Alternative reaction conditions: Enabling technologies in solvent-free protocols

Solventless and solid-state reactions have become increasingly popular and appealing options in the field of green chemistry and process intensification as they can often minimise waste and energy costs. A variety of strategies and protocols (in particular ball milling, dielectric heating and reactive extrusion) have been developed and improved over the last two decades. Although this account cannot be comprehensive, it will, however, provide a glimpse of such methods, highlight the advantages and limitations of strategies and discuss some mechanistic considerations. A few examples for each case, often from our own laboratories, will be used to illustrate specific applications.