- Tuning of α-Silyl Carbocation Reactivity into Enone Transposition: Application to the Synthesis of Peribysin D, E-Volkendousin, and E-Guggulsterone
-
A reliable method for enone transposition has been developed with the help of silyl group masking. Enantio-switching, substituent shuffling, and Z-selectivity are the highlights of the method. The developed method was applied for the first total synthesis of peribysin D along with its structural revision. Formal synthesis of E-guggulsterone and E-volkendousin was also claimed using a short sequence.
- Athawale, Paresh R.,Zade, Vishal M.,Rama Krishna, Gamidi,Reddy, D. Srinivasa
-
p. 6642 - 6647
(2021/09/02)
-
- Discovery and Engineering of Bacterial (?)-Isopiperitenol Dehydrogenases to Enhance (?)-Menthol Precursor Biosynthesis
-
Microbial synthesis of (?)-menthol, a compound of plant origin, is of great importance because of the high demand for this product and related sustainability issues. However, the total biosynthesis of (?)-menthol from easily available feedstocks like (?)-limonene by engineered microbial hosts is stalled by the poor protein expression or activity of several enzymes from the native (?)-menthol biosynthesis pathway of mint (Mentha piperita). Among these unsatisfied steps, (?)-isopiperitenol dehydrogenase (IPDH) catalyzed oxidation reaction of (?)-trans-isopiperitenol was one of the bottlenecks that need to be optimized. In this work, two novel bacterial enzymes with IPDH activity were discovered to replace their inefficient counterpart from plant cells in microbial (?)-menthol synthesis. Two key residues in PaIPDH from Pseudomonas aeruginosa were mutated to PaIPDHE95F/Y199V with 4.4-fold improved specific activity than PaIPDH. The mechanism for the beneficial mutations was elucidated by molecular dynamics simulations. PaIPDHE95F/Y199V was used to synthesize (?)-isopiperitenone from (?)-limonene in vivo via a self-sufficient cofactor cascade enzyme reaction, affording a 3.7-fold enhanced titer of (?)-isopiperitenone compared with that obtained using the original mint IPDH (MpIPDH). The bacterial enzyme PaIPDHE95F/Y199V can be applied in the future for constructing a more efficient artificial pathway to biosynthesize (?)-menthol in a microbial whole-cell system. (Figure presented.).
- Zhan, Jing-Ru,Shou, Chao,Zheng, Yu-Cong,Chen, Qi,Pan, Jiang,Li, Chun-Xiu,Xu, Jian-He
-
supporting information
p. 3973 - 3982
(2021/07/02)
-
- Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
-
The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
- Fiorio, Jhonatan L.,Rossi, Liane M.
-
p. 312 - 318
(2021/01/29)
-
- Scalable Aerobic Oxidation of Alcohols Using Catalytic DDQ/HNO3
-
A selective, practical, and scalable aerobic oxidation of alcohols is described that uses catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and HNO3, with molecular oxygen serving as the terminal oxidant. The method was successfully applied to the oxidation of a wide range of benzylic, propargylic, and allylic alcohols, including two natural products, namely, carveol and podophyllotoxin. The conditions are also applicable to the selective oxidative deprotection of p-methoxybenzyl ethers.
- Arseniyadis, Stellios,Clavier, Louis,Copin, Chloé,Fournier, Jean,Giffard, Jean-Fran?ois,Jean, Alexandre,Katsina, Tania,Macedo Portela Da Silva, Nayane,Tamion, Rodolphe
-
supporting information
p. 856 - 860
(2020/07/14)
-
- Combining Photo-Organo Redox- and Enzyme Catalysis Facilitates Asymmetric C-H Bond Functionalization
-
In this study, we combined photo-organo redox catalysis and biocatalysis to achieve asymmetric C–H bond functionalization of simple alkane starting materials. The photo-organo catalyst anthraquinone sulfate (SAS) was employed to oxyfunctionalise alkanes to aldehydes and ketones. We coupled this light-driven reaction with asymmetric enzymatic functionalisations to yield chiral hydroxynitriles, amines, acyloins and α-chiral ketones with up to 99 % ee. In addition, we demonstrate functional group interconversion to alcohols, esters and carboxylic acids. The transformations can be performed as concurrent tandem reactions. We identified the degradation of substrates and inhibition of the biocatalysts as limiting factors affecting compatibility, due to reactive oxygen species generated in the photocatalytic step. These incompatibilities were addressed by reaction engineering, such as applying a two-phase system or temporal and spatial separation of the catalysts. Using a selection of eleven starting alkanes, one photo-organo catalyst and 8 diverse biocatalysts, we synthesized 26 products and report for the model compounds benzoin and mandelonitrile > 97 % ee at gram scale.
- Zhang, Wuyuan,Fueyo, Elena Fernandez,Hollmann, Frank,Martin, Laura Leemans,Pesic, Milja,Wardenga, Rainer,H?hne, Matthias,Schmidt, Sandy
-
supporting information
p. 80 - 84
(2019/01/04)
-
- A Simple, Mild and General Oxidation of Alcohols to Aldehydes or Ketones by SO2F2/K2CO3 Using DMSO as Solvent and Oxidant
-
A practical, general and mild oxidation of primary and secondary alcohols to carbonyl compounds proceeds in yields of up to 99% using SO2F2 as electrophile in DMSO as both the oxidant and the solvent at ambient temperature. No moisture- and oxygen-free conditions are required. Stoichiometric amount of inexpensive K2CO3, which generates easy to separate by-products, is used as the base. Thus, 5-gram scale runs proceeded in nearly quantitative yields by a simple filtration as the work-up. The use of a polar solvent such as DMSO, which usually promotes competing Pummerer rearrangement, is also noteworthy. This protocol is compatible with a variety of common N-, O-, and S-functional groups on (hetero)arene, alkene and alkyne substrates (68 examples). The protocol was applied (99% yield) to a formal synthesis of the important cholesterol-lowering drug Rosuvastatin. (Figure presented.).
- Zha, Gao-Feng,Fang, Wan-Yin,Leng, Jing,Qin, Hua-Li
-
supporting information
p. 2262 - 2267
(2019/04/17)
-
- Catalytic performance of bulk and colloidal Co/Al layered double hydroxide with Au nanoparticles in aerobic olefin oxidation
-
A Co/Al layered double hydroxide material was synthesized in both bulk and exfoliated (colloidal) forms. Anion exchange with methionine allowed immobilization of Au nanoparticles previously prepared by a biomimetic method using an anti-oxidant tea aqueous extract to reduce the Au salt solution. The catalytic performance of bulk and exfoliated clays Au-hybrid materials was assessed in aerobic olefin epoxidation. Both catalysts were very active towards the epoxide products and with very interesting substrate conversion levels after 80 h reaction time. The Au-exfoliated material, where the nanosheets work as large ligands, yielded higher product stereoselectivity in the case of limonene epoxidation. This arises from a confined environment around the Au nanoparticles wrapped by the clay nanosheets modulating access to the catalytic active centres by reagents. Mechanistic assessment was also accomplished for styrene oxidation by DFT methods.
