784144-76-9Relevant academic research and scientific papers
Spiro[4H-chromene-4,5′-isoxazolines] and related compounds: Synthesis and reactivities
Sosnovskikh,Sizov,Usachev,Kodess,Anufriev
, p. 535 - 542 (2007/10/03)
Reactions of chromones with methyl ketoximes in the presence of lithium diisopropylamide follow the nucleophilic 1,2-addition mechanism to give spiro[4H-chromene-4,5′-isoxazolines] in good yields. The isoxazoline ring in spiro[4H-chromene-4,5′-isoxazolines] undergoes opening under the action of conc. H2SO4, yielding α,β-unsaturated oximes. Their nitrosation and bromination lead to the corresponding spiroisoxazolines, while the Beckmann rearrangement, to α,β- unsaturated amides. The latter are also formed directly from spiro[4H-chromene-4,5′-isoxazolines] under the action of PCl5. N-Substituted acetophenone hydrazones in the presence of lithium diisopropylamide react at the C(4) atom of 2-trifluoromethylchromone, while acetophenone anil under the same conditions, at the C(2) atom.
Novel chemical modifications at the 4-position of chromones. Synthesis and reactivity of 4H-chromene-4-spiro-5′-isoxazolines and related compounds
Sosnovskikh, Vyacheslav Ya.,Usachev, Boris I.,Sizov, Aleksei Yu.,Kodess, Mikhail I.
, p. 7351 - 7354 (2007/10/03)
Reactions of chromones with dilithiooximes proceed via nucleophilic 1,2-addition to give, on acidification, 4H-chromene-4-spiro-5′-isoxazoline derivatives in high yields. On treatment with concentrated H2SO 4 the isoxazoline ring of this novel spiroannulated heterocyclic system opens to give α,β-unsaturated oximes, which undergo nitrosation, bromination, and the Beckmann rearrangement to the corresponding spiroisoxazolines and α,β-unsaturated amides, respectively. The latter can be obtained directly by the Beckmann rearrangement of 4H-chromene-4-spiro-5′-isoxazolines.
