Chapter 14 - Green synthetic approaches for medium ring–sized heterocycles of biological and pharmaceutical interest

Abstract

Development of newer synthetic methodologies to access medium ring–sized heterocyclic compounds is an important current activity, partly because of the biological and pharmaceutical importance of such a relatively less-explored class of compounds. A plethora of metal-mediated transformations have been emerged over the last three decades or so for the synthesis of such otherwise difficult to access ring systems. However, due to the increased concern of environmental issues, equal emphasis is being given to applications of greener methods. In particular, use of several green chemical techniques such as microwave and ultrasound as alternative source of energy, ionic liquids, aqueous environment or environmentally benign solvents, solid-supported reagents, greener catalysts, and fluorous separations have provided useful alternatives to classical approaches in the synthesis of such ring systems. The present chapter is an updated attempt to cover the green synthetic approaches developed for such heterocyclic scaffolds since the publication of the first edition of the book. As before, an emphasis has also been given to some of the advantages offered by these techniques over classical approaches.