- Activated vs. pyrolytic carbon as support matrix for chemical functionalization: Efficient heterogeneous non-heme Mn(II) catalysts for alkene oxidation with H2O2
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Two types of heterogeneous catalytic materials, MnII-L3imid@Cox and MnII-L3imid@PCox, have been synthesized and compared by covalent grafting of a catalytically active [MnII-L3imid] complex on the surface of an oxidized activated carbon (Cox) and an oxidized pyrolytic carbon from recycled-tire char (PCox). Both hybrids are non-porous bearing graphitic layers intermixed with disordered sp2/sp3 carbon units. Raman spectra show that (ID/IG)activatedcarbon > (ID/IG)pyrolyticcarbon revealing that oxidized activated carbon(Cox) is less graphitized than oxidized pyrolytic carbon (PCox). The MnII-L3imid@Cox and MnII-L3imid@PCox catalysts were evaluated for alkene oxidation with H2O2 in the presence of CH3COONH4. Both showed high selectivity towards epoxides and comparing the achieved yields and TONs, they appear equivalent. However, MnII-L3imid@PCox catalyst is kinetically faster than the MnII-L3imid@Cox (accomplishing the catalytic runs in 1.5 h vs. 5 h). Thus, despite the similarity in TONs MnII-L3imid@PCox achieved extremely higher TOFs vs. MnII-L3imid@Cox. Intriguingly, in terms of recyclability, MnII-L3imid@Cox could be reused for a 2th run showing a ~20% loss of its catalytic activity, while MnII-L3imid@PCox practically no recyclable. This phenomenon is discussed in a mechanistic context; interlinking oxidative destruction of the Mn-complex with high TOFs for MnII-L3imid@PCox, while the low-TOFs of MnII-L3imid@Cox are preventive for the oxidative destruction of the Mn-complex.
- Simaioforidou,Papastergiou,Margellou,Petrakis,Louloudi
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p. 516 - 525
(2016/12/16)
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- Continuous flow photooxygenation of monoterpenes
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Photooxygenation of monoterpenes was conducted in two continuous flow reactors. The first, suitable for lab-scale research, had a maximum yield of 99.9%, and the second, focused on industrial applications, showed a daily output that was 270.0-fold higher than that in batch systems. The use of sunlight instead of an LED lamp gave 68.28% conversion.
- Park, Chan Yi,Kim, Young Joon,Lim, Hyo Jin,Park, Jeong Hyeon,Kim, Mi Jin,Seo, Seung Woo,Park, Chan Pil
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p. 4233 - 4237
(2015/02/19)
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- Influence of the Br?nsted and Lewis acid sites on the catalytic activity and selectivity of Fe/MCM-41 system
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The system Fe2O3/MCM-41, with high iron dispersion, was synthesized in order to introduce Lewis acid sites into the MCM-41 structure. Two calcination atmospheres (inert and oxidant) were used to produce iron nanoclusters with different structural properties. Besides, a silylation treatment was realized on both solids with the aim of neutralizing the Br?nsted acidity associated with the MCM-41 silanol groups. The samples were characterized by atomic absorption spectroscopy, X-ray diffraction at low angles, N2 adsorption, temperature-programmed reduction, Fourier transform infrared spectroscopy, nuclear magnetic resonance of 29Si, and M?ssbauer spectroscopy. The influence of the structural changes of the nanoclusters and the effect of the simultaneous presence of Lewis and Br?nsted acid sites were evaluated studying the product distribution from the α-pinene oxide isomerization reaction. It was determined that the Br?nsted acidity of the Fe/MCM-41 system has not the sufficient acid strength to modify the product distribution which is mainly governed by the Lewis sites.
- Fellenz,Bengoa,Marchetti,Gervasini
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scheme or table
p. 187 - 196
(2012/10/08)
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- Selective photosensitized oxidation and its catalytic regulation of monoterpene with molecular oxygen in different reaction media
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The photo-catalytic oxidation of α-pinene, β-pinene and limonene with molecular oxygen sensitized by tetrachlorotetraiodo-fluorescein sodium salt (RB) has been studied in different reaction media under green light irradiation. Simple and efficient photosensitized oxidation equipment was employed successfully to improve the efficiency of the photosensitized reaction. The results indicate that the photosensitized oxidation products can be directly obtained without after-treatment by reductive reagent. Furthermore, it was found that the product distributions are remarkably affected by reaction media, and that N,N-dimethylformamide (DMF) can regulate the selectivity to products. In particular, the good selectivity (85%) to the main product (myrtenal) and the excellent conversion (99%) were obtained in the absence of any other catalysts when DMF was used as reaction solvent in the photosensitized oxidation of β-pinene. Moreover, the possible photosensitized oxidation reaction mechanism in different media was suggested in the present work.
