Visible light-induced palladium-catalyzed ring opening β-H elimination and addition of cyclobutanone oxime esters.

A palladium catalyst under visible light irradiation activates cyclobutanone oxime ester through single electron transfer to induce radical ring opening to generate hybrid cyanoalkyl Pd(i) radical species. Hybrid cyanoalkyl Pd(i) radical species can undergo either β-H elimination to deliver (E)-4-arylbut-3-enenitrile or undergo radical addition with silyl enol ether and enamide to generate δ-cyano ketones. A dual ligand system composed of two phosphine ligands is essential for the high reactivity.

Irradiation-Induced Palladium-Catalyzed Decarboxylative Heck Reaction of Aliphatic N-(Acyloxy)phthalimides at Room Temperature.

It is reported that Pd(PPh)Cl in combination with 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) under irradiation of blue LEDs efficiently catalyzes a decarboxylative Heck reaction of vinyl arenes and vinyl heteroarenes with aliphatic N-(acyloxy)phthalimides at room temperature. A broad scope of secondary, tertiary, and quaternary carboxylates, including α-amino acid derived esters, can be applied as amenable substrates with high stereoselectivity. The experimental observation was explained by excitation-state reactivity of the palladium complex under irradiation to induce single-electron transfer to activate N-(acyloxy)phthalimides, and to suppress undesired β-hydride elimination of alkyl palladium intermediates.

Irradiation-Induced Heck Reaction of Unactivated Alkyl Halides at Room Temperature.

The palladium-catalyzed Mizoroki-Heck reaction is arguably one of the most significant carbon-carbon bond-construction reactions to be discovered in the last 50 years, with a tremendous number of applications in the production of chemicals. This Nobel-Prize-winning transformation has yet to overcome the obstacle of its general application in a range of alkyl electrophiles, especially tertiary alkyl halides that possess eliminable β-hydrogen atoms. Whereas most palladium-catalyzed cross-coupling reactions utilize the ground-state reactivity of palladium complexes under thermal conditions and generally apply a single ligand system, we report that the palladium-catalyzed Heck reaction proceeds smoothly at room temperature with a variety of tertiary, secondary, and primary alkyl bromides upon irradiation with blue light-emitting diodes in the presence of a dual phosphine ligand system.

Decarboxylative 1,4-Addition of α-Oxocarboxylic Acids with Michael Acceptors Enabled by Photoredox Catalysis.

Enabled by iridium photoredox catalysis, 2-oxo-2-(hetero)arylacetic acids were decarboxylatively added to various Michael acceptors including α,β-unsaturated ester, ketone, amide, aldehyde, nitrile, and sulfone at room temperature. The reaction presents a new type of acyl Michael addition using stable and easily accessible carboxylic acid to formally generate acyl anion through photoredox-catalyzed radical decarboxylation.

Copper-Catalyzed Cross-Coupling Reaction of Allyl Boron Ester with 1°/2°/3°-Halogenated Alkanes.

The cross-coupling reaction of allyl boron ester with 1°/2°/3°-halogenated alkanes in the presence of copper has been developed for the first time, which provides a mild and efficient method for the construction of saturated C(sp(3))-C(sp(3)) bonds. This protocol shows excellent compatibility with the nonactivated primary, secondary, and even tertiary halogenated alkanes under mild conditions.

AIBN-catalyzed oxidative cleavage of gem-disubstituted alkenes with O2 as an oxidant.

A 2,2-azobis(isobutyronitrile) (AIBN) catalyzed oxidative cleavage of gem-disubstituted alkenes with molecular oxygen as the oxidant has been described. Carbonyl compounds were obtained as the desired products in high yield under mild conditions. Based on previous documents and current experimental results, a relatively reasonable mechanism is proposed.