text: In contrast to traditional combinatorial synthesis where a library of catalysts were first generated and later screened (as in the two above approaches), dynamic combinatorial library approach utilizes a mixture of multicomponent building blocks that reversibly form library of catalysts. With out a template, the library consists of a roughly equal mixture of different combination of building blocks. In the presence of a template which is either a starting material or a TSA, the combination that provides the best binding to the template is thermodynamically favorable and thus that combination is more prevalent than other library members. The biased ratio of the desired catalyst to other combinatorial products could then be frozen by terminating the reversibility of the equilibrium by means such as change in temperature, pH, or radiation to yield the optimal catalyst. For example, Lehn et al. used this method to create a dynamic combinatorial library of imine inhibitor from a set of amines and a set of aldehydes. After some time, the equilibrium was terminated by an addition of NaBHCN to afford the desired catalyst.