8-diamino Boryl [B(dan)] Group by a Pd-Catalysed Selective Boryl Transfer Reaction. Chem. Commun. 2015, 51, 5656-5659. (r) Dzhevakov, P. B.; Topchiy, M. A.; Zharkova, D. A.; Morozov, O. S.; Asachenko, A. F.; Nechaev, M. S. Miyaura Borylation and One-Pot Two-Step Homocoupling of Aryl Chlorides and Bromides under Solvent-Free Conditions. Adv. Synth. Catal. 2016, 358, 977-983. (s) Yamamoto, Y.; Matsub-

ara, H.; Yorimitsu, H.; Osuka, A. Base-Free Palladium-Catalyzed Borylation of Aryl Chlorides with Diborons. ChemCatChem 2016, 8, 2317-2320. (14) (a) Mfuh, A. M.; Doyle, J. D.; Chhetri, B.; Arman, H. D.; Larionov, O. V. Scalable, Metal- and Additive-Free, Photoinduced Borylation of Haloarenes and Quaternary Arylammonium Salts. J. Am. Chem. Soc. 2016, 138, 2985-2988. (b) Mfuh, A. M.; Nguyen, V. T.; Chhetri, B.; Burch, J. E.; Doyle, J. D.; Nesterov, V. N.; Arman, H. D.; Larionov, O. V. Additive- and Metal-Free, Predictably 1,2- and 1,3-Regioselective, Photoinduced Dual C–H/C–X Borylation of Haloarenes. J. Am. Chem. Soc. 2016, 138, 8408-8411. (15) Zhang, L.; Jiao, L. Pyridine-Catalyzed Radical Borylation of Aryl Halides. J. Am. Chem. Soc. 2017, 139, 607-610. (16) Yao, W.; Fang, H.; Peng, S.; Wen, H.; Zhang, L.; Hu, A.; Huang, Z. Cobalt-Catalyzed Borylation of Aryl Halides and Pseudohalides Organometallics 2016, 35, 1559-1564. (17) (a) Pyzyojski J. A.; Arman H. D.; Tonzetich Z. J. NHC Complexes of Cobalt(II) Relevant to Catalytic C–C Coupling Reactions. Organometallics, 2013, 32, 723-732. (b) Lannuzzi, T.; Gao, Y.; Baker, T. M.; Deng, L.; Neidig, M. L. Magnetic Circular Dichroism and Density Functional Theory Studies of Electronic Structure and Bonding in Cobalt(II)–N-Heterocyclic Carbene Complexes. Dalton Trans., 2017, 46, 13290-13299. (c) Smart, K. A.; Vanbergen, A.; Lednik, J.; Tang, C. Y.; Mansaray, H. B.; Siewert, I.; Aldridge, S. Bulky N-Heterocyclic Carbene and Pyridine Donor Adducts of Co(II) Bromide: Influence on Reactivity of Stoichiometry, Sterics and Donor Capability. J. Organomet. Chem. 2013, 741-742, 33-39. (18) (a) Obligacion, J. V.; Semproni, S. P.; Chirik, P. J. CobaltCatalyzed C–H Borylation. J. Am. Chem. Soc. 2014, 136, 4133-4136. (b) Obligacion, J. V.; Chirik, P. J. Mechanistic Studies of CobaltCatalyzed C(sp2)–H Borylation of Five-Membered Heteroarenes with Pinacolborane. ACS Catal. 2017, 7, 4366-4371. (c) Obligacion, J. V.; Semproni, S.P.; Pappas, I.; Chirik, P. J. CobaltCatalyzed C(sp2)-H Borylation: Mechanistic Insights Inspire Catalyst Design. J. Am. Chem. Soc. 2016, 138, 10645-10653. (d) onard, N. G.; Bezdek, M. J.; Chirik, P. J. Cobalt-Catalyzed C(sp2)–H Borylation with an Air-Stable, Readily Prepared Terpyridine Cobalt(II) Bis(acetate) Precatalyst. Organometallics 2017, 36, 142-150. (e) Palmer, W. N.; Obligacion, J. V.; Pappas, I.; Chirik, P. J. Cobalt-Catalyzed Benzylic Borylation: Enabling Polyborylation and Functionalization of Remote, Unactivated C(sp3)-H Bonds. J. Am. Chem. Soc. 2016, 138, 766-769. (f) Schaefer, B. A.; Margulieux, G. W.; Small, B. L.; Chirik, P. J. Evaluation of Cobalt Complexes Bearing Tridentate Pincer Ligands for Catalytic C-H Borylation. Organometallics 2015, 34, 1307-1320. (19) Mo, Z.; Chen, D.; Leng, X.; Deng, L. Intramolecular C(sp3)H Bond Activation Reactions of Low-Valent Cobalt Complexes with Coordination Unsaturation. Organometallics 2012, 31, 70407043.

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