- Insight into the Mechanism of the Acylation of Alcohols with Acid Anhydrides Catalyzed by Phosphoric Acid Derivatives
-
Insight into the mechanism of a safe, simple, and inexpensive phosphoric acid (H3PO4)-catalyzed acylation of alcohols with acid anhydrides is described. The corresponding in situ-generated diacylated mixed anhydrides, unlike traditionally proposed monoacylated mixed anhydrides, are proposed as the active species. In particular, the diacylated mixed anhydrides act as efficient catalytic acyl transfer reagents rather than as Br?nsted acid catalysts simply activating acid anhydrides. Remarkably, highly efficient phosphoric acid (1-3 mol %)-catalyzed acylation of alcohols with acid anhydrides was achieved and a 23 g scale synthesis of an ester was demonstrated. Also, phosphoric acid catalyst was effective for synthetically useful esterification from carboxylic acids, alcohols, and acid anhydride. Moreover, with regard to recent developments in chiral 1,1′-bi-2-naphthol (BINOL)-derived phosphoric acid diester catalysts toward asymmetric kinetic resolution of alcohols by acylation, some phosphate diesters were examined. As a result, a 31P NMR study and a kinetics study strongly supported not only the acid-base cooperative mechanism as previously proposed by other researchers but also the mixed anhydride mechanism as presently proposed by us.
- Hayashi, Hiroyuki,Yasukochi, Shotaro,Sakamoto, Tatsuhiro,Hatano, Manabu,Ishihara, Kazuaki
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p. 5197 - 5212
(2021/04/12)
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- Method for synthesizing bornyl acetate from turpentine
-
The invention discloses a method for synthesizing bornyl acetate from turpentine, which relates to the technical field of deep processing of turpentine. The preparation method comprises the followingsteps of proportioning titanium sulfate and hydroxycarboxylic acid to form a composite catalyst, mixing turpentine, acetic acid and the composite catalyst, and reacting in a stirring state, after thereaction is finished, filtering, and removing acetic acid from the filtrate to obtain a solution containing bornyl acetate, neutralizing the solution containing the bornyl acetate, and washing with water to obtain a bornyl acetate crude product, and then fractionating the crude product of the bornyl acetate to obtain the bornyl acetate. The synthesis method provided by the invention is high in catalytic activity, low in cost and high in selectivity on the borneol acetate, and does not need to use a raw material with too high pinene content.
- -
-
Paragraph 0036-0280
(2021/01/29)
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- Simple Plug-In Synthetic Step for the Synthesis of (?)-Camphor from Renewable Starting Materials
-
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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- Manganese-mediated acetylation of alcohols, phenols, thiols, and amines utilizing acetic anhydride
-
Manganese(II) chloride-catalyzed acetylation of alcohols, phenols thiols and amines with acetic anhydride is reported. This method is environment-friendly and economically viable as it involves inexpensive, relatively benign catalyst, mild reaction condition, and simple workup. Acetylation is performed under the solvent-free condition at ambient temperature and acetylated products obtained in good to excellent yields. Primary, secondary heterocyclic amines, and phenols with various functional groups are smoothly acetylated in good yields. This method exhibits exquisite chemoselectivity, the amino group is preferentially acetylated in the presence of a hydroxyl/thiol group.
- Jain, Isha,Sharma, Ramandeep,Malik, Payal
-
supporting information
p. 2952 - 2960
(2019/09/13)
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- Heterogeneous zeolite-based catalyst for esterification of α-pinene to α-terpinyl acetate
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The purpose of this study is to determine the most effective type of heterogeneous catalyst such as natural zeolite (ZA), Zr-natural zeolite (Zr/ZA) and zeolite Y (H/ZY) in esterification of α-pinene. α-terpinyl acetate was successfully synthesized from α-pinene and acetic anhydride by their heterogeneous catalysts. The esterification reaction was carried out with reaction time, temperature and zeolite catalysts. The most effective catalysts used in the synthesis of α-terpinyl acetate is catalyst H/ZY with the yield is 52.83% at 40oC for the time 4 h with a selectivity of 61.38%. The results showed that the effective separation of catalyst could contribute to developing a new strategy for the synthesis of α-terpinyl acetate.
