Synthesis of arylboronic acids and arylboronates
A general and convenient protocol for the electrophilic borylation of aryl Grignard reagents prepared from arylbromides by direct insertion of magnesium in the presence of LiCl or by Mg/Br exchange with iPrMgCl·LiCl enables the synthesis of various aryl boronic acids in a straightforward manner in excellent yields at 0°C.
T. Leermann, F. R. Leroux, F. Colobert, Org. Lett., 2011, 13, 4479-4481.
A simple continuous flow setup for handling and performing of organolithium chemistry on the multigram scale enables the synthesis of various compounds following a reaction sequence of Hal/Li exchange and electrophilic quench. It was possible to synthesize building blocks within a 1 s total reaction time and with a remarkable throughput of 60 g / h.
A. Hafner, M. Meisenbach, J. Sedelmeier, Org. Lett., 2016, 18, 3630-3633.
A simple, metal- and additive-free, photoinduced borylation of haloarenes, including electron-rich fluoroarenes, as well as arylammonium salts directly provides boronic acids and boronic esters. This borylation method has a broad scope and functional group tolerance.
A. M. Mfuh, J. D. Doyle, B. Chhetri, H. D. Arman, O. V. Larionov, J. Am. Chem. Soc., 2016, 138, 2985-2988.
A diboron/methoxide/pyridine reaction system enables a photoactivation of an in situ generated super electron donor for an efficient, transition-metal-free borylation of unactivated aryl chlorides.
L. Zhang, L. Jiao, J. Am. Chem. Soc., 2019, 141, 9124-9128.
In an efficient and practical visible-light photoredox borylation of aryl halides and subsequent aerobic oxidative hydroxylation, readily available aryl halides and bis(pinacolato)diboron can be used as the starting materials and fac-Ir(ppy)3 as the photocatalyst. The reaction provides a wide range of arylboronic esters and phenols in good yields. The methods show some advantages including simple equipment, mild conditions, and easy operation.
M. Jiang, H. Yang, H. Fu, Org. Lett., 2016, 18, 5248-5251.
Aliphatic, aromatic, heteroaromatic, vinyl, or allylic Grignard reagents react with pinacolborane at ambient temperature in tetrahydrofuran to afford the corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride intermediate quickly eliminates hydridomagnesium bromide and affords the product boronic ester in very good yield. This reaction also can be carried out under Barbier conditions.
J. W. Clary, T. J. Rettenmaier, R. Snelling, W. Bryks, J. Banwell, W. T. Wipke, B. Singaram, J. Org. Chem., 2011, 76, 9602-9610.
A selective cross-coupling of an aryl radical and a pyridine-stabilized boryl radical enables a transition-metal-free borylation reaction of haloarenes under mild conditions. This pyridine-catalyzed borylation features a broad substrate scope, operational simplicity, and gram-scale synthetic ability.
L. Zhang, L. Jiao, J. Am. Chem. Soc., 2017, 139, 607-610.
A simple metal-free borylation of aryl iodides is mediated by a fluoride sp2-sp3 diboron adduct. The reaction conditions tolerate various functional groups. Whereas electronic effects of substituents do not affect the borylation, steric hindrance does. The reaction proceeds via a radical mechanism in which pyridine stabilizes intermediate boryl radicals.
S. Pinet, V. Liautard, M. Debiais, M. Pucheault, Synthesis, 2017, 49, 4759-4768.
In a transition-metal-free borylation of aryl and vinyl halides using 1,1-bis[(pinacolato)boryl]alkanes as boron source, one of the boron groups is selectively transferred in the presence of sodium tert-butoxide as the only activator. A broad range of organohalides are borylated with excellent chemoselectivity and functional group compatibility.
Y. Lee, S.-y. Baek, J. Park, S.-T. Kim, S. Tussupbayev, J. Kim, M.-H. Baik, S. H. Cho, J. Am. Chem. Soc., 2017, 139, 976-984.
Borylzincate can be generated in situ from dialkylzinc, diboron, and metal alkoxide. Model DFT calculations show that although the formation of borylzincate is kinetically favorable, it is thermodynamically unfavorable. A successive reaction sequence, that provides a compensating energy gain, therefore enables Zn-catalyzed borylation of aryl halides and borylzincation of benzynes and terminal alkyne from diborons without the need for any cocatalyst.
Y. Nagashima, R. Takita, K. Yoshida, K. Hirano, M. Uchiyama, J. Am. Chem. Soc., 2013, 135, 18730-18733.
A highly efficient palladium-catalyzed borylation allows the conversion of aryl and heteroaryl iodides, bromides, and several chlorides containing a variety of functional groups to the corresponding corresponding pinacol boronate esters with an inexpensive and atom-economical boron source, pinacol borane.
