Macrocycles, 5. Ring expansion of macrocyclic tin alkoxides with cyclic anhydrides

Abstract

SUMMARY: At moderate temperatures the dimeric 2,2-dibutyl-2-stanna-1,3-dioxolane (DSDOL) and the monomeric 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) add to equivalents of succinic anhydride by a clean insertion reaction into the Sn1O bonds. The resulting 30-and 17-membered macrocycles are stable up to temperatures around 115 8C and do not eliminate Bu 2 SnO in the contrast to literature reports. When succinic or glutaric acid were added to tin-containing macrocyclic poly(e-caprolactone) again no elimination of Bu 2 SnO was observed. After removal of the Bu 2 Sn groups under mild conditions telechelic poly(e-caprolactone)s with two carboxylic endgroups were isolated.

Macrocycles, 16. Macrocyclic Dibutyltin Dicarboxylates via Thermodynamically Controlled Polycondensations

“…It was known from previous measurements [14] that the Sn1O bond was cleaved during sample preparation for the MALDI-TOF mass spectrometry experiment, either by hydrolysis or by interaction with the matrix (containing phenolic OH groups). In this work two series of measurements were performed either using a Bruker "Biflex III" apparatus using dithranol as matrix or by means of a Shimadzu Kratos Kompact III using 2,4,6-trihydroxyacetophenone hydrate as matrix.…”

Ring-opening polycondensations

“…One obvious method consists of copolymerizations of two (or more) different lactones. For instance DSDOP initiated mixtures of two lactones (or cyclocarbonates) may yield random copolymers 17,24,25) . However, the stepwise addition of two lactones may yield a cyclic block copolyester 9 (Eq.…”

“…(10)) 17,24) , which upon polycondensation with a dicarboxylic acid dichloride (Eq. (11)) yields a multiblock copolyester 10 15,25) . Multiblock copolyester composed of polylactone blocks and blocks of quite different chemical structure can easily be prepared by using the large macrocycles of structure 4, 5 or 6 as initiators.…”

Topological polymer chemistry for designing multicyclic macromolecular architectures

“…However, the reactive propagating unit is inherently included in the backbone segment, and it is not readily removed by retaining the ring polymer structure. 41,42 To circumvent this problem, a ring-expansion polymerization has been combined with the end-linking technique. 43 Thus, as a typical example, a cyclic stannous dialkoxide has been used as an initiator for the ring-opening polymerization of e-caprolactone.…”