- Wijayati, Nanik,Kusumastuti, Ella,Alighiri, Dante,Rohmawati, Baiti,Lusiana, Retno Ariadi
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p. 399 - 403
(2019/06/05)
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- Method for synthesizing isobornyl acetate by camphene
-
The invention discloses a method for synthesizing isobornyl acetate by camphene. The method comprises the following steps of adding camphene, glacial acetic acid, a main catalyst (hydroxycarboxylic acid) and an additive into a reaction kettle according to a mass ratio of 100:(20 to 400):(1 to 50):(1 to 20), starting to stir, controlling the temperature to 40 to 100 DEG C, and reacting for 2 to 24h, so as to obtain a synthesized product; adding a small amount of water into the synthesized product, standing and delaminating, wherein the upper oil layer is a target product containing isobornyl acetate, the lower layer is acid water containing the catalyst and acetic acid, and the acid water is dewatered and recycled; adding the target product into a water washing tank, adding alkaline water to neutralize, and then adding water to wash, so as to obtain a crude product of the isobornyl acetate; relieving pressure and distilling, so as to obtain the refined isobornyl acetate. The method forsynthesizing the isobornyl acetate by catalyzing the camphene has the advantages that the obtained product has high yield and high purity, and is easy to separate; the used catalyst has high catalyzing activity; the preparation is simple, the repeatability is good, the toxicity is avoided, the corrosion property is low, the isobornyl acetate belongs to regeneration resources, and the industrialization product is easy.
- -
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Page/Page column 5-13
(2018/12/13)
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- Method for catalyzing alpha-pinene ethyl esterification by using glutamic-acid-functionalized phosphotungstic acid dihydric salt
-
The invention relates to an alpha-pinene ethyl esterification reaction method, particularly a method for catalyzing alpha-pinene ethyl esterification reaction by using acid-salt-structure glutamic-acid-functionalized phosphotungstic acid dihydric salt, belonging to the technical field of biomass catalytic conversion. The catalytic esterification capacity of the two carboxyl functional groups in the glutamic acid cations and the acid catalysis capacity of the acid salt protons in the acid-salt-structure glutamic-acid-functionalized phosphotungstic acid dihydric salt [Glu]H2PW12O40 are utilized to implement alpha-pinene one-step ethyl esterification reaction under the condition of no other cocatalysts. After the catalytic reaction finishes, standing is performed, the supernatant esterification product phase only needs a small amount of water for washing, thereby greatly reducing the wastewater generation as compared with the industrial sulfuric acid catalysis process and chloroacetic acid assisted catalysis process. The catalyst which is insoluble in the organic phase can be directly recycled only after simple drying treatment.
- -
-
Paragraph 0030; 0031; 0032; 0033
(2016/12/22)
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- Rice husk ash: A new, cheap, efficient, and reusable reagent for the protection of alcohols, phenols, amines, and thiols
-
Amild, efficient, and eco-friendly protocol for the protection of alcohols and phenols as trimethylsilyl ethers has been developed using rice husk ash as a reagent. This reagent is also able to catalyze the acetylation of alcohols, phenols, thiols, and amines with acetic anhydride. All reactions were performed under mild conditions in good to high yields. Copyright
- Shirini,Akbari-Dadamahaleh, Somayeh,Mohammad-Khah, Ali
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p. 577 - 586
(2014/06/09)
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- Iron(III) tosylate catalyzed acylation of alcohols, phenols, and aldehydes
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Iron(III) p-toluenesulfonate (tosylate) is an efficient catalyst for acetylation of alcohols, phenols, and aldehydes. The acetylation of 1° and 2° alcohols, diols, and phenols proceeded smoothly with 2.0 mol % of catalyst. However, the reaction worked well with only a few 3° alcohols. The methodology was also applicable to the synthesis of a few benzoate esters but required the use of 5.0 mol % catalyst. Aldehydes could also be converted into the corresponding 1,1-diesters (acylals) under the reaction conditions. Iron(III) tosylate is an inexpensive, and easy to handle, commercially available catalyst.
