Maria Luisa Saccarello

A paradigm for the structures of cyclic aspirin derivatives : 2-(2-Methoxy-Phenoxy)-2-Methyl-4-Oxo-1,3-Benzodioxane

Abstract Full characterization of the heterocyclic system of the title compound (3) was obtained by X-ray diffraction analysis. Crystals are orthorhombic, space group Pbca, with Z = 8 in a unit cell of dimensions a = 9.968(3), b = 23.808(4), c = 11.668(2) A; the structure was refined by full-matrix least-squares to Rw = 0.036 for 2055 independent reflections. The dioxane ring of the cyclic aspirin moiety exhibits a severely distorted half-boat conformation, with the phenoxy group axially oriented on the ring. With respect to the equatorial Me group the aromatic system of the guaiacol fragment is in a syn-clinal conformation favored by electrostatic interactions; relief from overcrowding is achieved mainly through angular deformations. Differences between the pertinent molecular dimensions of 3 and those of aspirin and salicylic acid are reported.

The reaction of 2,3-diamino-butadienes with 1,2-diimmonium dibromides: A direct synthesis of 1,2,4-triamino benzenes

Abstract A new benzene ring synthesis is reported: 1,2-diimmonium dibromides react in mild conditions with 2,3-diamino-butadienes affording 1,2,4-triamino benzenes with yields of preparative interest.

1,2-diaryl-4-amino-4,5-dihydro-5,5-disubstituted imidazoles: behaviour in acidic medium

Abstract The behaviour of 1,2,5-triaryl-4-amino-5-methyl-4,5-dihydro-imidazoles 2a–e and 1,2,5,5-tetraphenyl-4-morpholino-4,5-dihydro-imidazole 2f in acidic medium was studied. By heating in 50% H 2 SO 4 , 1,2,4-triaryl-5-methyl-imidazoles and 1,2,4,5-tetraphenyl-imidazole were obtained. When 5-aryl-5-methyl-derivatives were reacted with various nucleophiles in acidic medium the corresponding 4-substituted imidazolines were formed. Generally, only one isomer ( viz E ) was obtained. The 5,5-diaryl-derivative afforded the 1,2,4,5-tetraphenyl-imidazole even in the presence of nucleophiles.

2-Imidazolines. Part 2. Pyrolysis of 1-acyl-4,5-diamino-4,5-dihydroimidazoles: a novel pyrimidine synthesis

1-Acyl-2-phenyl-(or methyl-)4,5-diamino-4,5-dihydroimidazoles (1), when heated in refluxing xylene, afford 2,4-disubstituted-5,6-diaminopyrimidines in good yield. The relative position of the substituent at C-2 or C-4 of the pyrimidine ring depends on the basicity of the amino-group and the nature of the substituent at C-2 of the imidazole ring. The mechanism of the ring expansion is discussed.