Synthesis of Novel Isoxazole Fused Heterocycles

Synthesis of Fused Isoxazoles: A Comprehensive Review

“…The reaction of 10,11-dihydro-11-one with sodium hydroxide with carbon disulfide at 0 °C in THF, along with alkylation with methyl iodide, produced an α-oxoketene dithioacetal (18). When compound (19) reacted with hydroxylamine hydrochloride in the presence of sodium ethoxide in refluxing ethanol, a 3-ethoxydibenzenopino [4,5-c] isoxazole (20) was obtained, whereas in the presence of a non-nucleophilic base like barium hydroxide, 3-(methylthio)dibenzoxepino- [4,5-c]isoxazole was produced with an 86% yield, and in the presence of sodium acetate-acetic acid buffer, a regioisomeric 3-(methylthio)dibenzoxepino [4,5-d] isoxazole (21) was obtained [14]. Inga Cikotiene studied the intramolecular iodine-mediated oxygen transfer from nitro groups to C=C bonds (Scheme 12).…”

“…Zigmee T. Bhutia et al worked on the in situ mechanochemical synthesis of nitrones followed by 1,3 dipolar cycloaddition, providing a catalyst-free, "green" route to obtain cisfused chromano- [4,3-c]-isoxazole (37) (Scheme 14). Grinding an equimolar mixture of o-allyl salicylaldehyde and phenylhydroxylamine resulted in nitrones, and then intramolecular cycloaddition of the nitrones yielded compound (38) [20].…”

“…The reaction of 10,11-dihydro-11-one with sodium hydroxide with carbon disulfide at 0 • C in THF, along with alkylation with methyl iodide, produced an α-oxoketene dithioacetal(18). When compound(19) reacted with hydroxylamine hydrochloride in the presence of sodium ethoxide in refluxing ethanol, a 3-ethoxydibenzenopino[4,5-c] isoxazole(20) was obtained, whereas in the presence of a non-nucleophilic base like barium hydroxide,…”