- Baldwin, Neil J.,Nord, Anna N.,O'Donnell, Brendan D.,Mohan, Ram S.
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p. 6946 - 6949
(2013/01/15)
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- Liquid phase acetoxylation of α-pinene over Amberlyst-70 ion-exchange resin
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Heterogeneously-catalyzed and solvent-catalyzed liquid phase acetoxylation of α-pinene with acetic acid acting as both a solvent and a reagent was studied. Both solvent-catalyzed and catalytic experiments were carried out and various reaction conditions were studied. The influence of temperature, pressure, solvent and gas milieu were taken into account. Bornyl, fenchyl, verbenyl as well as α-terpinyl acetates, limonene, camphene and γ-terpinene were found among reaction products. The addition of the catalyst allowed for maximization of the yield of bornyl acetate. The predominant products obtained were α-terpinyl, verbenyl and bornyl acetates. The reaction pathways were identified and evaluated. The aim of this work was to study the feasibility of batch acetoxylation of α-pinene. The analysis of the complex product distribution is not trivial and, consequently, resolving the reaction network was important. The optimized reaction conditions were searched for aiming at an efficient conversion of α-pinene to a mixture of valuable products.
- Golets,Ajaikumar,Blomberg,Grundberg,W?rn?,Salmi,Mikkola
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scheme or table
p. 43 - 50
(2012/10/18)
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- Oxidation of α-pinene by atmospheric oxygen in the supercritical CO2-ethyl acetate system in the presence of Co(II) complexes
-
The reactivity of monoterpene α-pinene in a flow reactor in the presence of cobalt catalyst in a complex supercritical solvent consisting of CO2 and ethyl acetate is studied over the temperature range of 190-320°C and a pressure range of 110-125 atm. It was found that the main isomerization products include compounds with bicyclo[2.2.1]heptane and p-menthane backbones; the reaction is accompanied by partial racemization. The formation of oxidation products is observed in the presence of air, with epoxydation rather than allylic oxidation being the predominant process at the first stage. The oxidized products (campholenic aldehyde, verbenone, pinocamphone) are shown to be formed with a high enantioselectivity; the formation of acetoxylation products is observed at temperatures above 200°C.
- Anikeev,Ilina,Kurbakova,Nefedov,Volcho,Salakhutdinov
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experimental part
p. 190 - 195
(2012/03/12)
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- Microwave-assisted α-pinene acidic catalytic isomerisation
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A comparative study of microwave assisted α-pinene acidic catalytic isomerisation reactions with near-critical water procedure under microwave irradiation is presented. This study can be performed because in both cases the mechanism is similar, namely an acidiccatalyzed rearrangement. The non-critical method technique is milder using a lower temperature and pressure and a shorter reaction time than near-critical water conditions. The general aspect of the selectivity of the reaction products is changed, being higher for α-terpinolene and γ-terpinolene and lower for limonene and camphene compared to the non-critical conditions.
- Szuecs-Balazs, Jozsef Zsolt,Coros, Maria,Molnar, Diana,Vlassa, Mircea
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p. 209 - 213
(2013/03/13)
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- A mild and efficient method for the methoxymethylation and acetylation of alcohols promoted by benzyltriphenylphosphonium tribromide
-
A mild and efficient method for the conversion of alcohols to their corresponding methoxymethyl ethers and acetates using benzyltriphenylphosphonium tribromide (BTPTB) as catalyst is described. All reactions were performed under completely heterogeneous reaction conditions in good to high yields.
