Synthesis of 3-Hydroxy-4-Substituted Picolinonitriles from 4-Propargylaminoisoxazoles via Stepwise and One-Pot Isoxazolopyridine Formation/N-O Bond Cleavage Sequence

Methylene Insertion into Nitrogen-Heteroatom Single Bonds of 1,2-Azoles via a Zinc Carbenoid: An Alternative Tool for Skeletal Editing

The nitrogen-heteroatom single bonds of 1,2-azoles and isoxazolines underwent methylene insertion in the presence of CH2 I2 (6 equiv.) and diethylzinc (3 equiv.) to produce a wide variety of the ring-expanded six-membered heterocycles. Density functional theory calculations suggest that the methylene insertion proceeds via cleavage of nitrogen-heteroatom single bonds followed by ring closure.

Photochemical Conversion of Isoxazoles to 5-Hydroxyimidazolines

Photochemical conversion of isoxazole I to 5-hydroxyimidazoline VII proceeded via the trapping of the photogenerated acylazirine III with amines under UV light irradiation. This is the first report of the efficient synthesis of 5-hydroxyimidazolines that are not readily accessible by other means. 5-Hydroxyimidazolines were also converted into multisubstituted imidazoles in one step by treatment with trifluoroacetic anhydride (TFAA) and 2,6-lutidine in dichloromethane.

Rhodium(iii)-catalysed carboxylate-directed C-H functionalizations of isoxazoles with alkynes

An efficient oxidative [4+2] annulation of isoxazolyl-4-carboxylic acids with internal alkynes proceeded in the presence of the [Cp*RhCl₂]₂ catalyst. Oxidants controlled the formation of pyranoisoxazolones and isoquinolines. A decarboxylative approach for the hydroarylation of alkynes with isoxazolyl-4-carboxylic acids was also developed in the presence of the [Cp*Rh(CH₃CN)₃][SbF₆]₂ catalyst.

An efficient light on–off one-pot method for the synthesis of 3-styryl coumarins from aryl alkynoates

An efficient one-pot stepwise method to synthesize 3-styryl-4-arylcoumarins from simple alkynoates is demonstrated.