María B. García

A NEW SYNTHETIC APPROACH TO N,N′-DISUBSTITUTED 1,n-ALKANEDIAMINES

A general procedure is described for the synthesis of unsymmetrically substituted N-aryl-N′-alky1 (or aryl) 1,n-alkanediamines 1 (n = 2−5) by reduction of ω-alkyl (or aryl) aminoalkanamides 2 with borane. Compounds 2 are easily obtained by aminolysis of the corresponding ω-haloalkanamides 3.

Amidinoquinoxaline N-oxides as novel spin traps

A novel type of spin traps 1 derived from the pyrimidoquinoxaline N-oxide heterocyclic core is reported. EPR technique was used to evaluate their ability to trap methyl radicals generated in a Fenton reaction in the presence of DMSO. All the synthesized nitrones showed spin trapping properties and the corresponding nitroxides 2 were characterized by EPR. The novel spin traps showed remarkably persistent signals, as confirmed in a competition experiment with DMPO. The addition rate constants leading to the spin adducts (kadd) were determined, and very good correlations were found with steric and electronic parameters of the parent nitrones. The spin adducts decomposition rate constants (kdec) and the corresponding half-life times (t1/2) were also determined. DFT and MP2 calculations were used in order to rationalize the adducts hfcc and the structural factors influencing their addition and decomposition rates.

1-Aryl-3-alkyl-1,4,5,6-tetrahydropyrimidinium salts. Part 2. Reactions with nucleophiles

The reactivity of 1-aryl-3-alkyl-1,4,5,6-tetrahydropyrimidinium salts (1) towards nucleophiles was studied. Hydrolysis of salts (1) afforded initially compounds (2, kinetic products) through the corresponding amidinium hydroxides (4). The regioselectivity of the reaction was analyzed considering the relative leaving group abilities and the stereoelectronic control theory. Amino amides (2a-c) in the reaction medium underwent spontaneous formyl migration, affording compounds (3, thermodynamic products). Reduction of salts (1) with sodium borohydride led to acyclic trimethylenediamines (5) or to the corresponding hexahydropyrimidines (6), according to the reaction conditions. Aminolysis of compound (1f) with isopropylamine yielded an acyclic formamidine (7f).