Showing papers on "Boron tribromide published in 2010"

Access to Resorcylic Acid Lactones via Phosphonate Based Intramolecular Olefination

Abstract: An approach to resorcylic acid lactones is described, exploiting an intramolecular olefination reaction for the generation of the 14-membered macrolactone. The synthetic route gave zearalenone precursors, and the preparations of other RAL analogues, trans- and cis-resorcylides are included, the latter being prepared by photoisomerization of the trans-isomer. β-Haloketone derivatives were also prepared in a highly stereoselective manner by conjugate addition of chloride or bromide to the E-enone using boron trichloride and boron tribromide, respectively.

Luminescent alternating boron quinolate–fluorene copolymers exhibiting high electron mobility

Abstract: π-Conjugated copolymers composed of 9,9-didodecylfluorene and boron quinolate were synthesized by an efficient chelating reaction of quinolinol-based polyfluorene derivative, as a polymeric ligand, with arylborane compounds such as triphenylborane (BPh3) or fluorobis(pentafluorophenyl)borane diethyl etherate ((C6F5)BF·OEt2). The polymeric ligand was prepared from the deprotection reaction of boron tribromide and benzyloxyquinoline-based polyfluorene, which was produced via the efficient Suzuki cross-coupling reaction of 5,7-dibromo-8-benzylquinoline and 9,9-didodecylfluorene-2,7-diboronic acid in the presence of 2-(2′,6′-dimethoxybiphenyl)dicyclohexylphosphine (S-Phos) and palladium(II) acetate. Their optical properties were studied by UV-vis absorption and photoluminescence spectroscopies. The absorption and PL spectra of the obtained polymers were red-shifted in comparison with those of the polymeric ligand due to the decrease of the LUMO level by the formation of boron complexes, explained by theoretical calculations of the model compounds using the density-functional theory (DFT) method. The molar extinction coefficients and emission maxima of boron-chelating polymers were analogous values to those of (κ2-(N,O)-5,7-bis(9,9-dihexylfluoren-2-yl)-8-quinolinolate)diphenylborane (BFluorene2q). Furthermore, the electron mobilities of the polymers were determined from the space-charge limited current (SCLC) with electron-only device structure of ITO/Ca/polymer/LiF/Al. As a result, the mobilities for the polymers (3.9 or 2.0 × 10−5 cm2 V−1 s−1) were reasonably close to the value (7.9 × 10−5 cm2 V−1 s−1) calculated from the Alq3-fabricated device.

Modified approach for preparing ( E )-stilbenes related to resveratrol, and evaluation of their potential immunobiological effects

Abstract: Resveratrol and closely related stilbenoids belong to the most intensively studied biologically active compounds. This interest evoked several attempts to prepare such compounds in a convenient synthetic way. Our approach allowed obtaining largely methoxystilbenes, formed as E -isomers only (using Wittig–Horner synthesis as the key step), which were further demethylated by boron tribromide. The hydroxymethoxystilbenes (e.g. pterostilbene) were prepared using isopropyl protection, later selectively deprotected by boron trichloride. The method is suitable for preparing such compounds in a large amount. Effects of the obtained stilbene derivatives on immunobiological responses triggered by lipopolysacharide and interferon-γ were tested under in vitro conditions. Namely production of nitric oxide (NO) was investigated, and relation between the molecular structure and immunobiological activity was assessed.

Synthesis and biological activity of new etorphine analogues from 7-chloro-6-demethoxythebaine and 7-chloro-5β-methyl-6-demethoxythebaine (chemistry of opium alkaloids, part XXXVII)†

