Unusual Reaction of Macrocyclic Uracils with Paraformaldehyde

The ability of simple uracils to afford bis(uracil-5-yl)methanes upon reaction with paraformaldehyde is well documented. This reaction has been used in the preparation of pyrimidinophanes. The extension of the scope of this reaction to the synthesis of multipyrimidinophanes has been reported. Starting with isomeric pyrimidinophane containing 6-methyluracil and 5-methyluracil (thymine) moieties, linearly arranged multimacrocycles were prepared. A completely unexpected result was that the reactions of isomeric pyrimidinophanes containing 6-methyluracil moieties with paraformaldehyde produced only cyclic-arranged macrocycles, in particular, cryptand-like pyrimidinophanes and multipyrimidinophanes with a cyclic topology.