If given sufficient time and resources, chemists can synthesize almost any tiny organic molecule. Such efforts are the basis of many technologies that have enormous societal value, such as agrochemicals, polymers, and medicines. For these applications to make the range of molecules, chemists have various methods that promote specific chemical changes, often with exquisite selectivity.
Countless chemical-synthesis methods are discovered and published daily. The existing techniques most involve relatively small, practical changes or modest advances in the scope of known reaction types. For scientific progress, these advances are essential incremental improvements are crucial. Methods occasionally emerge that have more far-reaching implications.
Chemical syntheses are usually conceived using a process known as retrosynthetic analysis. In this analysis, the chemist starts by considering the chemical structure of the target molecule and then works backward in which individual bonds are mentally disconnected in the target molecule. The idea is to break it down into simpler and small chemical fragments. A synthetic route is then devised by working out a series of reactions that in the reverse sequence leads from the fragments back to the target. Any given target molecule can be a disconnect in many ways. But the primary consideration is that each step in the forward chemical synthesis must be a reaction that can be developed or a known type of chemistry. Therefore, for common molecular motifs, chemists typically rely on tried-and-tested disconnections because this usually ensures that the forward synthesis is productive.
Using established chemistry knowledge of which bonds can or cannot be disconnected and applying this knowledge systematically is essential. But there is also a large creative aspect to synthesis; indeed, many of the best syntheses are said to be on the borderline between science and art. Finding a disconnect for which no synthetic methods exist for the equivalent forward reaction requires creativity and inspiration, and subsequent development of the requisite techniques is complex. But chemists will always like such challenges because they open up strategies for synthesis that earlier couldn’t be achieved.