3-Aminoimidazo pyridines libraries

A library of biologically relevant 2-aryl-3-aminoimidazo[l,2-fl]pyridines and 2-aryl-3-aminoimidazo[l,2-fl]pyrazines was created using a combina-... 

The time consuming chromatographical purification of heterocycles 28 and 29 slowed down the rate of library production. A phase separation using fluorous chemistry was employed by Zhang and Lu to address the workup and purification of fused 3-aminoimidazo[ l,2-a]pyridines (such as 30) [54]. Thus, attachment of a perfluorooctanesulfonyl tag to aldehydes and subsequent Ugi three-component microwave-assisted condensations with 2-aminopyridines and isocyanides furnished the desired heterocycles 30, which were conveniently isolated by fluorous solid-phase extraction. The fluorous tag could be subsequently used as an activating group in the post-condensation modifications, such as Suzuki-Miyaura cross-coupling reactions. 

The same group reported on a library synthesis of 3-aminoimidazo[l,2-a]-pyridines/pyrazines by fluorous multicomponent reactions. Here the overall yields, as well as the yields for the separate Suzuki-Miyaura reactions that were a part of the synthesis, were relatively low due to competing reactions and the poor reactivities of the substrates, but the speed of the microwave-mediated syntheses and ease of separation underlined the usefulness of fluorous reagents [140]. A recent paper further illustrated the use of Suzuki-Miyaura couplings of aryl perfluorooctylsulfonates in the decoration of products derived from 1,3-dipolar cycloadditions [141]. 

---