Synthesis of p-tert-butylcalix[6]-1,4-2,5-bis-crowns

The synthesis and complexation properties of the first example of p-tert-butylcalix[6]-1,4-2,5-bis-crowns are reported. Their complexation abilities and selectivities are different from that of analogous calix[6]crown. Compound 2b exhibits high complexation selectivity towards n-PrNH3+.