- Isoprene related esters, significant components of Pandanus tectorius
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Isopentenyl and dimethylallyl acetates and cinnamates have been found in large amounts in an essential oil obtained from the ripe fruit of Pandanus tectorius, their identification has been confirmed by synthesis. This is the first time that these esters, apart from one, have been found in the plant kingdom and, generally speaking, that monoterpene precursors predominate in an essential oil.
- Vahirua-Lechat,Menut,Roig,Bessiere,Lamaty
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Read Online
- Functionalized α-bromocyclopropylmagnesium bromides: Generation and some reactions
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Functional derivatives of gem-dibromocyclopropanes (ethers and esters of gemdibromocyclopropylmethanol, 2,2-dibromocyclopropanecarboxylic acids and their esters) undergo partial hydrodebromination at the treatment with isopropyl magnesium bromide (3-6 mol-equiv) in THF and then in methanol at -60°C affording the corresponding monobromides in 64-95% yields. The addition of nonsolvated magnesium bromide to the reaction mixture results in the considerable reduction of the amount of the Grignard reagent (from 6 to 3 mol-equiv). This allows achieving the partial hydrodebromination of 2,2-dibromocyclopropanecarboxylic acids. Pleiades Publishing, Ltd., 2013.
- Bolesov,Solov'eva,Baird
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Read Online
- Synthesis of (2E)-4-hydroxy-3-methylbut-2-enyl diphosphate, a key intermediate in the biosynthesis of isoprenoids
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The synthesis of (2E)-4-hydroxy-3-methylbut-2-enyl diphosphate (HMBPP) was described by regioselective hydroxylation and diphosphorylation of dimethylallyl alcohol. The synthesis started from commercially available 3-methylbut-2-en-1-ol. The 1-alcohol function of starting material was converted to the acetate by treatment with pyridine acetic anhydride. Selective allylic hydroxylation was achieved using selenium dioxide and tert-butyl hydro-peroxide.
- Ward, Jane L.,Beale, Michael H.
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Read Online
- Evaluation of gem-Diacetates as Alternative Reagents for Enzymatic Regio-and Stereoselective Acylation of Alcohols
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Geminal diacetates have been used as sustainable acyl donors for enzymatic acylation of chiral and nonchiral alcohols. Especially, it was revealed that geminal diacetates showed higher reactivity than vinyl acetate for hydrolases that are sensitive to acetaldehyde. Under optimized conditions for enzymatic acylation, several synthetically relevant saturated and unsaturated acetates of various primary alcohols were obtained in very high yields up to 98% without E/Z isomerization of the double bond. Subsequently, the acyl donor was recreated from the resulting aldehyde and reused constantly in acylation. Therefore, the developed process is characterized by high atomic efficiency. Moreover, it was shown that acylation using geminal diacetates resulted in remarkable regioselectivity by discriminating among the primary and secondary hydroxyl groups in 1-phenyl-1,3-propanediol providing exclusively 3-acetoxy-1-phenyl-propan-1-ol in good yield. Further, enzymatic kinetic resolution (EKR) and chemoenzymatic dynamic kinetic resolution (DKR) protocols were developed using geminal diacetate as an acylating agent, resulting in chiral acetates in high yields up to 94% with enantiomeric excesses exceeding 99%.
- Koszelewski, Dominik,Brodzka, Anna,Madej, Arleta,Trzepizur, Damian,Ostaszewski, Ryszard
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p. 6331 - 6342
(2021/05/06)
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- Method for preparing 4-acetoxy-2-methyl-2-butenal
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The invention provides a method for preparing 4-acetoxy-2-methyl-2-butenal. The method comprises the following steps: esterifying isopentenol to generate isopentenol acetate; and carrying out illumination oxidation on the isopentenol acetate in the presence of a photosensitizer to generate 4-acetoxy-2-methyl-2-butenal. The method has the advantages of cheap and easily available starting raw material isopentenol, high atom economy of the process route, no use of precious metals, less three wastes, and economic and effective synthesis route.
