Polyether 'crown' compounds are of much recent intere~tl-~ because of their often remarkable metal-ion selecti~ity,~-~ their ability to transport alkali metal ions through biological and artificial membranes5 and their application to organic synthetic pro- cedure~.~,~ In the continuation of our studies involving the chemistry of mixed-heteroatom 'crown' compounds,' we have adapted established procedures to the facile syntheses of new cyclic compounds of types (1)-(5). ...
