Arylboron Reagents Research Articles

Ligand-Promoted Rh(III)-Catalyzed Coupling of Aryl C-H Bonds with Arylboron Reagents.

Rhodium(III)-catalyzed C-H arylation of arenes with phenylboronic acid pinacol esters has been achieved using a readily removable N-pentafluorophenylbenzamide directing group for the first time. The use of a bidentate phosphine ligand (Binap) significantly increased the yield of the cross-coupling of C-H bonds with organoboron reagents.

ChemInform Abstract: Ruthenium(II)‐Catalyzed C3 Arylation of 2‐Aroylbenzofurans with Arylboronic Acids/Aryltrifluoroborates via Carbonyl‐Directed C—H Bond Activation.

The Ru(II)-catalyzed carbonyl-directed C–H activation with (hetero)arylboron reagents has been executed for the synthesis of 2-aroyl-3-(hetero)arylbenzofurans. A hypothesis founded upon the involvement of an active carbonatoruthenium(II) complex for a coordinative insertion and the aerobic oxidation of the in situ generated Ru(0) to Ru(II), to continue the catalytic cycle, has been extended.

Asymmetric Conjugate Addition of Organoboron Reagents to Common Enones Using Copper Catalysts.

Copper complexes of phosphoramidites efficiently catalyzed asymmetric addition of arylboron reagents to acyclic enones. Importantly, rare 1,4-insertion of arylcopper(I) was identified which led directly to O-bound copper enolates. The new mechanism is fundamentally different from classical oxidative addition/reductive elimination of organocopper(I) on enones.

Oxidative Coupling of Aryl Boron Reagents with sp(3)-Carbon Nucleophiles: The Enolate Chan-Evans-Lam Reaction.

Reported is a versatile new oxidative method for the arylation of activated methylene species. Under mild reaction conditions (RT to 40 °C), Cu(OTf)2 mediates the selective coupling of functionalized aryl boron species with a variety of stabilized sp(3) -nucleophiles. Tertiary malonates and amido esters can be employed as substrates to generate quaternary centers. Complementing either traditional cross-coupling or SN Ar protocols, the transformation is chemoselective in the presence of halogen electrophiles, including aryl bromides and iodides. Substrates bearing amide, sulfonyl, and phosphonyl groups, which are not amenable to coupling under mild Hurtley-type conditions, are suitable reaction partners.

Oxidative Coupling of Aryl Boron Reagents with sp3‐Carbon Nucleophiles: The Enolate Chan–Evans–Lam Reaction

AbstractReported is a versatile new oxidative method for the arylation of activated methylene species. Under mild reaction conditions (RT to 40 °C), Cu(OTf)2 mediates the selective coupling of functionalized aryl boron species with a variety of stabilized sp3‐nucleophiles. Tertiary malonates and amido esters can be employed as substrates to generate quaternary centers. Complementing either traditional cross‐coupling or SNAr protocols, the transformation is chemoselective in the presence of halogen electrophiles, including aryl bromides and iodides. Substrates bearing amide, sulfonyl, and phosphonyl groups, which are not amenable to coupling under mild Hurtley‐type conditions, are suitable reaction partners.

Radiosynthesis of SPECT tracers via a copper mediated 123I iodination of (hetero)aryl boron reagents.

A general method for the copper mediated nucleophilic 123I-iodination of (hetero)aryl boronic esters and acids has been developed. The broad substrate scope of this radiosynthetic approach allows access to [123I]DPA-713, [123I]IMPY, [123I]MIBG and [123I]IPEB that are four commonly used SPECT radiotracers. Our results infer that aryl boronic reagents can now be employed as common precursors for both fluorine-18 and iodine-123 radiolabelling.

Nickel(ii)-catalyzed direct arylation of aryl C–H bonds with aryl-boron reagents directed by a removable bidentate auxiliary

Ni-catalyzed arylation of unactivated C(sp2)–H bonds with arylboron reagents using PIP as a removable directing group is described.

ChemInform Abstract: Asymmetric Synthesis of Triarylmethanes by Rhodium‐Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines.

AbstractThis novel reaction is assumed to proceed through o‐quinone methide intermediates, which undergo Rh‐catalyzed asymmetric 1,4‐addition of the arylboron reagents.

ChemInform Abstract: A Palladium‐Catalyzed Arylation of N‐Acyl‐N,O‐acetals with Arylboronic Reagents: Synthesis of Diarylmethylamines Protected by Easily Removable Acyl Group.

AbstractAttempts upon an asymmetric version of the reaction procedure based on the use of chiral ligands provides the products with low enantiomeric excess only.

Ruthenium(II)-Catalyzed C3 Arylation of 2-Aroylbenzofurans with Arylboronic Acids/Aryltrifluoroborates via Carbonyl-Directed C-H Bond Activation.

The Ru(II)-catalyzed carbonyl-directed C-H activation with (hetero)arylboron reagents has been executed for the synthesis of 2-aroyl-3-(hetero)arylbenzofurans. A hypothesis founded upon the involvement of an active carbonatoruthenium(II) complex for a coordinative insertion and the aerobic oxidation of the in situ generated Ru(0) to Ru(II), to continue the catalytic cycle, has been extended.

