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Harnessing Alkylpyridinium Salts as Electrophiles in Deaminative Alkyl-Alkyl Cross-Couplings.

ABSTRACT: A Negishi cross-coupling of alkylpyridinium salts and alkylzinc halides has been developed. This is the first example of alkyl-alkyl bond formation via cross-coupling of an alkyl amine derivative with an unactivated alkyl group, and allows both primary and secondary alkylpyridinium salts to react with primary alkylzinc halides with high functional group tolerance. When combined with formation of the pyridinium salts from primary amines, this method enables the noncanonical transformation of NH2 groups into a wide range of alkyl substituents with broad functional group tolerance.

PROVIDER: S-EPMC6434706 | BioStudies |

REPOSITORIES: biostudies

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Engaging Alkenes and Alkynes in Deaminative Alkyl-Alkyl and Alkyl-Vinyl Cross-Couplings of Alkylpyridinium Salts.

Project description:An alkyl-alkyl cross-coupling of Katritzky alkylpyridinium salts and organoboranes, formed in situ via hydroboration of alkenes, has been developed. This method utilizes the abundance of both alkyl amine precursors and alkenes to form C(sp3)-C(sp3) bonds. This strategy is also effective with alkynes, enabling a C(sp3)-C(sp2) cross-coupling. Under these mild conditions, a broad range of functional groups, including protic groups, is tolerated. As seen with previous alkylpyridinium cross-couplings, mechanistic studies support an alkyl radical intermediate.

| S-EPMC6933946 | BioStudies

Deaminative Reductive Cross-Electrophile Couplings of Alkylpyridinium Salts and Aryl Bromides.

Project description:A nickel-catalyzed reductive cross-coupling of alkylpyridinium salts and aryl bromides has been developed using Mn as the reductant. Both primary and secondary alkylpyridinium salts can be used, and high functional group and heterocycle tolerance is observed, including for protic groups. Mechanistic studies indicate the formation of an alkyl radical, and controlling its fate was key to the success of this reaction.

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Nickel-catalyzed deaminative Sonogashira coupling of alkylpyridinium salts enabled by NN<sub>2</sub> pincer ligand.

Project description:Alkynes are amongst the most valuable functional groups in organic chemistry and widely used in chemical biology, pharmacy, and materials science. However, the preparation of alkyl-substituted alkynes still remains elusive. Here, we show a nickel-catalyzed deaminative Sonogashira coupling of alkylpyridinium salts. Key to the success of this coupling is the development of an easily accessible and bench-stable amide-type pincer ligand. This ligand allows naturally abundant alkyl amines as alkylating agents in Sonogashira reactions, and produces diverse alkynes in excellent yields under mild conditions. Salient merits of this chemistry include broad substrate scope and functional group tolerance, gram-scale synthesis, one-pot transformation, versatile late-stage derivatizations as well as the use of inexpensive pre-catalyst and readily available substrates. The high efficiency and strong practicability bode well for the widespread applications of this strategy in constructing functional molecules, materials, and fine chemicals.

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Deaminative Arylation of Amino Acid-derived Pyridinium Salts.

Project description:A Suzuki-Miyaura cross-coupling of ?-pyridinium esters and arylboroxines has been developed. Combined with formation of the pyridinium salts from amino acid derivatives, this method enables amino acid derivatives to be efficiently transformed into ?-aryl esters and amides. Under the mild conditions, broad functional group tolerance on both the amino acid derivatives and the arylboroxine are observed, including protic functional groups. Mechanistic studies support an alkyl radical intermediate, similar to other cross-couplings of alkylpyridinium salts.

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Ni-catalyzed deaminative cross-electrophile coupling of Katritzky salts with halides via C?N bond activation.

Project description:The reductive cross-coupling of sp3-hybridized carbon centers represents great synthetic values and insurmountable challenges. In this work, we report a nickel-catalyzed deaminative cross-electrophile coupling reaction to construct C(sp)?C(sp3), C(sp2)?C(sp3), and C(sp3)?C(sp3) bonds. A wide range of coupling partners including aryl iodides, bromoalkynes, or alkyl bromides are stitched with alkylpyridinium salts that derived from the corresponding primary amines. The advantages of this methodology are showcased in the two-step synthesis of the key lactonic moiety of (+)-compactin and (+)-mevinolin. The one-pot procedure without isolation of alkylpyridinium tetrafluoroborate salt is also proven to be successful. This cross-coupling strategy of two electrophiles provides a highly valuable vista for the convenient installation of alkyl substituents and late functionalizations of sp3 carbons.

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Harnessing Alkyl Amines as Electrophiles for Nickel-Catalyzed Cross Couplings via C-N Bond Activation.

Project description:We developed a strategy to harness alkyl amines as alkylating agents via C-N bond activation. This Suzuki-Miyaura cross coupling of alkylpyridinium salts, readily formed from primary amines, is the first example of a metal-catalyzed cross coupling via C-N bond activation of an amine with an unactivated alkyl group. This reaction enjoys broad scope and functional group tolerance. Primary and secondary alkyl groups can be installed. Preliminary studies suggest a NiI/NiIII catalytic cycle.

| S-EPMC5480296 | BioStudies

Nickel-Catalyzed Alkyl-Alkyl Cross-Couplings of Fluorinated Secondary Electrophiles: A General Approach to the Synthesis of Compounds having a Perfluoroalkyl Substituent.

Project description:Fluorinated organic molecules are of interest in fields ranging from medicinal chemistry to polymer science. Described herein is a mild, convenient, and versatile method for the synthesis of compounds bearing a perfluoroalkyl group attached to a tertiary carbon atom by using an alkyl-alkyl cross-coupling. A nickel catalyst derived from NiCl2 ?glyme and a pybox ligand achieves the coupling of a wide range of fluorinated alkyl halides with alkylzinc reagents at room temperature. A broad array of functional groups is compatible with the reaction conditions, and highly selective couplings can be achieved on the basis of differing levels of fluorination. A mechanistic investigation has established that the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) inhibits cross-coupling under these conditions and that a TEMPO-electrophile adduct can be isolated.

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Alkyl-(Hetero)Aryl Bond Formation via Decarboxylative Cross-Coupling: A Systematic Analysis.

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| S-EPMC5792188 | BioStudies

Enantioconvergent Cross-Couplings of Alkyl Electrophiles: The Catalytic Asymmetric Synthesis of Organosilanes.

Project description:Metal-catalyzed enantioconvergent cross-coupling reactions of alkyl electrophiles are emerging as a powerful tool in asymmetric synthesis. To date, high enantioselectivity has been limited to couplings of electrophiles that bear a directing group or a proximal p/? orbital. Herein, we demonstrate for the first time that enantioconvergent cross-couplings can be achieved with electrophiles that lack such features; specifically, we establish that a chiral nickel catalyst can accomplish Negishi reactions of racemic ?-halosilanes with alkylzinc reagents with good enantioselectivity under simple and mild conditions, thereby providing access to enantioenriched organosilanes, an important class of target molecules.

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Highly selective palladium-catalyzed cross-coupling of secondary alkylzinc reagents with heteroaryl halides.

Project description:The highly selective palladium-catalyzed Negishi coupling of secondary alkylzinc reagents with heteroaryl halides is described. The development of a series of biarylphosphine ligands has led to the identification of an improved catalyst for the coupling of electron-deficient heterocyclic substrates. Preparation and characterization of oxidative addition complex (L)(Ar)PdBr provided insight into the unique reactivity of catalysts based on CPhos-type ligands in facilitating challenging reductive elimination processes.

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