- Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde catalyzed by sulfated zirconia
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The present work describes the novel application of sulfated zirconia (SZ) solid acid catalysts for the synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde. SZ catalysts with different percentages of sulfur loadings have been synthesized and characterized using various physico-chemical techniques like PXRD, FT-IR, surface area analysis and NH 3-TPD studies. The influences of various reaction parameters such as sulfur loading, reaction temperature, molar ratio of reactants, reaction time, solvent effect and reusability of the catalyst have been investigated. SZ catalyst synthesized by impregnation of 2N sulfuric acid solution over Zr(OH)4 was found to be a highly selective catalyst for β-pinene conversion (>99%) with ~99% selectivity to nopol. The catalyst could be reused up to five cycles with minor loss in catalytic activity for β-pinene conversion, while the nopol selectivity remains unaffected.
- Jadhav, Sumit V.,Jinka, Krishna Mohan,Bajaj, Hari C.
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- A comparative study of solvent-free and highly efficient pinene hydrogenation over pd on carbon, alumina, and silica supports
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Solvent-free catalytic hydrogenation of pinene over Pd on carbon, alumina, and silica supports were compared. Despite the absence of solvent, Pd catalyst on all three supports yields to a quantitative conversion of pinene to pinanes and a higher selectivity for the cis isomer (72-89%). The temperature affected similarly the selectivity of the reaction for all three catalysts in favor of the cis-pinane isomer. However, recycling of the Pd on the three tested supports varied greatly. If Pd/C and Pd/alumina were successfully recycled 13 and 14 times, respectively, Pd/silica could be used only once to convert pinenes into pinanes. Remaining very effective during all 13 cycles, Pd/C was the best catalyst/support of the three tested ones for the solvent-free hydrogenation of pinene. The influence of H2 pressure on pinene conversion rates were investigated for Pd/C catalyst. An extremely low leaching rate of palladium in pinenes and pinanes determined by ICP/MS confirmed the heterogeneous nature of this catalytic solvent-free reaction. The hydrogenation reaction presented in this paper is an alternate environmentally friendly pathway for pinane synthesis.
- Selka, Ayyoub,Levesque, Natalie A.,Foucher, Delphine,Clarisse, Olivier,Chemat, Farid,Touaibia, Mohamed
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- SYNTHESE VON ISOPINOCAMPHEYLHALOGENBORANEN UND IHRE VERWENDUNG ALS CHIRALE KATALYSATOREN FUER ASYMMETRISCHE DIELS-ALDER-REAKTIONEN
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The synthesis of a number of mono- and diisopinocampheylhalogenboranes is described.Their ability to act as chiral catalysts in asymmetric Diels-Alder reactions has been investigated in case of the reaction of cyclopentadiene with methacroleine.
- Bir, Gerhard,Kaufmann, Dieter
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- Iron Catalyzed Double Bond Isomerization: Evidence for an FeI/FeIII Catalytic Cycle
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Iron-catalyzed isomerization of alkenes is reported using an iron(II) β-diketiminate pre-catalyst. The reaction proceeds with a catalytic amount of a hydride source, such as pinacol borane (HBpin) or ammonia borane (H3N?BH3). Reactivity with both allyl arenes and aliphatic alkenes has been studied. The catalytic mechanism was investigated by a variety of means, including deuteration studies, Density Functional Theory (DFT) and Electron Paramagnetic Resonance (EPR) spectroscopy. The data obtained support a pre-catalyst activation step that gives access to an η2-coordinated alkene FeI complex, followed by oxidative addition of the alkene to give an FeIII intermediate, which then undergoes reductive elimination to allow release of the isomerization product.
- Woof, Callum R.,Durand, Derek J.,Fey, Natalie,Richards, Emma,Webster, Ruth L.
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supporting information
p. 5972 - 5977
(2021/03/17)
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- Amphiphilic polymeric nanoreactors containing Rh(i)-NHC complexes for the aqueous biphasic hydrogenation of alkenes
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A rhodium(i) complex bearing a monodentate N-heterocyclic carbene ligand has been confined into the core of amphiphilic polymeric core-crosslinked micelles (CCMs). The Rh complex was covalently bound to the polymeric chains by incorporation of a polymerizable unit on the NHC ligand. Nanoreactor Rh-NHCmes@CCM5bhas been evaluated as a catalyst for the aqueous biphasic hydrogenation of styrene and other alkenes. It has shown a high activity with styrene at a low catalytic loading (10?000/1 substrate/Rh ratio), greater than that of an analogous molecular Rh(i) complex, and its evolution to Rh0is slower. This is attributed to several factors, among which the confinement effect and the favourable polyoxygenated environment of the nanoreactor core. Finally, the CCMs could be recycled up to four times with almost no loss of activity over 3 h cycles and the loss of rhodium per cycle was on average lower than 0.6 ppm.
- Allandrieu, Audrey,Coppel, Yannick,Daran, Jean-Claude,Gayet, Florence,Hromov, Roman,Labande, Agnès,Manoury, Eric,Poli, Rinaldo,Ruzhylo, Illia,Sabatier, Cassandra,Sambou, Sasaline Salomon,Wang, Hui
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p. 6811 - 6824
(2021/10/25)
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- Iron-Catalyzed C-C Single-Bond Cleavage of Alcohols
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An iron-catalyzed deconstruction/hydrogenation reaction of alcohols through C-C bond cleavage is developed through photocatalysis, to produce ketones or aldehydes as the products. Tertiary, secondary, and primary alcohols bearing a wide range of substituents are suitable substrates. Complex natural alcohols can also perform the transformation selectively. A investigation of the mechanism reveals a procedure that involves chlorine radical improved O-H homolysis, with the assistance of 2,4,6-collidine.
