Introduction

Waste prevention and environmental protection are major requirements in an overcrowded world of increasing demands. Synthetic chemistry continues to develop various techniques for obtaining better products with less damaging environmental impacts. The control of reactivity and selectivity is always the central subject in the development of a new methodology of organic synthesis. Novel, highly selective reagents appear every month. New reactions or modifications of old reactions have been devised to meet the everincreasing demands of selectivity in modern synthesis. Periodic review articles and books appear in the literature on these newer reagents. The scope of this chapter is to focus on newer techniques (experimental) for improving the yield and reducing the duration of the reactions and also to discuss the need for a good synthetic design. In other words, newer methods of kinetic activation, which minimize the energy input by optimizing reaction conditions, will be discussed along with the need for an elegant synthetic design.

In most reactions, the reaction vessel provides three components (as shown in Fig. 2.1):

• solvent,

• reagent/catalyst,

• energy input.

Figure 2.1: Components of chemical reaction

Hence, efforts to green chemical reactions focus predominantly on "greening" these three components. By "greening," we mean to

• Use benign solvents or completely dispense with the solvent.

• Use alternate, more efficient and effective reagents/catalysts.

• Optimize the reaction conditions by using cost-effective, eco-friendly alternative processes.

The role of alternate reagents, solvents, and catalysts in greening chemical reactions is discussed in other chapters.

In this chapter we shall see newer methods of...