- A New, Highly Stereoselective Reducing Agent, Potassium 9-(2,3-Dimethyl-2-butoxy)-9-boratabicyclononane
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A new reagent, potassium 9-(2,3-dimethyl-2-butoxy)-9-boratabicyclononane (K9-OThx-9-BBNH), achieves highly stereoselective reductions of cyclic ketones with very simple recovery of the product.
- Brown, Herbert C.,Cha, Jin Soon,Nazer, Behrooz
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- Ruthenium complexes of phosphine-amide based ligands as efficient catalysts for transfer hydrogenation reactions
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This work presents three mononuclear Ru(ii) complexes of tridentate phosphine-carboxamide based ligands providing a NNP coordination environment. The octahedral Ru(ii) ion shows additional coordination with co-ligands; CO, Cl and CH3OH. All three Ru(ii) complexes were thoroughly characterized including their crystal structures. These Ru(ii) complexes were utilized as catalysts for the transfer hydrogenation of assorted carbonyl compounds, including some challenging biologically relevant substrates, using isopropanol as the hydrogen source. The binding studies illustrated the coordination of the isopropoxide ion by replacing a Ru-ligated chloride ion followed by the generation of the Ru-H intermediate that was isolated and characterized and was found to be involved in the catalysis.
- Yadav, Samanta,Vijayan, Paranthaman,Yadav, Sunil,Gupta, Rajeev
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p. 3269 - 3279
(2021/03/16)
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- Poisoning effect of N-containing compounds on performance of Raney nickel in transfer hydrogenation
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The effect of amines, imines and heterocycle compounds on conversion has been studied in transfer hydrogenation of camphor and 2-PrOH catalyzed by Raney nickel. Small amount (5 mol% to nickel) of N-containing compound significantly decreases catalyst activity. It has been shown that the poisoning effect mostly depends on molecular size of amines and heterocyclic compounds. For aniline and cyclohexylamine the dependence of camphor conversion on poison/nickel ratio was obtained. Additionally, benzaldehyde, cinnamaldehyde demonstrated higher reactivity compared corresponding imines under transfer hydrogenation conditions. Obtained data explain low activity of nickel-based catalysts when N-containing compounds are presented in reaction mixture.
- Martyanov, Oleg N.,Philippov, Alexey A.
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- Enantioselective Construction of Modular and Asymmetric Baskets
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The precise positioning of functional groups about the inner space of abiotic hosts is a challenging task and of interest for developing more effective receptors and catalysts akin to those found in nature. To address it, we herein report a synthetic methodology for preparing basket-like cavitands comprised of three different aromatics as side arms with orthogonal esters at the rim for further functionalization. First, enantioenriched A (borochloronorbornene), B (iodobromonorbornene), and C (boronorbornene) building blocks were obtained by stereoselective syntheses. Second, consecutive A-to-B and then AB-to-C Suzuki–Miyaura (SM) couplings were optimized to give enantioenriched ABC cavitand as the principal product. The robust synthetic protocol allowed us to prepare (a) an enantioenriched basket with three benzene sides and each holding either tBu, Et, or Me esters, (b) both enantiomers of a so-called “spiral staircase” basket with benzene, naphthalene, and anthracene groups surrounding the inner space, and (c) a photo-responsive basket bearing one anthracene and two benzene arms.
- Badji?, Jovica D.,Finnegan, Tyler J.,Gunther, Michael J.,Pavlovi?, Radoslav Z.,Wang, Xiuze
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supporting information
p. 25075 - 25081
(2021/10/25)
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- Simple Plug-In Synthetic Step for the Synthesis of (?)-Camphor from Renewable Starting Materials
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Racemic camphor and isoborneol are readily available as industrial side products, whereas (1R)-camphor is available from natural sources. Optically pure (1S)-camphor, however, is much more difficult to obtain. The synthesis of racemic camphor from α-pinene proceeds via an intermediary racemic isobornyl ester, which is then hydrolyzed and oxidized to give camphor. We reasoned that enantioselective hydrolysis of isobornyl esters would give facile access to optically pure isoborneol and camphor isomers, respectively. While screening of a set of commercial lipases and esterases in the kinetic resolution of racemic monoterpenols did not lead to the identification of any enantioselective enzymes, the cephalosporin Esterase B from Burkholderia gladioli (EstB) and Esterase C (EstC) from Rhodococcus rhodochrous showed outstanding enantioselectivity (E>100) towards the butyryl esters of isoborneol, borneol and fenchol. The enantioselectivity was higher with increasing chain length of the acyl moiety of the substrate. The kinetic resolution of isobornyl butyrate can be easily integrated into the production of camphor from α-pinene and thus allows the facile synthesis of optically pure monoterpenols from a renewable side-product.
