Chiral Spirophosphoric-Acid-Catalyzed Divergent Vinylogous Mannich and aza-Friedel-Crafts Reactions of 2-Methoxyfuran.

The first enantioselective vinylogous Mannich reaction is developed using 2-methoxyfuran under chiral spirophosphoric acid catalysis. The strategy involves 4-isoxazoline derivatives as cyclic ketimine surrogates and provides γ-butenolide scaffolds (up to 97% ee and >20:1 dr). The mechanistic investigations suggest that an in situ generated water molecule plays a crucial role in delivering γ-butenolide, while the use of molecular sieves delivers aza-Friedel-Crafts products. The synthetic utility of γ-butenolide is shown toward obtaining piperidone skeleton via a lactone-lactam rearrangement.

Synthetic Transformations Using Molecular Oxygen-Doped Carbon Materials.

Carbon materials like activated carbon (AC) undergo chemisorption with O2 to give species with electron deficiency in the carbon skeleton and negative charge at the oxygen end that upon reaction with PPh3 and benzoic acid afford Ph3P═O. Whereas amine donors react with O2-chemisorbed AC and nucleophiles to give dehydrogenatively coupled products in 67-89% yields via the corresponding radical cation and iminium ion intermediates, the reactions using ß-naphthoxide derivatives give the corresponding oxidatively coupled bi-2-naphthol products in 68-95% yields.