Calix[n]arenes represent a very attractive family of macrocyclic compounds with many potential supramolecular applications. Due to their well-established chemistry and many different synthetic strategies, enabling practically any derivatization of the basic skeleton, calixarenes are among the very popular building blocks used for the design and construction of various receptors, sensors and other sophisticated supramolecular systems. Regio- and/or stereo-selective derivatization of calixarenes currently represents a very extensive set of reactions, the overview of which would fill many thick books. Therefore, this review deals with only a small part of the above-mentioned reactions, specifically describes possible ways of bridging the upper rim of calixarenes, often leading to interesting rigidified structures, and also briefly mentions the potential use of these compounds.

• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

A Sonogashira coupling of meta-iodocalix[4]arene with various terminal acetylenes confirmed that the meta position of calixarene is well addressable, and that both thermal and microwave protocols led to good yields of alkynylcalixarenes. Alkynes thus obtained were subjected to the ferric chloride and diphenyl diselenide-promoted electrophilic closure. It turns out that the calix[4]arenes give completely different bridging products than those described for the non-macrocyclic starting compounds. This can be demonstrated not only by the isolation of products with a six-membered ring (6-exo-dig), but mainly by the smooth formation of the 5-endo-dig cyclization, which has never been observed in the aliphatic series. An attempt at electrocyclization led to a high yield of the 1,2-diketone (oxidation of the starting alkyne), again in contrast to the reaction described for the acyclic derivatives. The structures of the unexpected products were unequivocally established by X-ray analysis and clearly demonstrate how the preorganized macrocyclic skeleton favors a completely different regioselectivity of cyclization reactions compared to common aliphatic compounds.

• Klíčová slova
• 6-exo-dig and 5-endo-dig cyclization, Sonogashira coupling, X-ray analysis, alkyne cyclization, calixarene, diphenyl diselenide, electrochemistry, meta-substitution, regioselectivity,
• Publikační typ
• časopisecké články MeSH