4-TERT-BUTYLCALIX[8]ARENE

white to off-white micro-crystalline powder

Starting material for further derivatization, including halogenation, acylation, and diazo coupling.

The calixarene recrystallises from CHCl3 in fine colourless, glistening needles. It melts sharply between 400-401o and 411-412o depending on the sample and is sensitive to traces of metal ions. On TLC with silica gel (250\m thick) and elution with CHCl3/hexane (3:4) it has RF 0.75. The octa-acetate is prepared from 8g in Ac2O (50mL) and 2 drops of conc H2SO4 and refluxed for 2hours. On cooling, a colourless precipitate separates and is recrystallised from Ac2O (1.2g 48%) with m 353-354o. The (SiMe3)8 is prepared from 4-tert-butylcalix[8]arene (0.65g) in pyridine (4mL) with excess of hexamethyldisilazane (1mL) and trimethylchlorosilane (0.5mL) and refluxed under N2 for 2hours. Cool, evaporate the pyridine, triturate the gummy residue with MeOH. Chromatograph on silica gel using hexane/CH2Cl2 gave 0.5g (61%) with one spot on TLC. Recrystallise it from hexane/Me2CO to give colourless needles m 358-360o. [Gutsche et al. J Am Chem Soc 103 3782 1981, Gutsche & MuthuKrishnan J Org Chem 43 4905 1978, Gutsche & MuthuKrishnan J Org Chem 44 3962 1979, Andretti et al. J Chem Soc, Chem Commun 533 1981; see Kluawer in Calixarenes, Vicens & B.hner eds Academic Press 1991.]