Synthesis and evaluation of some variants of the Nefkens’ reagent

A series of N-substituted phthalimides have been prepared in an effort to explore synthetic variants of the Nefkens’ reagent. Three N-acylphthalimides [R = –CH₃, –CH₂CH₃, and –C(CH₃)₃] were prepared and employed for the protection of a series of representative amines. In addition, an N-methanesulfonylphthalimide and N-(diethylphosphoryl)phthalimide were also prepared. It was determined that among the phthalimides that were prepared N-propanoylphthalimide was the most effective reagent for the protection reaction.     

N-vinylpyrazole copolymers

Copolymers of N-vinylpyrazole with N-vinyl-4,5,6,7-tetrahydroindole and vinyl acetate were prepared by radical copolymerization. The composition, structure, and properties of the copolymers were studied. The reactivity constants of the monomers were calculated. Copolymer films were prepared from solutions by casting, and the proton conductivity of the films was determined.     

<Emphasis Type="Italic">meso</Emphasis>-octyl-substituted tetrabenzoazaporphines and their zinc complexes: Synthesis and spectra

Zinc complexes of meso-trioctyltetrabenzomonoazaporphine and trans- and cis-meso-dioctyltetrabenzodiazaporphine were prepared by the reaction of 1,3-diiminoisoindoline with excess capric acid in the presence of zinc oxide. The corresponding metal-free porphines were prepared by treatment of the metal complexes with sulfuric acid. The spectra of the azaporphyrins prepared were examined.     

Preparation of molecularly imprinted polymers with thiourea group for phosphate

Molecularly imprinted polymers selective for phosphate were prepared with the two types of functional monomers, 1-allyl-2-thiourea and N-methyl-N′-(4-vinylphenyl)-thiourea, and the binding abilities of the polymers were evaluated. Phenylphosphonic acid or diphenyl phosphate were used as the template molecules and the imprinted polymers prepared with 1-allyl-2-thiourea as functional monomer showed high binding ability to phosphate in aqueous media and nearly 90% of phosphate could be recovered. Also, the imprinted polymer prepared with N-methyl-N′-(4-vinylphenyl)-thiourea as functional monomer had a high binding ability and specific interaction with phosphate in acetonitrile solution and over 90% of phosphate-derivatives could be recovered selectively.     

meso-trans-Diphenyldi(2-quinolyl)tetrabenzoporphine and its zinc complex: Synthesis and spectra

(3-Oxoisoindolenyl)(3-oxoisoindolinylidene)phenylmethane and (3-oxoisoindolenyl)(3-oxoisoindolinylidene)(2-quinolyl)methane were prepared by condensation of phthalimide with phenylacetic acid or 2-methylquinoline, respectively, in the presence of zinc oxide. From these products, the zinc complex of meso-trans-diphenyldi(2-quinolyl)tetrabenzoporphine was prepared by two alternative pathways. Demetallation of this complex yielded free meso-trans-diphenyldi(2-quinolyl)tetrabenzoporphine. The spectra of the compounds prepared were examined.     

Influence of fuel-to-oxidizer ratio on the magnetic properties of Fe-doped In2O3 nanoparticles synthesized by solution combustion method

Two series of (In_1−xFe_x)₂O₃ were prepared by a solution combustion method using different fuel-to-oxidizer (i.e. glycine/metal nitrate, G/N) ratios. The crystal structure and magnetic properties of the compounds were investigated by means of X-ray diffraction, transmission electron microscopy and magnetic measurements. Detailed structural analysis shows the solubility limits of Fe in In₂O₃ are x=0.08 and 0.45 for the G/N ratios of 5/4 and 5/6, respectively. Crystallite size of the samples prepared with the G/N ratio of 5/6 is much smaller than that of the samples prepared with the G/N ratio of 5/4. At room temperature, the sample with x=0.01 prepared with the G/N ratio of 5/4 is paramagnetic and those with x=0.03-0.07 are ferromagnetic, whereas the samples with x=0.15-0.45 prepared with the G/N ratio of 5/6 show superparamagnetic behavior and those samples with x<0.15 are paramagnetic. Different magnetic behavior of these two series of samples could be attributed to different origins of magnetism. The magnetism of the samples prepared with the G/N ratio of 5/4 might originate from the existence of mixed valence Fe ions whereas the magnetism of the samples prepared with the G/N ratio of 5/6 could be due to the small crystallite size.     

