Organoboronic Acids Research Articles

Organoboron Acids and Their Derivatives as Catalysts for Organic Synthesis

An overview of the applications of boronic and borinic acids in catalysis is presented. Taking advantage of the Lewis acidity of trivalent boron and the reversible covalent interactions of organoboron acids with OH groups, diverse modes of catalytic reactivity have been achieved. Interactions with carbonyl compounds enable acceleration of addition and cycloaddition processes, whereas binding of their enol tautomers can lead to organoboron-catalyzed aldol and related reactions. Binding of organoboron acids to hydroxyl and carboxyl OH groups has been employed as a mode of electrophilic activation for catalysis of substitution, cycloaddition, rearrangement, and elimination reactions. By altering the nature of the interaction with the organoboron acid catalyst, activation of OH groups as pronucleophiles is also possible, resulting in catalyst-controlled methods for regioselective functionalization of diols and carbohydrate derivatives. Applications of organoboron acids in bifunctional and assisted catalysis a...

One‐Pot Synthesis of Heteroaryl and Diheteroaryl Ketones through Palladium‐Catalyzed 1,2‐Addition and Oxidation

AbstractA synthetic method was developed for the preparation of heteroaryl and diheteroaryl ketones from aldehydes and organoboronic acids through a palladium‐catalyzed 1,2‐addition and oxidation that uses an aryl iodide as the oxidant. This one‐pot process shows high tolerance for a broad range of heterocyclic substrates by using 1.0–3.0 mol‐% of the catalyst that is formed from allylpalladium chloride dimer and a thioether‐imidazolinium chloride. In addition to fine‐tuning the catalytic system, the use of a sterically hindered aryl iodide that has a substituent at the ortho position, such as 2‐iodotoluene, is important to obtain the desired ketones with heterocyclic moieties in good to excellent yields.

ChemInform Abstract: Catalytic Enantioselective Transformations of Borylated Substrates: Preparation and Synthetic Applications of Chiral Alkylboronates

Organoboronic acid derivatives are well-established intermediates for the prepara- tion of alcohols and amines, and in the formation of C-C bonds via different reactions, including homologations, carbonyl allylboration, or transition-metal-catalyzed cross-cou- pling chemistry. In the past decade, there has been great interest in the development of cat- alytic enantioselective methods for the preparation of chiral, optically enriched organoboronates as precursors of enantioenriched compounds. While the mainstream strat- egy remains the late-stage borylation of organic functional groups, our group has focused on an alternate strategy focused on modification of boron-containing substrates. In this way, acyclic and cyclic secondary alkyl - and allyl-boronates were prepared through catalytic enantio selective processes such as (4 + 2) cycloadditions, isomerizations, allylic substitu- tions, and conjugate additions. The resulting optically enriched boronates have been suc- cessfully utilized in the syntheses of complex natural products and drugs. One remaining challenge in the chemistry of secondary alkylboronate derivatives is their cross-coupling, especially with control of stereoselectivity. In this regard, our recent approach featured the conjugate asymmetric borylation of β-boronyl acrylates, providing the first enantioselective preparation of highly optically enriched 1,1-diboronyl derivatives. The chirality of these geminal diboron compounds is conferred through the use of two distinct boronate adducts, which can be coupled chemo- and stereoselectively with a variety of aryl and alkenyl halides under palladium catalysis.

Development of a palladium-catalyzed decarboxylative cross-coupling of (2-azaaryl)carboxylates with aryl halides

A catalytic method for the decarboxylative coupling of 2-(azaaryl)carboxylates with aryl halides is described. The decarboxylative cross-coupling presented is mediated by a system catalytic in both palladium and copper without requiring stoichiometric amounts of organometallic reagents or organoboronic acids. This method circumvents additional synthetic steps required to prepare 2-azaaryl organometallics and organoborates as nucleophilic coupling partners, which are prone to protodemetallation and protodeborylation and produce potentially toxic byproducts.

ChemInform Abstract: Palladium‐Catalyzed Highly Efficient Synthesis of Tetracenes and Pentacenes.

AbstractA novel Pd‐catalyzed cascade reaction for the synthesis of linear polyacenes, e.g. (III), (IV)/(V) and (VII), from bis(propargylic carbonates) and organoboronic acids is described.

ChemInform Abstract: Cobalt(II)‐Catalyzed 1,4‐Addition of Organoboronic Acids to Activated Alkenes: An Application to Highly cis‐Stereoselective Synthesis of Aminoindane Carboxylic Acid Derivatives.

It all adds up: The 1,4-addition of organoboronic acids to activated alkenes catalyzed by [Co(dppe)Cl(2)] is described. A [3+2]-annulation reaction of ortho-iminoarylboronic acids with acrylates to give various aminoindane carboxylic acid derivatives with cis-stereoselectivity is also demonstrated (see scheme; dppe = 1,2-bis(diphenylphosphino)ethane).

