James Sanderson

This work emphasizes the synthesis of substituted vinyl arenes by reductive coupling of aryl halides with vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of aryl halides, including heteroaromatics, and vinyl bromides were employed to yielding products in moderate to excellent yields with high functional-group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp²)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.

Down the path: A nickel-catalyzed reductive cross-electrophile coupling method between aryl halides and vinyl bromides was developed, thus leading to facile construction of vinyl arenes with good to excellent chemoselectivity. The catalytic system displays good chemoselectivity between the two C(sp²)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.

A double intramolecular 5-endo-dig cyclization of butyl[2-(phenylbuta-1,3-diynyl)phenyl]chalcogens has been employed in a selective preparation of benzo[b]chalcogenopheno[2,3-d]furans. Several reaction parameters were studied to determine the best reaction conditions and we observed that the reaction of butyl[2-(phenylbuta-1,3-diynyl)phenyl]chalcogens (0.25 mmol) with iron(III) chloride hexahydrate (2.0 equiv.) and diorganyl diselenides (1.75 equiv.) at reflux of dichloromethane was the most appropriate to give the products in 35–89% yields. These standard reaction conditions were compatible with many functional groups in the substrates, such as methyl, chlorine, fluorine, methoxy and heteroaryl. This protocol was also efficient for diorganyl diselenides but it was ineffective with diorganyl disulfides and ditellurides. In a competition among selenium, sulfur and oxygen nucleophiles we observed that the nucleophilicity and steric effects of the competing functional groups were determinant factors for the selectivity of the cyclization. The benzo[b]chalcogenopheno[2,3-d]furans had absorptions in the UV region (300–350 nm range) with molar absorptivity coefficient values ascribed to spin and symmetry allowed π–π* electronic transitions. An emission located in the purple region (380–440 nm range), with a Stokes shift of between 65–100 nm, is probably associated to the charge transfer character of the excited state.

The conversion of commercially available anilines into biaryl and biarylacetylene products was realized by using a telescoped, three-reactor flow diazotization/iododediazotization/cross-coupling process. The segmented flow stream created by off-gassing during the Sandmeyer sequence was restored to a continuous column of reaction solution by using a specially designed continuous-flow unit controlled by custom software created in-house. The resultant aryl iodide was then combined with a stream of cross-coupling solution that fed into the final reactor. The system proved versatile as modifications to the diazotization/iododediazotization sequence could be made rapidly to account for any substrate specificity (e.g., solubility problems), leading to a wide substrate scope of Suzuki–Miyaura and Sonogashira cross-coupled products.

Coupling under continuous flow: A versatile, high-yielding, flow process for the conversion of a wide variety of commercially available anilines into biaryl and biarylacetylene products is described. The system proved versatile as modifications to the diazotization/iododediazotization sequence could be made rapidly to account for any substrate specificity (e.g., solubility problems), leading to a wide substrate scope of Suzuki–Miyaura and Sonogashira cross-coupled products.

A combination of nickel and photoredox catalysts promoted novel cross-coupling reactions of aryl halides with 4-alkyl-1,4-dihydropyridines. 4-Alkyl-1,4-dihydropyridines act as formal nucleophilic alkylation reagents through a photoredox-catalyzed carbon–carbon (C−C) bond-cleavage process. The present strategy provides an alternative to classical carbon-centered nucleophiles, such as organometallic reagents.

Out with the old, in with the new: As an alternative to classical carbon-centered nucleophiles, such as organometallic reagents, 4-alkyl-1,4-dihydropyridines were used in cross-coupling reactions with aryl halides in the presence of a nickel and a photoredox catalyst. These formal nucleophilic alkylation reagents were activated by photoredox-catalyzed C−C bond cleavage (see scheme).