Phosphorus‐containing soybean‐oil copolymers: Cross‐metathesis of fatty acid derivatives as an alternative to phosphorus‐containing reactive flame retardants

Two different approaches to the creation of phosphorus‐containing soybean‐oil copolymers were investigated. First, two phosphorus‐containing styrene (ST) derivatives, diphenyl styryl phosphine oxide and dimethyl‐p‐vinylbenzylphosphonate (STP2), where tested as comonomers in the cationic copolymerization of soybean oil (SOY), ST, and divinylbenzene (DVB), to obtain heterogeneous systems in all cases. To overcome this drawback, the cross‐metathesis reaction of methyl 10‐undecenoate and STP2 was carried out to link the phosphorus moiety to the vegetable‐oil derivative. This second approach permitted the synthesis of a new reactive phosphorus‐containing plant‐oil derivative, which was incorporated into the soybean oil, ST, and DVB system. The cationic copolymerization was investigated, and the structure, thermal stability, and mechanical and flame‐retardant properties of the resulting copolymers were studied. Thermosets with moderate glass‐transition temperatures were obtained; this showed that the cross‐metathesis reaction is a convenient way to produce oil‐compatible monomers able to undergo homogeneous polymerization reactions. The resulting thermosets with 1% phosphorus had limiting oxygen index values about 24.0; this indicated an improvement in the fire‐retardant properties of the soybean‐oil‐based copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Ruthenium‐Indenylidene Complexes: Scope in Cross‐Metathesis Transformations

A comparative study examining the catalytic activity of a series of five indenylidene‐containing ruthenium complexes in olefin cross‐metathesis reactions is presented. Results reveal the greater efficiency of precatalyst 5 , highlighting the key role of the N,N′‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene (IPr) ligand for this transformation. The scope of this precatalyst was investigated and several microwave experiments were carried out allowing for catalyst loadings as low as 0.1 mol%. Overall, cross‐metathesis products were isolated in moderate to excellent yields with high stereoselectivity.     

Scope and Limitations of Palladium‐Catalyzed Cross‐Coupling Reactions with Organogold Compounds

Five different alkenylgold(I) phosphane complexes were prepared and then investigated in [1,1′‐bis(diphenylphosphino)ferrocene]palladium(II) dichloride‐catalyzed cross‐coupling reactions with different aryl halides, heterocyclic halides, an alkenyl halide, an alkynyl halide, allylic substrates, benzyl bromide and an acid chloride. With regard to the halides, the iodides were highly reactive, bromides or chlorides gave significantly reduced yields or failed, allylic acetates failed, too. The cross‐coupling partners contained a number of different functional groups, while free carboxylic acids did not deliver cross‐coupling products and o,o‐disubstituted arenes failed as well, a broad range of other functional groups like nitro groups, nitrile groups, ester groups, α,β‐unsaturated ester groups and lactones, aldehydes, alkoxy groups, pyridyl groups, thienyl groups, unprotected phenols and anilines, even aryl azides were tolerated. The structures of one alkenylgold(I) species and of four of the cross‐coupling products were proved by crystal structure analyses.     

Cross‐metathesis of methyl 10‐undecenoate with diethyl maleate: Formation of an α,ω‐diester via a metathesis reaction network

The cross‐metathesis of methyl 10‐undecenoate 1 derived from castor oil as a renewable raw material with diethyl maleate 2 was investigated. These reactions were carried out with several phosphine and N‐heterocyclic carbene ruthenium catalysts. The reaction conditions were optimised for high conversions in combination with high cross‐metathesis selectivity. This single‐step and atom‐economic synthetic method illustrates an efficient and selective preparation procedure of linear α,ω‐dicarboxylic acid esters starting from renewable resources and comparatively inexpensive base chemicals. Further by‐products are hardly obtained due to their consumption in secondary metathesis reactions. Hence, a sustainable alternative for polyamide and polyester monomers is presented.     

