Alkylation of thiacalix[4]arenes

Thiacalix[4]arenes were alkylated using procedures well established in ‘classical’ calixarene chemistry (PrI/K2CO3/acetone or PrI/NaH/DMF) to reveal conformational preferences in the thiacalixarene series. Surprisingly, the conformer distribution of tetraalkylated products is different from that of calix[4]arene. The 1,3-alternate conformers are well accessible in high yields (>60%) while the cone conformation forms only in very low yields (<20%). Moreover, the conformational outcome of the alkylation strongly depends on the upper rim substitution (tert-butyl versus H).