Complexation of quaternary ammonium ions by tetraester derivatives of [3.1.3.1]homooxacalixarene in mobile and in fixed conformation.
In the tetraalkylation of p-tert-butyl[3.1.3.1]homooxacalixarene with BrCH2CO2R and K2CO3 in acetone, the initially formed cone conformer is converted into the more stable 1,4-alternate conformer when R = Me or Et, but not when R = i-Pr or t-Bu. In the case of R = i-Pr, derivatives in fixed 1,4-alternate conformation and in partial cone conformation were also isolated. Compounds in fixed cone conformation are good ligands for tetramethylammonium, acetylcholine, and N-methylpyridinium salts in CDCl3, but the partial cone isomer proved to be somewhat better and even the 1,4-alternate conformer turned out to be active. The possible involvement of the ester functions as additional binding sites is discussed; moreover, an insight into the energetics of the complexation and conformational isomerization processes is given.
Masci
Bernardo
B
Dipartimento di Chimica and IMC-CNR, Università La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. bernardo.masci@uniroma1.it
Persiani
Daniela
D
Thuéry
Pierre
P
D000478:Alkylation; D001665:Binding Sites; D047250:Calixarenes / Q000138:chemical synthesis* / Q000737:chemistry; D004952:Esters / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D000644:Quaternary Ammonium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013237:Stereoisomerism
D004952:Esters; D008024:Ligands; D000644:Quaternary Ammonium Compounds; D012996:Solutions; C517332:p-tert-butyl(3.1.3.1)homocalixarene; D047250:Calixarenes