- Calderini, Elia,Drienovská, Ivana,Myrtollari, Kamela,Pressnig, Michaela,Sieber, Volker,Schwab, Helmut,Hofer, Michael,Kourist, Robert
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p. 2951 - 2956
(2021/06/18)
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- Efficient catalytic transfer hydrogenation reactions of carbonyl compounds by Ni(II)-diphosphine complexes
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The catalytic transfer hydrogenation reactions of a series of aromatic and aliphatic carbonyl compounds were investigated using divalent Ni(II)-diphosphine complexes, [L2NiCl2] (where L2 = 1,1-bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,1-bis(diphenylphosphino)ferrocene (dppf), and N-butyl-N-(diphenylphosphino)-1,1-diphenylphosphinamine (dppba)). This is a single-step reaction in the presence of potassium hydroxide and isopropyl alcohol to afford the corresponding alcohols. This protocol tolerates other sensitive functional groups like olefinic double bonds and also achieves high chemoselectivity. All the reactions were monitored by GC and GC–MS. The plausible mechanism is also discussed. The method reported in the present article is simple, cost-effective, and provides excellent conversions. Nickel-diphosphine complexes appear as a potential alternative to expensive transition metal complexes.
- Venkatesh, Sadhana,Panicker, Rakesh R.,Lenin Kumar, Verdhi,Pavankumar,Viswanath, Nukala,Singh, Shangrila,Desikan, Rajagopal,Sivaramakrishna, Akella
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p. 2963 - 2977
(2020/11/03)
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- Molecular cloning and functional characterization of a two highly stereoselective borneol dehydrogenases from Salvia officinalis L
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Enzymes for selective terpene functionalization are of particular importance for industrial applications. Pure enantiomers of borneol and isoborneol are fragrant constituents of several essential oils and find frequent application in cosmetics and therapy. Racemic borneol can be easily obtained from racemic camphor, which in turn is readily available from industrial side-streams. Enantioselective biocatalysts for the selective conversion of borneol and isoborneol stereoisomers would be therefore highly desirable for their catalytic separation under mild reaction conditions. Although several borneol dehydrogenases from plants and bacteria have been reported, none show sufficient stereoselectivity. Despite Croteau et al. describing sage leaves to specifically oxidize one borneol enantiomer in the late 70s, no specific enzymes have been characterized. We expected that one or several alcohol dehydrogenases encoded in the recently elucidated genome of Salvia officinalis L. would, therefore, be stereoselective. This study thus reports the recombinant expression in E. coli and characterization of two enantiospecific enzymes from the Salvia officinalis L. genome, SoBDH1 and SoBDH2, and their comparison to other known ADHs. Both enzymes produce preferentially (+)-camphor from racemic borneol, but (?)-camphor from racemic isoborneol.
- Drienovská, Ivana,Kolanovi?, Dajana,Chánique, Andrea,Sieber, Volker,Hofer, Michael,Kourist, Robert
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- Monoterpenoid-based inhibitors of filoviruses targeting the glycoprotein-mediated entry process
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In this study, we screened a large library of (+)-camphor and (?)-borneol derivatives to assess their filovirus entry inhibition activities using pseudotype systems. Structure-activity relationship studies revealed several compounds exhibiting submicromolar IC50 values. These compounds were evaluated for their effect against natural Ebola virus (EBOV) and Marburg virus. Compound 3b (As-358) exhibited the good antiviral potency (IC50 = 3.7 μM, SI = 118) against Marburg virus, while the hydrochloride salt of this compound 3b·HCl had a strong inhibitory effect against Ebola virus (IC50 = 9.1 μM, SI = 31) and good in vivo safety (LD50 > 1000 mg/kg). The results of molecular docking and in vitro mutagenesis analyses suggest that the synthesized compounds bind to the active binding site of EBOV glycoprotein similar to the known inhibitor toremifene.
- Baev, Dmitriy S.,Maksyutov, Rinat A.,Mordvinova, Ekaterina D.,Pyankov, Oleg V.,Salakhutdinov, Nariman F.,Shcherbakov, Dmitriy N.,Shcherbakova, Nadezhda S.,Sokolova, Anastasiya S.,Tolstikova, Tatyana G.,Yarovaya, Olga I.,Zaykovskaya, Anna V.,Zybkina, Anastasiya V.
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- Method for synthesizing (+)-borneol by using imidazole acidic ionic liquid
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The invention discloses a method for synthesizing (+)-borneol by using imidazole acidic ionic liquid, which comprises the following steps: synthesizing an intermediate from N-butyl imidazole and 1,4-butane sultone by using toluene as a solvent, washing with ethyl acetate, drying, and reacting the dried product with concentrated sulfuric acid to obtain the imidazole acidic ionic liquid catalyst that is 1-sulfobutyl-3-butyl imidazole bisulfate; applying the catalyst to alpha-pinene esterification saponification reaction to obtain (+)-borneol with high selectivity. According to the imidazole acidic ionic liquid, the selectivity of (+)-borneol can be improved without introducing other types of cocatalysts, the catalytic effect is stable, the preparation method of the ionic liquid as a catalystis simple, the period is short, the separation of the catalyst and a product can be realized by standing, and the catalyst is convenient to recycle.
