No abstract

No abstract

A one-step method for the synthesis of new phenol-containing cryptands and cryptohemispherands by treating N,"-bis(methoxymethy1)diazacrowns with the appropriate bis-and trisphenols is reported. This method, based on a special Mannich reaction, gives cyclized products without the need for protecting groups and high dilution conditions. Unusually high yields of cryptohemisherands were realized using a relatively high concentration of the starting materials (50 mmol/ L) and in the absence of metal cations as template agents in the reaction mixture. These excellent yields can be explained by intramolecular hydrogen bonding which prevents polycondensation. This new method also allowed preparation of new phenol-containing cylindrical tricyclic ligands by first forming bisphenol-substituted diaza-18-crown-6 at 80 "C followed by its reaction with a second bis(methoxymethy1)-substituted diaza-18-crown-6 at 144 "C. Crystal structures of two cryptohemispherands are reported herein. A shorter internal distance between N and 0 atoms in 27 as compared to 6 (R = NOz, n = m = 2) indicates intramolecular hydrogen bonding in phenol-containing macrocycle 27.

No abstract

No abstract