Novel base-induced reactions of substituted (1,2-benzisoxazol-3-yl)acetates

Synthesis of 2H‐Azirines by Iridium‐Catalyzed Decarboxylative Ring Contraction of Isoxazol‐5(4H)‐ones

“…[16,17] Thea dduct A liberates carbon dioxide immediately to generate the azairidacyclobutene B.I fa zirine 2 is produced by the irreversible reductive elimination from B, then the chirality of 1 must be completely maintained. However,s ignificant deterioration of the product ee value was observed, as shown in Equation (2). Therefore,t he reductive elimination step would be the reversible pathway and B is likely to be in equilibrium with the achiral imido (nitrene) complex C.F ormation of 4o from both 1o and 2o In conclusion, by using aphosphine-free iridium catalyst, we have developed ad ecarboxylative ring-contraction reaction of isoxazolones which affords highly strained 2H-azirines.…”

“…2H-Azirines,which are three-membered, nitrogen-containing,u nsaturated heterocyclic compounds bearing aC =N bond, are highly strained molecules.T hey are the structural motifs seen in some antibiotic molecules. [1] Ther eactivity of 2H-azirines is characterized by their high ring-strain energy, which can cause various ring-opening reactions,s uch as hydrolytic formation of aminocarbonyl compounds, [2] transition-metal-catalyzed cycloaddition with unsaturated molecules, [3] and various nucleophilic addition reactions leading to aziridines. [4] Synthetic approaches to 2H-azirines are limited to af ew types of reactions:d enitrogenative cyclization of alkenyl azides (Scheme 1a)o rb ase-mediated eliminative cyclization reactions of oxime esters,N-haloimines,orhydrazonium salts (Scheme 1b;N eber reaction).…”

Three‐Membered Heterocycles. Structure and Reactivity

“…Benzisoxazole derivatives (e.g., 215) exhibit a regiochemically distinct mode of thermal rearrangement. Instead of bonding to the internal a-carbon, the nitrogen instead forms the azirine ring with the adjacent carbon of the substituent, so that aromaticity is preserved [274]. …”

Synthesis of 2H‐Azirines by Iridium‐Catalyzed Decarboxylative Ring Contraction of Isoxazol‐5(4H)‐ones

“…[1] Ther eactivity of 2H-azirines is characterized by their high ring-strain energy, which can cause various ring-opening reactions,s uch as hydrolytic formation of aminocarbonyl compounds, [2] transition-metal-catalyzed cycloaddition with unsaturated molecules, [3] and various nucleophilic addition reactions leading to aziridines. [1] Ther eactivity of 2H-azirines is characterized by their high ring-strain energy, which can cause various ring-opening reactions,s uch as hydrolytic formation of aminocarbonyl compounds, [2] transition-metal-catalyzed cycloaddition with unsaturated molecules, [3] and various nucleophilic addition reactions leading to aziridines.…”