- Leandro, Sónia R.,Fernandes, Cristina I.,Viana,Mourato,Vaz, Pedro D.,Nunes, Carla D.
-
-
- Exploring the substrate specificity of Cytochrome P450cin
-
Cytochromes P450 are enzymes that catalyse the oxidation of a wide variety of compounds that range from small volatile compounds, such as monoterpenes to larger compounds like steroids. These enzymes can be modified to selectively oxidise substrates of interest, thereby making them attractive for applications in the biotechnology industry. In this study, we screened a small library of terpenes and terpenoid compounds against P450cin and two P450cin mutants, N242A and N242T, that have previously been shown to affect selectivity. Initial screening indicated that P450cin could catalyse the oxidation of most of the monoterpenes tested; however, sesquiterpenes were not substrates for this enzyme or the N242A mutant. Additionally, both P450cin mutants were found to be able to oxidise other bicyclic monoterpenes. For example, the oxidation of (R)- and (S)-camphor by N242T favoured the production of 5-endo-hydroxycamphor (65–77% of the total products, dependent on the enantiomer), which was similar to that previously observed for (R)-camphor with N242A (73%). Selectivity was also observed for both (R)- and (S)-limonene where N242A predominantly produced the cis-limonene 1,2-epoxide (80% of the products following (R)-limonene oxidation) as compared to P450cin (23% of the total products with (R)-limonene). Of the three enzymes screened, only P450cin was observed to catalyse the oxidation of the aromatic terpene p-cymene. All six possible hydroxylation products were generated from an in vivo expression system catalysing the oxidation of p-cymene and were assigned based on 1H NMR and GC-MS fragmentation patterns. Overall, these results have provided the foundation for pursuing new P450cin mutants that can selectively oxidise various monoterpenes for biocatalytic applications.
- Stok, Jeanette E.,Giang, Peter D.,Wong, Siew Hoon,De Voss, James J.
-
-
- From Bugs to Bioplastics: Total (+)-Dihydrocarvide Biosynthesis by Engineered Escherichia coli
-
The monoterpenoid lactone derivative (+)-dihydrocarvide ((+)-DHCD) can be polymerised to form shape-memory polymers. Synthetic biology routes from simple, inexpensive carbon sources are an attractive, alternative route over chemical synthesis from (R)-carvone. We have demonstrated a proof-of-principle in vivo approach for the complete biosynthesis of (+)-DHCD from glucose in Escherichia coli (6.6 mg L?1). The pathway is based on the Mentha spicata route to (R)-carvone, with the addition of an ′ene′-reductase and Baeyer–Villiger cyclohexanone monooxygenase. Co-expression with a limonene synthesis pathway enzyme enables complete biocatalytic production within one microbial chassis. (+)-DHCD was successfully produced by screening multiple homologues of the pathway genes, combined with expression optimisation by selective promoter and/or ribosomal binding-site screening. This study demonstrates the potential application of synthetic biology approaches in the development of truly sustainable and renewable bioplastic monomers.
- Ascue Avalos, Gabriel A.,Toogood, Helen S.,Tait, Shirley,Messiha, Hanan L.,Scrutton, Nigel S.
-
p. 785 - 792
(2019/01/29)
-
- Mild Chemoenzymatic Oxidation of Allylic sec-Alcohols. Application to Biocatalytic Stereoselective Redox Isomerizations
-
The design of catalytic oxidative methodologies in aqueous medium under mild reaction conditions and using molecular oxygen as final electron acceptor represents a suitable alternative to the traditional oxidative transformations. These methods are especially relevant if other functionalities that can be oxidized are present within the same molecule, as in the case of allylic alcohols. Herein we apply a simple chemoenzymatic system composed of the laccase from Trametes versicolor and 2,2,6,6-tetramethylpiperidinyloxy radical (TEMPO) to oxidize a series of racemic allylic sec-alcohols into the corresponding α,β-unsaturated ketones. Afterward, these compounds react with different commercially available ene-reductases to afford the corresponding saturated ketones. Remarkably, in the case of trisubstituted alkenes, the bioreduction reaction occurred with high stereoselectivity. Overall, a bienzymatic one-pot two-step sequential strategy has been described with respect to the synthesis of saturated ketones starting from racemic allylic alcohols, thus resembling the metal-catalyzed redox isomerizations of these derivatives that have been previously reported in the literature.
- Martínez-Montero, Lía,Gotor, Vicente,Gotor-Fernández, Vicente,Lavandera, Iván
-
p. 2413 - 2419
(2018/03/13)
-
- Enantiospecific Total Syntheses of (+)-Hapalindole H and (?)-12-epi-Hapalindole U
-
Enantiospecific total syntheses of (+)-hapalindole H and (?)-12-epi-hapalindole U as well as the formal syntheses of (+)-hapalindole Q and (+)-12-epi-fischerindole U isothiocyanate have been described. Key steps of our approach feature expedient, highly regio- and diastereoselective Lewis acid catalyzed Friedel–Crafts reaction of indole with cyclic allylic alcohols and intramolecular reductive Heck reaction. Efficiency of the synthetic route also relies on an alkynyl aluminate complex driven regioselective nucleophilic epoxide opening from a sterically hindered site.
- Dethe, Dattatraya H.,Das, Saikat,Kumar, Vijay B.,Mir, Nisar A.
-
supporting information
p. 8980 - 8984
(2018/06/04)
-
- Alcohol Oxidations Using Reduced Polyoxovanadates
-
A full account of our recently communicated room temperature alcohol oxidation using reduced polyoxovanadates (r-POVs) is presented. Extensive optimizations revealed optimal conditions employing 0.02 equiv. of r-POV catalyst Cs5(V14As8O42Cl), 5 equiv. tert-butyl hydrogen peroxide (tBuOOH) as the terminal co-oxidant, in an acetone solvent for the quantitative oxidation of aryl-substituted secondary alcohols to their ketone products. The substrate scope tolerates most aryl substituted secondary alcohols in good to quantitative yields while alkyl secondary and primary activated alcohols were sluggish in comparison under similar conditions. Catalyst recyclability was successful on a 1.0?mmol scale of starting alcohol 1-phenylethanol. The oxidation was also successfully promoted by the VIV/VV mixed valent polyoxovanadate (POV) Cs11Na3Cl5(V15O36Cl). Finally, a third POV, Cs2.64(V5O9)(AsO4)2, was investigated for catalytic activity using our established reaction protocol, but proved ineffective as compared to the other two r-POV catalysts. This study expands the field of POM-mediated alcohol oxidations to include underexplored r-POV catalysts. While our catalysts do not supplant the best catalysts known for the transformation, their study may inform the development of other novel oxidative transformations mediated by r-POVs.
- Campbell, McKenzie L.,Sulejmanovic, Dino,Schiller, Jacqueline B.,Turner, Emily M.,Hwu, Shiou-Jyh,Whitehead, Daniel C.
