- Complete 1H NMR assignment of cholesteryl benzoate
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The 750 MHz 1H NMR spectrum of cholesteryl benzoate (1b) could be assigned completely, which means all chemical shifts and all coupling constants, including some long-range values, were established. This task was possible by extracting many approximate coupling constant values in the overlapped spectrum region from an HSQC experiment, and using these values in the 1H iterative full spin analysis integrated in the PERCH NMR software. The task was facilitated using our published data for 3β-acetoxypregna-5,16-dien-20-one (3), the assignment data of the sesquiterpene benzoquinone dihydroperezone (2), also performed in the present study, which contains the same carbon atoms chain than cholesterol (1a), and an HSQC study of (25R)-27-deuteriocholesterol (1c) we prepared some 40 years ago. The HSQC values of 1c in combination with the coupling constants of 1b also allowed to completely assigning the spectrum of 1c. The complete assignment of 1b and 1c further provided the opportunity to estimate the hydrogen shifts induced upon benzoylation of cholesterol. Comparison of the experimental vicinal coupling constants of 1b with the values calculated using the Altona software provides an excellent correlation. In addition, a single crystal X-ray diffraction study of 1b provided the molecular conformation in the solid state, which revealed the side chain adopts an extended conformation.
- Pérez-Hernández, Nury,Becerra-Martínez, Elvia,Joseph-Nathan, Pedro
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Read Online
- Preparation of oxysterols by c–h oxidation of dibromocholestane with ru(Bpga) catalyst
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Seven mono-and dihydroxycholesterols were prepared by direct C–H oxidation of the cholestane skeleton with a recently developed Ru(Bpga) catalyst (Ru(Bpga) = [RuCl (bpga) (PPh3 )] Cl; bpga = 2-(bis(pyridin-2-ylmethyl)amino)-N-(2,6-dimethylphenyl)acetamide)). Due to the high selectivity of the Ru(Bpga) complex for tertiary C–H, the reaction afforded a mixture of 25-, 20-, 17-, and 14-oxygenated cholesterols that could be easily separated by high-performance liquid chromatography. These results suggest that late-stage C–H oxidation could be a viable strategy for preparing candidate metabolites of biologically important molecules.
- Doiuchi, Daiki,Fujii, Yui,Hirai, Go,Igawa, Kazunobu,Makino, Kana,Takeda, Daiki,Tomooka, Katsuhiko,Uchida, Tatsuya,Yoritate, Makoto
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supporting information
(2022/01/04)
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- Construction of Cholesterol Oxime Ether Derivatives Containing Isoxazoline/Isoxazole Fragments and Their Agricultural Bioactive Properties/Control Efficiency
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To explore natural-product-based pesticidal candidates and high value-added application of cholesterol in agriculture, oximinoether derivatives of cholesterol-containing isoxazoline/isoxazole fragments (I-1～I-16 and II-1～II-18) were semiprepared by structural optimization of cholesterol. Their structures were characterized by optical rotation, high-resolution mass spectrometry (HRMS), IR, and 1H NMR spectroscopy. Particularly, the Z configurations of oxime fragments at the C-7 position of target compounds were undoubtedly determined by X-ray crystallography. Against Mythimna separata Walker, compounds 3e, I-8, I-14, and II-3 showed 2.4-2.7-fold growth inhibitory activity of the precursor cholesterol. Against Plutella xylostella Linnaeus, compounds I-6, I-7, and I-9 showed 2.4-2.7-fold oral toxicity of cholesterol. Against Aphis citricola Van der Goot, compounds 2e and II-15 exhibited 4.9 and 5.8-fold aphicidal activity of cholesterol, respectively. Notably, they showed good control effects (3.0-5.0-fold promising control efficiency of 1) against A. citricola in the greenhouse. Structure-activity relationships (SARs) suggested that the C-3 hydroxyl group and the C-7 position of cholesterol are two important modification sites. It will pave the way for future structural optimization and application of cholesterol derivatives as potential pesticidal agents in agriculture.