Synthesis of novel planar chiral Ag and Rh N-heterocyclic carbene complexes derived from [2.2]paracyclophane and their application in ultrasound assisted asymmetric addition reactions of organoboronic acids to aldehydes

Three novel planar chiral N-heterocyclic carbene silver and rhodium complexes based on [2.2]paracyclophane have been prepared. These could be used as catalysts/precatalysts for the asymmetric 1,2-addition of organoboronic acids to aldehydes. We optimized the reaction conditions and have applied ultrasonic irradiation in the asymmetric arylation for the first time. Under ultrasound irradiation, the combination of planar chiral NHC–Ag complex 5 and RhCl3 can achieve higher catalytic activities in the asymmetric addition of organoboronic acids to aldehydes.

Synthesis and Structural Characterization of Heteroboroxines with MB2O3 Core (M = Sb, Bi, Sn)

Reaction of organoantimony and organobismuth oxides (LSbO)(2) and (LBiO)(2) (where L is [2,6-bis(dimethylamino)methyl]phenyl) with four equivalents of the organoboronic acids gave new heteroboroxines LM[(OBR)(2)O] 1a-2c (for M = Sb: R = Ph (1a), 4-CF(3)C(6)H(4) (1b), ferrocenyl (1c); for M = Bi: R = Ph (2a), 4-CF(3)C(6)H(4) (2b), and ferrocenyl (2c)). Analogously, reaction between organotin carbonate L(Ph)Sn(CO(3)) and two equivalents of organoboronic acids yielded compounds L(Ph)Sn[(OBR)(2)O] (where R = Ph (3a), 4-CF(3)C(6)H(4) (3b), and ferrocenyl (3c)). All compounds were characterized by elemental analysis and NMR spectroscopy. Their structure was described both in solution (NMR studies) and in the solid state (X-ray diffraction analyses 1a, 1c, 2b, 3b, and 3c). All compounds contain a central MB(2)O(3) core (M = Sb, Bi, Sn), and the bonding situation within these rings and their potential aromaticity was investigated by the help of computational methods.

ChemInform Abstract: Synthesis of 1,2‐Disubstituted Acetylenes via Copper‐Catalyzed Suzuki Coupling of Organoboronic Acids with 1,1‐Dibromo‐1‐alkenes.

AbstractVarious 1,2‐diarylacetylenes can be prepared under optimized conditions.

Nickel-catalyzed regio- and diastereoselective intermolecular three-component coupling of oxabicyclic alkenes with alkynes and organoboronic acids

Reaction of oxabicyclic alkenes with alkynes and organoboronic acids in the presence of Ni(cod)(2), P(t-Bu)(3), and CsF in a binary solvent toluene-methanol (1 : 3) at 75 to 85 °C provided exo-5,6-disubstituted 7-oxanorbornene derivatives in good to excellent yields.

Evaluation of TlOH Effect for Pd<sup>0</sup>-Mediated Cross-Coupling of Methyl Iodide and Excess Boronic Acid Ester toward Fabrication of [<sup>11</sup>C]CH<sub>3</sub>-Incorporated PET Tracer

The use of thallium(I) hydroxide (TlOH) as a base is known to extremely accelerate the Suzuki-Miyaura cross-coupling reaction using organoboronic acid or organoboronic acid ester as a substrate. Here, we investigated the effects of TlOH by comparing with other conventional bases such as KOH, K2CO3, and CsF for Pd0-mediated rapid cross-coupling reactions between CH3I and organoborane reagents, such as phenyl-, (Z)-4-benzyloxy-2-butenyl-, and benzylboronic acid pinacol esters under the conditions CH3I/borane/Pd0/base (1:40:1:3) in THF/H2O or DMF/H2O for 5 min with an aim to fabricate a PET tracer efficiently. Consequently, however, the use of TlOH was much less efficient than the other bases for the acceleration of cross-coupling reactions. Thus, it was reconfirmed that the milder and non-toxic conditions using K2CO3 or CsF so far developed by our group were most appropriate for the rapid C-methylations.

銅触媒を用いる有機ボロン酸類の電子欠損性アルキンへの共役付加反応

銅触媒を用いる有機ボロン酸類の電子欠損性アルキンへの共役付加反応

A general and green procedure for the synthesis of organochalcogenides by CuFe2O4nanoparticle catalysed coupling of organoboronic acids and dichalcogenides in PEG-400

A general and efficient procedure has been developed for the synthesis of organochalcogenides (selenides and tellurides) by a simple reaction of organoboronic acids and dichalcogenides catalysed by CuFe2O4 nanoparticles in PEG-400 without any ligand. This protocol offers the scope for access to a wide spectrum of chalcogenides including diaryl, aryl–heteroaryl, aryl–styrenyl, aryl–alkenyl, aryl–allyl, aryl–alkyl and aryl–alkynyl versions. The catalyst is magnetically separable and recyclable eight times without any loss of appreciable catalytic activity. The products are obtained in high purities after evaporation of solvent followed by filtration column chromatography.

