A Mild and Highly Diastereoselective Preparation of N-Alkenyl-2-Pyridones via 2-Halopyridinium Salts and Aldehydes

Reaction of Isatin and 2-Chloropyridinium Salt: An Efficient and Diastereoselective Synthesis of α,β-Unsaturated Oxindoles

A new, mild, and diastereoselective method has been developed for the synthesis of β-pyridone-α,β-unsaturated oxindoles by the reaction of isatins and 2-chloropyridinium salts in EtOH at room temperature for 5 min. This method operates under mild reaction conditions, providing the product with a good yield and diastereoselectivity, and it exhibits excellent tolerance toward various functional groups. The predominant isomer is the Z isomer, which can convert to the E isomer in the presence of NaN3.

Gold(I)-catalyzed synthesis of N-alkenyl 2-pyridonyl sec-amines

N-Alkenyl 2-pyridonyl amines are afforded in high yields via a gold-catalyzed rearrangement of 2-propargyloxypyridine and 2-(but-3-yn-1-yloxy)pyridine under acidic conditions. This approach exhibits significant utility due to its outstanding efficiency of conversion in the synthesis of secondary amines as a one-pot reaction. The initial step of the method involves a cyclization reaction for the production of pyridinium salts, followed by the next stage, where rearrangement is accomplished through the nucleophilic addition phenomenon. This approach provides the conversion of primary amines into secondary amines, resulting in a single product. Furthermore, the methodology presents a high degree of tolerance towards several pyridine and aniline derivatives, resulting in the formation of products with excellent yields.

Rhodium-NHC-Catalyzed gem-Specific O-Selective Hydropyridonation of Terminal Alkynes

The dinuclear complex [Rh(μ-Cl)(η2 -coe)(IPr)]2 is an efficient catalyst for the O-selective Markovnikov-type addition of 2-pyridones to terminal alkynes. DFT calculations support a hydride-free pathway entailing intramolecular oxidative protonation of a π-alkyne by a κ1 N-hydroxypyridine ligand. Subsequent O-nucleophilic attack on a metallacyclopropene species affords an O-alkenyl-2-oxypyridine chelate rhodium intermediate as the catalyst resting state. The release of the alkenyl ether is calculated as the rate-determining step.