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Paragraph 0019; 0046; 0047; 0049; 0050; 0052-0053; 0055-0056
(2020/04/29)
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- Method for synthesizing acetate perfume
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The invention provides a method for synthesizing acetate by alcohol esterification, which comprises the following steps: by using enol acetate as an esterification reagent, esterifying a primary alcohol, secondary alcohol or tertiary alcohol substrate at high selectivity and high yield under the action of an acidic catalyst to obtain the corresponding acetate products. The method has the main advantages that the synthesis method is novel, enol acetate is used as an esterification reagent, reaction byproducts are micromolecular acetaldehyde or acetone and the like, and the micromolecular compounds do not show acidity and are low in boiling point, so that rearrangement side reaction of an alcohol substrate cannot be caused; and the small molecule byproduct can be conveniently removed from the reaction solution, so that the esterification reaction is promoted to be completely carried out, the reaction stability is good, and the yield is high.
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Paragraph 0070-0073
(2021/01/15)
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- Preparation method of 4-acetoxy-2-methyl-2-butenal
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The invention provides a preparation method of a vitamin A intermediate, namely 4-acetoxy-2-methyl-2-butenal. The method comprises the following steps: (1) carrying out ring opening on 3-methyl-1,2-epoxybutane under the action of alkaline acetate to generate 2-hydroxyl-3-butyl methyl acetate; (2) dehydrating 2-hydroxyl-3-butyl methyl acetate to obtain 3-methyl-2-butene acetate; and (3) carrying out one step selective oxidation on 3-methyl-2-butenyl acetate to obtain 4-acetoxy-2-methyl-2-butenal. According to the method, 3-methyl-1,2-epoxybutane is used as an initial raw material, the reactionsynthesis route is short, the atom economy is high, the operation is simple, and the method is an industrially optimized synthesis route.
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- Scalable green approach toward fragrant acetates
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The advantageous properties of ethylene glycol diacetate (EGDA) qualify it as a useful substitute for glycerol triacetate (GTA) for various green applications. We scrutinised the lipase-mediated acetylation of structurally diverse alcohols in neat EGDA furnishing the range of naturally occurring fragrant acetates. We found that such enzymatic system exhibits high reactivity and selectivity towards activated (homo) allylic and non-activated primary/secondary alcohols. This feature was utilised in the scalable multigram synthesis of fragrant (Z)-hex-3-en-1-yl acetate in 70percent yield. In addition, the Lipozyme 435/EGDA system was also found to be applicable for the chemo-selective acetylation of (hydroxyalkyl) phenols as well as for the kinetic resolution of chiral secondary alcohols. Lastly, its discrimination power was demonstrated in competitive experiments of equimolar mixtures of two isomeric alcohols. This enabled the practical synthesis of 1-pentyl acetate isolated as a single product in 68percent yield from the equimolar mixture of 1-pentanol and 3-pentanol.
- Puchl'Ová, Eva,Szolcsányi, Peter
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- Preparing method and application of aminopyridine derivative
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The invention provides an aminopyridine derivative and a preparing method and application thereof. The structural formula of the aminopyridine derivative is shown in the description, wherein R represents substitute groups and is selected from one or more of alkyl groups of C1-C20, phenyl groups, naphthyls, methoxy groups, benzyloxy groups, fluorine, chlorine, bromine, trifluoromethyl, methoxycarbonyl groups. The preparing method comprises the steps of conducting benzylation on 4-aminopyridine and benzylic halides under action of an alkaline reagent. The aminopyridine derivative is used for catalyzing esterification reaction, and is especially suitable for catalyzing acetic acid esterification reaction with alcohol as the substrate; the reaction speed is high, the yield is high, and the reaction effect and the reaction speed are almost equal to those of 4-dimethylamino pyridine. The aminopyridine derivative has large molecular weight and a high boiling point and accordingly can be separated from primary products and auxiliary products through distillation or rectification and can be reused cyclically ten times or more, the cost of the catalyst is greatly reduced, and the aminopyridine derivative has good industrial application prospects.
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Paragraph 0101-0103; 0110; 0111; 0113
(2019/07/16)
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- Preparation method of 4-acetoxy group-2-methyl-2-butenal
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The invention discloses a preparation method of 4-acetoxy group-2-methyl-2-butenal. The method comprises the following steps: (1) enabling prenyl chloride and acetate to react to produce prenyl alcohol acetate under the catalysis of a phase transfer catalyst; (2) oxidizing the prenyl alcohol acetate obtained in the step (1) by using hydrogen peroxide under the catalysis of selenium dioxide to obtain the 4-acetoxy group-2-methyl-2-butenal. The method takes the prenyl chloride as the starting material, the prenyl chloride is a commonly seen intermediate of a fine chemical, is cheap and is easy to get, the reaction process does not need to use noble metal catalysts, the cost is relatively low, the synthetic route is short, the operation is simple, the environmental pollution is small, and thepreparation method is an effective synthetic route.
