Consequently, olefins have built-in reactivity that can be used for their transformation into useful intermediates and products. Of foremost importance, olefins are the progenitors of even higher energy intermediates, such as epoxides, aziridines, cyclic sulfates, aziridinium ions, and episulfonium ions. Modern organic chemistry is at the stage at which a molecule of virtually any complexity can be prepared in a number of synthetic steps. On the other hand, transition elements in general, and osmium in particular, often can carry out catalysis just as well in water, and often better than in nonaqueous solvents. In recent years, we realized that water is indeed an excellent solvent for many processes catalyzed by transition metals, and we are developing a number of practical oxidations that use water as the sole solvent.
Olefins are easy to oxidize selectively, producing a variety of even more reactive intermediates.
The reaction must be modular and wide in scope, give very high yields, generate only trivial byproducts that can be removed by nonchromatographic methods, and be stereospecific. Despite the apparent simplicity of click chemistry, quite complex molecules can be rapidly assembled. An example of a click reaction we exploited in the successful synthesis of diverse molecular libraries is the addition of heteronucleophiles to epoxides and aziridines. A generalized reaction sequence through which we have synthesized more than 1000 individual compounds is shown in Figure 3. In short, among the approximately infinite number of candidates of less than 500 amu, we aim to find the gems that are also simple to make.