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Paragraph 0008-0011
(2020/11/22)
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- Application of acidic ionic liquid in high-selectivity synthesis of n-borneol (by machine translation)
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The invention discloses an application of acidic ionic liquid in high-selectivity synthesis of n-borneol, which takes toluene as a solvent and N - methylimidazole, 1,4 - butenolide synthesis intermediate and reacts with ethyl ether to react with concentrated sulfuric acid to prepare the acidic ionic liquid catalyst 1 - sulfobutyl -3 - methylimidazolium bisulfate [HSO]. 3 (CH)2 )4 - Mimim] [HSO4 The method changes the current situation that the selectivity of borneol is improved by introducing chloroacetic acid or the like as a co-catalyst, and ionic liquid is used as a catalyst to improve the selectivity of the borneol. (by machine translation)
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Paragraph 0011-0014
(2020/11/22)
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- Hydrogen Sulfide: A Reagent for pH-Driven Bioinspired 1,2-Diol Mono-deoxygenation and Carbonyl Reduction in Water
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Hydrogen sulfide (H2S) was evaluated for its peculiar sulfur radical species generated at different pHs and was used under photolytical conditions in aqueous medium for the reduction of 1,2-diols to alcohols. The conversion steps of 1,2-cyclopentanediol to cyclopentanol via cyclopentanone were analyzed, and it was proven that the reaction proceeds via a dual catalytic/radical chain mechanism. This approach was successfully adapted to the reduction of a variety of carbonyl compounds using H2S at pH 9 in water. This work opens up the field of environmental friendly synthetic processes using the pH-driven modulation of reactivity of this simple reagent in water.
- Barata-Vallejo, Sebastián,Ferreri, Carla,Golding, Bernard T.,Chatgilialoglu, Chryssostomos
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supporting information
p. 4290 - 4294
(2018/07/29)
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- Preparation method of D-borneol
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The invention relates to a preparation method of D-borneol. The method comprises the following steps: ensuring that natural camphor is reacted for 1 to 8 hours at 0 to 40 DEG C under the existence ofan organic solvent and a chiral reagent (R)-BINAP-H serving as catalysts, and ensuring that the optimized ratio of the organic solvent to the chiral reagent (R)-BINAP-H to camphor is (10-30ml): (20-50mmol): 18mmol.
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Paragraph 0032; 0033; 0037; 0042; 0046
(2018/11/22)
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- Surface-Plasmon-Mediated Hydrogenation of Carbonyls Catalyzed by Silver Nanocubes under Visible Light
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Plasmonic nanoparticles are exciting and promising candidates for light-activated catalysis. We report herein the use of plasmonic nanocubes for the activation of molecular hydrogen and the hydrogenation of ketones and aldehydes via visible light irradiation at 405 nm, corresponding to the position of the plasmon band of the nanocubes, at 80 °C. Only 1 atm of molecular hydrogen is required to access, using catalytic amounts of silver, primary, and secondary alcohols, with complete chemoselectivty for C=O over C=C reduction. The resulting catalytic system was studied over a scope of 12 compounds. Exposure to other wavelengths, or absence of light failed to provide activity, thus proving a direct positive impact of the plasmonic excitation to the catalytic activity. By varying the irradiation intensity, we studied the relationship between plasmon band excitation and catalytic activity and propose a potential reaction mechanism involving plasmon-activated hot electrons. This study expands the scope of reactions catalyzed by free-standing plasmonic particles and sheds light on H2 activation by silver surfaces.
- Landry, Michael J.,Gellé, Alexandra,Meng, Beryl Y.,Barrett, Christopher J.,Moores, Audrey
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p. 6128 - 6133
(2017/09/15)
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- An efficient FeCl3-mediated approach for reduction of ketones through N-heterocyclic carbene boranes
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An efficient FeCl3-mediated approach for reduction of ketones by NHC-BH3 has been developed. A series of ketones were smoothly converted to the corresponding alcohols in good to excellent yields through NHC-BH3 reductive process.
- Wang, Ming-Hui,Chen, Ling-Yan
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supporting information
p. 732 - 735
(2017/03/31)
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- Reliable HPLC separation, vibrational circular dichroism spectra, and absolute configurations of isoborneol enantiomers
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Resolution of chiral compounds has played an important role in the pharmaceutical field, involving detailed studies of pharmacokinetics, physiological, toxicological, and metabolic activities of enantiomers. Herein, a reliable method by high-performance liquid chromatography (HPLC) coupled with an optical rotation detector was developed to separate isoborneol enantiomers. A cellulose tris(3, 5-dimethylphenylcarbamate)-coated chiral stationary phase showed the best separation performance for isoborneol enantiomers in the normal phase among four polysaccharide chiral packings. The effects of alcoholic modifiers and column temperature were studied in detail. Resolution of the isoborneol racemate displayed a downward trend along with an increase in the content of ethanol and column temperature, indicating that less ethanol in the mobile phase and lower temperature were favorable to this process. Moreover, two isoborneol enantiomers were obtained via a semipreparative chiral HPLC technique under optimum conditions, and further characterized by analytical HPLC, and experimental and calculated vibrational circular dichroism (VCD) spectroscopy, respectively. The solution VCD spectrum of the first-eluted component was consistent with the Density Functional Theory (DFT) calculated pattern based on the SSS configuration, indicating that this enantiomer should be (1S, 2S, 4S)-(+)-isoborneol. Briefly, these results have provided reliable information to establish a method for analysis, preparative separation, and absolute configuration of chiral compounds without typical chromophoric groups.
