Beneficial reactions, microwave scale

Scale-up as defined for this chapter covers batch reactions in closed vessels at the > 50 mL scale, flow systems employing flow cells > 5 mL, and SF containers of > 50 mL volume. Microwave-mediated scale-up reactions under open vessel conditions are not discussed in detail as up to date only a few examples have been published [33-37] and most of the beneficial rate enhancements have been reported under sealed vessel conditions. 

Overall, the authors expect that it is now clear to the reader that microwave technology not only can reduce reaction times from hours to seconds and improve yields and selectivities of known transformations but also can facilitate the discovery of new and unforeseen stereoselective reactions because of convenience in reactions parameters control provided by modem dedicated equipment. Also, the early scalability issues of microwave-assisted processes have been solved, and dedicated industrial-scale systems are available. Although the actual reasons for the beneficial effect of microwave irradiation are not completely well understood and are still debated, the bottom line is that when a thermal activation is needed to perform an organic transformation, microwave irradiation should be the first choice and not the last resort. 

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