Alkoxide-Initiated Regioselective Coupling of Carbon Disulfide and Terminal Epoxides for the Synthesis of Strongly Alternating Copolymers

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• 作者：Johannes Diebler ; Hartmut Komber ; Liane Häußler ; Albena Lederer ; Thomas Werner
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：July 12, 2016
• 年：2016
• 卷：49
• 期：13
• 页码：4723-4731
• 全文大小：442K
• 年卷期：0
• ISSN：1520-5835

文摘

The synthesis of highly regioregular and alternating polythiocarbonates from carbon disulfide and terminal epoxides has been achieved. The copolymerizations were performed under ambient and solvent-free conditions in the presence of LiO^tBu (0.125–0.5 mol %) as initiator. At higher loadings the reaction pathway switched in favor to the catalytic formation of cyclic dithiocarbonates. Under optimized reaction conditions polymers with molecular weights up to 109 kg mol^–1 were isolated. The NMR spectroscopic analysis of the polythiocarbonates revealed that 94% of backbone structure is formed by strongly alternating head-to-head arrangement of epoxypropane and 1,2-epoxybutane monomers, respectively, at a thiocarbonate group −CHR–OC(S)O–CHR– and tail-to-tail arrangement at a trithiocarbonate group −CH₂–SC(S)S–CH₂–. Atactic polymers were obtained using racemic mixtures of the epoxides, but an isotactic polymer was obtained when chiral (R)-epoxypropane was converted. A mechanism is proposed which rationalizes the regio- and stereochemistry observed for the alkoxide-initiated copolymerization of CS₂ and terminal epoxides.