Abtract:
Cyclophanes are a tremendously diverse class of compounds owing to the open-ended definition of what a cyclophane is. Small cyclophanes are among the most interesting sub-sets of cyclophanes due to their molecular strain, which often imbues them with unusual chemical and physical properties. Such systems can also pose stiff synthetic challenges. From a strategic perspective, there is only one general strategy that has proved to be up to the task of generating the most strained cyclophanes. Recently, we have developed a new strategy for the synthesis of small, strained cyclophanes called contractive annulation. This approach involves the annulation of both bridge and arene atoms such that the growth of the aromatic system is accompanied by a shortening of the bridge. The application of this strategy to the synthesis of some very unusual cyclophanes will be presented.