-
-
- Enhanced solvent-free selective oxidation of cyclohexene to 1,2-cyclohexanediol by polyaniline@halloysite nanotubes
-
One-dimensional polyaniline@halloysite (PANI@HA) nanotubes with enhanced selective oxidation activity of cyclohexene are fabricated by employing aniline (ANI) chemical polymerization on halloysite nanotubes in situ. By facilely controlling the doping acid, acidity, and ANI/HA weight ratio during the fabrication, PANI with a controllable doping degree, redox state, and content is grown on halloysite nanotubes. The cyclohexene selective oxidation result shows that PANI@HA nanotubes are effective catalysts in a solvent-free reaction system with H2O2 as the oxidant, and their catalytic activity relies on the doping acid, acidity, and ANI/HA weight ratio in the fabrication. PANI@HA synthesized with HCl as a doping acid to condition the acidity at 1 M and 2.04 ANI/HA weight ratio (PANI@HA/1 M/2.04-HCl) demonstrates highest catalytic activity (98.17% conversion and 99.50% selectivity to 1,2-cyclohexanediol). The cyclohexene selective catalytic activity matches well with the PANI doping degree in PANI@HA. In addition, the optimal reaction condition is 20 mg catalyst, 2.5 mL H2O2, 70 °C, and 24 h. Furthermore, PANI@HA/1 M/2.04-HCl exhibits superior dihydroxylation activity toward 2,3-dimethyl-2-butene and cycling performance with 99.11% conversion and 96.92% selectivity to 1,2-cyclohexanediol after five cycles. The CV of PANI@HA indicates that the cyclohexene selective oxidation is attributed to a reversible redox reaction of PANI in PANI@HA for catalytic decomposition of H2O2.
- Zhou, Tianzhu,Zhao, Yue,Han, Wenmei,Xie, Huazhong,Li, Cuiping,Yuan, Mingquan
-
supporting information
p. 18230 - 18241
(2017/09/08)
-
- Zeolite Y encaged Ru(III) and Fe(III) complexes for oxidation of styrene, cyclohexene, limonene, and α-pinene: An eye-catching impact of H2SO4 on product selectivity
-
A novel Ru(III) and Fe(III) complexes of ligands 1 and/or 2 {where 1 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol and 2 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene)) bis(4-nitrophenol)} have been synthesized as ‘neat’ and zeolite Y encapsulated complexes. These catalysts are characterized by various analytical tools such as FTIR, UV–vis, elemental analysis, ICP-AES, molar conductivity, 1H- and 13C NMR, TGA, SEM, AAS, BET, magnetic susceptibility and powder XRD to endorse the complex formation, absence of peripheral redundant ligands and complexes, conservation of zeolite Y morphology and crystallinity, and the encapsulation of complexes without devastation in the zeolite Y framework. Out of these synthesized catalysts, 5Y is found to be a potent candidate for styrene (Conv. 76.1%, TOF: 2130 h?1), cyclohexene (Conv. 84.4%, TOF: 2351 h?1), limonene (Conv. 81.6%, TOF: 2273 h?1), and α-pinene (Conv. 72.6%, TOF: 2023 h?1) oxidation with high selectivity of respective allylic products excluding the styrene oxidation, which undergoes epoxidation only. The addition of H2SO4 in an identical reaction catalyzed by 5Y not only surge the conversion up to 100% in a short time span with high TOF but also increase the selectivity of respective epoxidation products. This switchover in the selectivities could be credited to the presence of H2SO4 that facilitates the heterolytic [sbnd]O[sbnd]O[sbnd] bond cleavage of metal hydroperoxide and stimulates the epoxidation over allylic oxidation. Furthermore, the results establish that the heterogeneous systems are effortlessly recovered and reused without ample drop in the activity and selectivity.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
-
p. 223 - 237
(2016/12/09)
-
- Room-temperature catalytic oxidation of alcohols with the polyoxovanadate salt Cs5(V14As8O42Cl)
-
While many known methods for oxidation mediated by polyoxometalates (POMs) employ environmentally friendly co-oxidants, they tend to employ large catalyst loadings (e.g. 40 mol%) and costly high reaction temperatures (~90-135 °C) that potentially contribute to the degradation of the catalyst and reduce their effectiveness. Herein, we present some initial results demonstrating a room temperature catalytic oxidation using the reduced salt-inclusion polyoxometalate, Cs5(V14As8O42Cl), that contains polyoxovanadate (POV) clusters as an efficient catalyst (e.g., 2 mol%) in the transformation of secondary alcohols to their corresponding ketones in very good to quantitative yields. Further, the catalyst can be suspended on celite and recycled.
- Campbell, McKenzie L.,Sulejmanovic, Dino,Schiller, Jacqueline B.,Turner, Emily M.,Hwu, Shiou-Jyh,Whitehead, Daniel C.
-
p. 3208 - 3213
(2016/05/24)
-
- Acceptorless dehydrogenation of alcohols on a diruthenium(II,II) platform
-
The diruthenium(II,II) complex [Ru2(L1)(OAc)3]Cl (1), spanned by a naphthyridine-diimine ligand and bridged by three acetates, has been synthesized. The catalytic efficacy of complex 1 has been evaluated for the acceptorless dehydrogenation (AD) of alcohols and for the dehydrogenative coupling reactions of alcohols with Wittig reagents. The diruthenium(II,II) complex is an excellent catalyst for AD of a diverse range of alcohols, and it is shown to be particularly effective for the conversion of primary alcohols to the corresponding aldehydes without undesired side products such as esters. Triphenylphosphonium ylides in a one-pot reaction with alcohols afforded the corresponding olefins in high yields with excellent E selectivity. The liberated dihydrogen gas was identified and measured to be 1 equiv with respect to alcohol. Deuteration studies with PhCD2OH revealed the absence of isotope scrambling in the product, indicating the involvement of a Ru-monohydride intermediate. Kinetic studies and DFT calculations suggest a low-energy bimetallic β-hydride elimination pathway where rate-limiting intramolecular proton transfer from alcohol to metal-bound hydride constitutes the dehydrogenation step. The general utility of metal-metal bonded compounds for alcohol AD and subsequent coupling reactions is demonstrated here.
- Dutta, Indranil,Sarbajna, Abir,Pandey, Pragati,Rahaman, S. M. Wahidur,Singh, Kuldeep,Bera, Jitendra K.
-
p. 1505 - 1513
(2016/06/09)
-
- The studies on the limonene oxidation over the microporous TS-1 catalyst
-
The studies on the oxidation of limonene with 60 wt% hydrogen peroxide over the titanium silicalite TS-1 catalyst were carried out. The influence of the following parameters was examined: the temperature 0-120 °C, the molar ratio of limonene/H2O2 = 1:2-5:1, methanol concentration 60-95 wt%, TS-1 content 0.25-8 wt% and the reaction time 15 min to 11 days. The studies showed that the most beneficial conditions for the obtaining of high selectivity of 1,2-epoxylimonene, at simultaneously high values of the conversion of reactants and the efficiency of hydrogen peroxide, are as follows: the temperature 80 °C, the molar ratio of limonene/H2O2 = 1:1, the methanol concentration 80 wt%, the TS-1 content 3 wt% and the reaction time 10 days. Moreover, the research showed that the process of limonene oxidation is very complicated, because during this process also other very useful oxygenated derivatives of limonene can be obtained, for example: perillyl alcohol, carveol, carvone and 1,2-epoxylimonene diol. The studies on the reuse of the TS-1 catalyst showed that it is very stable catalyst at the studied conditions and it can be recycled to the oxidation process at least three times.
