Synthesis and host-abilities of some new corands bearing uncommon chiral spacer units

Benzo- and naphtho-ethylene glycols are prepared from dihydroxy-benzenes or -naphthalenes and the corresponding chloroethoxyethanols using known procedures. Cyclocondensation reactions of these open-chain diols with the chiral and concave tetra-t-butyl-2,6,9-trioxabicyclo[3.3.1]nonadiene ("bridged bisdioxine") bisacid chloride afford several new corands. In one case, besides the expected macrocycle, an open-chain podand is obtained and further cyclized to a large 2:2 macrocycle. The bridged bisdioxine spacer may also be converted into the tetraoxaadamantane scaffold as shown with an example. Extraction experiments employing selected corands towards various metal ions show a significant host-property towards Hg(II) salts for those macrocycles having o-disubstituted aryl groups incorporated, thus forming 1:1 complexes. NMR titration studies with sodium thiocyanate as well as with some organic guests do not exhibit significant host-guest interactions, in the case of Hg(II) thiocyanate a weak complexation was determined.