Regioselective Palladium(0)‐Catalyzed Cross‐Coupling Reactions and Metal‐Halide Exchange Reactions of Tetrabromothiophene: Optimization,Scope and Limitations

The Suzuki reaction of tetrabromothiophene with arylboronic acids provides a regioselective approach to various 5‐aryl‐2,3,4‐tribromothiophenes, symmetrical 2,5‐diaryl‐3,4‐dibromothiophenes, and tetraarylthiophenes. Unsymmetrical 2,5‐diaryl‐3,4‐dibromothiophenes are prepared by Suzuki reaction of 5‐aryl‐2,3,4‐tribromothiophenes. Tetraarylthiophenes containing two different types of aryl groups are obtained by Suzuki reactions of 2,5‐diaryl‐3,4‐dibromothiophenes. During the optimization of the conditions of each individual reaction, the solvent, the catalyst and the temperature play an important role. In several cases, classical conditions [use of tetrakis(triphenylphosphane)palladium(0), Pd(PPh₃)₄, as the catalyst] gave excellent yields. The yields of those transformations which failed or proceeded sluggishly could be significantly improved by application of a new biarylmonophosphine ligand developed by Buchwald and co‐workers. Regioselective metal‐halide exchange reactions of tetrabromothiophene provide a convenient approach to various 2,5‐disubstituted 3,4‐dibromothiophenes. 5‐Alkyl‐2‐trimethylsilyl‐3,4‐dibromothiophenes could be prepared in one pot by sequential addition of trimethylchlorosilane and alkyl bromides. The reaction of tetrabromothiophene with methyl chloroformate and subsequent Suzuki reactions afforded 3,4‐diaryl‐2,5‐bis(methoxycarbonyl)thiophenes.     

Lewis‐acid catalysed ene reaction of electrondeficient aldehydes and ketones at unsaturated fatty acid derivatives

The SnCl₄ catalysed reaction of oleic acid ethyl ester (1) with glyoxylic acid ethyl ester (2) or mesoxalic acid diethyl ester (5) proceeds with good results yielding the corresponding 1:1‐adducts. Besides the ene adducts also δ‐lactones are formed by the reaction of (1) with (5) . The product yield shows a strong dependency on type and quantity of the Lewis‐acid used. A maximum yield was obtained with a stoichiometric amount of SnCl₄. In contrast to the thermal ene reaction about 75% of the yield was attained already during the first 30 min of the reaction.     

Reaction of cyclopropenoid fatty acid derivatives with hydrogen halides

The treatment ofSterculia foetida oil with concentrated aqueous HCl or with HBr in acetic acid results in the addition of one hydrohalogen molecule per cyclopropenoid moiety. Iodine value (I.V.) and infrared absorption measurements indicate that the mechanism parallels that of the polymerization of sterculic acid and involves the formation of four isomeric monoun-saturated monohalo moieties. A laboratory of the So. Utiliz. Res. & Dev. Div., ARS, U.S.D.A.     

New perylene dyes,derivatives of 1,6,7,12‐tetrachloroperylene‐3,4,9,10‐tetracarboxylic acid: synthesis and application

New dyes – aliphatic esters of 1,6,7,12‐tetrachloroperylene‐3,4,9,10‐tetracarboxylic acid – were prepared as potential fluorescent light‐stable colorants for high‐visibility safety wear. The structure of the 15 perylenes was confirmed by ¹H and ¹³C nuclear magnetic resonance spectroscopy and mass spectrometry, and their spectroscopic and physicochemical properties were determined. An attempt was made to apply the synthesised products as disperse dyes in the coloration of polyester as well as in the mass coloration of polystyrene and poly(methyl methacrylate). The light, wash, and rubbing fastness of the dyeings were determined, and chromaticity coordinates of selected samples were measured and discussed.     