- Shirini, Farhad,Imanzadeh, Gholam Hossein,Mousazadeh, Seyyed Ali Reza,Mohammadpoor-Baltork, Iraj,Abedin, Masoumeh
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experimental part
p. 1187 - 1190
(2011/10/05)
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- Samarium trifluoromethanesulfonate: An efficient moisture tolerant acylation catalyst under solvent-free condition
-
Samarium trifluoromethanesulfonate catalyzed the acylation of phenols, alcohols, thiols, free reducing sugars, and glycosides in excellent yields at ambient temperature under solvent-free condition using stoichiometric amounts of various anhydrides. (Chemical Equation Presented). Copyright Taylor & Francis Group, LLC.
- Roy, Bimalendu,Dasgupta, Somnath,Kumar Rajput, Vishal,Mukhopadhyay, Balaram
-
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- A highly selective, high-speed, and hydrolysis-free O-acylation in subcritical water in the absence of a catalyst
-
(Chemical Equation Presented) Fast and furious: A wide range of alcohols are acylated by acetic anhydride, in the absence of catalyst, in subcritical water in a flow-type microreaction system. The esters are selectively produced in high yields at temperatures of 200 to 250°C. Varying the amount of acetic anhydride added with respect to the alcohols allows the regioselective acylation of one or both hydroxy groups of various dihydroxy compounds (see picture).
- Sato, Masahiro,Matsushima, Keiichiro,Kawanami, Hajime,Ikuhsima, Yutaka
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p. 6284 - 6288
(2008/04/05)
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- N, O-ligand accelerated zinc-catalyzed transesterification of alcohols with vinyl esters
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N-Phenyldiethanolamine (1f) is an efficient ligand for zinc-catalyzed transesterification of alcohols with vinyl acetate (R3 = Me) at room temperature. In the case of using other vinyl esters (R3 = Et, n-Pr, Ph), the corresponding products were easily obtained in the presence of pyridine-type ligand 2 instead of aminoalcohol 1f.
- Mino, Takashi,Hasegawa, Tae,Shirae, Yoshiaki,Sakamoto, Masami,Fujita, Tsutomu
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p. 4389 - 4396
(2008/02/13)
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- Magnesium bistrifluoromethanesulfonimide as a new and efficient acylation catalyst
-
Magnesium bistrifluoromethanesulfonimide catalyzed the acetylation of phenols, alcohols, and thiols under solvent-free conditions at room temperature and in short times. Electron-deficient and sterically hindered phenols provided excellent yields. The catalyst was found to be general for acylation with other anhydrides, such as propionic, isobutyric, pivalic, chloroacetic, and benzoic anhydrides. The rate of acylation was influenced by the electronic and steric factors associated with the anhydride. The reaction with less electrophilic anhydrides (e.g., chloroacetic and benzoic anhydrides) required higher temperature (~80 °C). Chemoselective acetylation, pivalation, and benzoylation took place with acid-sensitive alcohols without any competitive dehydration/rearrangement.
- Chakraborti, Asit K.,Shivani
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p. 5785 - 5788
(2007/10/03)
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- Zirconiuni(IV) chloride as a new, highly efficient, and reusable catalyst for acetylation of phenols, thiols, amines, and alcohols under solvent-free conditions
-
Zirconium(IV) chloride has been found to be a new, highly efficient, and reusable catalyst for acetylation of structurally diverse phenols, thiols, amines, and alcohols under solvent-free condtions. Acetylation of sterically hindered and electron deficient phenols is achieved in excellent yields with stoichiometric amounts of Ac2O at room temperature. Acid-sensitive alcohols undergo acetylation with excellent chemoselectivity without competitive side reactions such as dehydration or rearrangement. The mild Lewis acid property of the catalyst enables the acetylation to be carried out with optically active substrates without any detrimental effect on the optical purity.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 627 - 630
(2007/10/03)
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- Electrostatic catalysis by ionic aggregates: Scope and limitations of Mg(ClO4)2 as acylation catalyst
-
Alkali and alkaline earth metal perchlorates exhibit electrostatic catalysis in the activation of anhydrides for the acylation reaction. Perchlorates with higher values of the charge-size function of the metal ion exhibit better catalytic activity following the order Mg(ClO4) 2>Ba(ClO4)2>LiClO4. Acylation of structurally diverse phenols, thiols, alcohols, and amines have been carried out with stoichiometric amounts of anhydride at room temperature under solvent free conditions in the presence of catalytic amount of Mg(ClO4) 2. Sterically hindered and electron deficient phenols are efficiently acylated. Acylation with sterically hindered anhydrides such as iso-butyric, pivalic, and benzoic anhydrides are carried out with phenols and alcohols in excellent yields. Acid-sensitive alcohols are acylated in excellent yields without any competitive side reactions.
