the formylationreactions (Gross and/or Duff conditions) of the corresponding tetrapropoxythiacalix[4]arene immobilized in the 1,3-alternate conformation were systematically studied. Surprisingly, albeit using an excess of the formylation agent, only two formyl groups were introduced exclusively into the meta positions of thiacalixarene skeleton. Unexpected regioselectivity of these reactions opens
The formylation of the upper-rims of thiacalixarenes: synthesis of the first tetra-formylated and the first meta-substituted thiacalix[4]arenes
作者:Cedric Desroches、Vadim Kessler、Stephane Parola
DOI:10.1016/j.tetlet.2004.06.078
日期:2004.8
The conventional Gross reaction for the formylation of the tetrapropoxythiacalix[4]arene using TiCl4 affords the 18-(chloromethyl)-28-hydroxy-25,26,27-tripropoxythiacalix[4]arene substituted in the meta-position of the macrocycle. The p-tetraformyl-tetrapropoxythiacalix[4]arene, which is an interesting intermediate to the upper-rims functionalization of thiacalixarenes, was prepared with a very good