83152-72-1Relevant academic research and scientific papers
Chemistry of four-membered cyclic nitrones. Reaction with a non-nucleophilic base: Stereoselective ring opening of in situ generated 1,2-dihydroazetes and structure elucidation of the resulting α,β-unsaturated oximes by X-ray analysis
Eijk, Peter J. S. S. van,Reinhoudt, David N.,Harkema, Sybolt,Visser, Richard
, p. 103 - 110 (2007/10/02)
The four-membered cyclic nitrones (2,3-dihydroazete 1-oxides) 1a-g isomerize to the corresponding oximes 3 and 4 on treatment with potassium tert-butoxide.In N,N-dimethylformamide at room temperature, oxime 4 is formed preferentially; in tetrahydrofuran, both the oximes 3 and 4 are formed.The oximes 3c-e are converted into the corresponding 6H-1,2-oxazin-6-ones 5c-e by reaction in acetic acid.The oxime 4a has the (E,E) stereochemistry and the O-benzoyl derivative of 3b (6) the (Z,E) stereochemistry, as shown by X-ray analysis.In solution, NOE difference spectroscopy indicates the (Z,E) and (E,E) configuration for 3a and 4a, respectively.The α,β-unsaturated ketone (Z)-8 was prepared by reaction of (Z,E)-3b with bispyridine silver permanganate.Reaction of (Z)-8 with hydroxylamine in pyridine yields (Z,E)-3b and the 6H-1,2-oxazin-6-one 5b, which is formed by rapid cyclization of (Z,Z)-3b.The conversion of nitrones 1 into the corresponding oximes 3 and 4 is explained in terms of an electrocyclic ring opening of an intermediate N-hydroxy-1,2-dihydroazete.In this electrocyclic reaction, a strong preference for outward rotation of the hydroxy group is observed.
Chemistry of Four-Membered Cyclic Nitrones. 3. Reaction with Nucleophilic Reagents and Stereospecific Conversion into 1-Hydroxyazetidines
Pennings, Marcel L.M.,Reinhoudt, David N.,Harkema, Sybolt,Hummel, Gerrit J. van
, p. 4419 - 4425 (2007/10/02)
Four-membered cyclic nitrones (1) react with a variety of nucleophiles (MeMgI, CN-, OH-, MeO-, and H-) by stereospecific addition to the C=N bond.Reaction of 1a with potassium cyanide and with methylmagnesium iodide yields the 1-hydroxyazetidines 2a and 2b, respectively.Reduction of 1b with lithium aluminum hydride and with sodium borohydride affords the 1-hydroxyazetidine derivatives 3 and 4, respectively.Sodium hydroxide in methanol-water reacts with 1a to give a mixture of two isomeric 5-hydroxyisoxazolidines 5a and 5b, but under similar reaction conditions 1b and 1c rearrange to the oximes 6 and 7.In acetic acid at room temperature 6a cyclizes to the 6H-1,2-oxazin-6-one derivative 8, whereas 6b yields 5-methyl-3,4-diphenylisoxazole (9) after being refluxed in acetic acid, probably by carbon monoxide elimination from the intermediate oxazin-6-one derivative.Reaction of 1a with sodium hydroxide for 2 min gives exclusively the 1-hydroxy-4-methoxyazetidine 13a, whereas prolonged reaction gives the isomeric azetidine 13b together with 5 (mixture of 5a and 5b in a ratio 4:1).Single-crystal X-ray analysis of 13b reveals that all three relatively bulky substituents at C-2, C-3, and C-4 are on the same face of the azetidine ring.Treatment of 13b with acetic acid at room temperature gives the 5-methoxyisoxazolidine 15.The 1-hydroxyazetidines 2-4 are oxidized with yellow mercury(II) oxide to the corresponding four-membered cyclic nitrones 1b, 16 and 17.
