- Merging Iridium-Catalyzed C-H Borylations with Palladium-Catalyzed Cross-Couplings Using Triorganoindium Reagents
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A versatile and efficient method to prepare borylated arenes furnished with alkyl, alkenyl, alkynyl, aryl, and heteroaryl functional groups is developed by merging Ir-catalyzed C-H borylations (CHB) with a chemoselective palladium-catalyzed cross-coupling of triorganoindium reagents (Sarandeses-Sestelo coupling) with aryl halides bearing a boronic ester substituent. Using triorganoindium cross-coupling reactions to introduce unsaturated moieties enables the synthesis of borylated arenes that would be difficult to access through the direct application of the CHB methodology. The sequential double catalyzed procedure can be also performed in one vessel.
- Jayasundara, Chathurika R. K.,Gil-Negrete, José M.,Montero Bastidas, Jose R.,Chhabra, Arzoo,Martínez, M. Montserrat,Pérez Sestelo, José,Smith, Milton R.,Maleczka, Robert E.
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p. 751 - 759
(2021/12/27)
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- Iridium-Catalyzed Borylation of Primary Benzylic C-H Bonds without a Directing Group: Scope, Mechanism, and Origins of Selectivity
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Primary benzylic boronate esters are useful intermediates in organic synthesis, but these reagents cannot be prepared by hydroboration. The benzylic C-H borylation of methylarenes would be a method to form these products, but such reactions without neat methylarene or a directing group are unknown. We report an approach to divert the borylation of methylarenes from aromatic positions to benzylic positions with a silylborane as reagent and a new iridium catalyst containing an electron-deficient phenanthroline as ligand. This system forms benzylic boronate esters selectively over the corresponding aryl boronate esters. An Ir diboryl monosilyl complex ligated by the phenanthroline was isolated and determined to be the resting state of the catalyst. Mechanistic studies show that this complex is kinetically competent to be an intermediate in the catalytic process. Kinetic studies of benzylic and aryl C-H borylation catalyzed by various Ir complexes show that the rate of aryl C-H borylation decreases with decreasing electron density at the metal center of the Ir catalyst, but that the rate of benzylic C-H borylation is less sensitive to the degree of electron density at the metal center of the Ir catalyst. Kinetic and computational studies suggest that the two borylation reactions respond differently to the degree of electron density at the metal center because they occur with different turnover-limiting steps. The turnover-limiting step in the borylation of aryl C-H bonds is known to be C-H oxidative addition, but the turnover-limiting step of the borylation of benzylic C-H bonds appears to be an isomerization prior to C-B reductive elimination.
- Larsen, Matthew A.,Wilson, Conner V.,Hartwig, John F.
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supporting information
p. 8633 - 8643
(2015/07/15)
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- Harnessing C-H Borylation/Deborylation for Selective Deuteration, Synthesis of Boronate Esters, and Late Stage Functionalization
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Ir-catalyzed deborylation can be used to selectively deuterate aromatic and heteroaromatic substrates. Combined with the selectivities of Ir-catalyzed C-H borylations, uniquely labeled compounds can be prepared. In addition, diborylation/deborylation reactions provide monoborylated regioisomers that complement those prepared by C-H borylation. Comparisons between Ir-catalyzed deborylations and Pd-catalyzed deborylations of diborylated indoles described by Movassaghi are made. The Ir-catalyzed process is more effective for deborylating aromatics and is generally more effective in the monodeborylation of diborylated thiophenes. These processes can be applied to complex molecules such as clopidogrel.
- Kallepalli, Venkata A,Gore, Kristin A.,Shi, Feng,Sanchez, Luis,Chotana, Ghayoor A.,Miller, Susanne L.,Maleczka, Robert E.,Smith, Milton R.
