Autoaccelerative diazo coupling with calix[4]arene: substituent effects on the unusual co-operativity of the OH groups

Abstract

Diazo coupling between calix[4]arene and five substituted benzenediazonium ions in tetrahydrofuran at 5 °C in the presence of pyridine afforded the tetrasubstituted calix[4]arenes as main products and small amounts of mono-, di- and tri-substituted calix[4]arenes even in the presence of unchanged calix[4]arene: the unusual autoaccelerative substitution reaction is attributed to the specific hydrogen-bonding effect among the calix[4]arene OH groups. The products were applied as new ‘chromophoric calix[4]arenes’, which selectively recognised Li⁺.