- Gao, Rui-Qi,Fan, Jun,Tan, Qi,Guo, Dong,Chen, Tao,He, Ru-Jian,Li, Dan,Zhang, Hui,Zhang, Wei-Guang
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p. 550 - 557
(2017/08/26)
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- A saponified the ester is continual isoborneol acetate method of preparing isoborneol
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The invention discloses a method for preparing isoborneol by continuous saponification of isobornyl acetate. The method comprises the following steps: saponifying sodium hydroxide and isobornyl acetate as raw materials, rectifying, layering, washing with water, crystallizing and the like to prepare white isoborneol crystals. The saponification reaction of isobornyl acetate can be continuously carried out in an oscillatory flow reactor, a static mixer or an ultrasonic mixer; a polar solvent is added in the reaction, so that the saponification reaction is heterogeneously carried out, the reaction time can be shortened, the reaction temperature can be reduced, the conversion rate of isobornyl acetate is more than 99%, and the product yield is more than 95%. The method is low in production energy consumption and high in product yield.
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Paragraph 0043-0051
(2017/01/19)
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- An unexpected reaction of camphor with sodium metal
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Reaction of camphor with sodium metal at elevated temperature in refluxing THF or toluene, furnishes an unexpected product. The product has been identified by spectral analysis and its structure confirmed by single crystal X-ray diffraction study. A preliminary mechanistic explanation has been suggested to explain this reaction.
- Khanvilkar, Aditya N.,Gupta, Riddhi,Bedekar, Ashutosh V.
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p. 1327 - 1331
(2016/02/23)
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- An unexpected reaction of camphor with sodium metal
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Reaction of camphor with sodium metal at elevated temperature in refluxing THF or toluene, furnishes an unexpected product. The product has been identified by spectral analysis and its structure confirmed by single crystal X-ray diffraction study. A preliminary mechanistic explanation has been suggested to explain this reaction.
- Khanvilkar, Aditya N.,Gupta, Riddhi,Bedekar, Ashutosh V.
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p. 1327 - 1331
(2015/11/10)
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- Selective ruthenium-catalyzed epimerization of chiral sec-alcohols
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Extension of secondary alcohol racemization catalyzed by homogeneous half-sandwich ruthenium complexes to the epimerization of natural products containing additional non-functionalized stereo-centers has been investigated. Ruthenium-catalysed epimerization of the sec-alcohols (-)-menthol, (-)-isopulegol, (+)-borneol, (+)-fenchol and cholesterol under mild reaction conditions and low catalyst loadings (2mol%) provides rapid access to their less abundant diastereoisomers (+)-neomenthol, (+)-neoisopulegol, isoborneol, beta-fenchol and epicholesterol in admixture with the parent diastereomers in ratios ranging from 1:4.9 to 1:2.4 (epimer:parent).
- L?ngvik, Otto,Mavrynsky, Denys,Leino, Reko
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p. 255 - 259
(2015/03/14)
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- Selective ruthenium-catalyzed epimerization of chiral sec-alcohols
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Extension of secondary alcohol racemization catalyzed by homogeneous half-sandwich ruthenium complexes to the epimerization of natural products containing additional non-functionalized stereo-centers has been investigated. Ruthenium-catalysed epimerization of the sec-alcohols (-)-menthol, (-)-isopulegol, (+)-borneol, (+)-fenchol and cholesterol under mild reaction conditions and low catalyst loadings (2 mol%) provides rapid access to their less abundant diastereoisomers (+)-neomenthol, (+)-neoisopulegol, isoborneol, beta-fenchol and epicholesterol in admixture with the parent diastereomers in ratios ranging from 1:4.9 to 1:2.4 (epimer:parent).
- L?ngvik, Otto,Mavrynsky, Denys,Leino, Reko
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p. 255 - 259
(2015/02/19)
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- The Stereoselective Reductions of Ketones to the Most Thermodynamically Stable Alcohols Using Lithium and Hydrated Salts of Common Transition Metals
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A simple method is presented for the highly stereoselective reductions of ketones to the most thermodynamically stable alcohols. In this procedure, the ketone is treated with lithium dispersion and either FeCl2·4H2O or CuCl2·2H2O in THF at room temperature. This protocol is applied to a large number and variety of ketones and is both more convenient and efficient than those commonly reported for the diastereoselective reduction of five- and six-membered cyclic ketones.
