HETEROCALIXARENES FEATURING THE BENZIMIDAZOL-2-ONE SUBUNIT - SYNTHESIS AND X-RAY STRUCTURAL STUDIES OF SOLVENT INCLUSIONS

The heterocalixarenes 4a,b and 5a-f have been synthesized. Compounds 4 a,b and 5a-d were obtained by two-step fragment condensation from benz imidazol-2-one and 1,3-bis(bromomethyl)benzene building elements using blocking/deblocking, high dilution and template (Cs2CO3) techniques t o give 4a/5a and 4b/5b in an approximate 1:2 or 1:3 ratio of the cycle oligomers. The cleavage of the methyl ether groups of 5a and 5b yield ed the tetraphenols 5e and 5f, respectively The calix hosts 4a, 5a-c a nd 5f form crystalline inclusion compounds with organic solvent molecu les. X-Ray crystal structures of the solvent inclusions Sa methylene c hloride (1:1), Sb toluene water (1:2:1), Sc acetone methylene chloride (1:1:1) and Sf toluene (1:3)have been studied, The molecular structur es show a general trend of having enhanced calix-forming ability compa red with conventional calix[8]arenes of the same ring size. The shape of the host molecules appear to be determined by the packing of the sy mmetry centres of related host molecules on either one of the benzimid azolone rings yielding basket-like hosts (5a-c) or on one of the pheno l rings resulting in a chair-like host shape (5f), always exhibiting b ase-stacking characteristics between the aromatic planes concerned.