The application of silica-supported TEMPO as a recyclable catalyst in the Anelli oxidation of alcohols is reported. The catalyst is easily obtained in a one-step reductive amination procedure starting from a commercially available aminopropyl-functionalized silica. Details of the synthesis of the supported catalyst and its analysis by MAS NMR are presented. Various alcohol oxidations according to the Anelli protocol have been carried out and the stability of the applied silica-supported TEMPO has been studied.
Poly(esters amide)s from adipic anhydride and α,ω‐amino alcohols were obtained by polycondensation of α‐carboxyl‐ω‐hydroxyl amides under mild conditions in solution or by bulk polycondensation at elevated temperatures. For the polycondensation in bulk the influence of catalyst and of temperature on the number‐average molecular weight was studied. At a temperature of 170 °C the polycondensation process is followed by a ring‐closing depolymerisation and the formation of cyclic ester amides. Ten‐ to fourteen‐membered cyclic ester amides were obtained and characterized. The ring‐opening polymerisation of these cyclic ester amides leads, in a controlled mode, to poly(ester amide)s. The interconversion of poly(ester amide)s and cyclic ester amides by ring‐closing depolymerisation and ring‐opening polymerisation is possible. The poly(ester amide)s from adipic anhydride and homologous α,ω‐amino alcohols H2N(CH2)xOH (x = 2–6) are semicrystalline materials, their melting points show the odd/even effect observed for [n]‐polyamides and [n]‐polyurethanes.
The ring-opening polymerization of the cyclic ester amide (cEA, 2) (systematic name, 1-oxa-7-aza-cyclotridecane-8,13-dione)sprepared from adipic anhydride and 1-amino-5-pentanolsin the melt at temperatures above 145 °C with Bu2Sn(OMe)2, Ti(OBu)4, Al(O-sec-Bu)3, or Sn(octoate)2 as initiator yields the poly(ester amide) (PEA, 3) (systematic name, poly(5-(5-oxypentylcarbamoyl)pentanoate) with regular microstructure. This poly(ester amide) is a semicrystalline material with a melting point of 108 °C. The elementary chain growth reaction proceeds by a coordination insertion mechanism in analogy to the polymerization of lactones. The monomer-to-initiator ratio and the conversion determine the numberaverage molecular weight. By using hydroxy telechelic poly(ethylene oxide) with Sn(octoate) 2 as initiator poly(ester amide)-block-poly(ethylene oxide) and poly(ester amide)-block-poly(ethylene oxide)-block-poly-(ester amide) were obtained. Kinetic studies for different monomer-to-initiator ratios, different temperatures and initiators reveal that the ring-opening polymerization is a first-order reaction with respect to the monomer and shows no termination and transfer reactions.
The ring‐opening polymerization (ROP) of the cyclic ester amide (cEA) 5 (systematic name, 1‐oxa‐8‐aza‐cyclotetradecane‐9,14‐dione) ‐ prepared from adipic anhydride and 1‐amino‐6‐hexanol ‐ in the melt at 165 °C and in solution at 100 °C and 120 °C with Bu2Sn(OMe)2 or Ti(OBu)4 as initiator yields the alternating poly(ester amide) (PEA) 4 (systematic name, poly(5‐(6‐oxyhexylcarbamoyl)‐pentanoate) with regular microstructure. Kinetic studies for different monomer‐to‐initiator ratios, different reaction media, initiators and temperatures reveal that the ROP is a first‐order reaction with respect to the monomer. Under suitable polymerization conditions termination and transfer reactions are suppressed. The elementary chain growth reaction proceeds by a coordination insertion mechanism in analogy to the polymerization of lactones. By using monohydroxy‐ and bishydroxy‐functional telechelic poly(ethylene oxide) and Sn(octoate)2 as the initiating system poly(ethylene oxide)‐block‐poly(ester amide)s and poly(ester amide)‐block‐poly(ethylene oxide)‐block‐poly(ester amide)s are obtained. The poly(ester amide) 4 is a semicrystalline material with a melting point of 140 °C, the block copolymers are phase separated systems showing two melting points characteristic for the respective homopolymers.
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