A palladium-catalyzed arylation of N-acyl-N,O-acetals with arylboronic reagents: synthesis of diarylmethylamines protected by easily removable acyl group

An efficient process was developed to synthesis diarylmethylamines protected by a readily removable acyl group using a palladium-catalyzed arylation of N-acyl-N,O-acetals with arylboronic reagents. The attractive features of this protocol are: the ease of preparing substrate and the mild reaction condition under an air atmosphere. Moderate enantioselectivity was observed in preliminary screening studies of chiral ligands.

Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines.

The reaction of racemic diarylmethylamines, (Ar(1)Ar(2)CHNR2), where Ar(1) is substituted with a 2-hydroxy group, with arylboroxines (Ar(3)BO)3 in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar(1)Ar(2)CH*Ar(3)) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through o-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents.

Rhodium-catalyzed cross-coupling of aryl carbamates with arylboron reagents

A new method has been developed for the rhodium-catalyzed cross-coupling of aryl carbamates with organoboron reagents. The use of an NHC ligand bearing a 2-adamantyl group, i.e., I(2-Ad), is essential to the success of the reaction. The reaction involves the rhodium-mediated activation of the relatively inert C(aryl)-O bond of aryl carbamates.

ChemInform Abstract: Synthesis of α,α‐Difluoromethylene Alkynes by Palladium‐Catalyzed gem‐Difluoropropargylation of Aryl and Alkenyl Boron Reagents.

AbstractThe Pd‐catalyzed coupling of difluoropropargyl bromides (I) and (IV) with arylboronic acids (II) is reported for the first time.

Towards Iron-Catalysed Suzuki Biaryl Cross-Coupling: Unusual Reactivity of 2-Halobenzyl Halides

The reaction of 2-halobenzyl halides with the borate anion Li[(Ph)( t -Bu)Bpin] leads not only to the expected arylation at the benzyl position, but also to some Suzuki biaryl cross-coupling. Preliminary mechanistic investigations hint towards the intermediacy of benzyl iron intermediates that can either: (a) directly cross-couple with the aryl boron reagent to give observed monoarylated species, or (b) undergo oxidative addition of the aryl halide to generate the diarylated species on reaction with the boron-based nucleophile.

ChemInform Abstract: Palladium‐Catalyzed Synthesis of Heterocycle‐Containing Diarylmethanes Through Suzuki—Miyaura Cross‐Coupling.

The heterocycle-containing diarylmethane synthesis from chloromethyl(hetero)arenes with (hetero)arylboron reagents was attained using the palladium/ether-imidazolium chloride system. This coupling process tolerated a diverse range of heteroaromatic moieties with sufficient catalytic activity to achieve the efficient synthesis of various diheteroarylmethanes in good to excellent yields.

Cu(OAc)2-catalyzed coupling of aromatic C-H bonds with arylboron reagents.

Cu-catalyzed coupling of aryl C-H bonds with arylboron reagents was accomplished using a readily removable directing group, which provides a useful method for the synthesis of biaryl compounds. The distinct transmetalation step in this Cu-catalyzed C-H coupling with aryl borons provides unique evidence for the formation of an aryl cupperate intermediate.

Biscarboxy-Functionalized Imidazole and Palladium as Highly Active Catalytic System in Protic Solvents: Methanol and Water

The coupling reaction between aryl bromides and boron reagents is efficiently catalyzed by an in situ generated palladium complex obtained from palladium(II) acetate (0.1 mol%) and 1,3-bis(carboxymethyl)imidazole (0.2 mol%). The catalytic system is very active in protic solvents, especially in methanol. Biaryl derivatives have been prepared in good isolated yields (up to >99%), and additionally styrene and stilbene derivatives have also been prepared by means of this protocol.

Synthesis of α,α‐Difluoromethylene Alkynes by Palladium‐Catalyzed gem‐Difluoropropargylation of Aryl and Alkenyl Boron Reagents

gem-Difluoropropargyl bromides are versatile intermediates in organic synthesis, but have rarely been employed in transition-metal-catalyzed cross-coupling reactions. The first palladium-catalyzed gem-difluoropropargylation of organoboron reagents with gem-difluoropropargyl bromides is now reported. The reaction proceeds under mild reaction conditions with high regioselectivity; it features a broad substrate scope and excellent functional-group compatibility and thus provides an attractive approach for the synthesis of complex fluorinated molecules, in particular for drug discovery and development.

Synthesis of α,α‐Difluoromethylene Alkynes by Palladium‐Catalyzed gem‐Difluoropropargylation of Aryl and Alkenyl Boron Reagents

Abstractgem‐Difluoropropargyl bromides are versatile intermediates in organic synthesis, but have rarely been employed in transition‐metal‐catalyzed cross‐coupling reactions. The first palladium‐catalyzed gem‐difluoropropargylation of organoboron reagents with gem‐difluoropropargyl bromides is now reported. The reaction proceeds under mild reaction conditions with high regioselectivity; it features a broad substrate scope and excellent functional‐group compatibility and thus provides an attractive approach for the synthesis of complex fluorinated molecules, in particular for drug discovery and development.