Some aspects of nitrogen heterocyclic chemistry

Chapter One reviews the use of scandium and lanthanide trifluoromethanesulfonates (triflates) in organic synthesis. Their ability to act as Lewis acids and so promote a wide variety of reactions are illustrated. In particular the review highlights the advantages of scandium and lanthanide triflates over more conventional Lewis acids, such as aluminium(I1I) chloride. Chapter Two describes the use of scandium and lanthanide trifiates in the reaction of acetals with amines to produce imines. The extension of this methodology to the synthesis of nitrogen-containing heterocycles such as isoindolones, isoquinolinones and ~-carboline derivatives are elaborated on. Some limitations of the methodology and the problems encountered with its application to the synthesis of enamines are covered. Chapter Three reports our approach to a novel synthesis of ~-carboline derivatives. The formylation of indole-3-acetic acid derivatives in the 2- position proved difficult and several approaches to this problem are discussed. The attempted cyclisation of imines prepared from 2-formyl- and 2- acetyl-3-indolyl acetic acid compounds are also covered. Chapter Four describes a modified Clauson-Kaas pyrrole procedure using trimethylsilyl trifiate. The selection of reaction conditions in an effort to optimise the procedure are discussed. Chapter Five provides full experimental procedures and analytical data for the reactions described in Chapters Two, Three and Four.