220446-01-5Relevant academic research and scientific papers
Generation and trapping of N-acyliminium ions derived from isomunchnone cycloadducts. A versatile route to functionalized heterocycles
Brodney, Michael A.,Padwa, Albert
, p. 556 - 565 (2007/10/03)
A series of 2-diazo-N-hept-6-enoylmalonamides were prepared and treated with a catalytic amount of rhodium(II) perfluorobutyrate. The resultant carbenoids underwent facile cyclization onto the neighboring amide carbonyl oxygen atom to generate isomunchnone-type intermediates. Subsequent 1,3- dipolar cycloaddition across the pendant olefin afforded intramolecular cycloadducts in high yield. The cascade sequence is simple, direct, and extremely tolerant of structural diversity. Exposure of these cycloadducts to Lewis acids resulted in oxabicyclic ring opening. N-Acyliminium ions of wide structural variety can be easily generated by this sequence of reactions. Different cyclization pathways become available depending on the nature of the substituent group attached to the amide nitrogen. When the tethered group is electrophilic in nature, proton loss from the initially formed N- acyliminium ion occurs rapidly to give an acyl enamide which undergoes a subsequent cyclization at the electrophilic center.
