Palladium‐Catalyzed Oxidative C≡C Triple Bond Cleavage of 2‐Alkynyl Carbonyl Compounds Toward 1, 2‐Dicarbonyl Compounds †

1O2 Mediated Conversion of β-Enaminonitriles to α-Keto Amides Photosensitized by Recyclable H2TPP in Visible Light

We report a one-step approach for the conversion of β-enaminonitriles to synthetically versatile α-keto amides in moderate to high yields under visible light irradiation photosensitized by porphyrins. The method is mild, cost-effective, and sustainable and requires air as the sole reagent/oxidant. The reaction is believed to proceed via an ene-type pathway initiated by 1O2, followed by dehydration, imine hydrolysis, and subsequent nucleophilic substitution of the cyanide group by amine. The method offers a broad substrate scope and has also been extended for synthesis of α-keto esters with aliphatic alcohols as nucleophiles. The porphyrin recovered after the reaction can be reused multiple times.

Photoredox and Copper Dual-Catalyzed Cyclization of Alkyne-tethered α-Bromocarbonyls

The synergistic systems of photoredox and copper catalyst have already appeared as a novel formation of green synthetic chemistry, which open new avenues for chemical synthesis applications. We describe a novel strategy for the cyclization of alkyne-tethered α-bromocarbonyls initiated by the cleavage of C(sp3 )-Br bond via the collaboration of photoredox and copper catalyst. The present protocol exhibits mildness using economical copper catalyst and visible-light at room temperature. The gram-scale and sunlight irradiation experiments proceeded smoothly to show the practicality of the methodology. It is notable that the newly generated oxygen in the product originates from H2 O.

Copper-Catalyzed Regioselective Iodoformylation of Terminal Alkynes to Access Versatile Electrophiles (E)-β-Iodo-α,β-Unsaturated Aldehydes

Herein, we describe a method for synthesizing (E)-β-iodo-α,β-unsaturated aldehydes via the iodoformylation of terminal alkynes with TMSCF₃ and NaI. This synthetic method uses inexpensive and easy-to-handle chemical feedstocks and employs a commercially available CuI catalyst. It can transform a broad range of terminal alkynes into bis-electrophile (E)-β-iodo-α,β-unsaturated aldehydes with excellent chemoselectivity, regioselectivity, and stereoselectivity. Moreover, it was demonstrated that this protocol has abundant organic reactivity.

Copper-catalyzed switchable cyclization of alkyne-tethered α-bromocarbonyls: selective access to quinolin-2-ones and quinoline-2,4-diones

Copper-catalyzed cyclization of alkynes has played a significant role in modern catalytic chemistry.

Palladium-Catalyzed Cascade Carbonylation to α,β-Unsaturated Piperidones via Selective Cleavage of Carbon-Carbon Triple Bonds

A direct and selective synthesis of α,β-unsaturated piperidones by a new palladium-catalyzed cascade carbonylation is described. In the presented protocol, easily available propargylic alcohols react with aliphatic amines to provide a broad variety of interesting heterocycles. Key to the success of this transformation is a remarkable catalytic cleavage of the present carbon-carbon triple bond by using a specific catalyst with 2-diphenylphosphinopyridine as ligand and appropriate reaction conditions. Mechanistic studies and control experiments revealed branched unsaturated acid 11 as crucial intermediate.

CuII-Catalyzed Coupling with Two Ynone Units by Selective Triple and Sigma C-C and C-H Bond Cleavages

We report a new copper-catalyzed [2 + 2 + 1] annulation process through the selective cleavage of sigma and triple C-C and C-H bonds using two ynone units. This new methodology involves breaking multiple chemical bonds in a single operation, including C≡C, C-C, C-H, and N-O. These high-value adducts lead to a diverse collection of synthetically challenging trisubstituted indolizines by the simultaneous engagement of different bond-breaking events and show excellent fluorescence in green aqueous solutions.