The synthesis and polymerization of oxo‐crown ethers

Abstract

A novel synthetic route to and a polymerization procedure for 0x0-crown ethers 2,ll -dioxo-18-crown-6 (l), 2-0x0-12-crown-4(2) and 2-0x0-2 1-crown-7 (3) are described. Cyclization of the o-hydroxycarboxylic acid precursors of 1-3 has been achieved by heating these precursors in the presence of a Lewis acid catalyst (CoClZ) and a template salt (MCl). Cyclization yields up to 82% were reached, using CsCl as template salt. 0x0-crown ethers 1-3 have been polymerized using SnOctz as catalyst, giving polymers with molecular weights of approximately 5 kg/mol and dispersities of ca. 1.8 (measured with polyethylene oxide standards). The polymerization of 2 was monitored with 'H-NMR and SEC giving information about (a) the influence of monomerkatalyst ratio and temperature on polymerization rate and (b) the influence of temperature on molecular weight (distribution). The possibility of introducing endgroups into poly(2-0x0-12-crown-4) using SnOctz-catalyzed polymerization was also studied. 1 2 3 and 7 b were obtained in isolated vields of 55% and 76%. CO) e, O J L O J L J O L J w 0 Acta Polymer., 47,485491 (19%) 0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim, 1996

Polymer-supported syntheses of oxo-crown ethers and derivatives containing α-amino-acid residues

“…In agreement with earlier reports [24], we found that acids of this type tend to oligomerize on storage. For example acid 4 after storage for 14 days at 23°C had oligomerized to give, by high pressure liquid chromatography (HPLC) analysis and mass spectrometry (MS), a mixture of the starting acid (88%), the linear dimer (8%) and the linear trimer (2%).…”

“…Hydroxy-acids 4 [24], 5 [24] and 6 [25] were prepared, respectively, from di-, tri-and tetra-ethylene glycol by literature methods. In agreement with earlier reports [24], we found that acids of this type tend to oligomerize on storage.…”

“…Studies to prepare macrocycle libraries using products similar to the above by reversible cleavage of the ester linkages are in hand. ED-ROPs of macrocycles 11 and 12, and related compounds, have been reported [24,31].…”

Unconventional, Amphiphilic Polymers Based on Chiral Poly(ethylene oxide) Derivatives. 2. Ordering and Assembly

“…O-Monobenzyl hexaethylene glycol has been described elsewhere. 22 Oligomer 5 was synthesized by protection of Omonobenzyl hexaethylene glycol with MEMCl in refluxing CH 2 Cl 2 , employing N(i-Pr) 2 Et as HCl scavenger. Production of the quinoline-derivatized oligomer (SS)-6 was achieved by tosylation of the R,ω-diol (SS)-8 in CH 2 -Cl 2 using KOH as base and by coupling of the resulting tosylate (SS)-9 with 8-hydroxyquinoline (Scheme 1).…”

Unconventional, Amphiphilic Polymers Based on Chiral Poly(ethylene oxide) Derivatives. I. Synthesis and Characterization

“…The final cyclization step was achieved by heating the appropriate ω-hydroxycarboxylic acid precursor with the Lewis acid CoCl 2 (.11 mol %) at 250°C in a Kugelrohr apparatus. 12 An almost pure distillate could be collected, when reduced pressures of 2-3 and 8 mmHg were applied for (S)-21 and (S)-22, respectively. Chromatography afforded the 2-oxo-12-crown-4 compounds (S)-5 and (S)-6 in yields of 72% and 56%, respectively.…”