Marja Lajunen

Co(II) Catalysed Oxidation of α-Pinene by Molecular Oxygen. Part 2

Abstract This paper reports studies of factors affecting air oxidation of (−)-α-pinene catalysed by Co(II)–pyridine complexes without a concomitant co-oxidant. Observations are presented about the nature and amount of the catalyst, reaction temperature, oxygen flow and solvent vs. non-solvent conditions. In addition, attention has been paid to the influence of added base or acid, and identification of side products.

Co(II)-catalysed allylic oxidation of α-pinene by molecular oxygen; synthesis of verbenone

Abstract A facile, high-yield, catalytic air-oxidation entry to verbenone (2) from α-pinene (1) is presented.

Oxidation and degradation of native wheat starch by acidic bromate in water at room temperature.

Native wheat starch was oxidized by benign acidic bromate in water at room temperature. HPLC-ELSD study indicated that starch degraded in the course of oxidation but it still had a polymeric structure characterized by (1)H, (13)C, HSQC and HMBC NMR measurements. Products were generally water-soluble fragments but the use of a short reaction time and dilute reaction mixture yielded water-insoluble products. Titration of the products showed, that the increase of the starch content and reaction time increased the content of carbonyl and carboxyl groups in the range of 0.5-2.5% and 1.7-17.2%, respectively, in the product fragments. A mechanism for the oxidation reaction was proposed.

Dissolution and depolymerization of barley starch in selected ionic liquids

Polysaccharides like starch are poorly soluble in common solvents. However, certain ionic liquids (ILs) have been found to dissolve them, although some depolymerization happens during the dissolution. Dissolution and depolymerization of barley starch in ten ionic liquids have been studied with p-TsOH as a catalyst under controlled microwave heating. Dissolution time and the extent of the depolymerization of starch, determined by using HPLC-ELSD, were specific to each IL. Dialkylimidazolium halide ILs dissolved starch fast and depolymerized it substantially producing 79-100% water-soluble starch oligomers with the average molecular weight of 1000-2000Da. 1-Ethyl-3-methylimidazolium phosphate ([EMIM][Me2PO4]) and 2-hydroxyethylammonium formate ([NH3CH2CH2OH][HCOO]) dissolved starch slowly and depolymerized it least among the tested ILs. For the slow depolymerization of starch these ILs can be considered as suitable solvents for starch modifications where its depolymerization should be avoided.

Co(II)-catalysed oxidation of α-pinene by molecular oxygen: Part IV

Abstract Herein are described the results of t-BuOOH aided air oxidations of (−)-α-pinene, catalysed by [Co(pyridine)2Br2] or [Co(4-methylpyridine)2Br2], and observations about the nature of the reactions. The use of a small amount of t-BuOOH showed a clear beneficial influence on air oxidation under mild temperatures. Raising the temperature did not increase yields markedly. An increase of the hydroperoxide concentration sped up air oxidation and brought up the amount of oxidised products, especially allylic ones. The oxygen atom in oxidised products was not derived from peroxide. Instead, the reaction needed the presence of molecular oxygen to proceed. The present air oxidation is a homogeneous catalytic reaction, and the formation of verbenone took place via trans-verbenol.

Crystallographic Binding Studies with an Engineered Monomeric Variant of Triosephosphate Isomerase

Crystallographic binding studies have been carried out to probe the active-site binding properties of a monomeric variant (A-TIM) of triosephosphate isomerase (TIM). These binding studies are part of a structure-based directed-evolution project aimed towards changing the substrate specificity of monomeric TIM and are therefore aimed at finding binders which are substrate-like molecules. A-TIM has a modified more extended binding pocket between loop-7 and loop-8 compared with wild-type TIM. The A-TIM crystals were grown in the presence of citrate, which is bound in the active site of each of the two molecules in the asymmetric unit. In this complex, the active-site loops loop-6 and loop-7 adopt the closed conformation, similar to that observed in liganded wild-type TIM. Extensive crystal-soaking protocols have been developed to flush the bound citrate out of the active-site pocket of both molecules and the crystal structure shows that the unliganded open conformation of the A-TIM active site is the same as in unliganded wild-type TIM. It is also shown that sulfonate compounds corresponding to the transition-state analogue 2-phosphoglycolate bind in the active site, which has a closed conformation. It is also shown that the new binding pocket of A-TIM can bind 3-phosphoglycerate (3PGA; an analogue of a C4-sugar phosphate) and 4-phospho-D-erythronohydroxamic acid (4PEH; an analogue of a C5-sugar phosphate). Therefore, these studies have provided a rationale for starting directed-evolution experiments aimed at generating the catalytic properties of a C5-sugar phosphate isomerase on the A-TIM framework.

