Search

The development of site‐selective functionalization of N‐heteroarenes is highly desirable in streamlined synthesis. In this context, direct amination of pyridines stands as an important synthetic methodology, with particular emphasis on accessing 4‐aminopyridines, a versatile pharmacophore in medicinal chemistry. Herein, we report a reaction manifold for the C4‐selective amination of pyridines by employing nucleophilic substitution of hydrogen (SNH). Through 4‐pyridyl pyridinium salt intermediates, 4‐aminopyridine products are obtained in reaction with aqueous ammonia without intermediate isolation. The notable regioselectivity was achieved by the electronic tuning of the external pyridine reagents along with the maximization of polarizability in the proton elimination stage. Further mechanistic investigations provided a guiding principle for the selective C−H pyridination of additional N‐heteroarenes, presenting a strategic avenue for installation of diverse functional groups. [ABSTRACT FROM AUTHOR]

Herein, the selective ortho‐ and meta‐C−H bond borylation of NH‐aryl sulfoximines is reported. Regioselectivity is achieved by the choice of commercially available ligands giving fast excess to valuable borylated aryl sulfoximine building blogs. The utility of the borylated products is demonstrated for the formation of C−O, C−C, C−N, C−D, and C−I bonds. [ABSTRACT FROM AUTHOR]

Mechanochemical approaches are widely used for the efficient, solvent‐free synthesis of organic molecules, however their applicability to the synthesis of functional polymers has remained underexplored. Herein, we demonstrate for the first time that mechanochemically triggered free‐radical polymerization allows solvent‐ and initiator‐free syntheses of structurally and morphologically well‐defined complex functional macromolecular architectures, namely stimuliresponsive microgels. The developed mechanochemical polymerization approach is applicable to a variety of monomers and allows synthesizing microgels with tunable chemical structure, variable size, controlled number of crosslinks and reactive functional end‐groups. [ABSTRACT FROM AUTHOR]

A mechanochemical synthesis of diarylethynes from aryl iodides and calcium carbide as acetylene source is reported. The reaction is catalyzed by a palladium catalyst in the presence of copper salt, base, and ethanol as liquid assisting grinding (LAG) additive. Various aryl and heteroaryl iodides have been converted in up to excellent yields. [ABSTRACT FROM AUTHOR]

A mechanochemical synthesis of diarylethynes from aryl iodides and calcium carbide as acetylene source is reported. The reaction is catalyzed by a palladium catalyst in the presence of copper salt, base, and ethanol as liquid assisting grinding (LAG) additive. Various aryl and heteroaryl iodides have been converted in up to excellent yields. [ABSTRACT FROM AUTHOR]

Cyclizations of N H- S -(2-hydroxyaryl)sulfoximines with 1,1'-carbonyldiimidazol (CDI) give unprecedented benzo[ e ][1,4,3]oxathiazin-3-one 1-oxides in good yields. The standard synthetic protocol involves the use of DCE at an increased temperature for 16 h. Under mechanochemical conditions, a representative product was obtained without a solvent at ambient temperature in only 60 min. X-ray single-crystal structure analysis confirmed the molecular scaffold representing a three-dimensional heterocycle.

Esters and amides were mechanochemically prepared by palladium-catalyzed carbonylative reactions of aryl iodides by using molybdenum hexacarbonyl as a convenient solid carbonyl source and avoiding a direct handling of gaseous carbon monoxide. Real-time monitoring of the mechanochemical reaction by in situ pressure sensing revealed that CO is rapidly transferred from Mo(CO) 6 to the active catalytic system without significant release of molecular carbon monoxide., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO) 2 Br[HN(C 2 H 4 P i Pr 2 ) 2 ]] 1 ([HN(C 2 H 4 P i Pr 2 ) 2 ]=MACHO- i Pr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to "biohybrid" molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal-ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C-C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)