Calix[4]arene Derivatives Monosubstituted at All Four Methylene Bridges

The scope of the reaction of the tetrabromocalixarene derivative 2b with alcohols under solvolytic conditions in trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) was explored. The reaction proceeded readily with MeOH, EtOH, n-PrOH, ethylene glycol and i-PrOH affording preferentially the rccc isomer of the tetrasubstituted product. The methoxy derivative 6a undergoes isomerization upon attempted recrystallization from CHCl₃/MeOH and its rcct and rctt forms were characterized by X-ray crystallography. Incorporation of hydroxy groups on the bridges was accomplished via solvolysis in AcOH, followed by LiAlH₄ reduction of the acetoxy groups. Reaction of the tetra-(2-methylfuranyl)calixarene derivative 11 with benzyne followed by deoxygenation with Me₃SiCl/NaI afforded in low yield the tetra-(4-methylnaphthyl)calix[4]arene derivative 12. Reaction of de-tert-butylated tetrabromo derivative 2a with m-xylene in HFIP followed by methylation of the crude product afforded the tetraxylyl derivative 14.