Chiral olefin–sulfoxide as ligands for rhodium-catalyzed asymmetric conjugate addition of arylboronic acids to unsaturated esters

An efficient rhodium/olefin-sulfoxide catalyzed asymmetric conjugate addition of organoboronic acids to various unsaturated esters has been developed, where 2-methoxy-1-naphthyl sulfinyl functionalized olefin ligands have been shown to be highly effective, and are especially applicable to unsaturated methyl esters with up to 99% yield and 91% ee.

Palladium‐Catalyzed Synthesis and Isolation of Functionalized Allylboronic Acids: Selective, Direct Allylboration of Ketones

Palladium‐Catalyzed Synthesis and Isolation of Functionalized Allylboronic Acids: Selective, Direct Allylboration of Ketones

Enantioselective Petasis reaction among salicylaldehydes, amines, and organoboronic acids catalyzed by BINOL

The catalytic enantioselective three-component Petasis reaction among salicylaldehydes, amines, and organoboronic acids has been developed with readily available chiral BINOL as catalyst. Various salicylaldehydes, secondary amines, and organoboronic acids were found to be suitable substrates for the reaction. A broad range of desired alkylaminophenol products were obtained in good yields (up to 87%) and moderate to good enantioselectivities (up to 86% ee).

Cobalt(II)‐Catalyzed 1,4‐Addition of Organoboronic Acids to Activated Alkenes: An Application to Highly cis‐Stereoselective Synthesis of Aminoindane Carboxylic Acid Derivatives

It all adds up: The 1,4-addition of organoboronic acids to activated alkenes catalyzed by [Co(dppe)Cl(2)] is described. A [3+2]-annulation reaction of ortho-iminoarylboronic acids with acrylates to give various aminoindane carboxylic acid derivatives with cis-stereoselectivity is also demonstrated (see scheme; dppe = 1,2-bis(diphenylphosphino)ethane).

Highly efficient recyclable polymer anchored palladium catalyst for C[sbnd]C and C[sbnd]N coupling reactions

An inexpensive, air-moisture stable and reusable PS–Pd(II)-furfural complex was synthesized by reacting polymeric amine with furfural to get polymer anchored ligand which was then reacted with Pd(OAc)2 to get polymer anchored complex. This complex was characterized by different spectroscopic and elemental analyses. The activities of the Pd-complex were tested for the CC and CN cross-coupling reactions under various reaction conditions. The catalyst exhibits high catalytic activities for the coupling of various aryl halides with organoboronic acid, alkene, alkyne and amine providing excellent yields of desired product. Further, the catalyst can be easily recovered by simple filtration and reused up to five times without significant loss of its catalytic activity.

Modular Synthesis of Phenanthridine Derivatives by Oxidative Cyclization of 2‐Isocyanobiphenyls with Organoboron Reagents

Where HAS you been? A manganese-mediated annulation of 2-isocyanobiaryls with organoboronic acids is developed for the synthesis of a broad range of phenanthridine derivatives. Mechanistic studies indicate that the reaction proceeds by the intramolecular homolytic aromatic substitution (HAS) of an imidoyl radical intermediate.

Glucose-Responsive Disassembly of Polymersomes of Sequence-Specific Boroxole-Containing Block Copolymers under Physiologically Relevant Conditions.

Polymers containing organoboronic acids have recently gained interest as sugar-responsive materials owing to the reversible binding of saccharides to boronic acids, which triggers a change in the physical and chemical properties of these polymers, such as their water solubility. In particular, the ability of these polymers to bind glucose has attracted considerable attention because of the promise of these materials for the development of sensors and drug delivery systems for glucose-related human diseases, such as diabetes. We report here a new class of sugar-responsive polymers that are based on a sequence-specific copolymer of styreneboroxole and N-functionalized maleimide. The reversible addition-fragmentation and chain transfer (RAFT) polymerization of this pair of monomers ensured that a glucose receptor alternates with a nonresponsive solubilizing group throughout the sugar-responsive polymer chain. Due to the presence of hydrophilic solubilizing groups beween the solubility-switching boroxole moieties in the membrane-forming block, the polymersomes of the block copolymers responded to a lower level of glucose in the medium, resulting in diassembly of the bilayer membrane under a physiologically relevant pH and glucose level.