- Liu, Wei,Wu, Qiang,Wang, Miao,Huang, Yahao,Hu, Peng
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supporting information
p. 8413 - 8418
(2021/11/01)
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- Highly Selective Hydrogenation of C═C Bonds Catalyzed by a Rhodium Hydride
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Under mild conditions (room temperature, 80 psi of H2) Cp*Rh(2-(2-pyridyl)phenyl)H catalyzes the selective hydrogenation of the C═C bond in α,β-unsaturated carbonyl compounds, including natural product precursors with bulky substituents in the β position and substrates possessing an array of additional functional groups. It also catalyzes the hydrogenation of many isolated double bonds. Mechanistic studies reveal that no radical intermediates are involved, and the catalyst appears to be homogeneous, thereby affording important complementarity to existing protocols for similar hydrogenation processes.
- Gu, Yiting,Lisnyak, Vladislav G.,Norton, Jack R.,Salahi, Farbod,Snyder, Scott A.,Zhou, Zhiyao
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supporting information
p. 9657 - 9663
(2021/07/19)
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- Method and Means for Releasing a Terpene Mixture to a Cannabis Flower During Storage
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A method and means for releasing a terpene mixture to a Cannabis flower during storage with may be from a cotton pulp card or a two-way humidity pack with an additional terpene blend for keeping a Cannabis flower fresh while naturally increasing the desired terpene levels. The product is a blend of humidity regulating agents infused with terpenes (plant derived) which allows for the product to be paired with herbal material to increase and maintain the relative humidity, while transferring the flavor/aroma/taste terpenes from the package into the herbal material. There are two embodiments, the first is a Terp Pack+Humidity (“Terp Pack+RH”) which contains a herban material to increase and maintain relative humidity, while releasing the infused terenes, and the second is more simply a Terp Pack (“Terp Pack”) which contains no humidity enhancing material and is only a carrier for releasing the terpene mixture.
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- Synthetic method of chiral alcohol compound with 6 carbon skeleton structure
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To the invention, 6 pinene is used as the chiral auxiliary, and the chiral auxiliary compound (-) - a - is finally quenched and hydrolyzed to form the chiral alcohol pure, final product, with the purity 3, value, not only can obtain the target product, with high chiral purity and content, but also can carry out commercialized production, HPLC. 98.1%; The chiral alcohol compound has an. ideal yield 97.4%,e.e.
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Paragraph 0025-0027
(2020/03/16)
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- Palladium nanoparticles stabilized by novel choline-based ionic liquids in glycerol applied in hydrogenation reactions
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Palladium nanoparticles stabilized by choline-based ionic liquids in glycerol were prepared from Pd(II) precursors by simply heating at 80 °C under argon; in this process, the water present in the ionic liquid was found to be responsible for the reduction of Pd(II) into zero-valent palladium species. Palladium nanoparticles were fully characterized in both liquid phase and solid state. The as-prepared metal nanoparticles exhibited remarkable catalytic activity in hydrogenation processes for a significant variety of functional groups (alkenes, alkynes, nitro derivatives, benzaldehydes, aromatic ketones).
- Garg, Garima,Foltran, Stéphanie,Favier, Isabelle,Pla, Daniel,Medina-González, Yaocihuatl,Gómez, Montserrat
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- Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
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We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
- Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
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supporting information
p. 5723 - 5728
(2019/04/03)
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- Exploring the Keggin-Type Heteropolyacid-Catalyzed Reaction Pathways of the Β-Pinene with Alkyl Alcohols
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Abstract: In this work, we investigated the activity of Keggin heteropolyacid catalysts (i.e., H3PW12O40, H3PMo12O40 and H4SiW12O40) in β-pinene reactions with alkyl alcohols (i.e. methyl, ethyl, propyl, sec-propyl, butyl and sec-butyl alcohols), and exploring the different aspects that drive the selectivity of this process. We have found that carbon skeletal rearrangements and isomerization providing intermediate carbocations that controlling the reaction selectivity. β-pinene was preferentially converted to α-terpinyl ion which undergoes a nucleophilic attack of alcohol providing alkyl alcohol. Bornyl ion was converted to bornyl and fenchyl ethers. The other secondary products were β-pinene isomers obtained from bornyl and α-terpinyl carbocations. Phosphotungstic acid (i.e., H3PW12O40) was the most active catalyst and selective toward the main product (α-terpinyl alkyl ether); the highest conversion (ca. 96%) and ether selectivity (ca. 61%) was achieved in the reactions with β-pinene. Although having also been alkoxylate, α-pinene was less reactive (ca. 40%), while camphene and limonene remained unreactive under reaction conditions studied. An increase of temperature resulted in an improvement on conversion of β-pinene and selectivity toward α-terpinyl methyl ether. Similarly, the H3PW12O40 concentration played a crucial role on reaction selectivity. This work presents positive features such as a short reaction time, high atom economy, mild reaction conditions (i.e., low temperature and room pressure). Even though soluble the catalyst was easily recovered by liquid -liquid extraction and efficiently reused. Graphical Abstract: [Figure not available: see fulltext.].
- Polo, Henrique Priori,Lopes, Neide Paloma Goncalves,da Silva, Márcio José
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p. 2844 - 2853
(2019/05/28)
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- Temperature Controls Guest Uptake and Release from Zn4L4 Tetrahedra
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We report the preparation of triazatruxene-faced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host-guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.
- Zhang, Dawei,Ronson, Tanya K.,Güryel, Songül,Thoburn, John D.,Wales, David J.,Nitschke, Jonathan R.
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supporting information
p. 14534 - 14538
(2019/10/11)
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- [(NHC)CoR2]: pre-catalysts for homogeneous olefin and alkyne hydrogenation
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A novel synthesis for dialkyl cobalt compounds [(tmeda)CoR2] is presented. In these complexes tmeda is readily replaced by an NHC or a bidentate phosphine ligand to form 3- and 4-coordinate compounds, respectively. [(ItBu)Co(CH2SiMe3)2] (ItBu = 1,3-di-tert-butylimidazolin-2-ylidene) serves as an efficient, homogeneous olefin hydrogenation pre-catalyst and allows the preparation of the novel cobalt bis(alkyne) complex [(ItBu)Co(η2-PhCCPh)2].
