Regioselective Monoalkylation of Calixarenes. Synthesis of Homodimer Calixarenes

The selective monoalkylation at the smaller (lower) rim of the p-tert-butylcalix4]- and -6]arenes using bis(butyltin)oxide and different alkylating agents is described. The procedure is remarkable for the mild conditions used allowing an efficiently access to monoalkylated calixarene derivatives in moderate to good yields. Monoalkynylcalix4]arene and monoalkynylcalix6]arene have been synthetically exploited for the synthesis of bis-calixn]arenes (n = 4, 6) with a diyne bridge by oxidative coupling of alkynes. In addition, intermolecular methathesis of the obtained monoalkenyl-calix4]arene allowed the preparation of bis-calix4]arene that are single bridged at the smaller (lower) rim with a 2-butenyl moiety.