Ultrasound mediated selective monoalkylation of 4-tert-butylcalix[6]arene at the lower rim

Regioselective synthesis of monoalkyl ethers of 4-tert-butylcalix[6]arene in good yield was achieved with a variety of electrophiles using 2.2 equiv. of potassium carbonate as base in acetonitrile under ultrasonic irradiation at ambient temperature.