Synthesis and Complexation Properties of Pyrimidine‐Derived Crown Ether Ligands

Abstract

AbstractFive new proton‐ionizable macrocyclic ligands containing a pyrimidone‐subcyclic unit, 6–10, were prepared from the previously prepared pyrimidinocrown ethers 1–5 (see Figure 1 and Scheme 1). One of the new proton‐ionizable crown ethers is chiral. The proton‐ionizable pyrimidonocrown ethers were prepared in high yields by treating the appropriate methoxy‐substituted pyrimidinocrown with 5 M sodium hydroxide in a 50% alcohol‐water mixture. Complexation properties of four of the pyrimidine‐derived macrocycles were studied by various nmr techniques. Pyrimidono‐18‐crown‐6 (9) forms a strong complex with benzylammonium perchlorate and also forms a complex with benzylamine. (S, S)‐Dimethyl‐substituted pyrimidino‐ and pyrimidono‐18‐crown‐6 ligands 4 and 9 form stronger complexes with the (R)‐form of α‐(1‐naphthyl)ethylammonium perchlorate than with the (S)‐form. (S, S)‐Dimethyl‐substituted pyrimidono‐18‐crown‐6 (9) also forms a stronger complex with (R)‐α‐(1‐naphthyl)ethylamine than with the (S)‐form. The crystal structure for compound 7 is reported.