- Enachi, Andreea,Baabe, Dirk,Zaretzke, Marc-Kevin,Schweyen, Peter,Freytag, Matthias,Raeder, Jan,Walter, Marc D.
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supporting information
p. 13798 - 13801
(2018/12/14)
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- Bifunctional catalyst Pd-Al-MCM-41 for efficient dimerization-hydrogenation of β-pinene in one pot
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A new type of bimetallic palladium and aluminum incorporated mobile crystalline materials (Pd-Al-MCM-41) as bifunctional catalysts has been hydrothermally synthesized. Characterization shows that these molecular materials exhibit an ordered mesoporous structure, high surface area and a good dispersion of palladium in the frame. The catalytic activity of the Pd-Al-MCM-41 for the dimerization-hydrogenation reaction system of β-pinene in one pot has been systematically studied. Pd0.5-Al30-MCM-41 (SiO2/Al2O3 = 30, 0.5 wt% palladium content) was found to be the best catalyst which gave a dimer yield of up to 64.7%. It is worth noting that palladium shows a good synergic catalytic effect with aluminum in the dimerization reaction and enhances the dimerization yield. Furthermore, the bifunctional catalyst displayed a good activity over 4 runs.
- Zhang, Song,Xu, Chao,Zhai, Guoqing,Zhao, Mingliang,Xian, Mo,Jia, Yuxiang,Yu, Zongjiang,Liu, Fusheng,Jian, Fangfang,Sun, Weizhi
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p. 47539 - 47546
(2017/10/19)
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- Converting S-limonene synthase to pinene or phellandrene synthases reveals the plasticity of the active site
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S-limonene synthase is a model monoterpene synthase that cyclizes geranyl pyrophosphate (GPP) to form S-limonene. It is a relatively specific enzyme as the majority of its products are composed of limonene. In this study, we converted it to pinene or phellandrene synthases after introducing N345A/L423A/S454A or N345I mutations. Further studies on N345 suggest the polarity of this residue plays a critical role in limonene production by stabilizing the terpinyl cation intermediate. If it is mutated to a non-polar residue, further cyclization or hydride shifts occurs so the carbocation migrates towards the pyrophosphate, leading to the production of pinene or phellandrene. On the other hand, mutant enzymes that still possess a polar residue at this position produce limonene as the major product. N345 is not the only polar residue that may stabilize the terpinyl cation because it is not strictly conserved among limonene synthases across species and there are also several other polar residues in this area. These residues could form a “polar pocket” that may collectively play this stabilizing role. Our study provides important insights into the catalytic mechanism of limonene synthases. Furthermore, it also has wider implications on the evolution of terpene synthases.
- Xu, Jinkun,Ai, Ying,Wang, Jianhui,Xu, Jingwei,Zhang, Yongkang,Yang, Dong
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- An improved and efficient synthesis of pinene based bipyridyldiols and bipyridine
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An improved and efficient synthesis of pinene based two bipyridyldiols and bipyridine is reported. For the first time, the sealed tube-pressure reaction of pinene based pyridone with phosphoryl chloride produced an excellent yield (95%) of pinene based 2-chloropyridine, which renders synthesizing pinene based bipyridyldiols a highly inexpensive and high yielding process. Moreover, highly effective reaction condition was developed for homocoupling of chloropyridine with Ni(0) that afforded pinene based bipyridine in a high yield (84%). These newly demonstrated sealed tube-pressure chlorination and homocoupling reaction of chloropyridine afford extremely effect route for the synthesis of pinene based bipyridine.
- Boobalan, Ramalingam,Chen, Chinpiao
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supporting information
p. 1930 - 1934
(2016/04/19)
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- Support Functionalization with a Phosphine-Containing Hyperbranched Polymer: A Strategy to Enhance Phosphine Grafting and Metal Loading in a Hydroformylation Catalyst
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We present the design of a hydroformylation catalyst through the immobilization of air-stable Rh nanoparticles (NPs) on a magnetic support functionalized with a hyperbranched polymer that bears terminal phosphine groups. The catalyst modification with the hyperbranched polymer improved the metal–support interaction, the metal loading, and the catalytic activity. The catalyst was active for the hydroformylation of natural products, such as estragole, and could be used in successive reactions with negligible metal leaching. The phosphine grafting played a key role in the recyclability of Rh NPs under hydroformylation conditions. The catalytic activity was maintained in successive reactions, even if the catalyst was exposed to air during each recovery procedure. The modification of the support with hyperbranched polyester allowed us either to increase the number of Rh active species or to obtain more active Rh species on the catalyst surface.
- Garcia, Marco A. S.,Heyder, Rodrigo S.,Oliveira, Kelley C. B.,Costa, Jean C. S.,Corio, Paola,Gusevskaya, Elena V.,dos Santos, Eduardo N.,Bazito, Reinaldo C.,Rossi, Liane M.
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p. 1951 - 1960
(2016/07/06)
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- High-activity cobalt catalysts for alkene hydroboration with electronically responsive terpyridine and α-diimine ligands
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Cobalt alkyl complexes bearing readily available and redox-active 2,2′:6′,2″-terpyridine and α-diimine ligands have been synthesized, and their electronic structures have been elucidated. In each case, the supporting chelate is reduced to the monoanionic, radical form that is engaged in antiferromagnetic coupling with the cobalt(II) center. Both classes of cobalt alkyls proved to be effective for the isomerization-hydroboration of sterically hindered alkenes. An α-diimine-substituted cobalt allyl complex proved exceptionally active for the reduction of hindered tri-, tetra-, and geminally substituted alkenes, representing one of the most active homogeneous catalysts known for hydroboration. With limonene, formation of an η3-allyl complex with a C-H agostic interaction was identified and accounts for the sluggish reactivity observed with diene substrates. For the terpyridine derivative, unique Markovnikov selectivity with styrene was also observed with HBPin. (Figure Presented).