K. L. Billingsley, S. L. Buchwald, J. Org. Chem., 2008, 73, 5589-5591.
The combination of Pd(dba)2 and bis(2-di-tert-butylphosphinophenyl)ether is an efficient catalyst system for the crosscoupling of pinacolborane with aryl bromides. This system enables the synthesis of ortho-, meta-, and para-substituted electron-rich and -deficient arylboronates. A temperature of 120°C was required for the conversion of electron-rich aryl chlorides.
M. Murata, T. Sambommatsu, S. Watanabe, Y. Masuda, Synlett, 2006, 1867-1870.
A well-defined bicyclic NHC-CuCl complex was successfully applied to copper-catalyzed borylations of aryl halides at ambient temperature. This bicyclic NHC-CuCl compex proved to be a suitable catalyst particularly for sterically hindered substrates, which suggested that the bicyclic NHC ligand offered a bulky but accessible environment to the bound copper.
S. Ando, H. Matsunaga, T. Ishizuka, J. Org. Chem., 2015, 80, 9671-9681.
The CuI-catalyzed coupling reaction of pinacolborane with aryl iodides under the action of sodium hydride in THF at room temperature provided the corresponding arylboronates in good yields. Aryl bromides gave poor conversion.
W. Zhu, D. Ma, Org. Lett., 2006, 8, 261-263.
The highly active mixed-ligand catalytic system NiCl2(dppp)/dppf combined with the reducing effect of zerovalent Zn enables a dramatic acceleration of the rate of the neopentylglycolborylation of aryl halides. A diversity of electron-rich and electron-deficient aryl iodides, bromides, and chlorides were efficiently neopentylglycolborylated in very good yields, typically in 1 h or less.
P. Leowanawat, A.-M. Resmerita, C. Moldoveanu, C. Liu, N. Zhang, D. A. Wilson, L. M. Hoang, B. M. Rosen, V. Persec, J. Org. Chem., 2010, 75, 7822-7828.
Palladium- or iron-catalyzed cross-coupling reactions of aryl fluorides with bis(pinacolato)diboron (B2pin2) in the presence of LiHMDS provide arylboronic acid pinacol esters. The Pd-catalyzed defluoroborylation of fluoroarenes tolerates various functional groups such as primary and secondary amine, trifluoromethyl, ketone, alkoxy, and boryl.
X. Zhao, M. Wu, Y. Liu, S. Cao, Org. Lett., 2018, 20, 5564-5568.
The mixed-ligand system NiCl2(dppp)/dppf is an effective catalyst for the neopentylglycolborylation of ortho-, meta-, and para-substituted electron-rich and electron-deficient aryl mesylates and tosylates. The addition of Zn powder as a reductant dramatically increases the reaction yield and reduces the reaction time, providing complete conversion in 1-3 h.
D. A. Wilson, C. J. Wilson, C. Moldoveanu, A.-M. Resmerita, P. Corcoran, L. M. Hoang, B. M. Rosen, V. Percec, J. Am. Chem. Soc., 2010, 132, 1800-1801.
A base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents selectively affords aryl boronate esters. The method is applicable to various (hetero)aryl carboxylic acid fluorides as well as diverse diboron reagents. The acid fluorides can also be generated in situ directly from carboxylic acids.
C. A. Malapit, J. R. Bour, S. R. Laursen, M. S. Sanford, J. Am. Chem. Soc., 2019, 141, 17322-17330.
The appropriate choice of a nickel catalyst Ni(COD)2, ICy·HCl as a ligand, and the use of 2-ethoxyethanol as the cosolvent enables a highly efficient C-N bond borylative cleavage of sp2 and sp3 C-N bonds. This reaction shows good functional group compatibility and can serve as a powerful synthetic tool for gram-scale synthesis and late-stage C-N borylation of complex compounds.
J. Hu, H. Sun, W. Cai, X. Pu, Y. Zhang, Z. Shi, J. Org. Chem., 2016, 81, 14-24.
A photocatalyst- and additive-free, visible light induced borylation reaction of arylazo sulfones as starting materials offers mild conditions and wide substrate scope.
Y. Xu, X. Yang, H. Fang, J. Org. Chem., 2018, 83, 12831-12837.
In a conceptually novel borylation reaction via a mild photoinduced decarboxylation of redox-activated aromatic carboxylic acids, cheap and easily prepared N-hydroxyphthalimide esters act as the aryl radical precursors. The reaction is operationally simple, scalable, does not require the use of expensive transition metals or ligands and displays broad scope and functional group tolerance.
L. Candish, M. Teders, F. Glorius, J. Am. Chem. Soc., 2017, 139, 7440-7443.
Rhodium-catalyzed transformation of alkyl aryl sulfides into arylboronic acid pinacol esters via C-S bond cleavage allows the synthesis of a diverse range of multisubstituted arenes.