- Xu, Hui,Zhang, Kong,Lv, Min,Hao, Meng
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p. 8098 - 8109
(2021/08/03)
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- Preparation method of 7-dehydrocholesterol for production of vitamin D3
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The invention particularly discloses a preparation method of 7-dehydrocholesterol for production of vitamin D3. The preparation method comprises the following steps: an esterification reaction, a bromination reaction, a debromination reaction and a saponification hydrolysis reaction. The esterification reaction comprises the following steps: adding cholesterol, an acid-binding agent and a solid catalyst into petroleum ether, carrying out heating to 45-50 DEG C in a nitrogen atmosphere, dropwise adding benzoyl chloride, performing heating to 78-82 DEG C after dropwise adding, conducting stirring for a reaction for 3-5 hours, adding distilled water to quench the reaction, performing filtering to obtain filter residues and a filtrate, extracting the filter residues with distilled water, concentrating an oil layer, then adding acetone, carrying out a reflux reaction for 30-40 minutes, conducting cooling to 20-30 DEG C, and performing filtering to obtain cholesterol benzoate; and soaking, filtering and drying the filter residues to obtain a solid desiccant, and repeatedly using the solid desiccant. The method has the advantage of facilitating cyclic utilization of the catalyst.
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Paragraph 0028-0033; 0036
(2021/04/07)
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- Photochemical Activation of Aromatic Aldehydes: Synthesis of Amides, Hydroxamic Acids and Esters
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A cheap, facile and metal-free photochemical protocol for the activation of aromatic aldehydes has been developed. Utilizing thioxanthen-9-one as the photocatalyst and cheap household lamps as the light source, a variety of aromatic aldehydes have been activated and subsequently converted in a one-pot reaction into amides, hydroxamic acids and esters in good to high yields. The applicability of this method was highlighted in the synthesis of Moclobemide, a drug against depression and social anxiety. Extended and detailed mechanistic studies have been conducted, in order to determine a plausible mechanism for the reaction.
- Nikitas, Nikolaos F.,Apostolopoulou, Mary K.,Skolia, Elpida,Tsoukaki, Anna,Kokotos, Christoforos G.
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supporting information
p. 7915 - 7922
(2021/05/03)
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- Natural-product-based pesticides: Semisynthesis, structural elucidation, and evaluation of new cholesterol–matrine conjugates as pesticidal agents
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To develop new potential pesticide candidates from low value-added natural bioactive products, a series of new cholesterol–matrine conjugates (I(a–e)–IV(a–e)) were prepared from two lead compounds cholesterol and matrine. Against Mythimna separata Walker, compound IVa exhibited 3.0 and 2.6 folds promising insecticidal activity of cholesterol and matrine, respectively; against Aphis citricola Van der Goot, compound IVd showed 4.3 and 2.2 folds potent aphicidal activity of their precursors; notably, it also showed good control effects in the greenhouse; against Plutella xylostella Linnaeus at a dose of 20 μg/nymph, compound IIIe exhibited 2.8 and 2.0 folds oral toxicity of cholesterol and matrine, respectively. Compounds IIIe, IVd and IVe can be used as the leads for further structural optimization as the insecticidal and aphicidal agents.
- Hao, Meng,Li, Tianze,Lv, Min,Xu, Hui,Xu, Jianwei,Zhang, Shaoyong
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- Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters
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The amide C-N cleavage has drawn a broad interest in synthetic chemistry, biological process and pharmaceutical industry. Transition-metal, luxury ligand or excess base were always vital to the transformation. Here, we developed a transition-metal-free hydrogen-bond-assisted esterification of amides with only catalytic amount of base. The proposed crucial role of hydrogen bonding for assisting esterification was supported by control experiments, density functional theory (DFT) calculations and kinetic studies. Besides broad substrate scopes and excellent functional groups tolerance, this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C-N bonds for organic synthesis and pharmaceutical industry. [Figure not available: see fulltext.]
- Huang, Changyu,Li, Jinpeng,Wang, Jiaquan,Zheng, Qingshu,Li, Zhenhua,Tu, Tao
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- Benzyne-Mediated Esterification Reaction
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A benzyne-mediated esterification of carboxylic acids and alcohols under mild conditions has been realized, which is made possible via a selective nucleophilic addition of carboxylic acid to benzyne in the presence of alcohol. After a subsequent transesterification with alcohol, the corresponding esters can be produced efficiently. This benzyne-mediated protocol can be used on the modification of Ibuprofen, cholesterol, estradiol, and synthesis of nandrolone phenylpropionate. In addition, benzyne can also be used to promote lactonization and amidation reaction.