- Palmer, W. Neil,Diao, Tianning,Pappas, Iraklis,Chirik, Paul J.
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p. 622 - 626
(2015/03/04)
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- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
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The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- ODORANT COMPOSITION CONTAINING ALLYL ETHERS AS ODORANT PRECURSORS
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The deliberate release of odorants or aroma substances is desirable in many fields of application, and in particular in the field of washing and cleaning agents. Said deliberate release is achieved by using an odorant composition that comprises an odorant precursor, which is an allyl ether of the formula (I), R1R2C═CR3—CR4R5—O—CHR6R7, in which the residues R1, R2, R3, R4, R5, R6 and R7 mutually independently denote H or a hydrocarbon residue that can be acyclic or cyclic, substituted or unsubstituted, branched or unbranched, as well as saturated or unsaturated. Thus, in particular odorants in the form of an alkene having an allylic hydrogen atom, such as α-pinene, can be released in a deliberate manner.
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Paragraph 0123
(2014/02/16)
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- PHOTOLABILE PRO-FRAGRANCES
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Photolabile scent storage substance that are capable of photoinduced release of cyclic compounds have at least one cyclic double bond. These scent storage substances are special ketones, and enable greatly improved stability of the scent impression, in particular with a fresh character, in typical applications, for example in textile laundering, room scenting, and in the cosmetic sector. More economical utilization of the stored scents can thereby be ensured. Also described are corresponding washing or cleaning agents, scenting methods, and methods for manufacturing the special ketones.
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Page/Page column 8-9
(2012/12/14)
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- An efficient method for the transformation of naturally occurring monoterpenes into amines through rhodium-catalyzed hydroaminomethylation
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The hydroaminomethylation (hydroformylation/reductive amination) of the naturally occurring monoterpenes, i.e., limonene, camphene, and β-pinene, was studied having as condensation counterparts the amines di-n-butylamine, morpholine or n-butylamine. Moderate to good yields (75-94%) were obtained employing [Rh(cod)(μ-OMe)]2 as pre-catalyst in the presence or not of triphenylphosphine or tribenzylphosphine as ancillaries in toluene, at 100 °C and 60 bar of an equimolar mixture of carbon monoxide and hydrogen. Some of the hydroaminomethylation products derived from limonene have biological activity and the products derived from camphene and β-pinene are new.
- Melo, Daniela S.,Pereira-Júnior, Schubert S.,Dos Santos, Eduardo N.
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experimental part
p. 70 - 76
(2012/03/22)
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- Unique catalysis of gold nanoparticles in the chemoselective hydrogenolysis with H2: Cooperative effect between small gold nanoparticles and a basic support
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Gold nanoparticles on hydrotalcite act as a heterogeneous catalyst for the chemoselective hydrogenolysis of various allylic carbonates to the corresponding terminal alkenes using H2 as a clean reductant. The combination of gold nanoparticles and basic supports elicited significantly unique and selective catalysis in the hydrogenolysis.
- Noujima, Akifumi,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 6723 - 6725
(2012/07/28)
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- Photocatalytic removal of monoterpenes in the gas phase. Activity and regeneration
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We show the photocatalytic removal of various monoterpenes such as β-pinene, α-pinene, camphene and limonene in the gas phase as a function of the reaction temperature, from room temperature to 80°C, taking also into account the thermal catalytic isomeriz
- Salem, Ibtissam,Keller, Nicolas,Keller, Valerie
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experimental part
p. 966 - 973
(2010/04/23)
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- Biochemistry and molecular genetics of the biosynthesis of the earthy odorant methylisoborneol in Streptomyces coelicolor
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Methylisoborneol (2) is a volatile organic compound produced by a wide variety of Actinomycete soil organisms, myxobacteria, and cyanobacteria. It has an unusually low odor threshold and, together with geosmin, is responsible for the characteristic smell of moist soil as well as unpleasant taste and odor episodes associated with public water supplies and contamination of various foodstuffs, including fish, wine, and beer. Despite considerable interest in detection and remediation of methylisoborneol, the biosynthesis of this methylated monoterpene has been obscure. In Streptomyces coelicolor, the sco7700 and sco7701 genes are shown to correspond to a two-gene operon responsible for methylisoborneol biosynthesis. Both genes have been amplified by PCR and the resulting DNA has been cloned and expressed in Escherichia coli. Incubation of recombinant SCO7701 protein, annotated as a possible C-methyltransferase, with geranyl diphosphate (1) and S-adenosylmethionine gave the previously unknown compound, (E)-2-methylgeranyl diphosphate (3). Incubation of 3 in the presence of Mg2+ with recombinant SCO7700, previously annotated only as a possible metal-binding protein or terpenoid synthase, resulted in the formation of 2-methylisoborneol (2). The steady-state kinetic parameters for both biochemical reactions have been determined. Incubation of geranyl diphosphate and S-adenosylmethionine with a mixture of both SCO7700 and SCO7701 resulted in formation of methylisoborneol (2). Cyclization of 2-methylgeranyl diphosphate (3) to methylisoborneol (2) likely involves the intermediacy of 2-methyllinalyl diphosphate. Copyright
- Wang, Chieh-Mei,Cane, David E.
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supporting information; experimental part
p. 8908 - 8909
(2009/02/03)
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- Catalytic activity of the VIII group metals in the hydrogenation and isomerization of α- And β-pinenes
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The kinetic regularities of the liquid-phase hydrogenation and isomerization of α- and β-pinenes over the Pd/C, Ru/C, Rh/C, Pt/C, and Ir/C catalysts were studied at temperatures ranging from 20 to 100 °C and at hydrogen pressures of 1-11 bar using n-octane as the solvent. The hydrogenation and isomerization of α- and β-pinenes occur simultaneously on the Ru/C, Rh/C, Pt/C, and Ir/C catalysts, and the reaction mixture contains the products of double bond hydrogenation, viz., cis- and trans-pinanes. The Ru, Rh, and Pd metals have a higher catalytic activity in β-pinene isomerization than Ir and Pt. Among the VIII Group metals studied, the Pd-based catalyst has the highest catalytic activity in double bond isomerization of α- and β-pinenes. The general scheme of the mechanism of hydrogenation and isomerization of α- and β-pinenes on the Pd/C catalyst was proposed.