- Wróblewska, Agnieszka,Makuch, Edyta,Miadlicki, Piotr
-
p. 121 - 129
(2016/04/26)
-
- Copper(II) and cobalt(II) tetrazole-saccharinate complexes as effective catalysts for oxidation of secondary alcohols
-
Mononuclear Cu(II) and Co(II) complexes comprising 2-methyltetrazole-saccharinate bidentate N,N-chelating ligand have been synthesized for the first time and tested as homogeneous catalysts for oxidation of secondary alcohols in a solvent-free and microwave assisted protocol using aqueous tert-butyl hydroperoxide (TBHP) as oxidant. The developed catalytic system exhibits broad functional group compatibility, allowing efficient and selective conversion of a variety of secondary alcohols, including allylic ones, into the corresponding ketones. With typical 0.2 mol% content of the catalyst and under 20–50 W microwave irradiation, most reactions are complete within 10 min, presenting TONs up to 5.5 × 102 and TOFs up to 1.1 × 104 h?1. No additives and co-oxidants have been used, while TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) acts as inhibitor in most cases. A plausible reaction mechanism involving the new catalytic systems is outlined.
- Frija, Luís M.T.,Alegria, Elisabete C.B.A.,Sutradhar, Manas,Cristiano, M. Lurdes S.,Ismael, Amin,Kopylovich, Maximilian N.,Pombeiro, Armando J.L.
-
p. 283 - 290
(2016/11/04)
-
- Selective one-pot carvone oxime hydrogenation over titania supported gold catalyst as a novel approach for dihydrocarvone synthesis
-
It was shown for the first time that dihydrocarvone can be selectively produced by gold-catalyzed one-pot transformation of carvone oxime. This reaction was carried out at 100 °C under hydrogen pressure of 9 bar over 1.9 wt.% Au/TiO2 catalyst using methanol as a solvent. Dihydrocarvone synthesis was shown to occur via carvone formation with the subsequent hydrogenation of its conjugated C=C double bond. Application of Au/TiO2 catalyst for both deoximation and selective hydrogenation of olefinic C=C functional group is reported for the first time. The combination of these steps provides optimization of the synthetic method for dihydrocarvone production from carvone oxime which is a key intermediate in carvone synthesis from limonene. Despite a lower reaction rate than in the case of carvone, a significant increase in the stereoselectivity towards trans-dihydrocarvone was observed in the case of carvone oxime hydrogenation. The ratio between trans- and cis-dihydrocarvone was close to 4.0 compared to 1.8 achieved in the case of carvone hydrogenation.
- Demidova, Yu. S.,Suslov,Simakova,Volcho,Salakhutdinov,Simakova,Murzin, D. Yu.
-
p. 142 - 148
(2016/06/13)
-
- Scalable and sustainable electrochemical allylic C-H oxidation
-
New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as € classics €. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact.
- Horn, Evan J.,Rosen, Brandon R.,Chen, Yong,Tang, Jiaze,Chen, Ke,Eastgate, Martin D.,Baran, Phil S.
-
-
- Fe/EuroPh catalysts for limonene oxidation to 1,2-epoxylimonene, its diol, carveol, carvone and perillyl alcohol
-
The catalysts in the form of an activated carbon EuroPh supported Fe were prepared and characterized structurally and chemically by XRD, nitrogen sorption, FESEM, EDX, and ICP-AES methods. The active phase was magnetite Fe3O4. The concentration of Fe in the catalysts was equal to 0.68, 1.32, 2.64 wt%. The catalytic activity of the obtained catalysts was examined in limonene oxidation with hydrogen peroxide and tert-butyl hydroperoxide as oxidants. The studies were carried out in a batch reactor. The catalytic activity of the recovered catalysts was also tested. The research showed that all from the studied catalysts were active in the limonene oxidation. As a result of limonene oxidation the following products were mainly obtained: 1,2-epoxylimonene diol, carveol, carvone and perillyl alcohol - products with a great importance. The reused catalysts were characterized by considerably lover activity in the limonene oxidation than in the first run, especially when the oxidation was performed with t-butyl hydroperoxide.
- Mlodzik, Jacek,Wrblewska, Agnieszka,Makuch, Edyta,Wrbel, Rafal J.,Michalkiewicz, Beata
-
p. 111 - 120
(2016/04/26)
-
- Microwave assisted bi-functional activation of β-bromo-tert-alcohols
-
Microwave-assisted dehydration-oxidation of β-bromo-tert-alcohols to afford 2,3-unsaturated ketones in good yield is reported. The reaction of substrates with DMSO in 1:1 ratio (w/v) is promoted by ZnS in a solvent-free condition. A concurrent bi-functional activation of trans-vicinal bromo- and hydroxyl groups with ZnS is elucidated. This is a new observation under microwave and applies to β-bromo-tert-alcohols derived from 1,4-disubstitued-1-cyclohexenes. It is very useful in the synthesis of 2,3-unsaturated ketones derived from monoterpenes which are valuable flavour compounds. [Figure not available: see fulltext.]
- Kannan, Nandini,Rangaswamy, Manjunatha Javagal,Kemapaiah, Bettadaiah Bheemanakere
-
p. 1405 - 1410
(2015/11/09)
-
- MnO2/TBHP: A Versatile and User-Friendly Combination of Reagents for the Oxidation of Allylic and Benzylic Methylene Functional Groups
-
In the presence of activated MnO2, tert-butyl hydroperoxide (TBHP) in CH2Cl2 is able to oxidize the allylic and benzylic methylene groups of different classes of compounds. I describe a one-pot oxidation protocol based on two sequential steps. In the first step, carried out at low temperature, MnO2 catalyses the oxidation of the methylene group. This is followed by a second step where reaction temperature is increased, allowing MnO2 both to catalyse the decomposition of unreacted TBHP and to oxidize allylic alcohols that could possibly be formed. The proposed oxidation procedure is generally applicable, although its efficiency, regioselectivity, and chemoselectivity are strongly dependent on the structure of the substrate. A simple and user-friendly synthetic procedure for the oxidation of allylic and benzylic methylene groups to the corresponding conjugated carbonyl derivatives is described. The proposed oxidation protocol is based on the combined use of MnO2 and tert-butyl hydroperoxide, and is generally applicable.