- Kennedy, Nicole,Cohen, Theodore
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p. 8134 - 8141
(2015/09/02)
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- Colloid and nanodimensional catalysts in organic synthesis: VI.1 Hydrogenation and hydrogenolysis of carbonyl compounds
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Aldehydes and ketones are found to be hydrogenated to alcohols with hydrogen at atmospheric pressure under the catalysis with nickel nanoparticles. The reaction under study may be used as technologically available and cheap method for hydrogenation of carbonyl groups. It is found that in the case of aromatic ketones hydrogenolysis of C=O bond with partial hydrogenation of aromatic groups takes place.
- Mokhov,Popov,Nebykov
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p. 1656 - 1661
(2015/01/09)
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- Highly enantioselective organocatalytic oxidative kinetic resolution of secondary alcohols using chiral alkoxyamines as precatalysts: Catalyst structure, active species, and substrate scope
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The development and characterization of enantioselective organocatalytic oxidative kinetic resolution (OKR) of racemic secondary alcohols using chiral alkoxyamines as precatalysts are described. A number of chiral alkoxyamines have been synthesized, and their structure-enantioselectivity correlation study in OKR has led us to identify a promising precatalyst, namely, 7-benzyl-3-n-butyl-4-oxa-5-azahomoadamantane, which affords various chiral aliphatic secondary alcohols (ee up to >99%, krel up to 296). In a mechanistic study, chlorine-containing oxoammonium species were identified as the active species generated in situ from the alkoxyamine precatalyst, and it was revealed that the chlorine atom is crucial for high reactivity and enantioselectivity. The present OKR is the first successful example applicable to various unactivated aliphatic secondary alcohols, including heterocyclic alcohols with high enantioselectivity, the synthetic application of which is demonstrated by the synthesis of a bioactive compound.
- Murakami, Keiichi,Sasano, Yusuke,Tomizawa, Masaki,Shibuya, Masatoshi,Kwon, Eunsang,Iwabuchi, Yoshiharu
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supporting information
p. 17591 - 17600
(2015/02/19)
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- Rapid aqueous borohydride reduction of carbonyls under sealed-tube microwave conditions
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Ketones and aldehydes are conveniently and rapidly reduced to the corresponding alcohols in good yields using sodium borohydride under sealed-tube microwave conditions in either 95% ethanol or water. In purely aqueous systems, highly aliphatic substrates are sluggish, but this can be overcome by introducing sodium dodecyl sulfate (SDS) at the critical micelle concentration. With a 2:1 substrate/borohydride ratio and a reaction temperature of 100°C, reduction is typically complete within 1min in 95% ethanol and 5min in water/SDS. The methodology is well suited for parallel and combinatorial synthetic approaches.
- Murphree, S. Shaun,Mason, Jeremy D.,Bean, Theodore G.,Perry, Michelle C.
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experimental part
p. 1979 - 1986
(2012/06/04)
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- Nanocrystalline TiO2-HClO4 as a new, efficient and recyclable catalyst for the chemoselective trimethylsilylation of alcohols, phenols and deprotection of silyl ethers
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TiO2-HClO4, as a new solid acid, was found to be an efficient catalyst for the chemoselective trimethylsilylation of alcohols and phenols. Deprotection of the resulting trimethylsilylethers was achieved using the same catalyst in methanol solvent. The synthesized catalyst was characterized by FT-IR, SEM, TEM, BET and XRD analyses. Our novel synthetic method has the advantages of high yields, short reaction times, low cost and recyclability of the catalyst, simplicity and easy work-up compared to the conventional methods reported in the literature.
- Shirini, Farhad,Atghia, Seyyed Vahid,Jirdehi, Mojtaba Ghazi
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- TiO2 as an efficient catalytic surface for reduction of carbonyl compounds with NaBH4 under solvent-free, solid-gel and microwave irradiation
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Structurally different carbonyl compounds such as aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones and acyloins were reduced efficiently by NaBH4/TiO2 system under solvent-free, solid-gel and microwave irradiation. The chemoselective reduction of aldehydes over ketones was achieved successfully by NaBH4/TiO 2 system at solvent-free condition. In addition, regioselectivity and exclusive 1,2-reduction of Conjugated carbonyl compounds to their corresponding allylic alcohols in high to excellent yields was accomplished successfully with this reducing system.
- Setamdideh, Davood,Karimi, Zahra,Rahimi, Fatemeh
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experimental part
p. 1621 - 1634
(2012/06/16)
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- Metal-dependent reaction tuning with cyclopentylmetal reagents: Application to the asymmetric synthesis of (+)-α-conhydrine and (S)-2-cyclopentyl-2- phenylgrycolic acid
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The reaction profile of the cyclopentyl organometallic reagents with the aliphatic ketones can be tuned to reduction or addition by changing the metal atom. Cyclopentylmagnesium bromide (CPMB) reduces aromatic and aliphatic aldehydes and ketones to the corresponding alcohols without any C-C bond formation and shows good diastereoselectivity in the reduction of the substituted cyclic and polycyclic ketones as well as chiral α-oxygenated aliphatic ketones. However, in the presence of 10 mol% of ZnClα 2, the cyclopentylmagnesium halides follow a normal Grignard addition to the ketones to give tertiary alcohols with complete diastereoselectivity. The reductive as well as the addition protocols were used for the asymmetric synthesis of two medicinally important compounds, (+)-α-conhydrine and (S)-2-cyclopentyl-2-phenylglycolic acid.