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Paragraph 0073; 0074; 0076; 0077
(2019/01/08)
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- Scalable Microwave-Assisted Johnson-Claisen Rearrangement with a Continuous Flow Microwave System
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We demonstrated the rapid Johnson-Claisen rearrangement of allyl alcohol and triethyl orthoacetate with a continuous flow apparatus combined with a microwave reactor. The reaction could be carried out without solvent, and only a catalytic amount of acetic acid was sufficient to promote the reaction under microwave irradiation conditions. To confirm the optimal reaction conditions found experimentally, we performed Design of Experiments (DoE) by the Nelder-Mead method and a least-squares method regarding the amount of acetic acid and the flow rate. Consequently, the highest yield of the desired γ,δ-unsaturated ester was obtained, and the productivity at the reaction step of the continuous process was 89.5 g/h under the optimal conditions, suggesting that 2.1 kg of the product would be theoretically obtained in 1 day. We also investigated the Johnson-Claisen rearrangement using other allylic alcohols, and the corresponding products were obtained in good to high yields per unit of time.
- Egami, Hiromichi,Tamaoki, Souma,Abe, Masato,Ohneda, Noriyuki,Yoshimura, Takeo,Okamoto, Tadashi,Odajima, Hiromichi,Mase, Nobuyuki,Takeda, Kazuhiro,Hamashima, Yoshitaka
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supporting information
p. 1029 - 1033
(2018/08/03)
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- Method for combined production of 3-methyl-1,5-pentanediol and C1-C6 alcohols
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The invention provides a method for combined production of 3-methyl-1,5-pentanediol and C1-C6 alcohols. The method comprises the following steps: 1) subjecting 3-methyl-3-butene-1-alcohol and C1-C6 acids to an esterification reaction so as to obtain an esterified product containing C1-C6 acids-3-methyl-3-butene-1-alcohol ester; 2) subjecting the esterified product obtained in the step 1) and gas containing CO and H2 to a hydroformylation reaction; and 3) subjecting a reaction product obtained in the step 2) to a hydrogenation reaction so as to obtain the 3-methyl-1,5-pentanediol and the C1-C6alcohols. According to the invention, through a process route of esterification, hydroformylation and hydrogenation in turn, direct hydroformylation of 3-methyl-3-butene-1-alcohol is avoided, so inevitable side reactions generated by a direct hydroformylation reaction is easily avoided; meanwhile, by utilization of the process route provided by the invention, combined production of the C1-C6 alcohols (like ethyl alcohol) can be realized.
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Paragraph 0088; 0090; 0092; 0093; 0126; 0127
(2018/07/30)
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- Synthesis method of 3-methyl-2-butene-1-geranoil formate
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The invention belongs to the technical field of chemical synthesis and particularly relates to a synthesis method of 3-methyl-2-butene-1-geranoil formate. According to the synthesis method of the 3-methyl-2-butene-1-geranoil formate and on the basis of the existing technical process, sodium hydrogen sulfite serves as a catalyst, the yield of a 3-methyl-2-butene-1-geranoil formate product is further increased, more preferably, reaction is conducted under the existence of ionic liquid, the reaction time is effectively increased besides the yield of the products is effectively increased, and higher product yield can be obtained within shorter time.
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Paragraph 0021-0042
(2018/07/06)
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- Preparation of regio- and stereoisomeric di- and tetrahydrogeranylgeraniols and identification of esterifying groups in natural (bacterio)chlorophylls
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All regioisomeric di- and tetrahydrogeranylgeraniols possessing the C2[dbnd]C3 double bond were prepared as authentic samples. The synthetic C20-isoprenoid alcohols were separated well by gas chromatography. Based on the chromatographic analysis, the enzymatic reduction pathway of a geranylgeranyl group was investigated to identify the last stage of (bacterio)chlorophyll biosynthesis in phototrophs. The geranylgeranyl group was triply reduced to the phytyl group through the first regio- and stereospecific hydrogenation of C10[dbnd]C11 to C10H–C11(S)H, the second of C6[dbnd]C7 to C6H–C7(S)H, and the third of C14[dbnd]C15 to C14H–C15H. The identification of the reduction sequence completes the biosynthetic pathways for naturally occurring chlorophyll-a and bacteriochlorophyll-a bearing a phytyl group as the esterifying moiety in the 17-propionate residues.
