Upper rim substitution of thiacalix[4]arene

Upper rim bromination of thiacalix[4]arene has been achieved for the first time using a distally disubstituted thiacalix[4]arene as a starting materia l. Depending on the bromine:thiacalix[4]arene ratios, the corresponding dib romo- and tetrabromo derivatives were obtained which opens the door for sub sequent derivatisation of the upper rim of thiacalix[4]arenes. Interestingl y, direct bromination of tetraalkylated compounds did not yield brominated derivatives. The structure of the tetrabromo derivative in the 1.3-alternat ive conformation was proven by X-ray crystallography. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.