- Serra, Stefano
-
p. 6472 - 6478
(2015/10/19)
-
- Protecting group free enantiospecific total syntheses of structurally diverse natural products of the tetrahydrocannabinoid family
-
A simple, highly diastereoselective, Lewis acid catalyzed Friedel-Crafts coupling of a cyclic allylic alcohol with resorcinol derivatives has been developed. The method was applied for the enantiospecific total syntheses of structurally diverse natural products such as machaeriol-D, Δ8-THC, Δ9-THC, epi-perrottetinene and their analogues. Synthesis of both natural products and their enantiomers has been achieved with high atom economy, in a protecting group free manner and in less than 6 steps, the longest linear sequence, in a very good overall yield starting from R-(+) and S-(-)-limonene.
- Dethe, Dattatraya H.,Erande, Rohan D.,Mahapatra, Samarpita,Das, Saikat,Kumar B., Vijay
-
supporting information
p. 2871 - 2873
(2015/03/03)
-
- Hydrophobic effect of silica functionalized with silylated Ti-salicylaldimine complex on limonene oxidation by aqueous hydrogen peroxide
-
This research work describes the effect of hydrophobicity in inducing the diffusion of alkene substrates to the catalytic active sites. The aim of this research is to improve the catalytic activity by tailoring the degree of hydrophobicity of the catalyst. Silica functionalized with solid non-silylated Ti-salicylaldimine complex was prepared at room temperature by mixing imine ligand and Ti(IV) sulphate solution. The amorphous, solid complex formed was further silylated with octadecyltrimethoxysilane (OTMS) to induce hydrophobicity. The composition of the resulting silica functionalized with silylated Ti-salicylaldimine complex was varied with Ti:OTMS molar ratio in the range of 1:1/4 to 1:4 at room temperature. The successful attachment of alkylsilyl groups to silica functionalized with Ti-salicylaldimine complex was proven by the FTIR and 29Si solid state NMR spectra. The FTIR spectra showed increasing peak area for sp 3 C-H stretching mode (ca. 2919 cm-1 and 2850 cm-1) and decreasing peak area for Si-OH band with increasing amount of OTMS. TGA showed less water content with higher amount of alkylsilyl groups in the catalyst. This is in agreement with the lower kinetic rate of water adsorption capacity for the hydrophobic catalysts prepared. It was observed that the hydrophobic, silica functionalized with silylated Ti-salicylaldimine complex exhibited higher substrate conversion and reusability compared to the non-silylated catalyst.
- Yuan, Lai Sin,Chandren, Sheela,Efendi, Jon,Ho, Chin Siong,Nur, Hadi
-
p. 1905 - 1917
(2015/12/30)
-
- Dichlorodioxomolybdenum(VI) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts
-
Treatment of the solvent adduct [MoO2Cl2(THF)2] with either 2 equivalents of N,N-dimethylbenzamide (DMB) or 1 equivalent of N,N′-diethyloxamide (DEO) gave the dioxomolybdenum(vi) complexes [MoO2Cl2(DMB)2] (1) and [MoO2Cl2(DEO)] (2). The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. Both complexes present a distorted octahedral geometry and adopt the cis-oxo, trans-Cl, cis-L configuration typical of complexes of the type [MoO2X2(L)n], with either the monodentate DMB or bidentate DEO oxygen-donor ligands occupying the equatorial positions trans to the oxo groups. The complexes were applied as homogeneous catalysts for the epoxidation of olefins, namely cis-cyclooctene (Cy), 1-octene, trans-2-octene, α-pinene and (R)-(+)-limonene, using tert-butylhydroperoxide (TBHP) as oxidant. In the epoxidation of Cy at 55°C, the desired epoxide was the only product and turnover frequencies in the range of ca. 3150-3200 mol molMo-1 h-1 could be reached. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the cosolvent. Complexes 1 and 2 were also applied in liquid-liquid biphasic catalytic epoxidation reactions by using an ionic liquid of the type [C4mim][X] (C4mim = 1-n-butyl-3-methylimidazolium; X = NTf2, BF4 or PF6] as a solvent to immobilise the metal catalysts. Recycling for multiple catalytic runs was achieved without loss of activity.
- Oliveira, Tania S. M.,Gomes, Ana C.,Lopes, André D.,Louren?o, Jo?o P.,Almeida Paz, Filipe A.,Pillinger, Martyn,Gon?alves, Isabel S.
-
p. 14139 - 14148
(2015/08/18)
-
- Synthesis, spectral investigation and catalytic aspects of entrapped VO(IV) and Cu(II) complexes into the supercages of zeolite-Y
-
VO(IV) and Cu(II) complexes with Schiff base ligand derived from 1-phenyl-3-methyl-4-formyl-2-pyrazolin-5-one (PMFP) and 2-amino phenol have been synthesized as their neat and entrapped complexes into the supercages of zeolite-Y. The compounds were characterized by chemical analysis (ICP-OES and elemental), electronic and/or UV reflectance spectra, FTIR spectroscopy, X-ray powder diffraction patterns, SEMs, BET and thermogravimetric (TG) analysis. All the prepared catalysts were tested on the liquid phase limonene oxidation reaction, using 30% H2O2 as an oxidant. Limonene glycol, carveol, carvone and limonene 1,2-epoxide were the main products obtained. It was observed that zeolite-Y entrapped complexes exhibited higher catalytic activity than neat complexes. The catalysts undergo no metal leaching and can be easily recovered and reused. The use of inexpensive catalyst and oxidant are significant practical advantages of this environmentally friendly process.
- Modi, Chetan K.,Gade, Bhagyashree G.,Chudasama, Jiten A.,Parmar, Digvijay K.,Nakum, Haresh D.,Patel, Arun L.
-
p. 174 - 184
(2015/01/30)
-
- Simple, copper(I)-catalyzed oxidation of benzylic/allylic alcohols to carbonyl compounds: Synthesis of functionalized cinnamates in one pot
-
An environmentally benign [Cu(I)]-catalyzed oxidation of activated (benzylic/allylic) alcohols to the corresponding carbonyl compounds is presented. Interestingly, the reaction was also compatible with benzylic alcohols containing ortho-bromo substituents on the aromatic ring without competing with the expected intermolecular Buchwald coupling. Significantly, the catalytic system enables the synthesis of cinnamate-esters in a sequential domino one-pot fashion via oxidation followed by Wittig-Horner protocol. Copyright
- Reddy, Alavala Gopi Krishna,Mahendar, Lodi,Satyanarayana, Gedu
-
supporting information
p. 2076 - 2087
(2014/07/07)
-
- The epoxidation of limonene over the ts-1 and ti-sba-15 catalysts
-
Limonene belongs to a group of very important intermediates used in the production of fine chemicals. This monoterpene compound can be obtained from peels of oranges or lemon which are a (biomass) waste from the orange juice industry. Thus, limonene is a renewable, easy available and a relatively cheap compound. This work presents preliminary studies on the process of limonene epoxidation over zeolite type catalysts such as: TS-1 and Ti-SBA-15. In these studies methanol was used as a solvent and as an oxidizing agent a 60 wt % hydrogen peroxide solution was applied. The activity of each catalyst was investigated for four chosen temperatures (0 ° C, 40 ° C, 80 ° C and 120 ° C). The reaction time was changed from 0.5 to 24 h. For each catalyst the most beneficial conditions (the appropriate temperature and the reaction time) have been established. The obtained results were compared and the most active catalyst was chosen. These studies have also shown different possible ways of limonene transformation, not only in the direction of 1,2-epoxylimonene and its corresponding diol, but also in direction of carveol, carvone and perillyl alcohol-compounds with a lot of applications. The possible mechanisms of formation of the allylic oxidation products were proposed.