- Li, Yang,Shi, Jiarong,Zhao, Jinlong
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supporting information
p. 7274 - 7278
(2021/10/01)
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- Mechanically induced solvent-free esterification method at room temperature
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Herein, we describe two novel strategies for the synthesis of esters, as achieved under high-speed ball-milling (HSBM) conditions at room temperature. In the presence of I2 and KH2PO2, the reactions afford the desired esterification derivatives in 45% to 91% yields within 20 min of grinding. Meanwhile, using KI and P(OEt)3, esterification products can be obtained in 24% to 85% yields after 60 min of grinding. In addition, the I2/KH2PO2 protocol was successfully extended to the late-stage diversification of natural products showing the robustness of this useful approach. Further application of this method in the synthesis of inositol nicotinate was also discussed. This journal is
- Zheng, Lei,Sun, Chen,Xu, Wenhao,Dushkin, Alexandr V.,Polyakov, Nikolay,Su, Weike,Yu, Jingbo
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p. 5080 - 5085
(2021/02/05)
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- A solvent-reagent selection guide for Steglich-type esterification of carboxylic acids
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The Steglich esterification is a widely employed method for the formation of esters under mild conditions. A number of issues regarding the sustainability of this transformation have been identified, chiefly the use of hazardous carbodiimide coupling reagents in conjunction with solvents with considerable issues such as dichloromethane (DCM) and N,N-dimethylformamide (DMF). To overcome these issues, we have developed a solvent-reagent selection guide for the formation of esters via Steglich-type reactions with the aim of providing safer, more sustainable conditions. Optimum reaction conditions have been identified after high-throughput screening of solvent-reagent combinations, namely the use of Mukaiyama's reagent (Muk) in conjunction with solvent dimethyl carbonate (DMC). The new reaction conditions were also exemplified through the synthesis of a small selection of building-block like molecules and includes the formation of t-butyl esters.
- Jordan, Andrew,Sneddon, Helen F.,Sydenham, Jack,Whymark, Kyran D.
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supporting information
p. 6405 - 6413
(2021/09/10)
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- Base-Promoted Amidation and Esterification of Imidazolium Salts via Acyl C-C bond Cleavage: Access to Aromatic Amides and Esters
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Imidazolium salts have been effectively employed as suitable acyl transfer agents in amidation and esterification in organic synthesis. The weak acyl C(O)-C imidazolium bond was exploited to generate acyl electrophiles, which further react with amines and alcohols to afford amides and esters. The broad substrate scope of anilines and benzylic amines and base-promoted conditions are the benefits of this route. Interestingly, phenol, benzylic alcohols, and a biologically active alcohol can also be subjected to esterification under the optimized conditions.
- Karthik, Shanmugam,Muthuvel, Karthick,Gandhi, Thirumanavelan
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p. 738 - 751
(2019/01/24)
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- Metal-free transesterification catalyzed by tetramethylammonium methyl carbonate
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Environmentally benign metal-free tetramethylammonium methyl carbonate is effective as a catalyst for the chemoselective, scalable, and reusable transesterification of various esters and alcohols in common organic solvents. In situ-generated highly active species, tetramethylammonium alkoxides, can greatly avoid self-decomposition at ≤110 °C, and are reusable. In particular, chelating substrates, such as amino alcohols, diols, triols, sugar derivatives, alkaloids, α-amino acid esters, etc., which deactivate conventional metal salt catalysts, can be used. A 100 gram scale biodiesel production was also demonstrated.
