Macrocycles. 20. Cyclic Poly(ethylene glycol) Phthalates via Ring-Exchange Substitution

Abstract

Various oligo- and poly(ethylene glycol)s were transformed into tin-containing macrocycles by “polycondensation” with dibutyltin dimethoxide. These cyclic oligo- and poly(ethylene glycol)s were heated with a spirocycle derived from phthaloyl chloride and 1,2-dimercaptoethane. This spirocycle inserts into the Sn−O bonds with subsequent elimination of 2,2-dibutyl-2-stanna-1,3-dithiolane. By this ring-insertion/ring elimination mechanism, the Bu2Sn group in the cyclic polyethers was replaced by the phthalate unit without intermediate ring-opening. The cyclic poly(ethylene glycol) phthalates were characterized by elemental analyses by viscosity and DSC measurements, by 1H NMR, 13C NMR, and IR spectroscopy, and by MALDI−TOF mass spectrometry. Analogous experiments were conducted with a spirocycle derived from 4,5-dichlorophthalic acid which turned out to be less reactive than the unsubstituted phthalide. In summary, this new approach allows syntheses of cyclic polyether phthalates in high yields, in an “one-pot procedure” and without need of dilution.

Cyclic polymers: Synthetic strategies and physical properties

“…146 Since open chains are formed as reaction intermediates, both frequence distribution and average molecular weights of cyclic poly (ether phthalate)s are presumably different from the parent Sn-containing cyclic. This problem is avoided in the third approach which is based on a ring exchange reaction (3rd eq, Scheme 40), 147 which represents a new kind of ring modification. The resulting poly(phthalate)s were characterized by NMR spectroscopy and MT mass spectrometry.…”

Cyclic polymers: Methods and strategies

“…17 A variety of synthetic techniques have been used to remove Sn from the polymer without compromising the polymer's ring structure. 131 A more recent synthetic methodology, denoted as ringexpansion metathesis polymerization (REMP), is shown in Scheme 6. 84,88 The Ru-catalyst to produce cyclic polymers was designed with a N-heterocyclic carbene with a chelating N-to-Ru tether (where n in Scheme 6 represents the number of carbons within the ring).…”

Distinct topography of erosion and new bone formation in achilles tendon enthesitis: Implications for understanding the link between inflammation and bone formation in spondylarthritis

“…Since open chains are formed as reaction intermediates, both frequence distribution and average molecular weights of cyclic poly (ether phthalate)s are presumably different from the parent Sn‐containing cyclic. This problem is avoided in the third approach which is based on a ring exchange reaction (3rd eq, Scheme ),147 which represents a new kind of ring modification. The resulting poly(phthalate)s were characterized by NMR spectroscopy and MT mass spectrometry.…”