One- and two-step metal ion templated syntheses of the cryptands

Article abstract of DOI:10.1016/0040-4020(94)01051-Z

New cryptands [3.2.1], [4.2.1] and [4.2.2] were prepared in good yields by treating the appropriate diazacrown with the ditosylate esters of triethylene, tetraethylene or pentaethylene glycol as required. Treatment of 4,10-diaza-15-crown-5 with α,α'-dibromo-m-xylene gave a mixture of the cryptand (1:1 cyclization) and the tricyclic bisdiaza-15-crown-5 connected by two m-xylylene units (2:2 cyclization) when K₂CO₃ was used as the base. When Li₂CO₃ was used, the same reaction gave only the 1:1 cyclization. An ¹H NMR spectrum of the m-xylylene-containing cryptand exhibited a peak at δ 8.85 which suggests that the proton on benzene position 2 is close to the diaza-15-crown-5 cavity. The X-ray crystal structure of that compound showed that to be the case. A metal ion template effect was also observed in the preparation of [3.3.3] from 3,6,9-trioxa-1,11-diiodoundecane and its diamine analog. Only [3.3.3] was observed with K₂CO₃. When Cs₂CO₃ was used, mainly a bis(aza-12-crown-4) was isolated. When the diiodide was changed to the corresponding ditosylate, both [3.3.3] and the bis(aza-12-crown-4) were isolated.