- Hatano, Manabu,Tabata, Yuji,Yoshida, Yurika,Toh, Kohei,Yamashita, Kenji,Ogura, Yoshihiro,Ishihara, Kazuaki
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supporting information
p. 1193 - 1198
(2018/03/27)
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- Fe-Catalyzed Aerobic Oxidative C-CN Bond Cleavage of Arylacetonitriles Leading to Various Esters
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Fe-catalyzed aerobic oxidative esterifications of arylacetonitriles with alcohols, tri alkoxsilanes, silicate esters, or borate esters have been developed. The acyl groups which were in situ generated via chemoselective C(CO)-CN bond cleavage were directly used as electrophiles, leading to corresponding aryl esters in good to excellent yields under molecular oxygen when attacked by alcohols or alcohol surrogates. Dioxygen serves as both oxidant and reactant in this protocol. The reaction has a very broad substrate scope. Cheap starting materials as well as environmentally benign and inexpensive iron catalyst and ideal oxidant O2 feature this transformation and make it a practical and sustainable protocol to afford esters.
- Kong, Weiguang,Li, Bingnan,Xu, Xuezhao,Song, Qiuling
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p. 8436 - 8443
(2016/09/28)
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- Formamides as Lewis Base Catalysts in SNReactions—Efficient Transformation of Alcohols into Chlorides, Amines, and Ethers
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A simple formamide catalyst facilitates the efficient transformation of alcohols into alkyl chlorides with benzoyl chloride as the sole reagent. These nucleophilic substitutions proceed through iminium-activated alcohols as intermediates. The novel method, which can be even performed under solvent-free conditions, is distinguished by an excellent functional group tolerance, scalability (>100 g) and waste-balance (E-factor down to 2). Chiral substrates are converted with excellent levels of stereochemical inversion (99 %→≥95 % ee). In a practical one-pot procedure, the primary formed chlorides can be further transformed into amines, azides, ethers, sulfides, and nitriles. The value of the method was demonstrated in straightforward syntheses of the drugs rac-Clopidogrel and S-Fendiline.
- Huy, Peter H.,Motsch, Sebastian,Kappler, Sarah M.
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supporting information
p. 10145 - 10149
(2016/08/16)
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- METHOD OF CONVERTING ALCOHOL TO HALIDE
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The present invention relates to a method of converting an alcohol into a corresponding halide. This method comprises reacting the alcohol with an optionally substituted aromatic carboxylic acid halide in presence of an N-substituted formamide to replace a hydroxyl group of the alcohol by a halogen atom. The present invention also relates to a method of converting an alcohol into a corresponding substitution product. The second method comprises: (a) performing the method of the invention of converting an alcohol into the corresponding halide; and (b) reacting the corresponding halide with a nucleophile to convert the halide into the nucleophilic substitution product.
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Page/Page column 51; 144; 147; 181
(2017/01/02)
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- Allylic oxidation of steroidal olefins by vanadyl acetylacetonate and tert-butyl hydroperoxide
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Abstract Readily available vanadyl acetylacetonate was found to oxidize the allylic sites of Δ5 steroidal alcohols without protection of hydroxyl groups. Cholesterol, dehydroepiandrosterone, cholesterol benzoate, cholesterol acetate, pregnenolone, and 5-pregnen-3,20-diene were oxidized to 7-keto products using vanadyl acetylacetonate in one pot reactions at room temperature in the presence of oxygen and water.
- Grainger, Wendell S.,Parish, Edward J.
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p. 103 - 109
(2015/06/30)
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- Ligand-free, palladium-catalyzed dihydrogen generation from TMDS: Dehalogenation of aryl halides on water
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A mild and environmentally attractive dehalogenation of functionalized aryl halides has been developed using nanoparticles formed from PdCl2 in the presence of tetramethyldisiloxane (TMDS) on water. The active catalyst and reaction medium can be recycled. This method can also be applied to cascade reactions in a one-pot sequence.
- Bhattacharjya, Anish,Klumphu, Piyatida,Lipshutz, Bruce H.
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supporting information
p. 1122 - 1125
(2015/03/14)
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- An efficient dehydroxymethylation reaction by a palladium catalyst
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A general method for selective dehydroxymethylation has been discovered by using widely available Pd(OAc)2. The present study offers a new synthetic strategy for the regioselective functionalization by employing the steric, electronic and coordinating nature of the hydroxymethyl (-CH 2OH) group temporarily.