Synthesis And Structural Characterization Of 1-Butyl-2,3-Dimethylimidazolium Bromide And Iodide

1-Butyl-2,3-dimethylimidazolium bromide {(bdmim)Br} (1) and iodide {(bdmim)I} (2) were prepared conveniently by the reaction of 1,2-dimethylimidazole and the corresponding 1-halobutane. The compounds were characterized by 1H and 13C{1H} NMR spectroscopy as well as by X-ray single crystal crystallography. 1 crystallizes in the monoclinic crystal system, space group P21/n, with Z = 4, and unit cell dimensions a = 8.588(2), b = 11.789(1), c = 10.737(2) Å, β = 91.62(3)°. Compound 2 crystallizes in the monoclinic crystal system, space group P21/c, with Z = 8, and unit cell dimensions a = 10.821(2), b = 14.221(3), c = 15.079(2) Å , β = 90.01(3)°. The lattices of the salts are built up of 1-butyl-2,3- dimethylimidazolium cations and halide anions. The cations of 1 form a double layer with the imidazolium rings stacked together due to π interactions. The Br− anions lie approximately in the plane of the imidazolium ring, and the closest interionic Br···H contacts span a range of 2.733(1) - 2.903(1) Å. Compound 2 shows no π stacking interactions. The closest interionic I···H contacts are 2.914(1) - 3.196(1) Å

Effect of temperature on the purity of product in the preparation of 1-butyl-3-methylimidazolium-based ionic liquids

The preparation of room-temperature ionic liquids 1-butyl-3-methylimidazolium chloride, hexafluorophosphate, and dicyanamide by microwave-assisted reaction in non-solvent and solvent conditions has been studied in this contribution. A special emphasis is put on the effect of the reaction temperature on the purity of ionic liquids that was monitored by electrospray ionisation mass spectrometry and 1H NMR. The X-ray structure of 1-butyl-3-methylimidazolium chloride is presented.

Modification of potato peel waste with base hydrolysis and subsequent cationization.

Potato peel waste (PW) is a starch containing biomaterial produced in large amounts by food processing industry. In this work, the treatment of PW by alkaline hydrolysis and cationization in the water phase is reported. In order to improve the cationization of starch, PW was hydrolyzed by heating with alkaline (NaOH) ethanol solution (80%) in a water bath. The impact of variable molar ratios of anhydroglucose unit (AGU):NaOH, heating temperatures and times was studied on the degradation of starch and the molecular size distribution of the product. The hydrolyzed PW was cationized subsequently in water by using glycidyltrimethylammonium chloride and catalyzed by NaOH under microwave irradiation or in an oil bath. The impact of the various reaction conditions on the cationization and degree of substitution of starch was studied. The degree of substitution of the cationized starch varied in the range of 0-0.35.

Synthesis of some conjugated caradienes from 3-carene by the Wittig reaction and their reactivity in the diels-alder reaction

Abstract The applicability of the Wittig reaction for the preparation of conjugated cis -caradienes was studied by the preparation of 4-methyl-3(10)-carene ( 27 ). The method was applied for the study of the synthesis of 3-vinyl-3-apocarene ( 6 ), 4-methylene-3(10)-carene ( 7 ), 4-methyl-2-methylene-3(10)-carene ( 8 ), 4-isopropenyl-3-carene ( 9 and 4-isopropenyl-3-caren-2a-ol ( 11 ) starting from 3-carene ( 20 ). The reactivity of conjugated cis -caradienes 6 , 7 and 9 in the Diels-Alder reaction has also been studied.