- You, Kuiyi,Yin, Dulin,Mao, Liqiu,Liu, Pingle,Luo, He'An
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experimental part
p. 321 - 325
(2011/10/13)
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- Abnormal Cannabidiols as agents for lowering intraocular pressure
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The present invention provides a method of treating glaucoma or ocular hypertension which comprises applying to the eye of a person in need thereof an amount sufficient to treat glaucoma or ocular hypertension of a compound of formula I wherein Y, Q, Z, R, R1 and R2 are as defined in the specification. The present invention further comprises pharmaceutical compositions, e.g. ophthalmic compositions, including said compound of formula I.
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Page/Page column 9
(2008/06/13)
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- The enantioselective syntheses of bisabolane sesquiterpenes Lepistirone and Cheimonophyllon E
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The synthetic approach to the bisabolane sesquiterpenes Lepistirone 1 and Cheimonophyllon E 2 involves the transformation of (+)-2-carene (5) into the p-menthane furans 8 and 11. Regio- and stereoselective alkylation, and standard reactions complete the e
- Brocksom, Timothy John,Zanotto, Paulo R.,Brocksom, Ursula
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p. 2397 - 2398
(2007/10/03)
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- PROCESS FOR PREPARATION OF (+)-P-MENTHA-2,8-DIENE-1-OL
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A process for preparing (+)-p-mentha-2,8-diene-1-ol comprising reacting (+)-limonene oxide with at least one amine in the presence of at least one Lewis acid to form amine adduct intermediates. The amine adduct is then oxidized to form an N-oxide that is
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- Trypanocidal terpenoids from Laurus nobilis L.
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Trypanocidal constituents of dried leaves of Laurus nobilis L. (Lauraceae) were examined. Activity-guided fractionation of the methanol extract resulted in the isolation of two guaianolides, dehydrocostus lactone (1) and zaluzanin D (2), and a new p-menthane hydroperoxide, (1R,4S)-1-hydroperoxy-p-menth-2-en-8-ol acetate (3). The minimum lethal concentrations of these compounds against epimastigotes of Trypanosoma cruzi were 6.3, 2.5, and 1.4 μM, respectively.
- Uchiyama, Nahoko,Matsunaga, Keiji,Kiuchi, Fumiyuki,Honda, Gisho,Tsubouchi, Akiko,Nakajima-Shimada, Junko,Aoki, Takashi
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p. 1514 - 1516
(2007/10/03)
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- A Novel Cyclization of Geraniol and Nerol Initiated by Tris(p-bromophenyl)ammoniumyl Radical Cation
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Geraniol (1) and nerol (2) undergo a novel cyclization to cis-p-mentha-2,8-dien-1-ol (4) by reaction with tris(pbromophenyl)ammoniumyl radical cation (3) and the reaction mechanism is discussed.
- Wang, Wei,Liu, You-Cheng
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- Synthetic Chemistry with Fullerenes. Photooxygenation of Olefins
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Under irradiation with visible or UV (>290 nm) light in the presence of molecular oxygen and a minute amount of fullerenes, olefins and dienes undergo ene and Diels-Alder reactions with singlet oxygen to give photooxygenation products.The regio- and stereoselectivities of the photooxygenation of β-myrcene, (+)-pulegone, 4-methylpent-3-en-2-ol, and (+)-limonene were very similar to those observed in known singlet oxygen reactions, indicating that the fullerene-sensitized reaction generates free singlet oxygen.The efficiency of fullerenes and conventional sensitizers was qualitatively examined by using the Diels-Alder reaction between 1O2 and furan-2-carboxylic acid as a probe.Among those examined, C70 was found to be the most effective.The reaction was the fastest and completed with as little as 0.0001 equiv of C70.C60 and hematoporphyrin were found to be of similar efficiency.The methanofullerene 13, which lacks one olefinic conjugation in the C60 core, was as good as C60 itself, but the aminofullerene 14, lacking six double bonds, was quite inferior.The fullerene carboxylic acid 15, which was previously shown to show considerable biochemical activity, was found to be capable of generating singlet oxygen in aqueous DMSO.
