Synthesis and Ion Selectivity of Tetrakis[(N,N-dialkylaminocarbonyl) methoxy]homocalix[4]arenes

Abstract

An attempted O-alkylation of the flexible macrocycle 1 withN,N-dialkylchloroacetamides in the presence of NaH, K2CO3 or Cs2CO3 gave only one pure stereoisomer 1,4-alternate-2a–c, while other possible isomers were not observed. In contrast, only an intractable mixture was obtained when Na2CO3 was used as base. The structural characterization of these products is discussed. The two-phase solvent extraction data indicated that tetrakis(N,N-dialkylaminocarbonyl) derivatives 2b–c show strong alkali metal cation affinity and the extractabilities are much higher than that for the corresponding calix[4]arene tetraethyl ester 4 and homocalix[4]arene tetraethyl ester 3. High Li+ and Na+ extractabilities were observed for tetrakis[(N,N-diethylaminocarbonyl) derivative 2b. However, no significant high ion selectivity for alkali metal cations was observed in tetraamide 2b. 1H-NMR titration of tetraamide 2b with KSCN clearly demonstrates that a 1:1 complex is formed with retention of theoriginal symmetry to be conformationally frozen on the NMR time scale.