Water as an Electron Donor for Cross-Electrophile Coupling Reactions.

Cross-electrophile coupling (XEC) reactions are considered to be among the most fundamental construction of carbon-carbon bonds in organic chemistry. Traditionally, stoichiometric reductants, including metallic and organic reagents, are required to promote these conversions, resulting in significant waste that contributes to environmental pollution and increased disposal costs. In this study, we report a divided electrochemical synthesis-based cross-coupling platform in which HO is oxidized at the anode surface to generate electrons that produce a lower oxidation state nickel catalyst on the cathode surface, enabling XEC reactions without the need for metallic or organic reagents.

Redox-Neutral Carboxylation of Benzylic Tertiary C-H Bonds with Carbon Dioxide.

The direct catalytic carboxylation of benzylic tertiary C-H bonds with CO for the synthesis of all-carbon quaternary carboxylic acids represents a significant challenge. Here, we present a redox-neutral approach to address this difficulty by leveraging the synergistic interplay between photocatalysis and cascade hydrogen abstraction cycles. Remarkably, this strategy eliminates the need for sacrificial electron donors, electron acceptors, or stoichiometric additives, offering enhanced atom economy and environmental sustainability.

Regioselective Dearomative Amidoximation of Nonactivated Arenes Enabled by Photohomolytic Cleavage of N-nitrosamides.

Dearomative spirocyclization reactions represent a promising means to convert arenes into three-dimensional architectures; however, controlling the regioselectivity of radical dearomatization with nonactivated arenes to afford the spirocyclizative 1,2-difunctionalization other than its kinetically preferred 1,4-difunctionalization is exceptionally challenging. Here we disclose a novel strategy for dearomative 1,2- or 1,4-amidoximation of (hetero)arenes enabled by direct visible-light-induced homolysis of N-NO bonds of nitrosamides, giving rise to various highly regioselective amidoximated spirocycles that previously have been inaccessible or required elaborate synthetic efforts. The mechanism and origins of the observed regioselectivities were investigated by control experiments and density functional theory calculations.

Deconstructive Carboxylation of Activated Alkenes with Carbon Dioxide.

Carboxylation with carbon dioxide (CO ) represents one notable methodology to produce carboxylic acids. In contrast to carbon-heteroatom bonds, carbon-carbon bond cleavage for carboxylation with CO is far more challenging due to their inherent and less favorable orbital directionality for interacting with transition metals. Here we report a photocatalytic protocol for the deconstructive carboxylation of alkenes with CO to generate carboxylic acids in the absence of transition metals.

Synthesis of 4-Oxoisoxazoline N-Oxides via Pd-Catalyzed Cyclization of Propargylic Alcohols with tert-Butyl Nitrite.

A cyclization of propargylic alcohols with tert-butyl nitrite at room temperature in air was achieved using Pd(OAc) as catalyst. The first reported 4-oxoisoxazoline N-oxides could be directly accessed from a range of multisubstituted propargylic alcohols in moderate to excellent yields under mild conditions. Density functional theory calculations indicated that the reaction proceeds through a palladium-catalyzed NO addition that efficiently generates a ketoxime radical, which eventually produces 4-oxoisoxazoline N-oxide.

Preparation of Heterocycles via Visible-Light-Driven Aerobic Selenation of Olefins with Diselenides.

The aerobic dehydrogenative cyclization of alkenes with easily accessible diselenides facilitated by visible light is reported. Notably, the features of this transition-metal-free protocol are pronounced efficiency and practicality, good functional group tolerance, atom economy, and high sustainability, since ambient air and visible light are adequate for the clean construction of five- and six membered heterocycles in yields of up to 98%.