Ketone derivatives of diels‐alder adducts of levopimaric acid with acrylic acid and maleic anhydride: Synthesis,characterization, and polymerization

Two new ketone‐type derivatives were synthesized by the dehydrodecarboxylation of levopimaric acid acrylic acid adduct and of levopimaric acid maleic anhydride adduct in the presence of sulfonic catalysts. The two compounds were also synthesized by coupling of acrylic acid or maleic anhydride with dipimaryl ketone. These ketones, or rather ketone‐diacids, were condensed with polyalkylenepolyamines to give poly(amide)s or poly(imide)s with good thermal properties. New crosslinked polymers were obtained when these poly(amide)s or poly(imide)s were substituted with epichlorohydrin. The structures of the resulted ketone‐diacids and polymers were investigated by the usual physical and chemical methods. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2240–2252, 2004     

A Three‐Way Switchable Process for Suzuki Cross‐Coupling,Hydrodehalogenation, or an Assisted Tandem Hydrodehalogenation and Suzuki Cross‐Coupling Sequence

A three‐way switchable Pd‐catalyzed and microwave assisted process appropriate for selective arylation or hydrodehalogenation of the imidazole backbone was discovered and entirely optimized. The “arylation switch position” was adapted and optimized for the synthesis of 4,5‐diaryl‐1H‐imidazoles, while the “hydrodehalogenation switch position” was used for the preparation of 4(5)‐iodo‐1H‐imidazole. The hydrodehalogenation and the cross‐coupling reactions were also successfully combined in “the third switch position” that performs an assisted tandem reaction sequence that produced 4(5)‐aryl‐1H‐imidazole. All of the three pathways produced their corresponding products in excellent yield.

     

Gas chromatographic behavior of fatty acid derivatives for mass spectrometry on low‐polarity capillary columns

The gas chromatographic properties of four derivatives of fatty acids (FA), namely fatty acid methyl esters, picolinyl esters, N‐acyl pyrrolidides and 4,4‐dimethyloxazoline derivatives, which contain various structural features (double bonds, branching, hydroxyl group) in their acyl chains have been compared on a low‐polarity capillary column with a mass spectrometer as detector. Temperature programming rates yielding the highest resolution were optimized for each derivative by means of computer‐assisted column temperature optimization software. Indeed, the Drylab software represents a valuable assistance for estimating the optimum analysis conditions. Time and efforts required for such method development can greatly be reduced. Different parameters (derivatization procedure, total run time, resolution and response factor) are discussed. N‐Acyl pyrrolidides and picolinyl esters appear quite powerful for structure elucidation of polyunsaturated FA by GC‐MS, and both these types of FA derivatives can be very well separated on a low‐polarity phase.     

Fatty acid methyl ester heterogeneous self‐metathesis in hydrophobic green solvent: Mass transfer limitations,catalyst recyclability,and stability

The role of room‐temperature ionic liquids (RTILs), [bmim][PF₆] and [bmim][Tf₂N], as reaction media regarding the catalytic activity and stability of methyltrioxorhenium (MTO) supported on ZnCl₂‐modified mesoporous Al₂O₃ has been studied for self‐metathesis of a functionalized olefin, methyl oleate. The humidity influence on the catalytic activity was probed. The catalyst recycling ability and the kinetics of the metathesis reaction using these RTILs were also investigated. It was found that the MTO‐based catalyst was efficient in viscous hydrophobic RTIL solvents. However, their high viscosity was found to increase the mass transfer limitations thus somewhat impacting the reaction kinetics. Nevertheless, better catalyst stability was reached allowing its possible recycling when used in RTIL media.     

Influence of fatty alcohol and other fatty acid derivatives on fatty acid uptake into rat intestinal epithelial cells

We investigated the influence of various substrates on the uptake of long-chain fatty acid into IEC-6, rat intestinal epithelial cell line. The uptake of [³H]oleic acid into IEC-6 cells was a saturable function of the oleic acid concentration. Long-chain fatty acids significantly inhibited the oleic acid uptake into IEC-6 cells and shorter-chain fatty acids had little or no effect. Various fatty acid esters suppressed the oleic acid uptake into IEC-6. Fatty alcohols also inhibited oleic acid uptake into IEC-6 and the length of the carbon chain played an important role. These results suggest that long-chain fatty acid uptake was inhibited by the substrates which had a structure similar to long-chain fatty acids, especially those with a long carbon chain. At least two molecules, fatty acid translocase and fatty acid transport protein type 4, which are considered to be involved in the long-chain fatty acid transport into the cell, were expressed on IEC-6 cells, supporting the existence of the carrier-mediated system of long-chain fatty acid transport on IEC-6 cells.     