- Tamiaki, Hitoshi,Nomura, Kota,Mizoguchi, Tadashi
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p. 6361 - 6370
(2017/11/16)
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- Cross-metathesis reaction of functionalized and substituted olefins using group 8 transition metal carbene complexes as metathesis catalysts
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The invention pertains to the use of Group 8 transition metal carbene complexes as catalysts for olefin cross-metathesis reactions. In particular, ruthenium and osmium alkylidene complexes substituted with an N-heterocyclic carbene ligand are used to catalyze cross-metathesis reactions to provide a variety of substituted and functionalized olefins, including phosphonate-substituted olefins, directly halogenated olefins, 1,1,2-trisubstituted olefins, and quaternary allylic olefins. The invention further provides a method for creating functional diversity using the aforementioned complexes to catalyze cross-metathesis reactions of a first olefinic reactant, which may or may not be substituted with a functional group, with each of a plurality of different olefinic reactants, which may or may not be substituted with functional groups, to give a plurality of structurally distinct olefinic products. The methodology of the invention is also useful in facilitating the stereoselective synthesis of 1,2-disubstituted olefins in the cis configuration.
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Page/Page column 36; 45
(2016/08/29)
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- Synthesis of lipase nano-bio-conjugates as an efficient biocatalyst: Characterization and activity-stability studies with potential biocatalytic applications
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In the present study, we have synthesized lipase-nano-bio-conjugates via immobilization of various lipases on multiwall carbon nano-tubes (MCNT), in order to construct an efficient and recyclable biocatalytic system. In a screening study lipase Pseudomonas fluorescens (PFL) acted as an efficient biocatalyst (lipase-nano-bio-conjugates) which showed higher retention of lipase activity and protein loading. Consequently the immobilization support : lipase (MCNT : PFL) composition was screened in which MCNT : PFL (2 : 1) was calculated as a robust biocatalyst composition which showed higher activity retention and protein loading. This nano-bio-conjugate was then characterized in detail with physical and biochemical techniques using SEM, TEM, FTIR, Km, Vmax, catalytic efficiency and (%) water content analysis. This developed biocatalyst was further used for practical biocatalytic applications such as O-acylation reactions. Various reaction parameters were optimized in detail like reactant molar ratio (2 : 3.5), solvent, MCNT : PFL biocatalyst amount (36 mg), temperature (50°C) etc. The developed biocatalytic protocol was then extended to synthesize several (twenty-two) industrially important acylated moieties with an excellent yield, these products are well characterized by 1HNMR, 13CNMR and GCMS analysis. Moreover in the present study, we have reviewed the potential industrial applications of various synthesized compounds. Also, we have studied the thermodynamic aspect which demonstrated more feasibility of use of immobilized MCNT : PFL lipase over free lipase. Interestingly, immobilized MCNT : PFL lipase showed 2.3 fold higher catalytic activity than free PFL. Besides this, the biocatalyst was efficiently recycled for up to five cycles. Thus the present protocol demonstrated, (i) synthesis of nano-bio-conjugates as a bio-catalyst, (ii) detailed physical-biochemical characterization of nano-bio-conjugates, (iii) optimization of the biocatalytic protocol (iv) practical biocatalytic applications along with a mechanistic study (v) a thermodynamic feasibility study and (vi) recyclability study. 2015
- Badgujar, Kirtikumar Chandulal,Sasaki, Takehiko,Bhanage, Bhalchandra Mahadeo
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p. 55238 - 55251
(2015/07/07)
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- Achieving control over the branched/linear selectivity in palladium-catalyzed allylic amination
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Palladium-catalyzed reaction of unsymmetrical allylic electrophiles with amines gives rise to regioisomeric allylic amines. We have found that linear products result from the thermodynamically controlled isomerization of the initially formed branched products. The isomerization is promoted by protic acid and active palladium catalyst. The use of base shuts down the isomerization pathway and allows for the preparation and isolation of branched allylic amines. Solvent plays a key role in achieving high kinetic regioselectivity and in controlling the rate of isomerization. The isomerization can be combined with ring-closing metathesis to afford the synthesis of exocyclic allylic amines from their endocyclic precursors.