- Wrblewska, Agnieszka
-
p. 19907 - 19922
(2015/04/21)
-
- Catalytic oxidation of limonene over zeolite-Y entrapped oxovanadium (IV) complexes as heterogeneous catalysts
-
A series of VO(IV) complexes with Schiff base ligands derived from vanillin thiophene-2-carboxylic hydrazone (VTCH), vanillin furoic-2-carboxylic hydrazone (VFCH), salicylaldehyde thiophene-2-carboxylic hydrazone (H2STCH) and/or salicylaldehyde furoic-2-carboxylic hydrazone (H2SFCH) have been synthesized as neat and their entrapped complexes into the nanopores of zeolite-Y. These materials were characterized by several techniques: chemical analysis (ICP-OES and elemental) and spectroscopic methods (FT-IR, electronic, XRD, SEMs and BET). All the prepared catalysts were tested over the liquid phase limonene oxidation reaction, using t-butyl hydroperoxide (TBHP) and/or 30% H2O2 as oxidants. Limonene glycol, carveol and carvone were the main products obtained. It was observed that zeolite-Y based entrapped complexes exhibited higher catalytic activity than neat VO(IV) complexes. These zeolite-Y based entrapped complexes are stable and recyclable under current reaction conditions. Amongst them, [VO(VTCH)2]-Y showed higher catalytic activity (97.7%) with limonene glycol (45.1%), selectivity.
- Modi, Chetan K.,Chudasama, Jiten A.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Patel, Arun L.
-
p. 151 - 161
(2014/11/27)
-
- Grafted non-ordered niobium-silica materials: Versatile catalysts for the selective epoxidation of various unsaturated fine chemicals
-
Two kinds of niobium(V)-silica catalysts for the selective epoxidation were synthesised by post-synthesis modification of non-ordered mesoporous silica supports, starting from niobocene dichloride via solvent-less organometallic precursor dry impregnation
- Tiozzo, Cristina,Bisio, Chiara,Carniato, Fabio,Guidotti, Matteo
-
-
- Catalytic performance of a boron peroxotungstate complex under homogeneous and heterogeneous conditions
-
The preparation and characterization (FT-IR, FT-Raman, 11B MAS NMR, diffuse reflectance, elemental analysis) of a novel boron peroxotungstate (BTBA)4H[BW4O24] (BTBA = benzyltributylammonium) is reported, along with its use in the homogeneous oxidation of cis-cyclooctene, geraniol, linalool and (-)-carveol with H 2O2 as oxidant and acetonitrile as solvent. High catalytic activity was registered for all the substrates studied under homogeneous conditions, namely 99% of conversion of geraniol after 2 h, 93% for linalool after 5 h, 74% for cis-cyclooctene after 6 h, and 100% for (-)-carveol after 2 h of reaction. Some oxidation studies were carried out with the Venturello complex, [PW4O24]3-, in the same conditions. Furthermore, the boron peroxotungstate (BW4) was immobilized using two different strategies: (a) BW4 anchored into a functionalized silica (aptesSiO2) giving BW4@aptesSiO2 and (b) BW4 encapsulated on a metal organic framework, commonly referred as MIL-101, giving BW4@MIL-101. The catalytic activity of both heterogeneous materials was investigated for geraniol oxidation and the results were compared with those obtained with BW4 under homogeneous conditions. The encapsulated boron peroxotungstate (BW4@MIL-101) gave rise to the best results, reaching complete conversion of geraniol after 3 h of reaction and 78% selectivity for 2,3-epoxygeraniol. Additionally, this heterogeneous catalyst could be reused without appreciable loss of catalytic activity, affording similar 2,3-epoxygeraniol selectivity. The heterogeneous catalysts' stability was also investigated after the oxidation reactions by different characterization techniques.
- Santos, Isabel C.M.S.,Balula, Salete S.,Sim?es, Mário M.Q.,Cunha-Silva, Luís,Neves, M. Gra?a P.M.S.,De Castro, Baltazar,Cavaleiro, Ana M.V.,Cavaleiro, José A.S.
-
-
- Selective aerobic oxidation of allylic and benzylic alcohols catalyzed by N-hydroxyindole and copper(I) chloride
-
In the presence of copper(I) chloride, tert-butyl 1-hydroxy-2-methyl-6- trifluoromethyl-1H-indole-3-carboxylate acted as a catalyst for the chemoselective aerobic oxidation of allylic and benzylic alcohols. A variety of primary and secondary allylic and benzylic alcohols were oxidized into the corresponding α,β-unsaturated carbonyl compounds in good yields without affecting non-allylic alcohols.
- Shen, Shu-Su,Kartika, Vita,Tan, Ying Shan,Webster, Richard D.,Narasaka, Koichi
-
supporting information; experimental part
p. 986 - 990
(2012/03/12)
-
- Dauben-Michno oxidative transposition of allylic cyanohydrins - Enantiomeric switch of (-)-carvone to (+)-carvone
-
Allylic cyanohydrins were subjected to Dauben-Michno oxidation at low temperatures to provide β-cyanoenones in good to excellent yields. The potential of this oxidative transposition as a means of an enantiomeric switch of enones containing a latent plane of symmetry was tested by conversion of (-)-carvone to its enantiomer.
- Hudlicky, Jason R.,Werner, Lukas,Semak, Vladislav,Simionescu, Razvan,Hudlicky, Tomas
-
experimental part
p. 535 - 543
(2011/10/03)
-
- (N-Heterocyclic Carbene)-Pd-catalyzed anaerobic oxidation of secondary alcohols and domino oxidation-arylation reactions
-
The use of commercially available (SIPr)Pd(cinnamyl)Cl (SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene) as a precatalyst for the anaerobic oxidation of secondary alcohols is described. The use of this complex allows for a drastic reduction in the reaction times and catalyst loading when compared to the unsaturated counterpart. This catalytic system is compatible with the use of microwave dielectric heating, decreasing even further catalyst loading and reaction times. Domino Pd-catalyzed oxidation-arylation reactions of secondary alcohols are also presented.(Figure Presented)
- Landers, Brant,Berini, Christophe,Wang, Chao,Navarro, Oscar
-
experimental part
p. 1390 - 1397
(2011/05/02)
-
- Gold(III) complexes catalyze deoximations/transoximations at neutral pH
-
Golden solution: A neutral solution of AuBr3, containing [AuBr2(OH)2]- in equilibrium with [AuBr 3(OH)]- and [AuBr4]-, promotes the chemoselective hydrolysis of robust oximes into carbonyl compounds without racemization (see scheme). The food additive diacetyl acts as a NH 2OH-trapping agent, thus avoiding the formation of gold nanoparticles and allows the reaction to run catalytically. Copyright
- Isart, Carles,Bastida, David,Bures, Jordi,Vilarrasa, Jaume
-
experimental part
p. 3275 - 3279
(2011/05/12)
-
- Old yellow enzyme-catalyzed dehydrogenation of saturated ketones
-
Enzymes from extremophiles have always been of great interest for biotechnology because of their ruggedness against various stress factors. We have isolated, cloned, heterologously expressed and characterized a thermostable old yellow enzyme (OYE) from Geobacillus kaustophilus. In addition to the expected 'enone' reduction, GkOYE also catalyzes the reverse reaction, i.e., the desaturation of C-C bonds adjacent to a carbonyl to give the corresponding α,β-unsaturated ketone. The reaction proceeds at the expense of molecular oxygen without the need for a nicotinamide cofactor and represents an environmentally benign alternative to known chemical dehydrogenation methods.
