Chapter 8 - Green Synthetic Approaches for Biologically Relevant 2-amino-4H-pyrans and 2-amino-4H-pyran-Annulated Heterocycles in Aqueous Media

Abstract

4H-pyrans and 4H-pyran-annulated heterocyclic scaffolds represent a “privileged” structural motif that is well distributed in biologically active natural products and also in promising synthetic compounds in the field of medicinal, agrochemical, cosmetics, and pigment industries. It is worthy to mention that currently, a number of drug molecules bearing 4H-pyran moiety are in use in the treatment of various ailments such as hypertension, asthma, ischemia, and urinary incontinence. Such handful of diverse applications of such heterocyclic scaffolds in medicinal chemistry have drawn considerable interest during the last several years among the synthetic chemists to develop useful synthetic routes to these heterocycles of potential interest; and as a result, a good number of methods have already been developed. This chapter deals with the synthesis of biologically relevant 2-amino-4H-pyrans and 2-amino-4H-pyran-annulated heterocyclic scaffolds in water and ethanol–water media. With increasing public concern over environmental degradation, the use of environmentally benign solvents like water and/or organo-aqueous solvent offers very powerful green chemical protocols from both the economic and synthetic points of view with several advantages like reduced pollution, lower cost, and simplicity in processing, which are beneficial to the industry as well as to the environment. Water, due to its features, such as ecological friendliness, safe, nontoxic, nonflammable, clean, green, inexpensive as well as readily available, has been recommended for its prospective uses as a green solvent in organic syntheses.