Siegfried Warwel

Polymers and surfactants on the basis of renewable resources

A new strategy for the preparation of different polymers and special surfactants was developed. First, unsaturated fatty acid methyl esters obtained from plant oils were converted to terminally unsaturated esters and alpha-olefins by metathesis with ethylene using heterogeneous rhenium or homogeneous ruthenium catalysts. These esters were directly copolymerized with ethylene by an insertion-type palladium-catalyzed polymerization to functionalized polyolefins. Polyesters were synthesized by metathetical dimerization of omega-unsaturated esters and subsequent polycondensation of the produced internally unsaturated dicarboxylic esters or by acidic transesterification with petrochemical diols and additional acyclic diene metathesis polymerization. Omega-epoxy fatty acid methyl esters, achieved by a new method of chemo-enzymatic epoxidation, were converted into polyethers with comb-structure catalyzed by aluminoxanes on the one hand and into sugar surfactants by nucleophilic ring-opening with amino carbohydrates on the other hand.

Chemo-enzymatic epoxidation of unsaturated carboxylic acids

Abstract Unsaturated carboxylic acids are converted to percarboxylic acids catalyzed by an immobilized lipase from Candida antarctica (Novozym 435 R ). These unsaturated percarboxylic acids are only intermediates and epoxidize themselves in good yields and almost without consecutive reactions. The mechanism of the oxygen-transfer is found to be predominantly intermolecular and the formation of the percarboxylic acids proceeds via two different catalytic reactions. The lipase is surprisingly stable under the reaction conditions; it is recovered and reused fifteen times to produce epoxy-stearic acid on a multi-gram scale.

Lipase-catalyzed preparation of peroxy acids and their use for epoxidation☆

Abstract The lipase-catalyzed reactions of carboxylic acids and carboxylic acid esters with hydrogen peroxide are used to generate various peroxy acids at room temperature and without mineral acids. Whereas Novozym 435 R will only be able to catalyze the conversion of free unbranched carboxylic acids to peroxy acids, α-methylsubstituted carboxylic acid ethylesters can be converted to peroxy acids by perhydrolysis using the same enzyme. These peroxy acids are used in-situ for the epoxidation of unsaturated compounds and thus a new versatile epoxidation method for organic synthesis is proposed.

Polyesters of ω‐Unsaturated Fatty Acid Derivatives

Unsaturated polyesters, based on ω-unsaturated fatty acid esters from oleochemical resources and petrochemical diols, were synthesized via two different synthetic pathways. 9-decenoic and 10-undecenoic acid methyl ester Ia, b were transesterified with petrochemical diols to produce the a,ω-alkylene di(un)decenoates IIa-d, which were subsequently converted into unsaturated polyesters by acyclic diene metathesis polymerization. A sercening of ten homogeneous and beterogeneous metathesis catalysts was performed, implying optimum results for B 2 O 3 -Re 2 O 7 /Al 2 O 3 -SiO 2 + SnBu 4 . Molecular weights (M w ) up to 100000 g/mol were determined by MALLS-GPC. On the ether hand, C 10 , C 11 and C 14 -ω-unsaturated fatty acid methyl esters Ia-c were metathetically dimerized using homogeneous ruthenium and tungsten carbene complexes at an extremely low catalyst concentration. The resulting symmetrical, internally unsaturated, dicarboxylic acid dimethyl esters IIIa-c were polycondensated in bulk with conventional transesterification catalysts achieving molecular weights (M w ) up to 110000 g/mol. Melting temperatures of 6 to 92°C were determined by DSC.

Lipase-catalyzed conversions of trimethylsilyl ethers : deprotection, acetylation, epoxidation and one-pot-multi-step reactions

Abstract Unsaturated trimethylsilyl ethers are converted by lipase-catalyzed hydrolysis of ethyl acetate directly to alkenol acetates; the hydrolysis of diethyl carbonate yields unstable carbonic acid monoethylester, which deprotects trimethylsilyl ethers under mild conditions and without remaining acid. By the analogous lipase-catalyzed perhydrolysis of these esters with hydrogen peroxide, epoxyalkanol acetates and epoxyalkanols are obtained in one-pot reactions with selectivities of 90–97%. Using longer chain peroxy fatty acids, generated in-situ by lipase-catalyzed reaction of fatty acid and hydrogen peroxide, trimethylsilyl ethers are selectively (83–95%) epoxidized without removal of the protecting trimethylsilyl group.