- Schittmayer, Matthias,Glieder, Anton,Uhl, Michael K.,Winkler, Andreas,Zach, Simone,Schrittwieser, Joerg H.,Kroutil, Wolfgang,MacHeroux, Peter,Gruber, Karl,Kambourakis, Spiros,Rozzell, J. David,Winkler, Margit
-
experimental part
p. 268 - 274
(2011/04/22)
-
- A glandular trichome-specific monoterpene alcohol dehydrogenase from Artemisia annua
-
The major components of the isoprenoid-rich essential oil of Artemisia annua L. accumulate in the subcuticular sac of glandular secretory trichomes. As part of an effort to understand isoprenoid biosynthesis in A. annua, an expressed sequence tag (EST) collection was investigated for evidence of genes encoding trichome-specific enzymes. This analysis established that a gene denoted Adh2, encodes an alcohol dehydrogenase and shows a high expression level in glandular trichomes relative to other tissues. The gene product, ADH2, has up to 61% amino acid identity to members of the short chain alcohol dehydrogenase/reductase (SDR) superfamily, including Forsythia × intermedia secoisolariciresinol dehydrogenase (49.8% identity). Through in vitro biochemical analysis, ADH2 was found to show a strong preference for monoterpenoid secondary alcohols including carveol, borneol and artemisia alcohol. These results indicate a role for ADH2 in monoterpenoid ketone biosynthesis in A. annua glandular trichomes.
- Polichuk, Devin R.,Zhang, Yansheng,Reed, Darwin W.,Schmidt, Janice F.,Covello, Patrick S.
-
experimental part
p. 1264 - 1269
(2011/05/30)
-
- Specific adducts formed through a radical reaction between peptides and contact allergenic hydroperoxides
-
The first step in the development of contact allergy (allergic contact dermatitis) includes the penetration of an allergy-causing chemical (hapten) into the skin, where it binds to macromolecules such as proteins. The protein - hapten adduct is then recognized by the immune system as foreign to the body. For hydroperoxides, no relevant hapten target proteins or protein - hapten adducts have so far been identified. In this work, bovine insulin and human angiotensin I were used as model peptides to investigate the haptenation mechanism of three hydroperoxide haptens: (5R)-5-isopropenyl-2-methyl-2- cyclohexene-1-hydroperoxide (Lim-2-OOH), cumene hydroperoxide (CumOOH), and 1-(1-hydroperoxy-1-methylethyl) cyclohexene (CycHexOOH). These hydroperoxides are expected to react via a radical mechanism, for which 5,10,15,20-tetraphenyl- 21H,23H-porphine iron(III) chloride (Fe(III)TPPCl) was used as a radical initiator. The reactions were carried out in 1:1 ethanol/10 mM ammonium acetate buffer pH 7.4, for 3 h at 37 °C, and the reaction products were either enzymatically digested or analyzed directly by MALDI/ TOF-MS, HPLC/MS/MS, and 2D gel electrophoresis. Both hydroperoxide-specific and unspecific reaction products were detected, but only in the presence of the iron catalyst. In the absence of catalyst, the hydroperoxides remained unreacted. This suggests that the hydroperoxides can enter into the skin and remain inert until activated. Through the detection of a Lim-2-OOH adduct bound at the first histidine (of two) of angiotensin I, it was confirmed that hydroperoxides have the potential to form specific antigens in contact allergy.
- Redeby, Theres,Nilsson, Ulrika,Altamore, Timothy M.,Ilag, Leopold,Ambrosi, Annalisa,Broo, Kerstin,Boerje, Anna,Karlberg, Ann-Therese
-
body text
p. 203 - 210
(2011/02/16)
-
- 2-iodoxybenzenesulfonic acid as an extremely active catalyst for the selective oxidation of alcohols to aldehydes, ketones, carboxylic acids, and enones with oxone
-
Electron-donating group-substituted 2-iodoxybenzoic acids (IBXs) such as5-Me-IBX (1g), 5-MeO-IBX (1h), and 4,5-Me2-IBX were superior to IBX 1a as catalysts for the oxidation of alcohols with Oxone (a trad emark of DuPont) under nonaqueous conditions, although Oxone was almost insoluble in most organic solvents. The catalytic oxidation proceeded more rapidly and cleanly in nitromethane. Furthermore, 2-iodoxybenzenesulfonic acid (IBS, 6a) was much more active than modified IBXs. Thus, we established a highly efficient and selective method for the oxidation of primary and secondary alcohols to carbonyl compounds such as aldehydes, carboxylic acids, and ketones with Oxone in nonaqueous nitromethane, acetonitrile, or ethyl acetate in the presence of 0.05-5molpercentof 6a, which was generated in situ from 2-iodobenzenesulfonic acid (7a) or its sodium salt. Cycloalkanones could be further oxidized to α,β- cycloalkenones or lactones by controlling the amounts of Oxone under the same conditions as above. When Oxone was used under nonaqueous conditions, Oxone wastes could be removed by simple filtration. Based on theoretical calculations, we considered that the relatively ionic character of the intramolecular hypervalent iodine-OSO2 bond of IBS might lower the twisting barrier of the alkoxyperiodinane intermediate 16.
- Uyanik, Muhammet,Akakura, Matsujiro,Ishihara, Kazuaki
-
supporting information; experimental part
p. 251 - 262
(2009/06/28)
-
- Regio- and stereoselective allylic hydroxylation of D-limonene to (+)-trans-carveol with cellulosimicrobium cellulans EB-8-4
-
Cellulosimicrobium cellulans EB-8-4 was discovered by screening of microorganisms as a pow-erful catalyst for the regio- and stereoselective allylic hydroxylation of D-limonene to (+)-trans-carveol that is a useful and valuable fragrance and flavour compound. Cells of strain EB-8-4 were easily obtained, demonstrated more than 99% regio- and stereoselectivity, showed a specific hydroxylation activity of 4.0 U/g cdw (cell dry weight), and accepted 62 mM D-limonene without inhibition. The hydroxylation was possibly catalyzed by an nicotinamide adenine dinucleotide (NADH)-dependent oxygenase involved in the degradation of aromatic ring during cell growth. 13.4 mM of (+)-trans-carveol were obtained by biohydroxylation of D-limonene with resting cells of C. cellulans EB-8-4, thus being 11 times higher than that obtained with the best biocatalyst known thus far. High conversion and high yield were obtained in the biohydroxylation of 11.6 mM of D-limonene with the resting cells as catalyst in a closed shaking flask, giving 10 mM of (+)-irans-carveol, and 0.30 mM of carvone as the only by-product. Thus, a unique biocatalyst for the regio- and stereoselective allylic hydroxylation of D-limonene and an efficient synthesis of natural identical (.+)-trans-carveol by biohydroxylation have been developed.
