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 material. Depending on the bromine:thiacalix[4]arene ratios, the corresponding dibromo- and tetrabromo derivatives were obtained which opens the door for subsequent derivatisation of the upper rim of thiacalix[4]arenes. Interestingly, direct bromination of tetraalkylated compounds did not yield brominated derivatives. The structure of the tetrabromo derivative in the 1,3-alternate conformation was proven by X-ray crystallography.