- Deliy,Simakova
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body text
p. 2056 - 2064
(2010/05/02)
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- Synthesis of silylated alkylboronic acids and esters via hydroboration of allylic and vinylic trimethylsilanes
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Representative allylic trimethylsilanes and isopropenyltrimethylsilane were hydroborated with dichloroborane, and the products were transformed into the corresponding ssor γ-trimethylsilylboronates. Synthesis of 2-trimethylsilylethylboronic acid and its diethyl ester via hydroboration of trimethylvinylsilane with diisopinocampheylborane, followed by liberation of α-pinene is described.
- Cytarska,Kaczanowska,Zaidlewicz
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p. 1587 - 1594
(2008/09/18)
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- Regio- and stereoselective synthesis of the enantiomers of monoterpene-based β-amino acid derivatives
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The regio- and stereospecific addition of chlorosulfonyl isocyanate to cis-δ-pinene enantiomers has furnished monoterpene-fused β-lactams. The observed regioselectivity can be explained by ab initio DFT modeling of transition state structures. In contrast with the less reactive α-pinane-fused β-lactam 4, the resulting β-lactams 5 and 13 containing an amino group connected to a secondary carbon possess similar reactivity to the cycloalkane-fused analogues and can be easily converted to the β-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis-amino ester afforded the corresponding trans-amino ester in moderate yield.
- Szakonyi, Zsolt,Martinek, Tamas A.,Sillanpaeae, Reijo,Fueloep, Ferenc
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p. 2442 - 2447
(2008/03/13)
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- Thermolysis of α-pinene in supercritical lower alcohols
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Thermal isomerization of α-pinene in supercritical solvents, viz., ethanol, methanol, and propan-1-ol, was carried out, and differences in the rate and selectivity of the process were revealed. In supercritical ethanol the reaction rate increases sharply and the selectivity remains unchanged with an increase in the temperature (from 290 to 390°C) or pressure (from 90 to 270 atm). The main reaction products are limonene, isomeric alloocimenes, and pyronenes. The selectivity for limonene in propan-1-ol is higher than in other alcohols when the conversion of α-pinene not higher than 50%. In supercritical ethanol (430°C, 120 atm, 140 s) limonene is more stable than α-pinene (conversion 8%).
- Chibiryaev,Anikeev,Yermakova,Mikenin,Kozhevnikov,Sal'nikova
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p. 987 - 992
(2008/02/01)
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- Incorporation of an allene unit into α-pinene via β- elimination
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The two double-bond isomers 3-iodo-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene (6b) and 3-iodo-4,6,6-trimethylbicyclo[3.1.1]hept-2-ene (11) were synthesized by reacting 2,6,6-trimethylbicyclo[3.1.1]heptan-3-one (9) with hydrazine, followed by treatment with I2 in the presence of Et3N. Treatment of 11 with t-BuOK as base in diglyme at 220 resulted in the formation of 9 and 6,6-dimethyl-4-methylidenebicyclo[3.1.1]hept-2-ene (12). For the formation of 9, the cyclic allene 7 is proposed as an intermediate. Treatment of the second isomer, 6b, with t-BuOK at 170 gave rise to the diene 12 and the dimerization product 17. The underlying mechanism of this transformation is discussed. On the basis of density-functional-theory (DFT) calculations on the allene 7 and the alkyne 15, the formation of the latter as the intermediate was excluded. Verlag Helvetica Chimica Acta AG.
- Kilbas, Benan,Azizoglu, Akin,Balci, Metin
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p. 1449 - 1456
(2007/10/03)
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- Cationic rhodium(I) complexes containing 4,4′-disubstituted 2,2′-bipyridines: A systematic variation on electron density over the metal centre
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A series of [Rh(COD)(X2-bipy)]BF4 complexes (COD = 1,5-cyclooctadiene; X2-bipy = 4,4′-disubstituted 2,2′-bipyridines; X = OCH3, CH3, H, Cl or NO 2) has been prepared from [Rh(COD)Cl]2. The complexes for X = OCH3, Cl and NO2 have not been described previously in the literature. All complexes have been characterised by elemental analysis, IR, 1H NMR and UV-Vis spectrometry. This series of complexes presents a wide variation on electron density over the metal centre with virtually no variation on its steric environment which discloses interesting possibilities for catalytic and electro-catalytic studies. A preliminary evaluation of these complexes on the hydroformylation of camphene and β-pinene showed that under the rather drastic conditions employed the complexes acted as a precursor for [Rh(CO)3H], which accounts for most of the catalytic activity.
- Ribeiro, Paulo E.A.,Donnici, Claudio L.,Dos Santos, Eduardo N.
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p. 2037 - 2043
(2007/10/03)
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- Solvent extraction process
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A process for extracting a compound or composition of matter from a raw material containing that compound or composition as a constituent part is described. The process comprises the steps of (1) contacting the raw material with an extraction solvent comprising a heptafluoropropane so as to extract the compound or composition from the raw material into the solvent, and (2) separating the solvent containing the extracted compound or composition from raw material. The process is particularly adapted for extracting flavours, fragrances and neutraceuticals from materials of plant origin.
