83152-72-1Relevant articles and documents
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.
