Carla Ormachea

Experimental and theoretical studies on polar Diels–Alder reactions of 1-nitronaphathalene developed in ionic liquids

The reactions between 1-nitronaphthalene 1 and two nucleophilic dienes, Danishefskýs diene 2 and 1-trimethylsilyloxy-1,3-butadiene 3, to yield phenanthrenols 7 and 8 developed in protic and aprotic ionic liquids (ILs) with an imidazolium cation base permit to conclude that the reactions occur in better experimental conditions than in molecular solvents. The yields obtained with protic ILs are better than those observed with aprotic ILs. In this sense, the higher yields obtained with aprotic ILs, (working at 60 °C, 48 h) are comparable with the lower yields observed in protic ILs (60 °C, 24 h). DFT calculations for the reaction of 1-nitronaphthalene 1 with diene 3, in the absence and in the presence of tetrafluoroborate of 1-metilimidazolium [HMIM][BF4] as protic ILs, indicate that this reaction is a domino process that comprises two consecutive processes: i) a polar Diels–Alder (P-DA) reaction between 1 and 3, and ii) an elimination of nitroso acid 5 to yield dihydrophenanthrene 11. Thermodynamic calculations indicate that while the first reaction is the rate-determining step of this domino process, the nitroso acid elimination is the driving force responsible for the formation of dihydrophenanthrene 11. Implicit and explicit solvent effects indicate that while the hydrogen bond formation between HMIM and one oxygen atom of the nitro groups favour the two reactions, implicit solvent effects modelled by PCM decelerate the P-DA reaction by a large solvation of reagents. Finally, DFT analysis of reagents offers an explanation of the catalytic role of protic ILs in these P-DA reactions.

Protic and Nonprotic Ionic Liquids in Polar Diels-Alder Reactions Using Properly Substituted Heterocycles and Carbocycles as Dienophiles. A DFT study

The Diels-Alder (D-A) reaction is one of the most useful processes in preparative organic chemistry. Its potential in heterocyclic chemistry and natural products synthesis is very well known. It provides the chemist with one of his best tool for the preparation of cyclic com‐ pounds having a six-membered ring. The process is in one step inter or intramolecular from a diene and dienophile bearing an almost unlimited number of variants. It worth noting that these variants exist not only in the substitution of the reaction component but also in the elec‐ tronic nature of these dienes and dienophiles. (Carruthers W, 1990; Fringelli F. et al 2002)

Synthesis of Phenanthrenol Derivatives Through Polar Diels-Alder Reactions Employing Nitronaphthalenes and (E)-1-(Trimethylsilyloxy)-1,3- butadiene. Theoretical Calculations

Fil: Kneeteman, Maria Nelida. Universidad Nacional del Litoral. Facultad de Ingenieria Quimica. Departamento de Quimica; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe; Argentina