Cryptands Containing Sulfur and Nitrogen in the Bridges

Shortly after their first report of all-oxygen bridged cryptands, Dietrich, Lehn and Sauvage reported incorporation of sulfur in the strands. The experimental methods used were essentially similar to those applied in the syntheses of the parent cryptands. As in previous cases, a diacyl chloride was condensed with a diamine under high dilution conditions. In this case, however, the diamine contained sulfur atoms rather than oxygen. The synthesis of compound 5 was accomplished in two stages as illustrated below in Eq. (8.3). The first cyclization step affords the macrocyclic amine in 55% yield. The macrobicyclic product (5) is formed in 25% yield from the monocyclic diamine and the acid chloride. 

Compound 5 was analyzed by NMR spectroscopy to gain information relative to conformation and complexation preferences. When complexation with potassium cations was attempted, the N—CHj signals were affected more than others. When the cation present was Ag , the protons adjacent to sulfur were more strongly affected. This observation may indicate the relative binding sites for soft versus hard cations in this system.  

Synthesis of cryptands which contain nitrogen atoms in the bridges has also attracted Lehn s attention. In general, a similar synthetic strategy was utilized, but ni- 

An interesting alternative approach to the synthesis of a cryptand having nitrogen atoms in the bridges was presented by Newkome and coworkers. This group condensed triethanolamine with 2,6-dichloropyridine in a relatively straightforward but low yield (5%) nucleophilic aromatic substitution to form 7, illustrated below in Eq. (8.6). The identity of the compound was confirmed by X-ray structural analysis. 

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