Particular success has been achieved in the synthesis of new products and in processes since the twelve principles of "green chemistry" were formulated in the 1990s. These products and processes are more compatible with human health, society, and the environment. In this review, a collection of research reports have been documented from the viewpoint of green chemistry. The main theme of this review is neat reactions, which are solvent and catalyst-free reactions. Neat reactions in the absence of any solvent or catalyst with concise summaries of microwave, ball milling, and neat reactions have been described