**1. Introduction**

Microwaves are the portion of the electromagnetic spectrum with the wavelengths from 1 mm to 1 m with corresponding frequencies between 300 MHz and 300 GHz. The frequencies used for cellular phones, radar, and television satellite communications are within this portion of the electromagnetic spectrum [1]. Microwaves have been employed in a non-classical heating technique which is popularly known as "Bunsen Burner of the 21st century" and has attained enormous importance since many materials (solids or liquids) can transform electromagnetic energy into heat. The microwave-assisted organic synthesis (MAOS) has made revolutionary changes in the methodology since there is a dramatic enhancement in the yield of the reaction, modifications of selectivity, increased purity of products, simplified work-up procedure, and above all reduction in the reaction time. These are the primary benefits over conventional methods. The microwave technique has been applied efficiently in the organic synthesis, polymer chemistry, material sciences,

nanotechnology, biochemical processes, thermal food processing, hydrothermal and solvothermal processing, etc. [2]. The energy efficiency is higher in the case of microwave heating in comparison with the conventional heating as evidenced by one such Suzuki reaction in which there is an 85 fold reduction in energy demand when compared to a reaction on an oil bath and a microwave reactor [3].

During a chemical reaction under the conventional heating, the energy is introduced by convection, conduction, and radiation of heat from the surfaces of the reactants in the solution, and the energy transfer occurs due to thermal gradients. But in the case of the microwave irradiation, the energy is introduced through the electromagnetic field interaction into the molecules and the transfer of electromagnetic energy to thermal energy is energy conversion instead of heat transfer. This variation in the mode of introduction of energy leads to the advantages of using microwaves during chemical reactions. The microwaves penetrate easily into the bulk and, hence, heat evolves throughout the volume of the reaction mixture. As a result, fast and uniform heating of the reaction mixture can be advanced. In conventional heating, it is necessary to slow rates of heating to minimize the steep thermal gradients and obviate the process-induced stresses. As microwaves can transfer energy into all volumes of the reaction mixture, the potential exists to reduce the processing time and enhance the overall quality [4].

Although the use of microwaves for organic synthesis is widespread, the documentation of this technology to the synthesis of the functional dyes is a relatively new development. The use of microwave energy for their synthesis has the potential to offer similar advantages in reduced reaction times and energy savings for obtaining useful materials such as dyes possessing hi-tech applications.
