Meta substitution of calixarenes

Abstract

The electrophilic aromatic substitutions of calixarenes usually lead to their para-substituted derivatives due to the directing effect of hydroxy or alkoxy groups. However, introducing even one substituent to a meta-position, we can obtain inherently chiral compounds which, for example, could be used as ligands in enantioselective reactions. Whereas procedures leading to para-substituted derivatives are already quite well-known in calixarene chemistry, meta-substitutions usually need more demanding approaches to force the calixarene system to react in its meta-positions. In this chapter, we highlight the most common ways to obtain these derivatives: step-by-step fragment condensations, the use of ortho-orienting groups or intramolecular ring closing of already para-substituted compounds, p-bromodienone route and direct mercuration reactions leading to useful intermediates for further transformations.