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- Rhodium catalyzed hydroformylation of β-pinene and camphene: effect of phosphorous ligands and reaction conditions on stereoselectivity
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The effect of phosphorous ligands on the rhodium catalyzed hydroformylation of β-pinene and camphene has been studied. In unmodified systems, β-pinene undergoes a fast isomerization to α-pinene. At longer reaction times and higher temperatures, the isomerization equilibrium is shifted resulting in the 80 percent chemoselectivity for β-pinene hydrofromylation products (97 percent trans). The addition of various diphosphines or phosphites improves the chemoselectivity and shifts the hydroformylation towards cis aldehyde 3a. Both the rate and diastereoselectivity of the hydroformylation of β-pinene are largely influenced by the basicity of auxiliary ligands, but surprisingly no correlation between their steric characteristics and the diastereoselectivity of the catalytic system has been revealed for the ligands with cone angles 128-165 deg. The systems with more basic ligands show lower activities, higher diastereoselectivities and usually higher chemoselectivities in the β-pinene hydroformylation. Camphene gives linear aldehyde 6, with virtually 100 percent regio- and chemoselectivity in both modified and unmodified systems. The addition of phosphorous ligands favors the formation of endo isomer 6b:6a/6b ca. 1/1.5 , whereas the ratio ca. 1/1 unmodified systems. Neither steric nor electronic parameters of the ligands have been found to influence significantly the diastereoselectivity of the camphene hydroformylation.
- Barros, Humberto J. V.,Ospina, Maria L.,Arguello, Eduardo,Rocha, William R.,Gusevskaya, Elena V.,Santos, Eduardo N. dos
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p. 150 - 157
(2007/10/03)
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- Thrombin receptor antagonists
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Heterocyclic-substituted tricyclics of the formula or a pharmaceutically acceptable salts thereof, wherein: n1 and n2 are independently 0-2; Het is an optionally substituted mono-, bi- or tricyclic heteroaromatic group; B is alkyl or optionally substituted alkenyl; R22 is —COR23 or a carboxy, sulfinyl, sulfonyl, sulfonamide or amino acid derivative; R23 is haloalkyl; alkenyl; haloalkenyl; alkynyl; optionally substituted cycloalkyl; cycloalkyl-alkyl; aryl; arylalkyl; heteroaryl; heterocycloalkyl; or —COOH and/or —SO3H substituted alkyl; R1, R2, R3, R9, R10 and R11 are as defined in the specification; are disclosed, as well as pharmaceutical compositions containing them and a method of treating diseases associated with thrombosis, atherosclerosis, restenosis, hypertension, angina pectoris, arrhythmia, heart failure, and cancer by administering said compounds.
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- Monoterpene synthase activities in leaves of Picea abies (L.) Karst. and Quercus ilex L.
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In addition to direct ecological functions in the interaction of plants with the environment, the emission of monoterpenes, especially from the foliage of evergreen trees, is of great importance for the production of ozone and photochemical oxidants in the troposphere. In the present work, we established a reproducible non-radioactive standard enzyme assay and characterized monoterpene synthase activities in needles of Norway spruce (Picea abies (L.) Karst.) and in leaves of holm oak (Quercus ilex L.). In Norway spruce, the dominant monoterpenes formed were α-pinene, camphene, and to a lesser extent β-pinene and limonene. In holm oak, α-pinene, sabinene, and β-pinene were the main products, while limonene was a minor component. Under optimum conditions, in both Norway spruce and holm oak, monoterpene formation remained constant up to 180 min and 90 min, respectively, and varied with the buffer and Mg2+ and Mn2+ concentrations used. Optimum temperature for monoterpene synthase activity was 40°C in both species; optimal pH ranged between 6.5 and 7.5 in both species. Apparent Michaelis- constants for the substrate GDP were ca. 17.9 ± 5.1 μM for Norway spruce and ca. 69.4 ± 22.1 μM for holm oak. Molecular weight determination by FPLC indicated that the monoterpene synthases in Norway spruce and holm oak have native molecular weights of ca. 59 and 50 kDa, respectively. (C) 2000 Elsevier Science Ltd.
- Fischbach, Robert J.,Zimmer, Ina,Steinbrecher, Rainer,Pfichner, Andreas,Schnitzler, Joerg-Peter
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p. 257 - 265
(2007/10/03)
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- Rhodium and palladium complexes from 1,1′ and 1,2 ferrocenylphosphine as bidentate ligands. Versatile coordination
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The complexation of the mixed bidentate ligands 1-diphenylphosphino-1′-diphenylthiophosphinoferrocenyl and 1,2-bis-(diphenylphosphino)ferrocenyl with rhodium(I) and palladium(II) species yield a range of mono- and dirhodium or palladium complexes. Their interest as possible catalysts for alkene hydroformylation and alkoxycarbonylation and Heck coupling reactions has been assessed. Fe[C5Me4P(S)Ph2][C5Me 4PPh2]PdCl2 and Fe[C5H2-1,2-(PPh2)2-4- tBu][C5H5]PdCl2 have been characterized by single-crystal X-ray diffraction studies.
- Broussier, Roland,Bentabet, Emmanuelle,Laly, Myriam,Richard, Philippe,Kuz'mina, Lyudmila G.,Serp, Philippe,Wheatley, Nigel,Kalck, Philippe,Gautheron, Bernard
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- Fine particle and gaseous emission rates from residential wood combustion
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Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning-communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter(a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and se mivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8- C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and forts were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography. Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter (a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8-C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.
- Mcdonald, Jacob D.,Zielinska, Barbara,Fujita, Eric M.,Sagebiel, John C.,Chow, Judith C.,Watson, John G.
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p. 2080 - 2091
(2007/10/03)
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- HAPs release from wood drying
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Hazardous Air Pollutant (HAP) profiles from drying softwood and hardwood flakes (for the manufacture of oriented strand board) are very similar, indicating that they originate through a common mechanism, the breakdown of wood tissue. Hence, the strategies employed to reduce VOC (volatile organic compound) emissions from hardwood can also be extended to decreasing HAPs from softwood. Drying aspen flakes in the field and in the laboratory gives rise to different VOC species, and direct extension of laboratory data to the field may prove difficult. Formaldehyde emissions from drying fresh aspen flakes are lower than those from stored material; the opposite effect occurs for methanol and the other aldehydes. HAPs evolved from drying pine flakes surge sharply at 5-10% moisture content during drying at 130-160 °C. Emissions of methanol, formaldehyde, pentanal, and hexanal all begin simultaneously, with the release of methanol and formaldehyde being the most sensitive to dryer temperature. Hence, the nature of the VOC mix is partly governed by the dryer temperature. Pine and aspen give rise to similar HAPs profiles during either drying or pressing flakes that are already dried.