Y. Uetake, T. Niwa, T. Hosoya, Org. Lett., 2016, 18, 2750-2753.
The presence of bis[2-(N,N-dimethylamino)ethyl] ether allows a selective halide-magnesium exchange of iodo- and bromoaromatics bearing sensitive carboxylic ester and cyano groups with isopropylmagnesium chloride. A subsequent reaction with trimethylborate as electrophile afforded arylboronic acids in good to excellent yields.
X.-J. Wang, X. Sun, L. Zhang, Y. Xu, D. Krishnamurthy, C. H. Senanayake, Org. Lett., 2006, 8, 305-307.
Iridium(III) complexes of N,B-bidentate boryl ligands enable a practical, efficient catalytic ortho-borylation reaction of arenes with a broad range of directing groups.
G. Wang, L. Liu, H. Wang, Y.-S. Ding, J. Zhou, S. Mao, P. Li, J. Am. Chem. Soc., 2017, 139, 91-94.
Arylboronic acids and aryl trifluoroborates are synthesized in a one-pot sequence by Ir-catalyzed borylation of arenes. To prepare the arylboronic acids, the Ir-catalyzed borylation is followed by oxidative cleavage of the pinacol boronates with NaIO4. To prepare the aryltrifluoroborate, the Ir-catalyzed borylation is followed by displacement of pinacol by KHF2.
J. M. Murphy, C. C. Tzschucke, J. F. Hartwig, Org. Lett., 2007, 9, 757-760.
Ir complexes with bidentate silyl ligands that contain P- or N-donors are effective catalysts for ortho borylations of a broad range of substituted aromatics. The substrate scope is broad, and the modular ligand synthesis allows for flexible catalyst design.
B. Ghaffari, S. M. Preshlock, D. L. Plattner, R. J. Staples, P. E. Maligres, S. W. Krska, R. E. Maleczka, Jr., M. R. Smith, III, J. Am. Chem. Soc., 2014, 136, 14345-14348.
For achieving high para-selectivity in the Ir-catalyzed borylation of aromatic esters, an L-shaped bipyridine ligand is essential to recognize the functionality of the oxygen atom of the ester carbonyl group via noncovalent interaction.
M. E. Hoque, R. Bisht, C. Haldar, B. Chattopadhyay, J. Am. Chem. Soc., 2017, 139, 7745-7748.
A remarkably general, iridium-catalyzed borylation results in para-selectivity on some of the most common arene building blocks (anilines, benzylamines, phenols, benzyl alcohols) using standard borylation ligands. The strategy relies on a facile conversion of the substrates into sulfate or sulfamate salts, wherein the anionic arene component is paired with a tetrabutylammonium cation.
M. T. Mihai, B. D. Williams, R. J. Phipps, J. Am. Chem. Soc., 2019, 141, 15477-15482.
The palladium catalysed cross-coupling reaction of aryl iodides and bromides with pinacolborane in 1,3-dialkylimidazolium tetrafluoroborates and hexafluorophosphates offers simple product isolation by extraction and shorter reaction time as compared to conventional solvents.
A. Wolan, M. Zaidlewicz, Org. Biomol. Chem., 2003, 1, 3724-3276.
meta- and para-dibromoarenes can be converted to isopropoxide-protected bromo arylboronates. A subsequent metal-halogen exchange and reaction with an electrophile leads to functionalized arylboronates in a one-pot manner.
Q. Jiang, M. Ryan, P. Zhichkin, J. Org. Chem., 2007, 72, 6618-6620.
Diazotization of arylamines promoted by methanol with sodium nitrite and hydrochloric acid as diazotization agents followed by Sandmeyer borylation via a SN2Ar pathway provides a simple and green method to arylboronic acids and arylboronates.
C.-J. Zhao, D. Xue, Z.-H. Jia, C. Wang, J. Xiao, Synlett, 2014, 25, 1577-1584.
The reaction of aryl cyanides with diboron in the presence of a rhodium/Xantphos catalyst and DABCO affords arylboronic esters via carbon-cyano bond cleavage. The reaction allows the regioselective introduction of a boryl group in a late stage of synthesis.
M. Tobisu, H. Kinuta, Y. Kita, E. Rémond, N. Chatani, J. Am. Chem. Soc., 2012, 134, 115-118.
AuCl3-catalyzed halogenations of aryl borononates with N-halosuccinimides enables a convenient synthesis of aromatic boronates bearing halogen substituents in the aromatic ring.
D. Qiu, F. Mo, Z. Zheng, Y. Zhang, J. Wang, Org. Lett., 2010, 12, 5474-5477.