Structurally-unusual calix[4]arene derivatives generated by intra-and intermolecular McMurry reactions

A new class of calix[4]arene derivatives with highly strained structures has been synthesized by intramolecular reductive dimerization of appropriate formyl groups in the presence of low-valent titanium agents (so-called McMurry reaction). New derivatives possessed very interesting molecular structures with upper rims intramolecularly connected by a CH=CH bond and are immobilized either in cone or in 1,3-alternate conformation. The cage compound with inner space perfectly closed by four aromatic units has been obtained from a tetraformyl derivative in 1,3-alternate conformation. Intermolecular reductive coupling of two monoformylcalix[4]arenes has yielded a bis-calixarene derivative which was found to behave as a good host molecule for quaternary ammonium salts.