- Otwell, Lawrence P.,Hittmeier, Michael E.,Hooda, Usha,Yan, Hui,Su, Wei,Banerjee, Sujit
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p. 2280 - 2283
(2007/10/03)
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- Molecular addition compounds. 14. Convenient preparations of representative dialkylborane reagents using the new, highly reactive N- ethyl-N-isopropylaniline-borane reagent (BACH-EI(TM))
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Convenient procedures for the preparation of representative dialkylborane reagents, diisopinocampheylborane, [1S]-2-diisocaranylborane, 9-borabicyclo[3,3,1]nonane, dicyclohexylborane and disiamylborane, using the new, highly reactive N-ethyl-N-isopropylaniline-borane reagent (BACH-EI(TM)) in dioxane and tetrahydrofuran are described.
- Brown, Herbert C.,Kanth, Josyula V. B.,Zaidlewicz, Marek
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p. 5991 - 6000
(2007/10/03)
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- Chiral synthesis via organoboranes. 48. Efficient synthesis of trans- fused bicyclic and cyclic ketones and secondary alcohols in high optical purities via asymmetric cyclic hydroboration with isopinocampheylchloroborane etherate
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Highly stereo- and enantioselective annelation has been achieved for the synthesis of trans-fused bicyclic and cyclic ketones via the asymmetric cyclic hydroboration of suitable cyclic dienes, such as 1-allyl-1- cycloalkenes or 1-vinyl-1-cycloalkenes and appropriate acyclic 1,4-dienes, respectively, with enantiomerically pure isopinocampheylchloroborane etherate (IpcBHCl·Et2O). The IpcBHCl· Et2O (an 86-90% equilibrium mixture) was readily synthesized by the reaction of an equivalent amount of hydrochloric acid in ethyl ether (Et2O) with optically pure isopinocampheylborane (IpcBH2). The hydroboration of the terminal double bond of a representative diene with IpcBHCl·Et2O readily provided the corresponding isopinocampheylalkylchloroborane (IpcRBCl). Subsequent hydridation of the IpcRBCl with lithium aluminum hydride (LAH, 0.25 equiv) at -20 or -25 °C generated the intermediate isopinocampheylalkylborane (IpcRBH) almost instantly, which then underwent a rapid stereospecific and enantioselective intramolecular cyclic hydroboration to provide the intermediate cyclic trialkylborane. This trialkylborane, on treatment with an aldehyde, liberated the optically pure auxiliary as α-pinene (readily recovered for recycle) to provide the corresponding cyclic borinate ester. This ester reacted smoothly with α,α-dichloromethyl methyl ether (DCME) in the presence of a hindered base (the DCME reaction) to yield, after oxidation with buffered hydrogen peroxide, the trans-fused bicyclic or cyclic ketone in high enantiomeric excess (ee). In another improved approach, in situ generated IpcBHCl·Et2O, from the reduction of isopinocampheyldichloroborane (IpcBCl2) with trimethylsilane (Me3SiH), in the presence of representative dienes in Et2O provided considerably improved optical yields of the bicyclic and cyclic ketones. The trialkylboranes obtained from suitable acyclic dienes can be easily protonolyzed to provide the secondary alcohols in high ee.
- Dhokte, Ulhas P.,Pathare, Pradip M.,Mahindroo, Verinder K.,Brown, Herbert C.
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p. 8276 - 8283
(2007/10/03)
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- The First Stereoselective Palladium-Catalyzed Cyclocarbonylation of β,γ-Substituted Allylic Alcohols
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β,γ-Substituted allylic alcohols react with CO in the presence of catalytic quantities of palladium acetate and 1,4-bis(diphenylphosphino)butane affording α,β-substituted-γ-butyrolactones in 42-85% isolated yields. The complete stereoselectivity observed
- Brunner, Melanie,Alper, Howard
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p. 7565 - 7568
(2007/10/03)
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- New Chiral Dichlorophosphines and Their Use in the Synthesis of Phosphetane Oxides and Phosphinic Chlorides
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Myrtanyl-, bornyl- and isopinocampheyldichlorophosphines have been prepared from the corresponding alkyl chlorides via diastereospecific reactions of the Grignard reagents with PCl3 or (Et2N)2-PCl. Two applications of these compounds to synthetic asymmetric organophosphorus chemistry have been examined: their reactions with 2,3,3-trimethylbutene and AlCl3 afford either P-chiral phosphetane oxides or, in the presence of gaseous HCl, P-chiral phosphinic chlorides with moderate to high diastereoselectivity.
- Marinetti, Angela,Buzin, Francois-Xavier,Ricard, Louis
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p. 297 - 301
(2007/10/03)
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- Medium- and sensitizer-dependent radical cation reactions: Deprotonation in fluid solution and solid matrices
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Radical cations generated by photo-induced electron transfer in solution or by chemical oxidation in the channels of a redox-active zeolite (NaZSM-5) may be deprotonated, giving rise to neutral radicals. In solution, the geminate radical anion or an added nucleophile (methanol) may serve as the proton acceptor. Deprotonations in solution are not efficient; the corresponding products may be suppressed by several competing intra- or bi-molecular reactions. Although methanol serves as the base deprotonating at least one radical cation, it often is more efficient as a nucleophile, thereby depressing deprotonation. Deprotonations in the zeolite are more effective, presumably, because competing reactions with outside reagents are precluded. Occasionally, NaZSM-5 zeolites promote complex reaction sequences, such as the conversion of p-propylanisole to the radical cation of anethole or the deprotonation-ring opening of 1,2-diphenylcyclopropane radical cation to exo,exo-diphenylallyl radical. Acta Chemica Scandinavica 1997.
