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Macrocycles, 1. Macrocyclic polymerizations of (thio)lactones – stepwise ring expansion and ring contraction
Author(s) -
Kricheldorf Hans R.,
Lee SooRan,
Schittenhelm Nicole
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980201)199:2<273::aid-macp273>3.0.co;2-d
Subject(s) - chemistry , thiolactone , trimethylene carbonate , pentaerythritol , ring opening polymerization , polymer chemistry , polymerization , insertion reaction , thio , epoxide , organic chemistry , catalysis , polymer , fire retardant
2,2‐Dibutyl‐2‐stanna‐1,3‐dioxacycloalkanes were prepared from dibutyltin oxide and 1,2‐ethanediol, 1,3‐propanediol or 1,4‐butanediol. These tin heterocycles reacted stoichiometrically with double molar amounts of γ‐thiobutyrolactone by a stepwise insertion. In contrast to γ‐thiobutyrolactone an excess of γ‐thiocaprolactone resulted in additional insertion steps, i.e., polymerization of the thiolactone. Analogous insertion reactions were performed with a spirocyclic stannoxane derived from pentaerythritol. With ε‐caprolactone macrocyclic polymerization took place without stoichiometric intermediates. When the 2,2‐dibutylstanna‐dioxepane was reacted with an equimolar amount of 1,3‐dithian‐2‐one, the insertion step was immediately followed by a ring contraction reaction yielding 2‐stanna‐1,3‐dithiane and trimethylene carbonate which polymerized immediately. The application of this reaction sequence to macrocyclic stanna poly(ε‐caprolactone) yielded tin‐free macrocycles along with 2,2‐dibutyl‐2‐stanna‐1,3‐dithiane. This reaction sequence allows the synthesis of nontoxic, biodegradable macrocyclic polyesters.