Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

Abstract

SummaryThe base-mediated photochemical cyclization of 2-azidobenzoic acids with the formation of 2,1-benzisoxazole-3(1H)-ones is reported. The optimization and scope of this cyclization reaction is discussed. It is shown that an essential step of the ring closure of 2-azidobenzoic acids is the formation and photolysis of 2-azidobenzoate anions.

Synthesis of-4-((4-trimethylsilyl-1H-1,2,3-triazol-1-yl)methyl)-2H-chromen-2-ones: A novel class of heteroaryl anionic synthon

“…the synthesis of larger molecules with a wide range of chemical and pharmocodynamic properties. [9] The one-pot reaction of 4-bromomethylcoumarins 1a-j with trimethylsilylacetylene (TMSA) and sodium azide in the presence of CuI catalyst in acetone/water solvent system over 8 h yielded the novel anionic synthons: the substituted-4-((4-trimethylsilyl-1H-1,2, 3-triazol-1-yl)methyl)-2H-chromen-2-one. 2a-j in 70-92% yields (Scheme 1).…”

Isoxazol-5-ones as Strategic Building Blocks in Organic Synthesis

“…Finally, a protonation event affords the corresponding benzo [c]isoxazol-3-ones 33b [Scheme 4 (b)]. 39 A third strategy reported by Xu, Zhang, and co-workers described a synergistic Rh-and Cu-catalyzed C-H functionalization protocol for the formation of N-Boc-substituted benzo [c]isoxazol-3-ones 33c starting from benzamides 39 and N-Boc-hydroxylamine 40. The mechanism of this reaction is proposed to proceed via the reversible formation of a five-membered rhodacycle 42 that undergoes 1,2-migratory insertion with the nitroso compound 41 (prepared in situ by the oxidation of N-Boc-hydroxylamine 40 using CuCl catalysis and air).…”

Photoinitiated Rearrangement of Aromatic Azides to 2-Aminonicotinates

“…Photochemical methods for synthesizing N-heterocycles from aryl azides allow for the creation of complex heterocyclic frameworks from relatively simple starting materials. − The diversity of these structures is due to the ability of the resulting intermediates to undergo various rearrangements. After the aryl azide absorbs light, the benzene ring expands through a sequential reversible electrocyclic rearrangement of aryl nitrene A into benzazirine B and 1,2-didehydroazepine C. − The sp-hybridized carbon atom of the ketenimine fragment of intermediate C undergoes nucleophilic attack to form azepine (Scheme , Path 1), which exists in four tautomeric forms: 1 H -, 2 H -, 3 H -, and 4 H -azepines, with the 3H-form being the most stable .…”