- Roy, Siddharth,Sharma, Anubha,Mula, Soumyaditya,Chattopadhyay, Subrata
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experimental part
p. 1713 - 1722
(2009/09/07)
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- Silica triflate as a new, efficient, and reusable reagent for the chemoselective silylation of alcohols and phenols and deprotection of silyl ethers
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Silica triflate was easily prepared via reaction of silica gel and trifluoromethane sulfonyl chloride at room temperature. This compound can be employed as an efficient and reusable reagent for the chemoselective silylation of alcohols and phenols in solution and under solvent-free conditions. This reagent also effectively catalyzed the deprotection of silyl ethers in refluxing methanol.
- Shirini,Marjani,Nahzomi, H. Taherpour,Zolfigol
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p. 168 - 177
(2008/12/22)
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- Synthesis of a new thiocarbamate by the reaction of benzyl thiocyanate with camphene, catalyzed by heteropoly acids
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The reaction of benzyl thiocyanate with camphene in the presence of heteropoly acids, 12-phosphotungstic and 12-silicotungstic, at 65 C was studied. S-Benzyl (1,7,7-trimethylnorbornyl)thiocarbamate was prepared in 66% yield.
- Arkhipova,Malkova,Sokolova,Kartashov
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p. 162 - 163
(2008/01/05)
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- Silica triflate as a new, mild and efficient catalyst for tetrahydropyranylation of alcohols and deprotection of tetrahydropyranyl ethers
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Silica triflate, a new stable derivative of silica gel, is easily prepared by the reaction of silica gel with trifluoromethanesulfonyl chloride. Silica triflate acts as a highly effective and reusable catalyst for tetrahydropyranylation of alcohols and deprotection of tetrahydropyranyl ethers under mild and completely heterogeneous reaction conditions.
- Shirini,Marjani,Nahzomi, H. Taherpour
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p. 2235 - 2240
(2008/02/08)
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- New active-iron based reducing system for carbonyl compounds and imines. Stereoselective reduction of cyclic ketones
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The reaction of different carbonyl compounds and imines with a mixture of iron(II) chloride tetrahydrate, an excess of lithium powder, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The new reducing system exhibited good to excellent diastereoselectivity toward the reduction of different monocyclic and polycyclic ketones.
- Moglie, Yanina,Alonso, Francisco,Vitale, Cristian,Yus, Miguel,Radivoy, Gabriel
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p. 2812 - 2819
(2007/10/03)
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- Wet THF as a suitable solvent for a mild and convenient reduction of carbonyl compounds with NaBH4
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NaBH4 in wet THF can readily reduce varieties of carbonyl compounds such as aldehydes, ketones, conjugated enones, acyloins, and α-diketones to their corresponding alcohols in good to excellent yields. Reduction reactions were performed at room temperature or under reflux condition. In addition, the chemoselective reduction of aldehydes over ketones was accomplished successfully with this reducing system.
- Zeynizadeh, Behzad,Behyar, Tarifeh
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p. 307 - 315
(2007/10/03)
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- The effects of added ammonium chloride in the reductive amination of some carbonyl compounds over Ru and Pd catalysts
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The reductive amination of acetophenone, (+)-camphor, and 5α-cholestan-3-one over Ru and Pd metals as well as their carbon-supported catalysts gave corresponding amines together with alcohols as by-products. However, we found that the corresponding amines are selectively synthesized by the addition of ammonium chloride to the reaction system with depression of the formation of alcohol, as exemplified with acetophenone. Although alcohols are usually not formed over Pd with alicyclic ketones, the alcohols formation was effectively depressed over Ru in the presence of ammonium chloride. The effects of the additive on the stereoselectivity of the formation of amines are also discussed in the cases of (+)-camphor and 5α-cholestan-3-one.
- Ikenaga, Tomoaki,Matsushita, Kumiko,Shinozawa, Junichi,Yada, Satoru,Takagi, Yuzuru
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p. 2105 - 2109
(2007/10/03)
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- Al-isopropoxydiisobutylalane: A study of the effect of solvent on the rate and stereoselectivity of cyclic ketone reduction
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The effect of solvent on the rate and stereoselectivity of cyclic ketone reduction by Al-isopropoxydiisobutylalane (DIBAiOPr) has been investigated. In dichloromethane, DIBAiOPr behaves as a bulky reducing agent, approaching the carbonyl group along an equatorial trajectory to produce the axial alcohol with > 10:1 stereoselectivity. In sharp contrast, reduction in toluene gives the complementary outcome, affording the thermodynamically more stable isomer with > 99:1 stereoselectivity.
- Bahia, Perdip S.,Jones, Matthew A.,Snaith, John S.
