Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki–Miyaura Reactions of Diarylmethyl Esters

Abstract

The synthesis of triarylmethanes via Pd-catalyzed Suzuki–Miyaura reactions between diarylmethyl 2,3,4,5,6-pentafluorobenzoates and aryl boronic acids is described. The system operates under mild conditions and has a broad substrate scope, including the coupling of diphenylmethanol derivatives that do not contain extended aromatic substituents. This is significant as these substrates, which result in the types of triarylmethane products that are prevalent in pharmaceuticals, have not previously been compatible with systems for diarylmethyl ester coupling. Furthermore, the reaction can be performed stereospecifically to generate stereoinverted products. On the basis of DFT calculations, it is proposed that the oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrate occurs via an SN2 pathway, which results in the inverted products. Mechanistic studies indicate that oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrates to (IPr)­Pd(0) results in the selective cleavage of the O–C­(benzyl) bond in part because of a stabilizing η3-interaction between the benzyl ligand and Pd. This is in contrast to previously described Pd-catalyzed Suzuki–Miyaura reactions involving phenyl esters, which involve selective cleavage of the C­(acyl)–O bond, because there is no stabilizing η3-interaction. It is anticipated that this fundamental knowledge will aid the development of new catalytic systems, which use esters as electrophiles in cross-coupling reactions.

Earth‐Abundant Recyclable Magnetic Iron Oxide Nanoparticles for Green‐light Mediated C−H Arylation in Heterogeneous Phase

“…The Supporting Information contains images of photochemical set up, complete experimental procedures, complete characterization of the iron oxide nanoparticles, compound characterization data including copies of NMR spectra, control experiments and other synthetic and technical details. The authors have cited additional references within the Supporting Information [30–55] …”

Palladium-Catalyzed Cross-Coupling Reaction of Diarylmethanol Derivatives with Diborylmethane

“…Traditionally, organic halides (C–X; X = I, Br, Cl) were employed as carbon electrophiles, but recent advances in transition metal catalysis and supporting ligands allow the readily available and stable but usually less reactive alcohol derivatives (C–O) to be adopted in the C–C bond-forming cross-coupling reaction . Among them, benzylic alcohol derivatives are relatively well studied as the reactive benzylic sp 3 carbon electrophiles by research groups of Kuwano, Jarvo, Watson, Fu, Fan/Yang, and Balcells/Hazari, and selective cross-coupling reactions with aryl organometallic reagents such as arylboranes, -tins, -zincs, and -magnesiums are possible under suitable Pd and Ni catalysis, giving di- and triarylmethane products (Scheme a). On the other hand, the application of alkyl metals still remains underdeveloped: only highly reactive dialkylzincs and alkylmagnesiums are successfully used in the presence of Ni catalysts, which was reported by Shi and co-workers and Jarvo and co-workers − (Scheme b).…”

Deoxygenative Hetero- and Carbofunctionalizations of Diarylketones

“…Substituted diarylmethanes are fascinating structural motifs frequently encountered in pharmaceuticals, photocatalysts, dyes, and natural products (Figure A) . Therefore, the development of efficient synthetic methods for substituted diarylmethanes is highly desirable. , In a recent method, palladium-catalyzed substitutions of diarylcarbonates have been reported (Figure B). − The action of a nucleophile on diarylmethylcarbonate in the presence of a palladium catalyst yielded a range of substituted diarylmethanes via a π-benzyl palladium complex with liberation of CO 2 . Kuwano discovered arylation of diarylmethylcarbonate with arylboronic acids .…”