Synthesis and characterization of p-tert-butylcalix[6]-1,4-crown-4-2,6-crown-5, p-tert-butylcalix[6]-1,4-benzocrown-4-2,3-crown-5

Two new types of calix[6]-bis-crowns, p-tert-butylcalix[6]-1,4-crown-4-2,6-crown-5 and p-tert-butylcalix[6]-1,4-benzocrown-4-2,3-crown-5, have been synthesized and characterized. The conformation of p-tert-butylcalix[6]-1,4-crown-4-2,6-crown-5 may be (u,d,d,u,d,d) or (u,d,u,u,u,d), and can not be further assigned, the latter adopts (u,u,u,u,u,u) conformation at room temperature.