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p. 9289 - 9291
(2007/10/03)
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- Hydrolysis of Alkenyl Esters and Ethers Catalyzed by Metal Complexes
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(Equation presented) Various kinds of transition metals catalyzed the hydrolysis of alkenyl esters and ethers under buffer-free, high concentration conditions compared to usual biocatalysts. Hydrolytic kinetic resolution of cis-2-tert-butylcyclohexyl vinyl ether was achieved by chiral (salen)Co complexes with good selectivity (krel = 10.0).
- Aoyama, Hiroshi,Tokunaga, Makoto,Hiraiwa, Shin-Ichiro,Shirogane, Yuki,Obora, Yasushi,Tsuji, Yasushi
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p. 509 - 512
(2007/10/03)
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- Dichloromethane activation. Direct methylenation of ketones and aldehydes with CH2Cl2 promoted by Mg/TiCl4/THF
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(Chemical Equation Presented) This Mg-TiCl4-promoted CH 2-transfer reaction of CH2Cl2 represents an extremely simple, practical, and efficient methylenation of a variety of ketones and aldehydes, especially in enolizable or sterically hindered ketones such as 2,2-dimethylcyclohexanone, camphor, and fenchone.
- Yan, Tu-Hsin,Tsai, Chia-Chung,Chien, Ching-Ting,Cho, Chia-Ching,Huang, Pei-Chen
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p. 4961 - 4963
(2007/10/03)
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- Titanyl Acetylacetonate as an Efficient Catalyst for a Mild and Convenient Reduction of Carbonyl Compounds with NaBH4 under Aprotic Condition
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Titanyl acetylacetonate, TiO(acac)2, is used as an efficient catalyst for the reduction of carbonyl compounds with sodium borohydride under aprotic condition. Reduction reactions are performed in CH3CN and THF. The corresponding alcohols are obtained in high to excellent yields and the chemoselective reduction of aldehydes over ketones is achieved successfully.
- Zeynizadeh, Behzad
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p. 1220 - 1226
(2007/10/03)
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- Method for preparing a benzylic-type ether
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The invention concerns a method for preparing a benzylic-type ether from an aromatic compound. The inventive method for preparing a benzylic-type ether from an aromatic compound is characterised in that it consists in: in a first step, acylating an aromatic compound by reacting said aromatic compound with an acylating agent, in the presence of an efficient amount of zeolite or a Friedel-Crafts catalyst leading to a ketonic compound; in a second step, reducing the carbonyl group into carbinol leading to a benzylic alcohol; in a third step, etherifying the hydroxyl group, by reacting the benzylic alcohol with another alcohol, in the presence of an efficient amount of zeolite.
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- Method of oxidizing an alcohol using a recyclable fluorous sulfoxide
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A method of oxidizing primary and secondary alcohols to an aldehyde or ketone using a fluorous sulfoxide or a fluorous sulfide is disclosed. The method includes regenerating and recycling the fluorous sulfoxide.
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- The reactions of selected terpene alcohols with acetonitrile in the presence of boron trifluoride etherate
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A series of thirteen terpene alcohols 1-13 of bornane, fenchane and isotricyclene systems was subjected to the reaction with acetonitrile in the presence of BF3·Et2O as a catalyst to give respective acetamides and/or alkenes. The use of boron trifluoride etherate instead of the usually applied protonic donors let us establish beyond any doubt the carbonium ion stage participation. The assumed reaction course was corroborated by cationic Wagner-Meerwein, Namietkin and homoallylic rearrangements observed during studies under investigation. Simultaneously no evidence for the imidate formation was found. Such a mode of the reaction mechanism was alternatively suggested earlier by Sjoeberg [9] for the reaction of sec- and tert-butanol with acetonitrile in the presence of boron trifluoride etherate.
- Welniak
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p. 1405 - 1411
(2007/10/03)
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- Selective removal of silyl protecting groups from hydroxyl functions with ammonium chloride in aqueous acetonitrile
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Silyl ethers are efficiently hydrolyzed to their corresponding alcohols with NH4Cl in aqueous acetonitrile. Benzylic, secondary and tert-trimethyl silyl ethers are readily cleaved at room temperature, whereas deprotection of primary and some crowded secondary trimethyl silyl ethers takes place at 80°C.
- Shaabani, Ahmad,Karimi, Ali Reza,Alamshahi, Ali Reza
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p. 1972 - 1974
(2007/10/03)
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- PERFUME COMPOSITION
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A perfume composition contains specified ketones, salicylates and alcohols/acetates/propionates. Use of such a perfume composition inhibits development of human body malodour. The combination of specified materials makes it possible to avoid inclusion of individual components with powerful, unacceptable odours. The perfume composition may be used in various products notably in a fabric conditioning product used during the rinsing or tumble drying of fabrics after washing to soften the fabrics.