- Dubovyk, Igor,Watson, Iain D. G.,Yudin, Andrei K.
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p. 1559 - 1575
(2013/03/28)
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- Lewis basic ionic liquid as an efficient and facile catalyst for acetylation of alcohols, phenols, and amines under solvent-free conditions
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The Lewis basic ionic liquid 1,8-diazabicyclo[5.4.0]undec-7-en-8-ium acetate was employed for the acetylation of various phenols, alcohols, and amines in good-to-excellent yields at 50 C under solvent-free conditions in a short time. Compared with existing methods based on conventional catalysts and toxic solvents, the reported method is simple, mild and environmentally viable. Furthermore, the ionic liquid was conveniently separated from the products and easily recycled to catalyze other acetylation reactions with excellent yields. .
- Ji, Li,Qian, Chao,Chen, Xin-Zhi
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p. 369 - 374
(2013/05/21)
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- Ni- and pd-catalyzed synthesis of substituted and functionalized allylic boronates
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Two highly efficient and convenient methods for the synthesis of functionalized and substituted allylic boronates are described. In one procedure, readily available allylic acetates are converted to allylic boronates catalyzed by Ni/PCy3 or Ni/PPh3 complexes with high levels of stereoselectivity and in good yields. Alternatively, the borylation can be accomplished with commercially available Pd catalysts [e.g., Pd 2(dba)3, PdCl2, Pd/C], starting with easily accessed allylic halides.
- Zhang, Ping,Roundtree, Ian A.,Morken, James P.
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supporting information; scheme or table
p. 1416 - 1419
(2012/06/01)
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- Palladium-catalyzed ring-contraction and ring-expansion reactions of cyclic allyl amines
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Ring around the rosy: An amino group can act as the leaving group or the nucleophile in a palladium-catalyzed allylic amination. As a result, readily accessible cyclic amines can be either ring contracted or ring expanded (see scheme).
- Dubovyk, Igor,Pichugin, Dmitry,Yudin, Andrei K.
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supporting information; experimental part
p. 5924 - 5926
(2011/08/04)
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- Cobalt-catalyzed reductive allylation of alkyl halides with allylic acetates or carbonates
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An efficient method for the direct allylation of alkyl halides catalyzed by simple cobalt(II) bromide has been developed. This reaction, using a variety of substituted allylic acetates or carbonates, provides the linear product as the major product. It displays broad substrate scope and good functional group tolerance. Copyright
- Qian, Xin,Auffrant, Audrey,Felouat, Abdellah,Gosmini, Corinne
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supporting information; experimental part
p. 10402 - 10405
(2011/12/03)
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- Catalytic asymmetric synthesis of chiral allylic esters
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A broadly useful catalytic enantioselective synthesis of branched allylic esters from prochiral (Z)-2-alkene-1-ols has been developed. The starting allylic alcohol is converted to its trichloroacetimidate intermediate by reaction with trichloroacetonitrile, either in situ or in a separate step, and this intermediate undergoes clean enantioselective SN2′ substitution with a variety of carboxylic acids in the presence of the palladium(II) catalyst (Rp,S)-di-μ-acetatobis[(η5- 2-(2′-(4′-methylethyl)oxazolinyl)cyclopentadienyl-1-C,3′-N) (η4-tetraphenylcyclobutadiene)cobalt]dipalladium, (R p,S)-[COP-OAc]2, or its enantiomer. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined.
- Cannon, Jeffrey S.,Kirsch, Stefan F.,Overman, Larry E.
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supporting information; experimental part
p. 15185 - 15191
(2010/12/25)
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- Chasing the proton culprit from palladium-catalyzed allylic amination
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We have found that the addition of base has a significant effect on palladium-catalyzed allylic amination. The long-standing problem of controlling the branched-to-linear ratio has been solved. In the presence of DBU and inexpensive, readily available ligands, palladium-catalyzed allylation proceeds under kinetic control, leading to high branched selectivity. Given the widespread utility of palladium-catalyzed allylic amination, we expect that these findings will be relevant in many areas ranging from asymmetric catalysis to target-oriented synthesis. Copyright
- Dubovyk, Igor,Watson, Iain D. G.,Yudin, Andrei K.