C18‐unsaturated branched‐chain fatty acid isomers: Characterization and physical properties

Iso‐oleic acid is a mixture of C₁₈‐unsaturated branched‐chain fatty acid isomers with a methyl group on various positions of the alkyl chain, which is the product of the skeletal isomerization reaction of oleic acid and is the intermediate used to make isostearic acid (C₁₈‐saturated branched‐chain fatty acid isomers). Methyl iso‐oleate, a mixture of C₁₈‐unsaturated branched‐chain fatty acid methyl ester isomers, is obtained via acid catalyzed esterification of iso‐oleic acid with methanol. The branched‐chain materials are liquid at room temperature and their “oiliness” property makes them an attractive candidate for the lubricant industry. In this paper, we report characterization of these branched‐chain materials using comprehensive two‐dimensional GC with time‐of‐flight mass spectrometry (GC × GC/TOF‐MS) and their physical and lubricity properties using tribology measurements.     

Electronegativity Governs Enantioselectivity: Alkyl‐Aryl Cross‐Coupling with Fenchol‐Based Palladium‐Phosphorus Halide Catalysts

A series of bulky, modular, monodentate, fenchol‐based phosphites has been employed in an intramolecular palladium‐catalyzed alkyl‐aryl cross‐coupling reaction. This enantioselective α‐arylation of N‐(2‐bromophenyl)‐N‐methyl‐2‐phenylpropanamide is accomplished with [Pd(C₃H₅)(BIFOP‐X)(Cl)] as precatalysts, which are based on biphenyl‐2,2′‐bisfenchol phosphites (BIFOP‐X, X=F, Cl, Br, etc.). The phosphorus fluoride BIFOP‐F gives the highest enantioselectivity and good yields (64% ee, 88%). Lower selectivities and yields are found for BIFOP halides with heavier halogens (Cl: 74%, 47% ee, Br: 63%, 20% ee). NMR studies on catalyst complexes reveal two equilibrating diastereomeric complexes in equal proportions. In all cases, the phosphorus‐halogen moiety remains intact, pointing to its remarkable stability, even in the presence of nucleophiles. The increasing enantioselectivity of the catalysts with the phosphorus halide ligands correlates with the rising electronegativity of the halide (bromine<chlorine<fluorine), as can be rationalized from structural parameters and DFT computations.     

Iron‐Catalyzed Mizoroki–Heck Cross‐Coupling Reaction with Styrenes

In the presence of iron(II) chloride (FeCl₂; 20 mol%) and potassium tert‐butoxide (t‐BuOK; 4 equiv.) in dimethyl sulfoxide (DMSO), aryl and heteroaryl iodides undergo stereoselective Mizoroki–Heck C C cross‐coupling reactions with styrenes at 60 °C giving the corresponding (E)‐alkenes. The best yields are obtained upon adding a ligand (80 mol%) such as proline or picolinic acid. Aryl bromides and pyridinyl bromides are also coupled with styrenes but in lower yields.     

Cross‐Linked Enzyme Aggregates of Chloroperoxidase: Synthesis,Optimization and Characterization

In this study we have optimized the conditions to precipitate and cross‐link the enzyme chloroperoxidase (EC 1.11.1.10) from Caldariomyces fumago (CPO) using 1,2‐dimethoxyethane as the precipitating agent. The coprecipitation of the enzyme with albumin and pentaethylenehexamine was needed for optimum results, presumably due to the low number of lysines available in CPO. The enzyme was immobilized with an activity recovery of 68%. The cross‐linked enzyme aggregate showed higher temperature and pH stability, and better hydrogen peroxide tolerance than the free enzyme.     

Nickel‐ or Iron‐Catalyzed Cross‐Coupling of Aryl Carbamates with Arylsilanes

Aryl carbamates were for the first time applied as electrophiles in the cross‐coupling with arylsilanes via nickel or iron catalysis to construct valuable biaryl compounds. This new coupling reaction features a good group tolerance and non‐sensitivity to steric hindrance on both aryl carbamates and arylsilanes.