- Modak, Atanu,Naveen, Togati,Maiti, Debabrata
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supporting information
p. 252 - 254
(2013/02/22)
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- Solvent free, highly chemoselective N and O-acylation on silica and silica magnesium oxide: A recyclable solid surface
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Silica or silica/magnesium oxide mixed surface mediates the N and O-acylation, benzoylation or sulfonylation of hosts of substrates under solvent free conditions at ambient temperature with high chemoselectivity.
- Ghosh, Pranab,Mandal, Amitava
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p. 261 - 268
(2012/10/29)
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- Transesterification catalyzed by iron(III) β-diketonate species
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A practical and clean protocol for transesterification catalyzed by a 5 mol % cheap, non-toxic and moisture stable Fe(acac)3 or other iron(III) β-diketonate species in solvent, such as heptane under azeotropic condition is developed. A remarkable rate enhancement was observed upon the addition of 5 mol % of an inorganic base, such as Na2CO3, which suggests that faster formation of a dimeric μ-alkoxy-bridged iron(III) species under alkaline conditions facilitates catalytic turnover. This system provides smooth transesterification over a wide range of structurally diverse esters and alcohols without disturbing functional groups. In addition, the use of iron β-diketonate complexes as catalysts is more environmentally friendly, safer, and economical than other transition-metal catalysts. Preliminary mechanistic studies indicate that the active catalyst is likely a dimeric μ-alkoxy-bridged iron(III) species, as determined by X-ray crystallography of [Fe(dbm)2(O-n-Bu)]2 derived from the alcoholysis of Fe(dbm)3 under alkaline conditions.
- Weng, Shiue-Shien,Ke, Chih-Shueh,Chen, Fong-Kuang,Lyu, You-Fu,Lin, Guan-Ying
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supporting information; experimental part
p. 1640 - 1648
(2011/04/17)
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- Ligand-assisted rate acceleration in lanthanum
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The transesterification of an equimolar mixture of carboxylic esters and primary (1°), secondary (2°), and tertiary (3°) alcohols in hydrocarbon solvents was promoted with high efficiency by a lanthanum(III) complex, which was prepared in situ from lanthanum (III) isopropoxide (1 mol %) and 2-(2-methoxyethoxy)ethanol (2 mol %). The present La(III) catalyst was highly effective for the chemoselective transesterification in the presence of competitive 1°-and 2°-amines. Remarkably, esters were obtained in good to excellent yields as colorless materials without an inconvenient workup procedure.
- Hatano, Manabu,Furuya, Yoshiro,Shimmura, Takumi,Moriyama, Katsuhiko,Kamiya, Sho,Maki, Toshikatsu,Ishihara, Kazuaki
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supporting information; experimental part
p. 426 - 429
(2011/04/15)
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- Cl3CCONH2/PPh3: A versatile reagent for synthesis of esters
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Cl3CCONH2/PPh3 was a versatile reagent to convert carboxylic acids into their corresponding acid chlorides. This intermediate was clearly confirmed by spectroscopic methods (IR, 1H, 13C NMR). This one-pot reaction of in situ acid chloride generated with various alcohols successfully furnished the corresponding esters in moderate to excellent yields. Copyright ? Taylor & Francis Group, LLC.
- Chantarasriwong, Oraphin,Jang, Doo Ok,Chavasiri, Warinthorn
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scheme or table
p. 2845 - 2856
(2009/04/11)
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- A simple procedure for the esterification of alcohols with sodium carboxylate salts using 1-tosylimidazole (TsIm)
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An efficient and selective method for esterification of alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, alcohols are refluxed with a mixture of RCO2Na (R: alkyl and aryl), TsIm, and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in DMF to afford the corresponding esters in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.