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p. 14172 - 14173
(2008/09/18)
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- PROCESSES FOR PRODUCING 3-METHYL-2-BUTENYL ACETATE
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The present invention relates to a method for producing 3-methyl-2-butenyl acetate which comprises reacting 3-methyl-2-buten-1-ol with acetic anhydride in the presence of an inorganic base catalyst and a method for producing purified 3-methyl-2-butenyl acetate which comprises subjecting crude 3-methyl-2-butenyl acetate to a step (A) of contacting it with an aqueous solution of an alkali metal hydrogen sulfite, or a step (B) of contacting it with an aqueous solution of a base, or both steps (A) and (B).
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Page/Page column 4
(2008/06/13)
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- New insights into the mechanism of palladium-catalyzed allylic amination
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A comparative investigation into palladium-catalyzed allylic amination of unsubstituted aziridines and secondary amines has been carried out. The use of NH aziridines as nucleophiles favors formation of valuable branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. Our study provides evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. In contrast, the branched allyl products obtained from unsubstituted aziridines do not undergo the isomerization process. Crossover experiments indicate that the isomerization of branched allylamines is bimolecular and is catalyzed by Pd0. The reaction has significant solvent effect, giving the highest branched-to-linear ratios in THF. This finding can be explained by invoking the intermediacy of σ-complexes, which is consistent with NMR data. The apparent stability of branched allyl aziridines towards palladium-catalyzed isomerization is attributed to a combination of factors that stem from a higher degree of s-character of the aziridine nitrogen compared to other amines. The reaction allows for regio- and enantioselective incorporation of aziridine rings into appropriately functionalized building blocks. The resulting methodology addresses an important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained in this study should facilitate synthesis of complex heterocycles, design of new ligands to control branched-to-linear ratio, as well as absolute stereochemistry of allylamines.
- Watson, Iain D. G.,Yudin, Andrei K.
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p. 17516 - 17529
(2007/10/03)
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- Practical synthesis of allylic silanes from allylic esters and carbamates by stereoselective copper-catalyzed allylic substitution reactions
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The first copper-catalyzed allylic substitution reactions of allylic acetates and carbamates employing a bis(triorganosilyl)zinc reagent are reported. This novel procedure avoids the use of stoichiometric amounts of copper salts which are usually mandatory with this chemistry. Application of this methodology to standard model substrates substantiates a high diastereoselectivity for the double bond geometry (E:Z) as well as the relative configuration (syn:anti).
- Oestreich, Martin,Auer, Gertrud
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p. 637 - 640
(2007/10/03)
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- PROCESSES FOR SYNTHESIZING ESTERS BY 1,4-ADDITION OF ALKANOIC ACIDS TO MYRCENE OR ISOPRENE
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Processes are disclosed for synthesizing esters useful in flavorings and fragrances from ?-pinene, myrcene and/or isoprene. The esters can be used in the manufacture of citral, precursors to citral and other products or precursors such as vitamins, nutritional supplements, flavorings, fragrances and other products. The process includes a 1,4-addition of an alkanoic acid to the conjugated diene of myrcene (which can be generated from ?-pinene) or the conjugated diene of isoprene to produce esters thereof.
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Page/Page column 20-21
(2008/06/13)
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- Reaction of orthoesters with alcohols in the presence of acidic catalysts: A study
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Allylic and benzylic alcohols are converted into corresponding unsymmetrical ethers when reacted with various orthoesters in the presence of montmorillonite KSF at ambient temperature. A detailed study has been undertaken to examine the mechanism and generality of these reactions with regard to various acidic catalysts, which reveal interesting competitive reactions mainly O-acetylation, together with trace amount of dimerized product. The type of the side product and their relative quantity depends upon the nature of the catalyst employed. Furthermore, the low yields of the Claisen rearrangement product obtained from allylic alcohols under heating is rationalized due to the formation of some of these products.
- Sampath Kumar,Joyasawal, Sipak,Reddy,Pawan Chakravarthy,Krishna,Yadav
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p. 1686 - 1692
(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
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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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- Ruthenium(III) chloride catalyzed acylation of alcohols, phenols, thiols, and amines
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Ruthenium(III) chloride catalyzes the acylation of a variety of phenols, alcohols, thiols, and amines under mild conditions. Some of the major advantages of this method are high yields, short reaction times, ease of operation, and compatibility with other protecting groups.
