ABSTRACT
Nitrogen-containing heterocyclic compounds, because of their presence in biologically active compounds and natural products, are by far the most explored heterocycles. Five-membered nitrogen-containing heterocycles like indoles, pyrroles, and carbazoles are present in a number of biologically active compounds. This chapter describes the approaches for the synthesis of five-membered nitrogen heterocycles with the aid of metals and non-metals. Pyrroles are an important class of heterocycles and are widely used in material science and synthetic organic chemistry. Many N-heterocycles are synthesized using enamines substituted with an electron-withdrawing group in β-position as useful building blocks. S. Watanuki et al. synthesized N-heterocycles using chromium Fischer carbenes to promote the ring-closing ene-yne metathesis. N-Heterocycles are found in naturally occurring alkaloids. These N-heterocycles are generated by organolanthanide-catalyzed intramolecular hydroamination of aminoalkenes. Secondary amines are formed in moderate to good yields upon subsequent nucleophilic addition of phenyllithium or n-butyllithium, while reaction with methyllithium is sluggish.
