Visible-Light-Induced Acylative Coupling of Benzoic Acid Derivatives with Alkenes to Dihydrochalcones

Anti-Markovnikov Hydroacylation of Aryl Alkenes with Aldehydes Enabled by Photo/Cobalt Dual Catalysis

Herein we describe a dual photo/cobalt-catalyzed anti-Markovnikov hydroacylation of aryl alkenes using aldehyde as acyl source. The key to success is the cobalt catalyzed hydrogen atom transfer, which enables effective formation of the desired products and efficient regeneration of the photocatalyst under mild conditions. This protocol features broad substrate scopes, good functional group tolerance, high efficiency and regioselectivity.

Photoredox-Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

Despite the preliminary success of transition metal-catalyzed [3+2] annulation of amides with olefins, the corresponding radical-type [3+2] annulation remains a laborious challenge. Herein we report the first photoredox-catalyzed radical-type [3+2] annulation of aromatic amides with olefins. We established an approach to generate unprecedented iminium radicals by reducing the oxyiminium intermediates, formed in situ from corresponding amides with Tf2O, via photoredox catalysis. The [3+2] annulation was achieved via stepwise radical process, instead of forming linear products via other pathways as previously reported. This annulation protocol exhibits excellent functional group tolerance, and a diversity of substrates are united under the photoredox conditions, affording iminium products that can be in situ diversified into 1-indanones, enamines and amines. Mechanistic investigations indicate reduction of the oxyiminium intermediate to the iminium radicals by excited-state of the photocatalyst initiates the catalytic cycle.

Organocatalyzed Hydroacylation of Enones by Photosensitization of Acyl Silanes

A mild protocol for hydroacylation of enones through photosensitization of acyl silanes with thioxanthone under blue light (455 nm) irradiation is reported. A Brønsted acid is used as a cocatalyst in the reaction. The versatility of the method is demonstrated through inter- and intramolecular hydroacylation reaction. The hydroacylation product is applied for synthesizing an anti-HCV agent. Mechanistic insights are also provided through control experiments.

Photoredox Catalytic Phosphine-Mediated Deoxygenative Hydroacylation of Azobenzenes with Carboxylic Acids

The convenient and precise preparation of N,N'-diarylhydrazides, especially from readily available raw materials, remains highly challenging. Here, a photoredox catalytic phosphine-mediated deoxygenative hydroacylation of azobenzenes with abundant and readily available carboxylic acids has been developed. With Ir[dF(CF3)ppy]2(dtbbpy)PF6 as the photocatalyst, the reactions proceeded smoothly in the presence of PPh3 under visible light irradiation, delivering various N,N'-diarylhydrazides in up to 92% yields. Mechanistic studies revealed that the reaction proceeds via photoredox catalysis and phosphoranyl-radical-mediated C-O bond cleavage of carboxylic acids.

Visible Light-Induced Hydroacylation of Benzylidenemalononitriles with Aroyl Chlorides Using Silane as a Hydrogen Donor

A novel photoredox-catalyzed direct hydroacylation of benzylidenemalononitriles is described. In this method, aroyl chlorides are employed as a readily available and affordable source of acyl groups, while commercially available tris(trimethylsilyl)silane acts as both the hydrogen atom donor and electron donor. By eliminating the requirement for complex synthesis of acyl precursors and hydrogen atom-transfer (HAT) reagents, this approach offers a convenient and efficient strategy for the hydroacylation of benzylidenemalononitriles.