A decarboxylativeintramolecularaziridination reaction of alkene‐tethered 4H‐isoxazol‐5‐ones with a palladium/phosphine catalyst gave 1‐azabicyclo[3.1.0]hex‐2‐enes in moderate to high yields (see scheme; dba=dibenzylideneacetone). The resulting N‐fused bicyclic aziridines readily reacted with various reagents to afford ring‐opening pyrroline derivatives.
A phosphine‐free iridium‐catalyzed reaction of isoxazol‐5(4H)‐ones (isoxazolones) has been developed, and affords 2H‐azirines through decarboxylation and ring contraction. This method provides an efficient and environmentally benign protocol which could replace the conventional approaches used to synthesize 2H‐azirines.
2H-Azirines are synthetically versatile, highly strained, three-membered heterocycles containing an imino double bond. We report their efficient Ru-catalyzed synthesis using low catalyst loadings under neutral conditions from isoxazolinone substrates, which are readily accessible from β-ketoesters. The azirines were shown to be efficient precursors for functionalized pyridine, indole, dihydropyrrole
Isoxazol-5(4H)-ones were used as nitrene precursors for the selective formation of trisubstituted pyrroles by applying a palladium-catalyzed decarboxylative ring-reconstruction method. The use of bulky biaryl-type monophosphine ligands was effective for improving the selectivity. Deuterium-labeling experiments suggested a mechanism involving beta-hydride elimination followed by reductive elimination from an aza-pi-allyl intermediate.