Michele Ruccia

Addition reactions of heterocycles—IV : Indoles and nitrilimines

Abstract The reactivity of indole derivatives towards nitrilimines has been studied. Substituents at positions 1, 2 and 3 of the indole ring greatly affect the course of the reaction. 1,3-Dipolar cycloaddition products (3a,8a,dihydropyrazole-[3,4-b]-indole derivatives) and non-cyclic addition products (3-indolyl derivatives) were obtained depending on these substituents. The structures reported were assigned on the basis of satisfactory analytical, spectroscopic and chemical data.

Mononuclear heterocyclic rearrangements—vi : Conversion of 1,2,4-oxadiazoles into imidazoles

Abstract The rearrangement of N - (1,2,4 - oxadiazol - 3 - yl)β - enamino ketones 3 a–d and N-(1,2,4 - oxadiazol - 3 - yl)β - enaminoesters 3 e–h into 2 - acylamino - imidazolyl derivatives 9 a–h by the action of sodium ethoxide in N,N-dimethylformamide is the first example of a mononuclear heterocyclic rearrangement involving a nucleophilic carbon. Compounds prepared by condensation of 3 - amino - 1,2,4 - oxadiazoles 1 a–b with β - dicarbonyl compounds 2 a–d, show spectroscopic properties in agreement with cis-chelated structures 4. By condensation between 1 a–b and benzoylacetic ester 2 d, N - (1,2,4 - oxadiazol - 3 - yl)β - ketoamides 6 a–b have been obtained as secondary products. In solution, these compounds are in equilibrium with the corresponding tautomers 7 a–b.

Heterocyclic rearrangements: rearrangement of N-(1,2,4-oxadiazol-3-yl)-β-anamino ketones into pyrimidine N-oxides

The behaviour of N-(5-R-1,2,4-oxadiazol-3-yl)-β-enamino ketones towards rearrangement has been investigated. In the presence of anionic reagents in ethanol solution, they rearrange to pyrimidine N-oxides. The synthesis and hydrolytic ring opening of a [1,2,4]oxadiazolo[2,3-a]pyrimidinium system is also reported.

Mononuclear heterocyclic rearrangements. Part 10. Rearrangements in the 1,2,5-oxadiazole series

By studying the chemical behaviour of N-(4-methyl-1,2,5-oxadiazol-3-yl)-N′-phenylurea and of N-(4-methyl- or phenyl-1,2,5-oxadiazol-3-yl)-N′-arylformamidines in mononuclear heterocyclic rearrangements and comparing these results with those already obtained in the 1,2,4-oxadiazole and isoxazole series, relative tendencies towards mononuclear heterocyclic rearrangement have been estimated; viz. 1,2,4-oxadiazole > isoxazole > 1,2,5-oxadiazole.

A new rearrangement in the 1,2,4-oxadiazole series

The base-induced rearrangement of N-(5-R-1,2,4-oxadiazol-3-yl)-N′-phenylureas (R = Me or Ph) into 4-acylamino-1-phenyl-1,2,4-triazolin-5-one (acyl = acetyl or benzoyl, respectively) is described.