- Soltani Rad, Mohammad Navid,Behrouz, Somayeh,Faghihi, Mohammad Ali,Khalafi-Nezhad, Ali
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p. 1115 - 1120
(2008/09/17)
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- 3,6-Dibenzoxyl-1,2-pyridazine: A new versatile benzoyl transferring agent for NH2, -OH and -SH benzoylations
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A newly synthesized 3,6-dibenzoxyl-1,2-pyridazine 3 has been investigated for its potential to transfer the benzoyl group to various organic substrates carrying -NH2, -OH and -SH groups. The benzoyl transfer is fairly general in scope, occurs under convenient conditions and provides good to excellent yields of benzoylated products. Moreover, by choosing proper conditions, it is possible to achieve chemoselective benzoylation in bi-functional molecules. For instance, N-benzoylation of aromatic amines can be selectively accomplished over that of aliphatic amines and vice versa by manipulating reaction conditions. Selective N- or O-benzoylation in aminophenols is also possible. Although, not studied in detail, we final that dibenzoate 3 can also be used to effect C-benzoylation of reactive phenols and ketones, as exemplified by the C-benzoylation of resorcinol and acetophenone, respectively. Dibenzoate 3, besides being a crystalline, easy to handle, solid possesses twice the potential as an acyl carrier compared to the other known acyl carriers. These features make 3 as an attractive choice for many applications pertaining to benzoyl transfer reactions.
- Mashraqui, Sabir Hussain,Shivaji, Jadhav Latika
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p. 927 - 935
(2007/10/03)
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- Research on antiviral agents. 4. Studies on the chemistry of 6-methyl-2-methoxy-4-O-acyloxy and 6-methyl-2,4-di-O-acyloxypyrimidine derivatives as new acylation reagents and inhibitors of uracil DNA glycosylases.
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The synthesis of 6-methyl-2-methoxy-4-O-acyloxy and 6-methyl-2,4-di-O-acyloxypyrimidine derivatives 2 and 5 along with their properties as acylating agents of amines, alcohols, thiols and α-amino acids have been reported. Interestingly some of the title products revealed an inhibitory activity against the human and herpetic DNA glycosylases.
- Botta,Saladino,Gentile,Summa,Nicoletti,Verri,Focher,Spadari
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p. 3603 - 3618
(2007/10/02)
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- 6-ALKYL-2-METHOXY-4-(3H)-PYRIMIDINONES IN THE TRANSFORMATION OF PYRIMIDINES: REGIOSPECIFIC PREPARATION, ANTITUMOR AND ANTIMICROBIAL ACTIVITY OF 4-O-ACYLATED PYRIMIDINE DERIVATIVES. NEW AGENTS FOR SELECTIVE ACYLATION OF AMINES.
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A high yielding synthesis of 4-O-acylated pyrimidines is presented.These products are selective reagents for amine acylation.The antitumor and antimicrobial activity of compounds 1 and 2c is also reported.
- Botta, Maurizio,Angelis, Francesco De,Nicoletti, Rosario,Pani, Alessandra,Marongiu, Maria Elena,Colla, Paolo La
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p. 2741 - 2744
(2007/10/02)
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- BENZOTRIAZOLE-MEDIATED SELECTIVE CHROMIUM(VI) OXIDATIONS
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Complexation of chromium trioxide with benzotriazole has been found to be an effective reagent for allylic oxidation.Pyridinium chlorochromate complexed with benzotriazole was found to selectively oxidize steroidal allylic alcohols in high yield.
- Parish, Edward J.,Chitrakorn, Sarawanee
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p. 393 - 400
(2007/10/02)
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- Benzoyl Trifluoromethanesulfonate. A Mild Reagent for the Benzoylation of Sterically Hindered Hydroxyls
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Benzoyl trifluoromethanesulfonate (BzOTf) is a highly efficient reagent for the benzoylation of a variety of alcohols under mild conditions.These include hindered secondary and tertiary hydroxyls, phenols, and α-glycols.Sensitive functionality is stable when the reaction is performed in the presence of pyridine.Several unique rearrangements of Lewis acidsensitive compounds were also effected.
- Brown, Lindsey,Koreeda, Masato
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p. 3875 - 3880
(2007/10/02)
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- Oxidation process using tellurium oxide catalysts
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The present invention relates to the use of telluroxides as mild and selective oxidizing agents serving to oxidize certain functions, notably >C=S groups, in the presence of other relatively easily oxidized functions which remain unaffected; telluroxides of interest as oxidizing agents include, for example, compounds of the formula: STR1 wherein R and R1, which may be the same or different, each represent an optionally substituted aryl or heterocyclic group; or R and R1 together with the tellurium atom therebetween represent a heterocyclic ring, which may contain one or more further heteroatoms, and which may carry substituents and/or fused aromatic rings.