- Chakraborti, Asit K.,Sharma, Lalima,Gulhane, Rajesh,Shivani
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p. 7661 - 7668
(2007/10/03)
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- Perchloric acid adsorbed on silica gel as a new, highly efficient, and versatile catalyst for acetylation of phenols, thiols, alcohols, and amines
-
Perchloric acid adsorbed on silica gel efficiently catalyses acetylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 1896 - 1897
(2007/10/03)
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- Indium(III) chloride as a new, highly efficient, and versatile catalyst for acylation of phenols, thiols, alcohols, and amines
-
Indium(III) chloride efficiently catalyses the acylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions. Acid sensitive alcohols are smoothly acylated without competitive side reactions. Acylation of 2-hydroxynaphthalene is carried out with carboxylic acids adopting the mixed anhydride protocol using trifluoroacetic anhydride.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 6749 - 6753
(2007/10/03)
-
- Fluoroboric acid adsorbed on silica gel as a new and efficient catalyst for acylation of phenols, thiols, alcohols, and amines
-
Fluoroboric acid supported on silica gel efficiently catalyzes acylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions. Acid-sensitive alcohols are smoothly acylated without competitive side reactions.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 3521 - 3525
(2007/10/03)
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- Microwave enhanced acetylation of alcohols
-
Microwave irradiation of alcohols with acetic anhydride in the presence of a catalytic amount of NaOH for a few minutes yielded the corresponding acetylated products in excellent yield.
- Patnam, Ramesh,Chang, Fang-Rong,Kuo, Reen-Yen,Pan, Wen-Bin,Wu, Yang-Chang
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p. 301 - 302
(2007/10/03)
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- Lithium perchlorate catalyzed acetylation of alcohols under mild reaction conditions
-
Lithium perchlorate is found to efficiently catalyze the acetylation of alcohols and phenols with acetic anhydride in good to excellent yields.
- Nakae,Kusaki,Sato
-
p. 1584 - 1586
(2007/10/03)
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- P(RNCH2CH2)3N: Efficient catalysts for transesterifications, acylations, and deacylations
-
Extremely strong nonionic superbases of the type P(RNCH2CH2)3N catalyze the transesterification of carboxylic acid esters with high selectivity and yields at 25 °C. These bases also catalyze the deacetylation of alcohols under mild conditions in quantitative yields. Using enol acetates as acylating agents, primary and secondary alcohols are efficiently protected as acetates through the action of these catalysts. Substituents such as epoxide, carbamate, acetal, oxazoline, nitro, and alkynyl functionalities are tolerated under the reaction conditions. N-Protected peptides undergo clean transesterification without significant racemization, making this methodology potentially very useful.
- Ilankumaran, Palanichamy,Verkade
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p. 3086 - 3089
(2007/10/03)
-
- Superbase-promoted acylation of hindered alcohols
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The commercially available nonionic superbase P(MeNCH2CH2)3N (1a) is very useful for the acylation of unreactive hindered alcohols as well as acid-sensitive alcohols. The reactions proceed in high yields using an acid anhydride, and 1a can be regenerated in a single step. The relative rates for benzoylation of (±)-menthol in C6D6 using conventional acylation reagents and strong nonionic bases are compared. In general, acetylation with 1a is accelerated in the polar solvent CH3CN whereas benzoylation is faster in the nonpolar solvent C6H6. The benzoylation intermediate RC(O)P(MeNCH2CH2)3N+ was found to be in equilibrium with 1a, with lower temperatures favoring the intermediate. The relative stabilities of several known acylating intermediates are compared.
