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2005
Isoxazole derivatives
R 0240
Structural Characterization of Isomeric 2,3,5-Substituted TetrahydropyrroPrepared by Cycloaddition of N-Methyl-C-arylni05- 111 lo[3,4-d]isoxazole-4,6-diones
trones to N-Phenyl- or N-Methylmaleimide. — 1,3-Dipolar cycloaddition reactions
of nitrones (I) with N-phenylmaleimide (II) yield both cis and trans cycloadducts (III)
and (IV) with respect to the ring fusion and the aromatic group. Of the 5-methyl substituted cycloadducts prepared earlier, only the para-substituted chloro- and nitrophenyl
groups afford both forms, whereas only the cis-form (V) is detected for the dimethylamino- and 4-benzyloxy-3-methoxyphenyl substituted derivatives. All cis-adducts attain a biased conformation while the trans forms are mixtures of two invertomers. The
o- and i-conformations of the trans adduct are of comparable stability and represent
energy minima. — (PIHLAJA*, K.; TAEHTINEN, P.; SHAIKHUTDINOV, R.;
HARTIKAINEN, H.; OVCHARENKO, V.; J. Heterocycl. Chem. 41 (2004) 5,
741-746; Dep. Chem., Univ. Turku, SF-20014 Turku, Finland; Eng.) —
H. Hoennerscheid
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