Chapter 28 - Polycyclic compounds comprising a pyridine and two or more carbocyclic rings

Abstract

Publisher Summary This chapter presents the preparation methods and properties of polycyclic compounds comprising a pyridine and two or more carbocyclic rings. A range of derivatives of 2-nitroacridine is obtained by the acid catalyzed cyclization of 2-arylamino-5-nitrobenzaldehydes which probably proceeds through protonation of the carbonyl group. The quinone methide derived from flavan by a retro-Diels–Alder reaction gives only a 4% yield of acridine when heated with aniline. The nuclear magnetic resonance spectra of some substituted aminoacridines showed that the electron density is significantly higher at the sites adjacent to the amino substituent in agreement with the observed pattern of electrophilic substitution. The susceptibility of pyrylium salts to attack at C-2 by nucleophiles and the subsequent ring opening and ring closure is of significant value in the synthesis of a range of heterocyclic compounds. Much of the interest in heterocycles is associated with their natural occurrence as alkaloids, an area reviewed in the chapter.