Functionalized binaphthyl salophen crown ethers as models for the enzyme urease

Functionalized binaphthyl salophen crown ethers 2 and 3 containing a Lewis‐acidic uranyl cation were prepared by the Ba2+‐templated cyclization of dialdehydes 15 and 22, for which two convenient synthetic routes were developed, with diamines 23 and 24. Intramolecular complexation of the amide groups in metallomacrocycles 2 and 3 was demonstrated by the isolation of two different forms of 2a, which were observed to interconvert, by 1H‐NMR and IR spectroscopy and by electrochemical measurements. Use of diamine 24 during the cyclization resulted in the formation of two different stereoisomers of the monofunctionalized metallomacrocycles 3a‐d and in “sidedness” of the bisfunctionalized metallomacrocycles 3e and 3f. Solid complexes of urea and 2c and 2d were isolated, but no catalytic activity was observed for 2a in the hydrolysis of urea in dioxane / water.