- D'Sa, Bosco A.,Verkade, John G.
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p. 2963 - 2966
(2007/10/03)
-
- Steric Structure of Mono- and Bicyclic Terpene Derivatives as Determined by NMR Spectroscopy
-
The 1H and 13C NMR spectral data for a series of newly prepared mono- and bicyclic terpene derivatives are presented. The feasibility of NMR spectroscopy for examining cis-trans isomerism in terpenes and E-Z isomerism in oximes is discussed. From the values of vicinal spin-spin coupling constants, the signal multiplicities, and the appearance of W-interaction in the 1H spectra the steric orientation of the substituents in the complex structures of p-menthane, pinane, carane, and norbornane derivatives are unambiguously assigned. The steric structure of derivatives with a tetracoordinated carbon atom, where the characteristic spin-spin coupling constants are absent, can be correctly determined from 13C NMR spectral data.
- Koval'skaya,Kozlov
-
p. 306 - 315
(2007/10/03)
-
- HALOALDEHYDE POLYMERS XLVIII. OPTICAL ACTIVITY OF DIASTEREOMERIC BORNYLOXY TERMINATED ALDEHYDE UNIMERS
-
Bornyl oxide initiated, acetate endcapped unimers of trifluoroacetaldehyde, trichloroacetaldehyde and tribromoacetaldehyde were prepared and their optical rotations were determined.The value of the optical rotations of the unimers was correlated to the bulk size of the trihalomethyl group and they were compared to those of the unimer of formaldehyde and bornyl acetate.The bornyloxy terminated trihaloacetaldehydes consist of 2 diastereomeric unimers.In the cases of the chloral and bromal unimers they have been isolated.One diastereomer of the trichloroacetaldehyde unimers was crystallized and its absolute configuration was established by x-ray spectroscopy.
- Hatada, Koichi,Ute, Koichi,Nishimura, Tohru,Xi, Fu,Vogl, Otto
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p. 903 - 910
(2007/10/02)
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- ENANTIOSELECTIVITY IN THE HYDROLYSIS OF BICYCLIC MONOTERPENE ACETATES WITH THE CULTURED CELLS OF NICOTIANA TABACUM
-
Key Word Index - Nicotiana tabacum; Solanaceae; tissue culture; biotransformation; hydrolysis; enantioselectivity; bicyclic monoterpene acetates.The enantioselectivity in the hydrolysis of bornyl acetate; isobornyl acetate and isopinocampheyl acetate with the cultured cells of Nicotiana tabacum was investigated.The cultured cells were found to have the ability to hydrolyse enantioselectively the acetates, of which the configuration at the carbon atom bearing the acetoxyl group is R.
- Suga, Takayuki,Hirata, Toshifumi,Izumi, Shunsuke
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p. 2791 - 2792
(2007/10/02)
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- The endo- and exo-1,7,7-Trimethylbicyclo-heptan-2-amines (Bornan-2-amines) and Their Acetamides
-
Melting points provide a poor method for differentiation between the exo and endo N-(bornan-2-yl)-acetamides, and have led to errors by previous workers.Spectral differences leading to unambiguous assignment are discussed in this paper.Trapping of the bornan-2-yl carbenium ion with acetonitrile leads to exo products.
- Carman, Raymond M.,Greenfield, Kay L.
