Monatshefte f€ ur Chemie 134, 509–518 (2003) DOI 10.1007/s00706-002-0547-y Synthesis and Complexation Properties of Some Novel Lariat-Crown Ethers Ralf Smounig 1 , C. Oliver Kappe 1 , Curt Wentrup 2 , and Gert Kollenz 1; 1 Institut f€ ur Chemie, Bereich Organische & Bioorganische Chemie, Karl-Franzens Universit€ at Graz, A-8010 Graz, Austria 2 Department of Chemistry, The University of Queensland, Brisbane, Qld 4072, Australia Received July 5, 2002; accepted July 19, 2002 Published online March 6, 2003 # Springer-Verlag 2003 Summary. Several new lariat-crown ethers bearing either bridged bisdioxine or tetraoxaadamantane units as chiral substituents are prepared by reacting the corresponding amino-crown ether derivatives with the dimeric -oxoketene, the latter obtained by flash vacuum pyrolysis of a furan-2,3-dione precursor. Complexation properties towards differently charged metal ions are investigated by 1 H NMR titration to obtain complexation constants (K c -values for potassium=sodium rhodanides: 480–1100 mol dm  3 ), as well as extraction experiments to explore the metal ion transportation abil- ities of the new lariat crown derivatives. In particular, a significantly increased ability to transport metal ions from water into chloroform was found with spherical tetraoxaadamantyl derivatives when com- pared with the free amino-benzocrown ethers. Keywords. Lariat-crown compounds; Complexes; NMR titration; Extraction experiments. Introduction Flash vacuum pyrolysis of t-butyl-pivaloylfuran-2,3-dione generates dipivaloyl- ketene (1), a remarkably stable -oxoketene, which smoothly dimerizes to afford the extraordinarily stable dimeric dipivaloylketene 2 in nearly quantitative yield [1]. Oxoketene 2, when reacted with primary arylamines, rearranges into function- alized 2,6,9-trioxabicyclo[3.3.1]nona-3,7-dienes (‘‘bridged bisdioxines’’) 3, rather rare concave heterocyclic systems exhibiting axial chirality [2]. Furthermore, com- pounds 3 may easily be converted into 2,4,6,8-tetraoxaadamantanes 4 in high yields by simple acidic hydrolysis [3]. Both heterocyclic systems (3 and 4) have been applied as novel spacer units by incorporation into macrocyclic systems of the  Corresponding author. E-mail: kollenz@kfunigraz.ac.at