An efficient method for lipase-catalysed preparation of acrylic and methacrylic acid esters

Novozym 435 — a commercially available immobilized lipase from Candida antarctica — shows an activity for the transesterification using acrylic or methacrylic methylester as solvent and as acylating agent superior to all other enzymes tested. This transesterification is very fast compared to other enzyme-catalysed reactions (1.5 h). Novel acrylic and methacrylic esters from unsaturated fatty alcohols can be prepared this way in yields of 65 to 94 % and under mild conditions (30 °C, atmospheric pressure).

Synthesis of hydrophobic starch esters by reaction of starch with various carboxylic acid imidazolides

A novel efficient method of preparing hydrophobic starch esters with a DS = 1.55-2.0 using amylose enriched starch (amylomaize starch) or potato starch and a fatty acid imidazolide in DMSO as solvent is described. The fatty acid imidazolides can be easily prepared by conversion of the corresponding acyl chloride with imidazole in toluene according to a synthesis route developed by Staab et al. [1-4]. The by-product imidazole hydrochloride could be converted to imidazole by alkaline work up with Na 2 CO 3 . As compared with the direct esterification of starch in presence of a fatty acid chloride the presented synthesis method does not need toxic amines like pyridine as catalyst. Only a catalytic amount of a methanolic KOCH 3 solution is required. Furthermore no hydrolytic degradation of starch could be observed in contrast to the direct esterification reaction with a fatty acid chloride.

Copolymerization of Ethylene with ω‐Unsaturated Fatty Acid Methyl Esters Using a Cationic Palladium Complex

The copolymerization of ethylene with ω-unsaturated fatty acid methyl esters with chain length of C 6 , C 7 , C 10 , C 11 and C 14 Ia-e using the cationic palladium catalyst {[(2,6-i-PrPh) 2 DABMe 2 ]Pd[(CH 2 ) 3 COOMe]}SbF 6 (II) (DAB: diazabutadiene) was investigated. The effects of temperature, ethylene pressure and comonomer concentration were studied conducting the copolymerization of ethylene and 9-decenoic acid methyl ester as a standard reaction. Branched functionalized polyolefins were produced with molecular weights up to 85 000 g/mol (M w ) as determined by GPC versus polystyrene calibration standards. Maximum incorporation of polar comonomer of 31 wt.-% were achieved and a maximum ester turnover number (TON ester ) of 223. Polymers exhibited viscoelastic properties with glass transition temperature of -65 to -55°C.

Hydrophobic modification of starch by alkali-catalyzed addition of 1,2-epoxyalkanes

An efficient method of preparing hydrophobic α-hydroxy starch ethers using aqueous alkaline conditions is described. α-Hydroxy starch ethers were synthesized by addition of 1,2-epoxyalkanes to an aqueous alkaline starch gel in the presence of sodium sulfate as a co-catalyst. The reaction, carried out in a stirred autoclave at 140 °C and 3.9 bar, was optimized with respect to the concentrations of sodium hydroxide and 1,2-epoxyalkane. Optimum yields and molar substitutions (MS) were obtained at molar ratios of sodium hydroxide to anhydroglucose unit (AGU) of 0.5 to 1.0. The amount of molar substitution could be controlled by 1,2-epoxyalkane concentration. Thus, a series of α-hydroxyoctyl starch ethers with MS from 0.7 to 2.4 were synthesized in yields up to 90% by using these conditions. Starches with different amylose contents were also converted to the corresponding ethers using a threefold excess of 1,2-epoxyoctane and an equimolar ratio sodium hydroxide : AGU. The reaction is hardly effected by the origin of the starch and its amylose content. The influence of the 1,2-epoxyalkane chain length was investigated by performing the conversion with a series of terminal epoxyalkanes from 1,2-epoxyhexane to 1,2-epoxydodecane. The results indicated that the hydrophobic character of the starch ethers increased by increasing the molar substitution and alkyl chain length. All products were insoluble in water, but soluble in mixtures of methanol and methylene chloride. Furthermore the starch ethers can be converted into shaped articles by extrusion technology without the addition of plasticizers.

Synthesis of dicarboxylic acids by transition-metal catalyzed oxidative cleavage of terminal-unsaturated fatty acids

9-Decenoic- and 13-tetradecenoic methylesters, obtained by Re-catalysed metathesis of natural C18- and C22-fatty esters with ethylene as well as the industrially produced 10-undecenoic methylester were used as starting materials for the preparation of dicarboxylic esters. Two different reaction routes were applied. Ketonisation of the terminal unsaturated fatty acid esters by Wacker-oxidation using PdCl2/CuCl or RhCl3/FeCl3 as catalysts led to methyl keto-fatty acid esters, which were oxidatively cleaved by Mn-catalysed oxidation with air at 115 °C to mixtures of C8-/C9-, C9-/C10- and C12-/C13-dicarboxylic monomethylesters with conversion rates and selectivities of 90%.