The major advances in Green Chemistry, especially Industrial Green Chemistry, over the past decade have been in the area of catalysts. One of such techniques is Phase Transfer Catalysis. The use of a Phase Transfer Catalyst (PTC), which Permits or accelerates the reaction between chemical species situated in different phases to overcome the various problems encountered in synthesis. The reaction in organic synthesis can be achieved under solid –liquid PTC and microwaves irradiation in the absence of solvent, generally under normal pressure in open vessel. Therefore, the review presents a brief introduction to PTC and PTC in the generation of compound libraries of over last few years.