- Tokuyama, Hidetoshi,Nakamura, Eiichi
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p. 1135 - 1138
(2007/10/02)
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- Photosensitized Oxygenation of Olefins with Zinc Tetraphenylporphine-1,4-Diazabicyclooctane Complex
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In the presence of a proper amount of amines such as 1,4-diazabicyclooctane (DABCO) and piperidine, zinc tetraphenylporphine (ZnTPP) works as a not only apparently more effective but also more photoresistant sensitizer for singlet-oxygen oxygenation of olefins than in the absence of the amines.This is ascribed to the facts that ZnTPP forms a 1:1 complex with DABCO, and that DABCO coordinated to ZnTPP has no ability to quench singlet oxygen, as revealed by detection of singlet oxygen phosphorescence and product distributions in oxygenation of d-limonene, 1,2-dimethylcyclohexene, and 1-phenylcyclobutene.
- Sakuragi, Masako,Ichimura, Kunihiro,Sakuragi, Hirochika
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p. 1944 - 1949
(2007/10/02)
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- Acid-catalysed Terpenylations of Olivetol in the Synthesis of Cannabinoids
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Examination of the toluene-p-sulphonic acid-catalysed reaction of (1S,2S,3R,6R)-(+)-trans-car-2-ene epoxide with olivetol shows that, inconsistently with the accepted mechanism, (3R,4R)-(-)-o- and -p-cannabidiols are produced as well as (3R,4R)-(-)-Δ1- and Δ6-tetrahydrocannabinols.Evidence is now presented that, as in Petrzilka's reaction employing chiral p-mentha-2,8-dien-1-ols, the reacting species is the delocalised (4R)-p-mentha-2,8-dien-1-yl cation (9).Similar terpenylation using (1S,3S,4R,6R)-(+)-trans-car-3-ene epoxide shows that besides the reported (-)-Δ6-THC, o- and p-cannabidiols, Δ1-THC and Δ4,8-iso-THC can also be produced.The nature of the products, the chirality, and the characteristics of the reaction implicate again the delocalised cation (9).Its formation via Kropp-type rearrangement is excluded and a pathway leading to (4R)-p-mentha-2,6,8-triene, which on protonation gives (9), is proposed.Protonated on C-8, the triene can be trapped and isolated as (4R)-p-mentha-2,6-dien-8-ol.The latter, made in (+/-)-form from citral, proved to be an excellent terpenylating agent for producing cannabinoids.Terpenylation of olivetol by the pinanes (1S,4S,5S)-(-)-cis-verbenol and (1R,5S,7R)-(+)-cis-chrysanthenol is compared.A major drawback of the latter is partial racemisation which occurs in the verbenone-chrysanthenone isomerisation during its photochemical preparation.Whilst Δ1-THC cannot be directly obtained from verbenol, its tertiary allylic cation permits a much higher yielding terpenylation than the secondary cation from chrysanthenol.
- Crombie, Leslie,Crombie, W. Mary L.,Jamieson, Sally V.,Palmer, Christopher J.
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p. 1243 - 1250
(2007/10/02)
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- Stereoselective Cyclization assisted by the Selenyl Group. Biogenetic-type Synthesis in the p-Menthane Series
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Acid-catalysed cyclization of the β-hydroxyselenide (3), derived from linalyl acetate (1), afforded the trans-p-menthanes (4) and (5), the structures of which were confirmed by their transformation into (6), (11), (8), and (13), and alternative syntheses of these compounds.The structure determination of some products obtained by the reaction of limonene and α-terpineol epoxides with phenylselenium anion was also carried out.
- Kametani, Tetsuji,Kurobe, Hiroshi,Nemoto, Hideo
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p. 756 - 760
(2007/10/02)
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- Studies on the stereochemical course of selenium-assisted cyclisation: Biogenetic-type synthesis in the p-menthan series
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Acid-catalysed cyclisation of the β-hydroxy selenide (3) denved from linalyl acetate (1) afforded the trans-p-methans (4) and (5), the structures of which were confirmed by their transformation into (6), (8), (9), and (11) and by alternative synthesis of these compounds.
- Kametani, Tetsuji,Kurobe, Hiroshi,Nemoto, Hideo
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p. 762 - 763
(2007/10/02)
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