Sustainable routes to polyurethane precursors

Kreye, Oliver; Mutlu, Hatice; Meier, Michael A. R.

doi:10.1039/c3gc40440d

Cited by 361 publications

(324 citation statements)

References 462 publications

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“…The phosgene route, however, has serious drawbacks such as handling of toxic feedstock and formation of corrosive HCl as a byproduct; thus, phosgene-free routes are now being developed in industry and academia [3,4]. The reductive carbonylation of nitro compounds was introduced as a promising and sustainable pathway [3], but the presence of highly toxic residues in the final products was reported [5]. Additional attractive routes are the conversion to carbamates, including the reductive carbonylation in alcohols [6] and the other reaction of primary or secondary amine with dialkyl carbonates, particularly dimethyl carbonate [7].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phosgene-free decomposition of dimethylhexane-1,6-dicarbamate over ZnO

et al. 2015

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In catalytic decomposition of dimethylhexane-1,6-dicarbamate (HDC) into hexamethylene-1,6-diisocyanate (HDI), Zn-containing homogeneous (i.e., zinc acetate) and heterogeneous (i.e., ZnO) catalysts were active among a number of catalysts tested, due to the great electron withdrawing ability of Zn ions. Particularly, when polyethylene glycol dimethyl ether was used as a solvent, ZnO was found to be relatively robust, because the catalytic performance was maintained up to the third use (HDC conversion of 93 % and HDI yield of 67 % at 180°C for 1 h). Through investigation of a HDC/ZnO mixture at elevated temperatures by IR spectroscopy, a possible reaction scheme of ZnO-catalyzed decomposition of HDC was proposed. The H atom is removed from the N-H group of HDC by hydrogen bonding with an O site on the ZnO surface, followed by coordination of an O-C=O group in monodentate mode to a Zn site. The C-O group in the O-C=O linkage is then cleaved yielding the isocyanate and surface methoxide species. Finally, methanol is released from ZnO by a reaction between the surface methoxide and the hydroxyl species.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Phosgene-free decomposition of dimethylhexane-1,6-dicarbamate over ZnO

et al. 2015

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“…However because of their high toxicity and highly exothermic isocyanate reactions, the traditional isocyanate route of making polyurea has been criticized for major contradiction to the principles of green chemistry [3]. For the last four decades, a non-isocyanate route (NIR) [4,5] has been an important subject of research in PU synthesis. However, few practical and low-cost non-isocyanate routes (NIRs) have been accomplished in industries.…”

Section: Introductionmentioning

confidence: 99%

Solvent-free processes to polyurea elastomers from diamines and diphenyl carbonate

Pan

Liao²,

Lin

et al. 2015

J Polym Res

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Two solvent-free processes without using volatile organic chemical (VOC) for making polyurea elastomers have been successfully developed from diamines and diphenyl carbonate (DPC) to meet stringent public demands for a high standard green alternative Anastas and Eghbali (Chem Soc Rev 39 (1): [301][302][303][304][305][306][307][308][309][310][311][312] 2010). In this new non-isocyanate route (NIR) which is an improvement over our previous process to polyurea elastomers, molten DPC are utilized as the carbonylation agents, where DPC reacts sequentially with 1,6-hexanediamine (HDA), polyether diamines of 2000 molecular weight and short chain diamines such as isophorondiamine (IPDA) or 4,4′-diaminodicyclohexylmethane (H 12 MDA). No solvent was added in the synthesis of these new non-solvent polyurea. Alternatively, the above process was modified with an 3 % addition of a water dispersant such as 3-[(2-aminoethyl)amino]-1-propane sulfonic acid sodium salt (ESA) to make waterborne polyurea elastomers to facilitate the mixing in the preparation and in the film-making steps for the final products. In both solvent-free processes, the longchained polyether diamine and the phenol generated from the displacement reaction of diphenyl carbonate were utilized as diluents to lower the viscosities of the reaction mixtures. Unexpectedly, ultra high molecular weight products were resulted particularly for the waterborne polyurea products measuring in excess of 1,000,000 g/mol in some cases. All samples were characterized by FT-IR, H-NMR, TGA, DSC, AFM and GPC. Since the polymers were prepared under mild conditions in absence of a VOC solvent, the new products were found to mostly exist in highly phase-segregated states, exhibiting high heat-resistant temperatures with T d(5%) of well over 300°C with high elongation (>600 %) for the optimized products. Thus, this solvent-free syntheses and environmentfriendly polyurea products should find usefulness in many practical applications.

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“…Recently, transition metal-catalyzed crosscoupling reactions allowed for the synthesis of ureas. [7] Guans group reported a palladium-catalyzed coupling reaction of aromatic amines with CO for the synthesis of symmetrical ureas. [8] Buchwald provided an efficient protocol for construction of unsymmetrical ureas via palladium-catalyzed cross-coupling reactions of aryl chlorides and triflates with sodium cyanate.…”

mentioning

confidence: 99%

Cobalt(II)‐Catalyzed Isocyanide Insertion Reaction with Amines under Ultrasonic Conditions: A Divergent Synthesis of Ureas, Thioureas and Azaheterocycles

Zhu

Cao

et al. 2014

Adv Synth Catal

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Abstract:Cobalt(II) acetylacetonate-catalyzed isocyaA C H T U N G T R E N N U N G nide insertion reactions with amines utilizing tert-butyl hydroperoxide (TBHP) as an oxidant under ultrasound conditions have been developed, which lead to the synthesis of ureas, thioureas, as well as 2-aminobenzimidazoles, 2-aminobenzothiazoles, and 2-aminobenzoxazoles under the general reaction conditions in up to 96% yields, respectively. The intermediate amino methylidyneaminiums, initiated by cobalt(II) acetylacetonate-catalyzed reactions of isocyanides with amines, could be easily trapped by different nucleophiles such as water, sulfur, and intramolecular nucleophilic functional groups. This method provides a simple, general and practical protocol for the divergent synthesis of ureas, thioureas and azaheterocycles.

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Sustainable routes to polyurethane precursors

Cited by 361 publications

References 462 publications

Phosgene-free decomposition of dimethylhexane-1,6-dicarbamate over ZnO

Phosgene-free decomposition of dimethylhexane-1,6-dicarbamate over ZnO

Solvent-free processes to polyurea elastomers from diamines and diphenyl carbonate

Cobalt(II)‐Catalyzed Isocyanide Insertion Reaction with Amines under Ultrasonic Conditions: A Divergent Synthesis of Ureas, Thioureas and Azaheterocycles

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