Abstract: The Diels-Alder reaction of 7-chloro-6-demethoxythebaine (8) and 7-chloro-5β-methyl- -6-demethoxythebaine (14) each with ethyl acrylate yielded four (14:6:4:1) and three adducts (15:4:1), respectively. The main adduct from diene 8 was the ethyl 6α,14α-ethenoisomorphinan-7α- -carboxylate 15, while diene 14 afforded the ethyl 6β,14β-ethenomorphinan-8β-carboxylate congener 17 in which the dienophile has reacted from the opposite face. Cycloaddition of 8 and 14 with maleic anhydride, followed by esterification, yielded the 6α,14α-ethenoisomorphinans 23 and 24, respectively, as the main adducts in both cases. In the case of diene 14 a considerable amount (20%) of the 6β,14β-ethenomorphinan 25 was also isolated. The adducts 15, 16, and 19 were 3-O-demethylated using boron tribromide to their 3-hydroxy esters 26, 28, and 30. Conversion of these esters into the tertiary alcohols 27, 29, and 31 was performed using methylmagnesium bromide. Compared to morphine and etorphine, the compounds 26–29 exhibit high affinity for all the opiate receptor subtypes with a higher selectivity for the μ-receptor. The compounds 30 and 31 were inactive. The outcome of the cycloadditions is discussed in terms of the electronic influence of the 7-chloro substituent in the presence or absence of the 5β-methyl group.

Rigid etheno‐bridged metopon analogues from Diels‐Alder reaction of 5‐methylthebaine. (Chemistry of opium alkaloids, Part XXXII)

Abstract: Diels-Alder reaction of 5-methylthebaine (2) with ethyl acrylate, methyl vinyl ketone or p-benzoquinone yielded ethyl 4,5α-epoxy-3,6-dimethoxy-5,N-dimethyl-6α,14α-ethenoisomorphinan-7α-carboxylate (3), 7α-acetyl-4,5α-epoxy-3,6-dimethoxy-5,N-dimethyl-6α,14α-ethenoisornorphinan (4), and 4,5α-epoxy-3,6-dimethoxy-5,N-dimethyl-6α,14α-ethenobenzo[7,8]isomorphinan-3′,6′-diol (5b), respectively. Both ester 3 and ketone 4 were converted into 4,5α-epoxy-3,6-dimethoxy-α,α,5,N-tetramethyl-6α,14α-ethenoisomorphinan-7α-methanol (7) with methylmagnesium iodide. The 3-methoxy group was hydrolysed to give 4,5α-epoxy-3-hydroxy-6-methoxy-α,α,5,N-tetramethyl-6α,14α-etheno-isomorphinan-7α-methanol (8). Demethylation of 3 with boron tribromide afforded ethyl 4,5α-epoxy-3,6-dihydroxy-5,N-dimethyl-6α,14α-ethenoisomorphinan-7α-carboxylate (6). Structure elucidation was mainly based on 1H and 13CNMR spectroscopy. It is remarkable that, in all cases, β-face approach of the diene system of 2 has taken place. The new rigid metopon analogues 6, 7, and 8, will be tested for biological activity**.

Production method for high-purity boron tribromide

Abstract: The invention discloses a production method for high-purity boron tribromide, which comprises the following steps of: placing industrial grade boron tribromide into a container, adding 1 to 2 percent of decoloration adsorbent, keeping with slightly stirring for 60 to 80 minutes, and filtering by using a microfilter of below 0.05 micron; distilling the obtained filtrate by using a sub-boiling distiller, and adjusting the heating pipe voltage-stabilized liquid level temperature to be 60 to 75 DEG C; feeding the obtained distillate into a plate rectification column for distillation reflux, controlling the reflux time to be 5 to 6 hours, removing a low-boiling-point substance, feeding a boron tribromide pure product obtained from 89 to 93-degree centigrade distillate to another rectification column for rectification again, and controlling the reflux time to be 5 to 6 hours; and feeding 89 to 92.5-degree centigrade distillate into a finished product groove, and after the product is detected to be qualified, filtering and packing under the purification environment of which the whole is no more than a thousand level and of which the part is no more than a hundred level to obtain a high-purity boron tribromide product of 99.99999 percent. The method has the advantages of simple process, convenient operation, easy quality control and low finished product cost.

Synthesis of ParacyclophaneThiols via an Unprecedented Reduction-DeprotectionSequence: Direct Conversion of tert-ButylSulfoxides into Thiols with Boron Tribromide

Abstract: Starting from readily available paracyclophane-substituted sulfoxides, a two-step procedure including a directed orthometalation and an unprecedented deoxygenation-deprotection sequence allows the generation of versatile functionalized paracyclophane thiols.