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- Formation of Iodides and Esters from Alcohols and Tributyldiiodophosphorane and Diiodotriphenylphosphorane
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Tributyldiiodophosphorane and diiodotriphenylphosphorane, prepared in situ from the corresponding phosphine and iodine, are generally able to convert primary and secondary alcohols into iodides at room temperature in diethyl ether or benzene containing two equivalents of hexamethylphosphoric triamide.Tertiary alcohols, as gauged by the lack of the reactivity of t-butyl alcohol, are, however, inert to this iodinating agents. 6-Hydroxyhexanoic acid yields a mixture of 6-iodohexanoic acid and 7-heptanolide.The first reagent also promotes facile condensation of secondaryand tertiary alcohols with carboxylic acids to form hindered esters in good yields.The phosphorane derived from tris(dimethylamino)phosphine and iodine, while less effective as an iodinating agent, rapidly converts 6-hydroxyhexanoic acid into 6-iodo-N,N-dimethylhexanamide, and hexanoic and benzoic acids into the corresponding N,N-dimethylamides in excellent yields at room temperature.Treatment of 3β-tosylocholest-5-ene with lithium iodide yields 3β-iodocholest-5-ene, and not 3α-iodocholest-5-ene, as previously reported.
- Haynes, Richard K.,Holden, Malcolm
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p. 517 - 524
(2007/10/02)
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- Catalytic oxidation of thiocarbonyl compounds involving the use of 1,2-Dibrometatrachloroethane as a brominating reagent for diaryl teII species
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1,2-Dibromotetrachloroethane acts as a useful brominating reagent for diaryl TeII species in the establishment of a room temperature catalytic cycle for the conversion of thiocarbonyl compounds to their oxo analogues.
- Ley, Steven V.,Meerholz, Clive A.,Barton, Derek H.R.
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p. 1785 - 1788
(2007/10/02)
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- Conversion of Thiocarbonyl Compounds into their Corresponding Oxo-derivatives using Benzeneseleninic Anhydride
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A series of thiocarbonyl compounds including xanthates, thioesters, thioureas, thiocarbonates, and thiones have been converted into their oxo-analogues by treatment with benzeneseleninic anhydride in tetrahydrofuran at room temperature.Except for readily enolised thiones where further oxidation can take place, the method works well and compares favourably with other literature procedures.One example of a selenocarbonyl ester was likewise converted efficiently into the corresponding ester.
- Cussans, Nigel J.,Ley, Steven V.,Barton, Derek H. R.
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p. 1650 - 1653
(2007/10/02)
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- Reactions of Relevance to the Chemistry of Aminoglycoside Antibiotics. Part 13. A Novel Synthesis of Benzyl Ethers
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Benzyl ethers were prepared from alcohols by reaction with chloro(phenylmethyl)dimethylammonium chloride and sodium hydrogen telluride in sequence.The salt (1) 1)OR2Cl-; R1=H, R2=cholest-5-en-3β-yl> and sodium borohydride gave the borane complex of 3β-dimethylaminomethoxycholest-5-ene.Salt (1; R1=Ph, R2=cholest-5-en-3β-yl or 5α-cholestan-3β-yl) and ammonia or hydrazine gave the steroidal benzimidates or benzhydrazonate.
- Barrett, Anthony G. M.,Read, Roger W.,Barton, Derek H. R.
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p. 2184 - 2190
(2007/10/02)
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- Transacylations with Acyl Derivatives of 4-Pyridones
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Aliphatic and aromatic amines as well as thiols react with N-acyl-4-pyridones (2a, b) and with 4-(benzoyloxy)pyridine (3a) in methylene chloride or chloroform to give the N-substituted amides 4-6 and the thiol esters 7 and 8, respectively, with very good yields.Primary and secondary alcohols react more slowly, tert-butyl alcohol only with 3a to the tert-butyl esters 12 under basic catalysis or with the much more reactive N-(trihaloacetyl)-4-pyridones 3b, c.N-Acetyl-4-pyridone (2a) possesses a much higher acylation potential than N-acetylimidazole (13a).
- Effenberger, Franz,Bessey, Eberhard
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p. 2100 - 2109
(2007/10/02)
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