F. De Sarlo

Rearrangement of nitrone cycloadducts to methylene cyclopropane. Synthesis of indolizidine and quinolizidine derivatives.

Abstract Isoxazolidines 3 , obtained by cycloaddition of nitrones with methylene cyclopropane, undergo thermal rearrangement to piperidin-4-one derivatives. Indolizidine and quinolizidine derivatives are obtained from cyclic nitrones. Piperidin-4-ones 2 including indolizidines and quinolizidines are obtained by thermal rearrangement of 5-spirocyclopropylisoxazolidines 1 .

The preparation and tautomerism of 3,4-dimethyl-isoxazolin-5-one

Abstract The preparation and tautomerism of 3,4-dimethyl-isoxazolin-5-one has been studied. A comparison of the IR and UV spectra as well as of the dipole moment of this compound with those of the three possible methyl derivatives establishes that the 4-H tautomeric form predominates in non-polar solvents, whereas the 2-H form predominates in dioxan and in hydroxylic solvents.

2-methylisoxazolin-5-ones—I

Abstract N-methylisoxazolin-5-ones were obtained, in addition to the isomeric 5-methoxy-isoxazoles, by methylation of isoxazolin-5-ones or, through a more direct way, by reaction of N-methylhydroxylamine on β-oxoesters. The structures assigned are proved by catalytic hydrogenation or by alkaline hydrolysis (see next paper). Bromination of both 3-phenyl and 4-phenyl compounds by N-bromosuccinimide is described. Some remarkable differences between physical properties of 3-aryl and 4-aryl compounds in the solid phase are pointed out.

2-Methylisoxazolin-5-ones—II : Ring-opening by bases

Abstract N-methylisoxazolin-5-ones without substituentsin position 3 undergo alkaline ring-opening in the cold, yielding N-methyl monoamides of C-substituted malonic acid, whereas 3-substituted compounds react only by heating with alkali yielding corresponding ketones, or with hydrazines yielding substituted pyrazolin-5-ones.

Correlation Times Measurements from Tin-Proton Dipolar Interactions: A 1H NMR Spin-Lattice Relaxation Study

Abstract The simultaneous analysis of nuclear relaxation behaviour of 119Sn-1H and 117Sn-1H dipolar vectors from the proton spinlattice relaxation rates of the relative satellite peaks may yield a very accurate calculation of correlation times. The dipolar interaction between the proton and the bound tin nucleus is differently observed on the 119Sn and 117Sn satellite resonances in the 1H partially relaxed spectra. Provided that the internuclear proton - tin distance is known, from the difference of the relaxation rate of the lH-118Sn signal with those measured from its satellite peaks, the correlation time can be calculated from the two independent set of data.