Besides a brief overview, the thesis in hand is divided into 6 chapters, discussing some solutions to the problems associated with microwave assisted organic synthesis like simultaneous product distillation, energy efficiency of microwave heating, presence of any specific microwave effects, and finally, the continuous flow organic synthesis under high-temperature and high-pressure conditions (high T/p), investigated in detail in an effort to propose a way out of the problematic scale-up of the microwave optimized synthesis.Chapter A summarizes the state-of-the-art in high T/p microreactor technology and provides a survey of successful applications of this technique from the recent synthetic organic chemistry literature.Chapter B describes the combination of microwave heating with the simultaneous preparative distillation of one of the reaction products. Chapter C reports a comprehensive study on the energy efficiency of microwave synthesis compared to classical techniques. Chapter D gives a detailed account of the use of silicon carbide (SiC) passive heating elements as power modulators and their use for the investigation of microwave effects. In Chapter E & F, we have successfully demonstrated that high-speed microwave chemistry can not only be performed with equal efficiency but also can be directly scaled up in a conventionally heated stainless steel micro-tubular flow reactor capable of achieving temperatures of 350 C and 200 bar. For applying the concept of Novel Process Windows, the Claisen rearrangement of allyl phenyl ether together with the ensuing rearrangement chemistry of the resulting 2-allylphenol product was investigated using a high T/p flow-reactor. This flow system additionally allowed studying these transformations in low boiling solvents in or near their supercritical state. In general, chemistry optimized under high-temperature microwave batch conditions could be successfully translated to a scalable flow regime.