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p. 1785 - 1790
(2007/10/02)
-
- Acid-induced 13C Nuclear Magnetic Resonance Chemical Shift Changes of Ether and Ester Carbon Atoms
-
13C N.m.r. chemical shifts of ehters dissolved in tetrachloromethane are displaced on addition of trifluoroacetic acid.The displacements result from independent interactions of the acid with the substrate oxygen atoms and alkyl residues.The structure-dependent and stereoselective shift changes are useful for signal assignments, structure determination, conformational analysis, assessment of the distribution of rapidly interconverting conformers of esters, and estimation of the relative basicity of ethers.
- Begtrup, Mikael
-
p. 1609 - 1618
(2007/10/02)
-
- Electronic Effects of Polar Substituents in the Gas Phase Unimolecular Elimination of 4-Substituted Isobornyl Acetates
-
The rates of gas-phase elimination of a series of 4-substituted isobornyl acetates have been measured in the presence of propene between 209-370 deg C and within a pressure range 37-153 Torr; a static system with seasoned vessels was used.The reaction are unimolecular, homogeneous, and obey a first-order rate law; electron-withdrawing substituents at C(4) cause a diminution in the elimination rate, such that ρ1 -0.69 in a Hammett treatment.The temperature dependence of the rate coefficients is illustrated for the Arrhenius equation for isobornyl acetate: logk/s-1=(12.82+/-0.13)-(189.2+/-1.5)kJmol-1/2.303RT.The results are consistent with a cyclic transition state in which C(2)-O cleavage is more advanced than that of C(3)-H.The major primary product of elimination of isobornyl acetate is bornylene, which partially isomerises to camphene and tricyclene under the reaction conditions.Bornylene also undergoes a retro-Diels-Alder reaction to yield the trimethylcyclopentadiene and ethylene.
- Chuchani, Gabriel,Hernandez A, Jose A.,Morris, David G.,Shepherd, Alistair G.
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p. 917 - 922
(2007/10/02)
-
- Kondakof Acylation of Logifolene/Camphene: A Comparative Study Using Boron Trifluoride Etherate/Stannic Chloride as Catalysts
-
The Kondakof acylation of the ectocyclic methylene moiety in comphene (1) and its isoprene homologue longifolene (2) has been studied in acetic anhydride using BF3*OEt2/SnCl4 as catalysts.Ac2O-BF3*OEt2 fails to acylate (1) but gives isobornylacetate (3) (46percent) as the sole product.Acylation of (1) with Ac2O-SnCl4 affords ω-acetyl comphene (4) in a negligible yield (2percent) along with (3) in a much reduced yield (19percent).In sharp contrast, longifolene (2) generates ω-acetyllongifolene (5) with both the catalysts: BF3*OEt2 (24percent) and SnCl4 (16percent).The other compounds isolated in the former case are isolongifolene (6) (50percent) and transannular acetate (7) (2percent); in the latter case, (6) (17percent), (7) (5percent) and the novel tetracyclic methylketone (8) (11percent) are the co-products.The precurser for (8) has been shown to be the isomerized hydrocarbon (6), on direct acylation with SnCl4 generates (8).
- Dalavoy, V. S.,Deodhar, V. B.,Nayak, U. R.
-
p. 907 - 910
(2007/10/02)
-
- Rearrangement of Pinane Derivatives. Part 8. Deamination of 2αH-Pinan-3α-ylamine
-
Solvolysis of 2αH-pinan-3α-yl toluene-p-sulphonate has been shown to proceed with concomitant 1,2-hydride shift to give the pinan-2-yl carbocation.Contrary to earlier reports, this species reacts normally to give, in good yield, pinan-2-yl substitution products.In contrast the pinan-3-ylamines react via a similar route, but give much smaller amounts of pinan-2-yl products.The usual reasons for differences between solvolysis and deamination (i.e. the intermediacy of diazonium ions and/or high-energy ions) can be discounted, and possible reasons for the differences in behaviour are discussed.
- Giddings, Rodney M.,Jones-Parry, Richard,Salmon, J. Roger,Whittaker, David
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p. 725 - 728
(2007/10/02)
-