Diels-Alder

36
Molecular Medicinal Chemistry

IDECEFYN
vol 12 January-April 2007, 36-38 http//:www.idecefyn.com.ar ISSN 1666-888X

Reactivity of nitrated quinolinic systems in reactions with isopreneSilvina Cancian, Lucila Brusa, Romina Brasca and Maria Kneeteman Laboratorio Fester, Área Química Orgánica, Departamento de Química, Facultad de Ingeniería Química, Universidad Nacional del Litoral,Santiago del Estero 2829, 3000 Santa Fe, Argentina. e-mail: mkneetem@fiqus.unl.edu.ar Introduction We have recently demonstrated that naphthalene substituted with a nitro group in 1- or 2-positions canreact via C1-C2 bond by a [4π + 2π] cycloaddition when the used diene is sufficiently nucleophilic, such as trans-1-methoxy-3trimethylsilyloxy-1,3-butadiene (diene of Danishefsky) (Paredes et al., 2000).The tricyclic adduct obtained at temperatures from 80 to 150oC suffers extrusion of nitrous acid and methanol to form the hydroxyphenantrenic derivative (Fig. 1). However, the use of poor ormoderately activated dienes, such as isoprene and 1-methoxy-1,3-butadiene, leads to the corresponding N-naphthylpyrroles (Fig. 1), obtained by heterocycloaddition and later thermal rearrangement (Della Rosaet al., 2004; Paredes et al., 2003).

Figure 1 In view of the above findings, our interest has been to extend this study to a series of nitroquinolines and nitroisoquinolines, and their reactionswith isoprene as diene partner. Taking into account that it has been demonstrated for Diels-Alder reactions that the classification of the diene/dienophile pair on a single electrophilicity scale is atool for predicting the feasibility of a cycloaddition process (Domingo, 2002; Domingo and Aurell, 2002; Domingo et al., 2002 a,b), theoretical studies were performed in order to predict the reactivityof the forementioned systems based on the Density Functional Theory. Methodology * Experimental Conditions: Experiences were carried out in closed ampules using benzene as solvent. The reaction time...