- Wang, Zunsheng,Lie, Felicia,Lim, Estella,Li, Keyang,Li, Zhi
-
experimental part
p. 1849 - 1856
(2011/02/26)
-
- Selective synthesis of carvone and cryptomerlone from α-pinene
-
Carvone and cryptomerlone were synthesized selectively using electrochemical oxidation of α-pinene in the key step. 2006 Springer Science+Business Media, Inc.
- Macaev,Vlad,Gudima
-
p. 301 - 303
(2008/02/07)
-
- A new method for the selective oxidation of allylic and benzylic alcohols
-
A new method is described for the selective oxidation of allylic or benzylic alcohols, in the presence of saturated alcohols, using trimethylamine-N-oxide in the presence of an iron carbonyl.
- Pearson, Anthony J.,Kwak, Yoonhyun
-
p. 5417 - 5419
(2007/10/03)
-
- Towards the bio-production of trans-carveol and carvone from limonene: Induction after cell growth on limonene and toluene
-
Rhodococcus opacus PW4 cells were found to produce trans- and cis-carveol and/or carvone as result of limonene metabolism, depending on the type and concentration of the carbon source used for cell growth. In aqueous systems, cells grown on ethanol and toluene only produced trans-carveol, whilst cells grown on limonene and on toluene with a larger head-space available produced both trans-carveol and carvone. In biphasic systems, limonene was converted to trans- and cis-carveol as well as to carvone, regardless of the carbon source used, although carveol and carvone production rates were higher in toluene and limonene grown cells, respectively. A good and stable emulsion was obtained in a magnetically stirred two-phase reactor but both trans-carveol and carvone were produced at low rates: 0.08 and 0.02 nmol/min mg prot, respectively. No cis-carveol was formed. When (-)-carveol was added, carvone production increased 4.7 fold to 0.12 nmol/min mg prot. Using an aerated two-phase reactor, carvone production was enhanced even with cells grown on toluene. The highest trans- and cis-carveol and carvone production rates were attained with cells grown on limonene by continuously supplying limonene to the reactor through the air stream, carvone production reaching 0.58 nmol/min mg prot. The best trans-/cis-carveol ratio (2.26) was observed with cells grown on toluene when limonene was supplied in the gas phase. When 50 mM limonene was added initially, carvone was produced 27.9 and 141.4 times faster than trans-carveol with cells grown on toluene and limonene, respectively.
- De Carvalho, Carla C. C. R.,Da Fonseca, M. Manuela R.
-
p. 3925 - 3931
(2007/10/03)
-
- Catalyst system and process for rearrangement of epoxides to allylic alcohols
-
A catalyst system that can be used to achieve (a) preparation of allylic alcohols by rearrangement of the corresponding epoxide, when the allylic alcohol is a desired product; (b) subsequent reaction, e.g., selective oxidation, of the allylic alcohols obtained in step (a) to afford a desired product, e.g., alpha, beta-unsaturated carbonyl compounds; and/or (c) the ability to perform steps a) and b) in a one-pot process. In one embodiment, the catalyst system includes (i) at least one primary catalyst includes one or more homogeneous or heterogeneous, inorganic, organic or complex metal-containing compound, and (ii) at least one activator/modifier comprising at least one phenolic compound.
- -
-
-
- Carbenoid-mediated elimination of sulfides and selenides. A mild and efficient method for introducing α,β-double bonds to electron-withdrawing substituents
-
Cycloalkanes bearing both an electron-withdrawing group and an arylsulfenyl or arylselenenyl function in β-position are shown to react with 2 equiv. of a carbenoid species to generate the corresponding Michael acceptor. The reaction occurs under very mild conditions and affords the products in good to excellent yields. The process constitutes a useful alternative to the oxidation/syn-elimination sequence.
- Gautier, Arnaud,Garipova, Goulnara,Deléens, Reynald,Piettre, Serge R.
-
p. 4959 - 4962
(2007/10/03)
-
- Modelling the biokinetic resolution of diastereomers present in unequal initial amounts
-
The enantiomeric ratio (E) is commonly used to evaluate enzyme-catalysed kinetic resolutions. Chen et al. (1982) proposed a model for the enantiomeric ratio, which relates the extent of substrate conversion and the enantiomeric excess. The model, however,
- De Carvalho, Carla C.C.R.,Van Keulen, Frederik,Da Fonseca, M.Manuela R.
-
p. 1637 - 1643
(2007/10/03)
-
- A Mild and Efficient Oxidation of Alcohols to Carbonyl Compounds by Periodic Acid Catalyzed by 2,2,6,6-Tetramethylpiperidinyl-1-oxyl
-
Numerous alcohols are effectively oxidized to corresponding aldehydes and ketones with H5IO6-TEMPO. The rate of oxidation parallels decreasing α-C-H bond dissociation energy, that is secondary alcohols react faster than primary alcohols.
- Kim, Sung Soo,Nehru, Kasi
-
p. 616 - 618
(2007/10/03)
-
- Synthesis and reactions of organic compounds with a nitrogen atom. Part XVII. Reactions of acyclic and monocyclic chlorides with phenyltelluro- and phenylselenosodium
-
The reaction of neryl (3), geranyl (4), (+)-carvotanacetyl (5), (-)-carvyl (6) and perillyl (7) chlorides with phenylseleno-(1) or phenyltellurosodium (2), and then with chloramine-T afforded α,β-unsaturated toluenesulfonamides 8-11, which were reduced with sodium in liquid ammonia to allylic amines 12-15. Allylic phenyltellurides were oxidized by air to carbonyl compounds 29-31 or alcohol 28.
- Bakowska-Janiszewska,Scianowski,Uzarewicz
-
p. 649 - 656
(2007/10/03)
-
- Direct C-nitration of cyclic α,β-unsaturated oximes under the action of sodium nitrite and acetic acid in methanol
-
Using a number of cyclic α,β-unsaturated oximes of the terpene series and some simplest model compounds as examples, unsaturated oximes bearing a hydrogen atom at the β-carbon atom were demonstrated to be converted into β-hydroxyiminonitroalkenes under the action of sodium nitrite and acetic acid in methanol. In the case of the introduction of an alkyl substituent at the terminal carbon atom of the diene C = C-C=NOH fragment, the reaction performed under the same conditions gave rise exclusively to conjugated ketone (a deoximation product).
- Chibiryaev,Denisov,Pyshnyi,Tkachev
-
p. 1410 - 1418
(2007/10/03)
-