106490-02-2Relevant academic research and scientific papers
Stereoselective synthesis of cis and trans four-membered cyclic nitrones
Eijk, Peter J. S. S. van,Overkempe, Cor,Trompenaars, Willem P.,Reinhoudt, David N.,Manninen, Lauri M.,et al.
, p. 27 - 39 (1988)
Nitroalkenes 3-5 react with ynamines (1-aminoacetylenes) 6 to yield four-membered cyclic nitrones (2,3-dihydroazete 1-oxides) 7-13.The nitroalkenes 3 and 5c give the cis four-membered cyclic nitrones 7-11, whereas 4 and 5b yield the trans four-membered cyclic nitrones 12-13 upon reaction with 6.Nitroalkene 4i reacts with 6c to give a 1:1 mixture of the cis and trans four-membered cyclic nitrones 9g and 13i.The trans stereochemistry of trans-N,N-diethyl-2,3-dihydro-3-(2-methoxynaphthalenyl)-2-methyl-4-phenyl-2-azetecarboxamide 1-oxide (13k) was elucidated by means of X-ray analysis.Only from the reaction of 1-nitrocyclopentene (5a) with 6g, the initially formed (4+2) cycloadduct, the nitronic ester 17 has been isolated.The thermal ring contraction of 17 yields 3a,4,5,6-tetrahydro-N,N-dimethyl-3-phenyl-3H-cyclopentisoxazole-3-carboxamide (19), the structure of which was established by X-ray analysis.The trans four-membered cyclic nitrones are thermally relatively stable compared with the cis nitrones.The mechanism of the stereoselective formation of the nitrones is related to the conformation of the (4+2) cycloadduct 16, which could be correlated with Chem-X and MNDO calculations.
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.