Rhodium-catalyzed cyclopropanations of 2-aryl-2H-chromenes with dialkyl malonate esters. A comparison of α-diazo derivatives and phenyliodonium ylides

Rhodium-catalyzed reactions of 2-aryl-substituted 2H-chromenes with α-diazo esters prepared from dimethyl and tert-butyl methyl malonates were investigated, and the results were compared with reactions carried out with phenyliodonium ylides prepared from the same esters. The phenyliodonium ylide prepared from dimethyl malonate was found to give superior yields of cyclopropane products compared to the corresponding α-diazo equivalent. However, this result was reversed with tert-butyl methyl malonate when Rh₂(S-TBSP)₄ was used to decompose the diazo compound. All reactions gave 1,1-cyclopropane diesters as single diastereomers.     

Aromatic motifs in the design of Ephedra ligands for application in the asymmetric addition of diethylzinc to aldehydes and diphenylphosphinoylimines

Using N-benzylephedrine as a model, a collection of N-arylmethylephedrine derivatives has been prepared. These derivatives were prepared by treatment of ephedrine with selected aldehydes to create oxazolidines 8a–e. Reduction of the oxazolidines with lithium aluminum hydride afforded the target β-amino alcohols 9a–e. When applied in the catalytic asymmetric addition of diethylzinc to aldehydes and diphenylphosphinoylimines, the derivatives yielded product enantioselectivities that were comparable to those of N-benzylephedrine. An N-cyclohexylmethylephedrine derivative was also prepared; this β-aminoalcohol did not perform well in the catalytic addition of diethylzinc to 2-naphthaldehyde, thus suggesting that the aromatic motif is important in terms of maintaining a reasonable level of asymmetric induction. Finally, N-benzyl-N-methyl-2-amino-1,2-diphenyl-1-ethanol, an analogue of the N-benzylephedrine derivative, was prepared. This compound yielded comparable enantioselectivities in the catalytic asymmetric addition when employed as a ligand.     

Stereoselective synthesis of separable amide rotamers using π-allyl-Pd catalyst and their thermodynamic behavior

Separable amide rotamers were prepared with moderate to excellent Z-selectivities by N-allylation of 2,4,6-tri-tert-butyl-NH-anilides using a π-allyl-Pd catalyst. The present allylation proceeded through a unique mechanism involving O-allylation and the subsequent O,N-allylic rearrangement. The prepared amide rotamers of Z-major changed to equilibrium mixtures of E-major when heated in toluene.     

Synthesis and structural study of α-amino- and α,ω-diamino oligoamides-11

α-Amino (MAO) and α,ω-diamino (DAO) oligoamides were prepared using dodecylamine or 1,6 diaminohexane as a chain limitator. These were characterized by GPC, ¹H-NMR and ¹³C-NMR; molecular models: N-dodecyldodecanamide and 1,6 bis dodecylaminohexane; trifluoroacetylation was used to dissolve the oligoamides. DAO prepared in the melt contains two types of chains, depending on the position of the limitator. When oligomers were prepared in solution using the Yamazaki method, the presence of residual phosphorus derivatives in the oligoamides could not be avoided.     

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone were prepared by phase inversion technique. ATRP grafting of tert-butylacrylate from chloromethylated polysulfone was used for the grafted polymer synthesis. The copolymer was characterized with FTIR, NMR, DSC and TGA. The prepared membranes were characterized in terms of pure water flux, water contact angle, cut off molecular weight, salt rejection and scanning electron microscopy.     

A convenient approach to the synthesis of 2-(2-aminoethyl)pyrroles and their heterocyclization into hydrogenated pyrrolopyridines and related pyrroloindolizines

2-(2-Aminoethyl)pyrroles and 2-(2-succinimidoethyl)pyrroles were prepared from acetals of ethyl 4-oxoalkanoates via latent vinyl 1,4-dicarbonyl compounds as the key intermediates. The Pictet-Spengler condensation of 2-(2-aminoethyl)pyrroles with aromatic aldehydes gave 4,5,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridines in good yields. 4,5,7,8,9,9a-Hexahydro-3H-pyrrolo[2,3-g]indolizines were prepared in a similar way starting from 2-(2-succinimidoethyl)pyrroles.     