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p. 8341 - 8353
(2015/09/02)
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- Regioselective conversion of arenes to N-aryl-1,2,3-triazoles Using C-H Borylation
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A one-pot protocol for the synthesis of N-aryl 1,2,3-triazoles from arenes by an iridium-catalyzed C-H borylation/copper catalyzed azidation/click sequence is described. 1mol % of Cu(OTf)2 was found to efficiently catalyze both the azidation and the click reaction. The applicability of this method is demonstrated by the late-stage chemoselective installation of 1,2,3-triazole moiety into unactivated molecules of pharmaceutical importance.
- Srinivasan, Rajavel,Coyne, Anthony G.,Abell, Chris
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supporting information
p. 11680 - 11684
(2014/10/15)
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- Practical one-pot C-H activation/borylation/oxidation: Preparation of 3-bromo-5-methylphenol on a multigram scale
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A practical one-pot C-H activation/borylation/oxidation sequence for the generation of 3,5-disubstituted phenols is presented. Specifically, 3-bromo-5-methylphenol is prepared from 3-bromotoluene, without isolation of intermediates, on a multigram scale, and in high yield. The process proceeds under mild conditions and can be completed within one day. Georg Thieme Verlag Stuttgart - New York.
- Norberg, A. Monica,Smith III, Milton R.,Maleczka Jr., Robert E.
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scheme or table
p. 857 - 859
(2011/05/02)
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- A one-pot, single-solvent process for tandem, catalyzed C-H borylation-Suzuki-Miyaura cross-coupling sequences
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Methyl tert-butyl ether is a suitable solvent for iridium-catalyzed C-H borylation followed, in the same pot, by palladium-catalyzed Suzuki-Miyaura cross-coupling sequences, giving high yields of biaryls. Georg Thieme Verlag Stuttgart.
- Harrisson, Peter,Morris, James,Steel, Patrick G.,Marder, Todd B.
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experimental part
p. 147 - 150
(2009/05/30)
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- One-pot synthesis of arylboronic acids and aryl trifluoroborates by Ir-catalyzed borylation of arenes
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(Chemical Equation Presented) The synthesis of arylboronic acids and aryl trifluoroborates in a one-pot sequence by Ir-calalyzed borylation of arenes is reported. To prepare the arylboronic acids, the Ir-catalyzed borylation is followed by oxidative cleavage of the boronic ester with NaIO4. To prepare the aryltrifluoroborate, the Ir-catalyzed borylation is followed by displacement of pinacol by KHF2. These two-step sequences give products that are more reactive toward subsequent chemistry than the initially formed pinacol boronates.
- Murphy, Jaclyn M.,Tzschucke, C. Christoph,Hartwig, John F.
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p. 757 - 760
(2007/10/03)
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- Process for the synthesis of phenols from arenes
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A process to synthesize substituted phenols such as those of the general formula RR′R″Ar(OH) wherein R, R′, and R″ are each independently hydrogen or any group which does not interfere in the process for synthesizing the substituted phenol including, but not limited to, halo, alkyl, alkoxy, carboxylic ester, amine, amide; and Ar is any variety of aryl or hetroaryl by means of oxidation of substituted arylboronic esters is described. In particular, a metal-catalyzed C—H activation/borylation reaction is described, which when followed by direct oxidation in a single or separate reaction vessel affords phenols without the need for any intermediate manipulations. More particularly, a process wherein Ir-catalyzed borylation of arenes using pinacolborane (HBPin) followed by oxidation of the intermediate arylboronic ester by OXONE is described.
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Page 15; 19-21
(2008/06/13)
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- C-H activation/borylation/oxidation: A one-pot unified route to meta-substituted phenols bearing ortho-/para-directing groups
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An efficient one-pot C-H activation/borylation/oxidation protocol for the preparation of phenols is described. This method is particularly attractive for the generation of meta-substituted phenols bearing ortho-/para-directing groups, as such substrates are difficult to access by other phenol syntheses. Copyright
- Maleczka Jr., Robert E.,Shi, Feng,Holmes, Daniel,Smith III, Milton R.
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p. 7792 - 7793
(2007/10/03)
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