Use of Hazardous Elements and Building Blocks - Direct Routes

3 Use of Hazardous Elements and Building Blocks - Direct Routes 

One way of process simplification is to make molecular complex compounds out of much simpler building blocks (e.g., by multi-component one-pot syntheses like the Ugi reaction), at best directly out of the elements. Especially in the latter case, this is often quoted as a dream reaction [14]. Typically, such routes have been realized so far with hazardous elements, easily undergoing reaction, but lacking selectivity. One example is direct fluorination starting with elemental fluorine, which has been performed both with aromatics and aliphatics. Since the heat release cannot be controlled with conventional reactors, the process is deliberately slowed down. While, for this reason, direct fluorination needs hours in a laboratory bubble column it is completed within seconds or even milliseconds when using a miniature bubble column operating close to the kinetic limit. Also, conversions with the volatile and explosive diazomethane, commonly used for methylation, have been conducted safely with microreactors in a continuous mode [14]. 

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