Direct Conversion of Carboxylic Acids to Alkyl Ketones

An efficient and mild method for acyl–C_sp3 bond formation based on the direct conversion of carboxylic acids has been established. This protocol is enabled by the synergistic, Ir-photoredox/nickel catalytic cross-coupling of in situ activated carboxylic acids and alkyltrifluoroborates. This versatile method is amenable to the cross-coupling of structurally diverse carboxylic acids with various potassium alkyltrifluoroborates, affording the corresponding ketones with high yields. In this operationally simple cross-coupling protocol, aliphatic ketones are obtained in one step from bench stable, readily available carboxylic acids

Synergistic Photoredox/Nickel Coupling of Acyl Chlorides with Secondary Alkyltrifluoroborates: Dialkyl Ketone Synthesis

Visible light photoredox/nickel dual catalysis has been employed in the cross-coupling of acyl chlorides with potassium alkyltrifluoroborates. This protocol, based on single-electron-mediated alkyl transfer, circumvents the restriction of using reactive alkylmetallic nucleophiles in transition-metal-catalyzed acylation and achieves a mild and efficient method for the synthesis of unsymmetrical alkyl ketones. In this approach, a variety of acyl chlorides have been successfully coupled with structurally diverse potassium alkyltrifluoroborates, generating the corresponding ketones with good yields

Toward Efficient Nucleophilic Azaborine Building Blocks for the Synthesis of B–N Naphthyl (Hetero)arylmethane Isosteres

To develop a method for the synthesis of a class of azaborines, potassium 2-(trifluoroboratomethyl)-2,1-borazaronaphthalenes have been synthesized to serve as nucleophilic building blocks. In palladium-catalyzed cross-coupling reactions with (hetero)­aryl chlorides they serve to produce a variety of pseudobenzylic (hetero)­aryl substituted azaborines. Potassium 2-(trifluoroboratomethyl)-2,1-borazaronaphthalenes are crystalline solids that are more stable than 2-(chloromethyl)-2,1-borazaronaphthalenes and have a broader substrate scope in cross-coupling reactions compared to their pseudobenzylic chloride counterparts

Visible Light Photoredox Cross-Coupling of Acyl Chlorides with Potassium Alkoxy­methyl­trifluoro­borates: Synthesis of α‑Alkoxyketones

A visible-light, single-electron-transfer (SET), photoredox cross-coupling for the synthesis of α-alkoxyketones has been developed. In this method, various aliphatic and aromatic acyl chlorides were successfully coupled with structurally diverse potassium alkoxy­methyl­trifluoro­borates, producing the corresponding α-alkoxyketones with high yields. In this operationally simple and mild cross-coupling protocol, the desired ketones are obtained in one step from bench stable starting materials by a bond connection that is unique to both alkylboron chemistry and photoredox/Ni catalysis

Single-Electron Transmetalation: Photoredox/Nickel Dual Catalytic Cross-Coupling of Secondary Alkyl β‑Trifluoro­borato­ketones and -esters with Aryl Bromides

The first cross-coupling of secondary alkyl β-trifluoro­borato­ketones and -esters has been achieved through application of photoredox/nickel dual catalysis. Although the related β-trifluoro­borato­amides have been effectively cross-coupled via Pd-catalysis, the corresponding ketones and esters had proven recalcitrant prior to this report. Reactions occur under mild conditions, and a variety of functional groups and sterically and electronically diverse reaction partners are tolerated

Accessing an Azaborine Building Block: Synthesis and Substitution Reactions of 2‑Chloro­methyl-2,1-borazaro­naph­thalene

One major synthetic route to the synthesis of benzyl amines, ethers, and esters is the nucleophilic substitution of a benzylic halide. To develop a method for the facile synthesis and functionalization of the isosteric azaborines, 2-chloro­methyl-2,1-borazaro­naph­thalene has been synthesized in one step to afford a similar common precursor to a benzylic halide. This B–N isostere has been shown to be an effective building block by serving as an electrophile in substitution reactions with a large variety of nucleophiles

Accessing 2‑(Hetero)arylmethyl‑, -allyl‑, and -propargyl-2,1-borazaronaphthalenes: Palladium-Catalyzed Cross-Couplings of 2‑(Chloromethyl)-2,1-borazaronaphthalenes

The synthesis of 2-(chloromethyl)-2,1-borazaronaphthalene has provided an opportunity to expand dramatically the functionalization of the azaborines. This azaborinyl building block can serve as the electrophile in palladium-catalyzed cross-coupling reactions to form sp³–sp and sp³–sp² bonds. The cross-coupling reactions of 2-(chloromethyl)-2,1-borazaronaphthalene with potassium (hetero)­aryl- and alkenyltrifluoroborates as well as terminal alkynes provides access to a variety of novel azaborines, allowing a library of pseudobenzylic substituted azaborines to be prepared from one common starting material