New methodology for the preparation of N-tosyl aziridine-2-carboxylates

N-Tosyl aziridine-2-carboxylate methyl esters were prepared from methyl N-tosyl-l-serinate or N-tosyl-l-threoninate, tosyl chloride, and K₂CO₃, under phase-transfer catalysis (PTC) conditions. The same methodology, as applied to the tert-butyl N-tosyl-l-serine amide, afforded the corresponding newly prepared aziridine-2-carboxamide, as an enantiomerically pure compound.     

Improved synthetic routes to methylene-bridged P-chiral diphosphine ligands via secondary phosphine–boranes

Improved methods for the preparation of methylene-bridged diphosphine ligands are described. Both enantiomers of the key intermediate tert-butylmethylphosphine–borane were prepared via resolution or by the conversion of one enantiomer into the opposite enantiomer. The precursor borane complexes of bis(tert-butylmethylphosphino)methane (t-Bu-MiniPHOS), bis((1,1,3,3-tetramethylbutyl)methylphosphino)methane (t-Oct-MiniPHOS), and (tert-butylmethylphosphino)(di-tert-butylphosphino)methane (trichickenfootphos) were prepared in good yields and enantiopure form.     

Preparation of the HgCr2(SexS1−x)4 type compounds and the X ray control of the process of formation of their spinel structures

Compounds of the HgCr₂(Se_xS_1?x)₄ type were prepared for 0.750 ? x ? 0.250 by thermal synthesis from parent elements. Individual reaction stages were controlled röntgenographically. The values of electrical conductivity activation energy of the compounds have been calculated and chemical analyses of the substances prepared have been developed.     

Synthesis of (+)- and (−)-dihydropinidine by diastereoselective dimethylzinc promoted allylation of 2-methyltetrahydropyridine-N-oxide with an allylboronic ester

The enantiomers of the naturally occurring alkaloid dihydropinidine 1, potential antifeedants against the pine weevil, Hylobius abietis, were prepared by diastereoselective, dimethylzinc mediated addition of pinacolyl 2-propenylboronate 14 to nitrones (R)- and (S)-2-methyl tetrahydropyridine-N-oxide 3, prepared from d- and l-alanine, respectively.     

Efficient access to β- and γ-carbolines from a common starting material by sequential site-selective Pd-catalyzed C–C,C–N coupling reactions

Two efficient and practical approaches are reported for the synthesis of β- and γ-carboline derivatives from 3,4-dibromopyridine as a common starting material. The β-carbolines were prepared by site-selective Pd-catalyzed C–C coupling with o-bromophenylboronic acid and subsequent cyclization by double C–N coupling with amines. γ-Carbolines were prepared from the same starting material by C–N coupling with anilines and subsequent annulation by domino C–C/C–N coupling with o-bromophenylboronic acid.     

Spectroscopy of large molecules in inert gas clusters

Aromatic hydrocarbons provide nucleation centers for the formation of clusters of inert gases in high-flow supersonic beams. Large clusters of Ar, each containing a single tetracene (T) molecule, were prepared by supersonic expansion of the seeded gas at pressures p = 3000–13000 Torr and interrogated by laser-induced fluorescence spectroscopy Evidence is reported for homogeneous line broadening of large TAr_n clusters prepared at p? 8000 Torr.     

Preparation of fluoride anion responsive poly(N-vinylcarbazole)-borane complexes

A series of novel fluoride anion responsive materials were facilely prepared by complex formation of poly(N-vinylcarbazole) with organoboron compounds in tetrahydrofuran. After addition of fluoride anion, visual color changes of fluorescence emission from green to blue were observed. The ¹¹B NMR spectra shown that poly(N-vinylcarbazole)-borane complexes were converted to poly(N-vinylcarbazole) and fluoroborate in the presence of fluoride anion. Among the obtained poly(N-vinylcarbazole)-borane complexes prepared, poly(N-vinylcarbazole)-triethylborane complex exhibited the most distinct visual changes in fluorescence emissions.     

Ultalong nanowires self-assembled from a [b]-bisphenanthrene-fused azadipyrromethene

The 1D microwires based on π-extended azaBODIPY were successfully prepared and characterized for the first time. The bisphenanthrene-fused azaBPP-12C with four hydrophobic chains was prepared through de novo synthesis method involving the Suzuki reaction and subsequent oxidative ring-fused coupling. The microwires and aggregation behavior were studied using SEM, XRD and absorption spectroscopy. Finally, an H-type aggregation was confirmed in the solution process.