- Roth, Heinz D.,Weng, Hengxin,Zhou, Dahui,Lakkaraju, Prasad S.
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p. 626 - 635
(2007/10/03)
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- Electron transfer induced deprotonation of α- and β-pinene: Evidence for ring-closed vinylcyclobutane radical cations
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Electron transfer from α- (1) or β-pinene (2), to 2,3,5,6-tetrachlorobenzoquinone generates radical cations, which are rapidly deprotonated by the semiquinone radical anion. (1S, 5S)-2 is converted to (1S,5S)-1 and (1R,5R)-1 yields a dehydrogenation product, verbenene, (1R,5R)-9 with essentially quantitative retention of optical activity. The results support chiral, 'ring-closed' radical cation structures in which the allylic-quaternary cyclobutane C-C bond retains a significant degree of bonding.
- Zhou,Sheik,Roth
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p. 2385 - 2388
(2007/10/03)
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- Isomerization of 1-alkenes using the Na2Fe(CO)4/CuCl and Na2Fe(CO)4/BrCH2CH2Br reagent systems
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The reagent Na2Fe(CO)4 prepared in situ in THF by the reduction of Fe(CO)5 with sodium naphthalenide reacts with certain alkenes in the presence of CuCl to bring about isomerization of the alkenes.Thus the 1-alkenes (1-dodecene, 1-decene, safrole and allyl benzene) are isomerized to trans-2-alkenes, and β-pinene is isomerized to α-pinene.Reactions involving BrCH2CH2Br in place of CuCl give similar results.Keywords: Isomerization; Supernucleophile; Iron tetracarbonyl; Iron-copper bonds; Iron pentacarbonyl; Copper(I) chloride
- Reddy, Malladi Rama,Periasamy, Mariappan
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p. 263 - 266
(2007/10/02)
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- Chemoselective removal of allylic formyloxy group using SmI2
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A variety of allylic formates are chemoselectively transformed into th corresponding olefins in excellent yields on treatment with SmI2 in THF-HMPA-H2O (20:5:1), even though allylic acetate and allylic ether groups are present in the same molecule.
- Shibuya,Shiratsuchi
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p. 431 - 449
(2007/10/02)
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Reaction of alkyl hydroperoxides (1(ary), 2(ary) or 3(ary)) upon tertiary alkyl trichloroacetimidates under acidic catalysis yielded unsymmetrical dialkyl peroxides with yields in the range 30-70%.
- Bourgeois,Montaudon,Maillard
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p. 2477 - 2484
(2007/10/02)
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- Chemoselectivity in Catalytic Transfer Hydrogenation - Reduction of Alkenes and Alkynes with the H2PO2-NH4+*H2O/Pd-C System
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The H2PO2-*H2O/Pd-C system acts as an unusually powerful reducing agent, which is able to reduce cyclooctene to cyclooctane, Δ9,10-octalin to decalins, α- and β-pinenes to pinanes at room temperature in high yield without the formation of byproducts.This system reduces each of these compounds or partly (alkynes to alkenes), depending on the competition between the transfer hydrogenation to give alkanes and the protonolysis to give hydrogen gas on the palladium catalyst. - Key Words: Chemoselectivity/ Protonolysis/ Transfer hydrogenation/ Alkenes, reduction of/ Alkynes, reduction of
- Khai, Bui The,Arcelli, Antionio
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p. 2265 - 2268
(2007/10/02)
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- Chiral Synthesis via Organoboranes. 35. Simple Procedures for the Efficient Recycling of the Terpenyl Chiral Auxiliaries and Convenient Isolation of the Homoallylic Alcohols in Asymmetric Allyl- and Crotylboration of Aldehydes
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Asymmetric allyl- and crotylboration of aldehydes, RCHO, with terpenyl-based allyl- and crotylborane reagents Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3, Ter* = Ipc, 4-Icr and 2-Icr; All = allyl and Crt = crotyl), afford Ter2*BOCH*(R)C*(1R)(2R)CH=CH2 intermediates 4.In these reactions, the isolation of homoallylic alcohols, HOCH*(R)C*(1R)(2R)CH=CH2 (5), can be accomplished via oxidation of 4 with alkaline hydrogen peroxide.Unfortunately, oxidative workup destroys the chiral auxiliary and produces a large amount of nonrecyclable byproduct, terpenol (Ter*OH).Further, isolation of the pure homoallylic alcohol by distillation can be difficult if it boils in the range of the abundant byproduct.Therefore, in order to recycle the chiral auxiliaries and isolate the product homoallylic alcohols in an efficient manner, we have developed the following procedures: (1) elimination workup, in which enantiomerically pure α-pinene and Δ2- and Δ3-carenes are liberated from terpenylborinates 4 by treatment with isobutyraldehyde and 1 mol percent BF3*OEt2; (2) ethanolamine workup involving treatment of 4 with ethanolamine (EA) to achieve the precipitation of the ethanolamine adducts (EA-BTer2*, Ter* = Ipc and 2-Icr, 11 and 12) from which the Ter2*BOMe can be easily regenerated; and (3) 8-hydroxyquinoline workup, involving treatment of 4 with 8-hydroxyquinoline (8-HQ) to precipitate the 8-HQ adducts (8-HQ-BTer2*, Ter* = Ipc, 4-Icr and 2-Icr, 13-15), from which the various Ter2*BOMe intermediates can be conveniently liberated.It is hoped that these procedures will significantly enhance the scope of asymmetric allyl-/crotylboration of aldehydes with Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3) and serve as excellent alternatives for any catalytic versions yet to be discovered.
- Brown, Herbert C.,Racherla, Uday S.,Liao, Y.,Khanna, Vijay V.
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p. 6608 - 6614
(2007/10/02)
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