Condensed Heteroaromatic Ring Systems. Part 24. Synthesis of Rigidin, a Pyrrolo(2,3-d)pyrimidine Marine Alkaloid.

Abstract: The marine alkaloid rigidin has been synthesized from 2,4-dimethoxy-7-phenylsulfonylpyrrolo[2,3-d]pyrimidine. Lithiation of the pyrrolo[2,3-d]pyrimidine followed by electrophilic substitution with N, 4-dimethoxy-N-methylbenzamide afforded a 6-(4-methoxy)benzoyl derivative which by alkaline hydrolysis and subsequent iodination was converted into 2,4-dimethoxy-5-iodopyrrolo [2,3-d] pyrimidin-6-yl 4-methoxyphenyl ketone. The palladium-catalysed arylation of this with 2-(4-methoxyphenyl)-1,3,2-dioxaborinane followed by demethylation with boron tribromide gave rigidin.

5,5' position connected 1,1'-biphenyl axial chiral 2,2'-biphosphine ligand and preparation method thereof

Abstract: The invention relates to a 5,5' position connected 1,1'-biphenyl axes chiral 2,2'-biphosphine ligand and a preparation method thereof, which belong to the technical field of chemical engineering. Theaxes is provided with compound I with (R) configuration and (S) configuration or provided with optic pure compounds II and III with R and S configurations. The preparation method comprises the following steps: substituted 4-metoxyphenol is transformed into a compound IV in organic solution; the compound IV is transformed into a compound V; the compound V and bisphosiphine (R1) oxyhydrogen react tobe transformed into a compound VI; the compound VI is transformed into a compound VII; the compound VII and boron tribromide react to prepare a compound VIII; the compound VIII and dihalogenated hydrocarbon react to prepare 5,5'-associated compound IX mixed with (R) and (S) configurations, and chiral FPLC is adopted for splitting to obtain compounds X and XI with single configuration of (R) and (S); and the compound I or the compounds II and III are prepared. The 5,5' position connected 1,1'-biphenyl axes chiral 2,2'-biphosphine ligand can be synthesized into a catalyst with divalent metal ofpalladium and retinervus and can obtain high catalytic property and enantioselectivity.

Synthesis of a Range of Polyhydroxy 8-Aryl Flavones.

Abstract: The 8-iodo flavones formed by cyclization of benzyl-protected chalcones with iodine in dimethyl sulfoxide have been transformed by a Suzuki coupling reaction into a variety of 8-aryl derivatives. Deprotection with boron tribromide has generated a family of new 8-aryl flavones containing four to eight hydroxyl groups.

Benzylic Bromination of Toluene Derivatives with Boron Tribromide.

Abstract: A facile method for the benzylic bromination of toluene derivatives was developed. Various substituted toluenes were brominated with boron tribromide as bromine source in carbon tetrachloride at room temperature, affording their corresponding benzyl bromides in good yields.

Bisphenol compound containing numerous benzene rings and synthesis method thereof

Abstract: The invention discloses a bisphenol compound containing numerous benzene rings and a synthesis method thereof and the structural formula of the bisphenol compound is shown in the formula (I). The synthesis method comprises the following steps: using p-methoxyphenol, anhydrous potassium carbonate, polar aprotic solvent and toluene to react at 140-150 DEG C, evaporating toluene while carrying out the generated water, then adding decafluorobiphenyl to react at 80-100 DEG C for 1-3 hours, separating and purifying the obtained product to react with R-OH in polar aprotic solvent at 180-220 DEG C, separating and purifying the obtained product, reacting with boron tribromide at -60 to -90 DEG C, wherein the reactive solvent is dichloromethane or trichloromethane; and separating and purifying the product to obtain white powder. The bisphenol compound containing numerous benzene rings of the invention is characterized by accessible reaction raw materials, simple steps, high yield, easy purification of the product and the like. The obtained bisphenol compound containing numerous benzene rings can be used in the synthesis of epoxy resin.