Gloria I. Yranzo

Synthesis of 4-alkylpyrazoles from 3,5-diaminopyrazoles

The possibility of preparing 4-alkylpyrazoles from malononitrile (through C-alkyl malononitriles and 3,5-diamino-4-alkylpyrazoles) has been explored. Although some difficulties arise in the doubledeamination step, the method has allowed the synthesis of 4-benzyl- and 4-phenethyl-pyrazoles. New 3-halogenopyrazoles have also been prepared. The synthesis of 3,5-diamino-4-iodopyrazole is reported. This elusive compound has a 13C NMR spectrum in which an aromatic carbon (C-4) appears at δ 29.53.

Flash vacuum pyrolysis of 2-alkoxyiminated alkyl α-pyrone and 1,3-diazine derivatives

Abstract Flash vacuum pyrolysis of 6-ethyl-3-(1-ethoxyiminopropyl)-4-hydroxy-2H-pyrane-2-one (1) and 1,3-dimethyl-5-(1-ethoxyiminopropyl)-6-hydroxy-1,2,3,4-tetrahydropyrimidine-2,4-dione (2) were studied between 300 and 400°C, with nitrogen as the carrier gas. Compound 1 afforded a 1-azirine and the isomeric oxazole, while an oxime and an amide were the reaction products of 2. The difference in reactivity is discussed in terms of the tautomeric structures present in both compounds.

A surface active benzodiazepine receptor ligand for potential probing membrane order of GABAA-receptor surroundings.

A conjugable analogue of the benzodiazepine 5-(2-hydroxiphenyl)-7-nitro-benzo[ e][1,4]diazepin-2(3 H)-one N 1-substituted with an aliphatic chain (CNZ acyl derivative, CAd) was synthesized. CAd inhibited FNZ binding to GABA A-R with an inhibition binding constant K i = 176 nM and expanded a model membrane packed up to 13 mN/m when penetrating from the aqueous phase. CAd exhibited surface activity with a collapse pressure pi = 18.8 mN/m and minimal molecular area A min = 49 A (2)/molecule at the closest molecular packing, resulting in full and nonideal mixing with a phospholipid in a monolayer up to a molar fraction x congruent with 0.1, decreasing its surface potential and contributing with a dipole that pointed its positive end toward the air and reoriented at the interface upon compression. These findings suggested that CAd could be stabilized at the membrane-water interface with its CNZ moiety stacked at the GABA A-R while its acyl chain can be inserted into the membrane depth.

Azirines from the flash vacuum pyrolysis of oximes

Abstract Flash vacuum pyrolysis of a 2-alkoxyiminated-alkyl and a 2-alkoxyiminated-aryl cyclohexane-1, 3-dione derivative was carried out. In these reactions isoxazoles as well as isomeric oxazoles and azirines were found. Two reaction mechanisms involving an iminyl radical and an α elimination are discussed.

Formation of santonide and parasantonide in the pyrolysis of santonic acid. A new insight of an old reaction

Thermal reactions of santonic acid (1) in solution and flash vacuum pyrolysis were carried out in order to study the mechanism of formation of parasantonide (3) and santonide (4). Heating an acetic acid solution of 1 in a sealed tube at 200oC led to 3, while heating at 175 oC afforded 4. Flash vacuum pyrolysis of 1 was carried out between 300 and 550 oC, 10 torr and contact times of 10s. Results showed that 1 decomposed by at least two different mechanisms. One involving isomerization and lactonization affording 4 which affords 3 and the other involving radical scission and formation of aromatic and conjugated products. A mechanism involving isomerization to isosantonic acid (6) previous to lactonization is proposed for formation of 4.