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- Chiral β- and γ-aminoalcohols derived from (+)-camphor and (-)-fenchone as catalysts for the enantioselective addition of diethylzinc to benzaldehyde
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The addition of Me3SiCN and LiCH2CN to (+)-camphor and (-)-fenchone, respectively, followed by reduction leads to chiral β- and γ-aminoalcohols. The enantioselectivities realized using these aminoalcohols as ligands in the addition of Et2Zn to benzaldehyde were lower than those obtained using the corresponding δ-aminoalcohols.
- Dimitrov, Vladimir,Dobrikov, Georgi,Genov, Miroslav
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p. 1323 - 1329
(2007/10/03)
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- Camphene hydration catalyzed by heteropoly acids
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Camphene hydration catalyzed by heteropoly acids H4SiW12O40 and H3PW12O40, their advantages as catalysts in comparison with simple mineral acids, and the mechanism of the homogeneous acid-catalyzed camphene hydration in aqueous-organic solvents were studied.
- Radbil',Kulikov,Sokolova,Kartashov,Klimanskii,Radbil',Zolin
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p. 253 - 256
(2007/10/03)
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- Preparation of chiral hydroxy carbonyl compounds and diols by ozonolysis of olefinic isoborneol and fenchol derivatives: Characterization of stable ozonides by 1H-, 13C-, and 17O-NMR and electrospray ionization mass spectrometry
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The allylic and homoallylic alcohols 1-8, prepared from (+)-camphor and (-)-fenchone, were ozonized in Et2O at -78°and treated with Et3N or LiAIH4 to give the chiral hydroxy carbonyl compounds 9-16 and the diols 17- 24, respectively (Scheme 1). In the case of the diols 19 and 24, the formation of new chiral centers proceeded with high diastercoselectivity. These diols were prepared highly diastereoselectively also by LiAIH4 reduction of the hydroxy carbonyl compounds 11 and 16a, respectively (Scheme 2). The absolute configuration of the new chiral centers in 19 and 24 was determined by X-ray and NMR methods. The ozonization of compounds 2, 3, 7, and 8 provided the relatively stable hydroxy-substituted 1,2,4-trioxolane derivatives (ozonides) 37-40 (Scheme 5) which were characterized by 1H- and 13C-NMR spectra, ESI-MS, and natural-abundance 17O-NMR spectra.
- Kostova, Kalina,Dimitrov, Vladimir,Simova, Svetlana,Hesse, Manfred
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p. 1385 - 1399
(2007/10/03)
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- Stereocontrolled synthesis of novel enantiomerically pure sulfides and selenides from (+)-camphor and (+)-camphor-10-sulfonyl chloride
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Synthetic approaches to novel enantiomerically pure sulfides and selenides derived from (+)-camphor and (+)-camphor-10-sulfonate esters are described. Lewis acid mediated hemiacetal formation between a camphor- derived ketone and a thiol or selenol, and subsequent in situ reduction using triethylsilane selectively gives the exo-sulfide or -selenide in moderate overall yields. The initial sulfonate ester products can be converted into the corresponding sulfones by subsequent treatment with Grignard or organolithium reagents.
- Procter, David J.,Archer, Nicolas J.,Needham, Robert A.,Bell, David,Marchington, Allan P.,Rayner, Christopher M.
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p. 9611 - 9622
(2007/10/03)
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- Methyltriphenylphosphonium tetrahydroborate (MePh3PBH4). A stable, selective and versatile reducing agent
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Methyltriphenylphosphonium tetrahydroborate as a stable quaternary phosphonium borohydride is introduced. This compound is able to reduce aldehydes, ketones, acyl chlorides, and azides efficiently in CH2Cl2. α,β-Unsaturated carbonyl compounds are reduced selectively via 1,2-reduction. The effect of Lewis acids upon the mode and the rate of the reaction of epoxides and acetophenone are also described. This reagent is also able to bring about reductions effectively in the absence of solvent.
- Firouzabadi, Habib,Adibi, Mina
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p. 125 - 147
(2007/10/03)
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- Modofied Borohydride Agents, (1,4-Diazabicyclooctane)(tetrahydroboronato)zinc Complex . A New Ligand Metal Borohydride as a Stable, Efficient, and Versatile Reducing Agent
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(1,4-Diazabicyclooctane)(tetrahydroborato)zinc complex is a stable compound which has been used for the selective reduction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyloins and acyl chlorides to their alcohols and aldehydes in THF or CH2Cl2/hexane at room temperature or under reflux conditions.
- Firouzabadi, Habib,Zeynizadeh, Behzad
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p. 156 - 168
(2007/10/03)
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- Modified borohydride agents, methyltriphenylphosphonium tetrahydroborate; MePh3P+BH4- as a selective and an efficient reducing agent
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MePh3P+BH4- is able to reduce aldehydes and ketones to their corresponding alcohols in CH2Cl2. Aldehydes are reduced with high selectivity in the presence of ketones. α,β-Unsaturated carbonyl compounds undergo 1,2-reduction and produce their corresponding allylic alcohols in high yields. Carboxylic acid chlorides are also converted to their alcohols with high yields.
- Firouazabadi,Adibi
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p. 2429 - 2441
(2007/10/03)
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