Stereocontrolled oxidation of a thiacalix[4]arene to the sulfinyl counterpart of a defined SO configuration

Treatment of p-tert-butylthiacalix[4]arene (1) with benzyl bromide in THF–DMF using NaH as the base catalyst afforded the tetrabenzyl ether of cone conformation (4C) as the major product, oxidation of which, with NaBO3 in CHCl3–acetic acid, proceeded readily to give the corresponding sulfinyl compound (5) with the four SO groups disposed on the same side of the plane defined by the macrocyclic ring probably to avoid the steric hindrance imposed by the benzyllic moieties. Cleavage of the ether bonds gave a new stereoisomer of p-tert-butylsulfinylcalix[4]arene (2(ccc)) with the four SO groups arranged in a cis–cis–cis configuration.