- Kanta De, Surya
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p. 2919 - 2922
(2007/10/03)
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- Unusual Selectivity of Unprotected Aziridines in Palladium-Catalyzed Allylic Amination Enables Facile Preparation of Branched Aziridines
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Functionalized branched aziridines can be prepared in high yields and with high levels of regioselectivity using unprotected aziridines as nitrogen sources in palladium-catalyzed allylic amination. High levels of enantioselectivity can be achieved with BINAP on palladium. This methodology allows for strategic placement of an aziridine-containing fragment within a complex molecule environment for further elaboration. Copyright
- Watson, Iain D. G.,Styler, Sarah A.,Yudin, Andrei K.
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p. 5086 - 5087
(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
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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)
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- Aluminium dodecatungstophosphate (AlPW12O40) as a highly efficient catalyst for the selective acetylation of -OH, -SH and -NH2 functional groups in the absence of solvent at room temperature
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AlPW12O40 was found to be an effective catalyst for the selective acetylation of alcohols, thiols, and amines in the absence of solvent at room temperature.
- Firouzabadi, Habib,Iranpoor, Nasser,Nowrouzi, Farhad,Amani, Kamal
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p. 764 - 765
(2007/10/03)
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- Fluoroboric acid adsorbed on silica gel as a new and efficient catalyst for acylation of phenols, thiols, alcohols, and amines
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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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- Electrostatic catalysis by ionic aggregates: Scope and limitations of Mg(ClO4)2 as acylation catalyst
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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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- Iron-catalyzed electrochemical allylation of carbonyl compounds by allylic acetates
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Homoallylic alcohols were synthesized from aldehydes or ketones and allylic acetates, using an electrochemical process catalyzed by iron complexes. We first studied the reactivity of allyl acetate, using N,N-dimethylformamide (DMF) or acetonitrile (AN) as solvent, FeBr2 as catalyst, and Fe as the sacrificial anode. Then we tested the regioreactivity of crotyl acetate and other allylic derivatives.
- Durandetti, Muriel,Meignein, Clotilde,Perichon, Jacques
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p. 3121 - 3124
(2007/10/03)
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- Synthesis of Symmetrical Trisubstituted Olefins by Cross Metathesis
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(Matrix Presented) Trisubstituted alkenes have been prepared via intermolecular olefin cross-metathesis (CM) between α-olefins and symmetrically 1,1-disubstituted olefins using an imidazolylidene ruthenium benzylidene complex. Of particular interest is th
- Chatterjee, Arnab K.,Sanders, Daniel P.,Grubbs, Robert H.
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p. 1939 - 1942
(2007/10/03)
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- Synthesis of β-ionone
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Preparation of β-ionone by a reaction sequence starting from acetone is described.
- Vani,Chida,Srinivasan,Chandrasekharam,Singh
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p. 219 - 224
(2007/10/03)
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- Palladium(II)-catalyzed phenylation of unsaturated compounds using phenylantimony chlorides under air
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Diphenylantimony chloride and phenylantimony dichloride, mainly the former, react smoothly with alkenes in acetonitrile at r.t. in the presence of a catalytic amount of Pd(OAc)2 under air to afford the corresponding phenylated alkenes (Heck-type reaction). The addition of AgOAc as reoxidant is not necessary for this reaction in sharp contrast to similar reactions using triarylstibines. The oxygen absorption is confirmed in this catalytic reaction and the reaction does not proceed catalytically in palladium(II) under inert gases, such as nitrogen or argon. Even under air the addition of a radical scavenger stopped the reaction. The regeneration of PhPdOAc species from Ph2SbCl, HPdOAc species and oxygen is proposed as a key step in the catalytic cycle where oxygen-containing radical species might be present as intermediates.
- Matoba, Kazutaka,Motofusa, Shin-Ichi,Sik Cho, Chan,Ohe, Kouichi,Uemura, Sakae
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- Methods for preparing prenyl alcohol
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Methods for preparing 3-methyl-2-buten-1-ol (prenyl alcohol) from 2-methyl-1,3-butadiene (isoprene) and carboxylic acids are disclosed. Carboxylic acids which can be used in the process have a Ka (relative to water) greater than 10-4 ; dichloroacetic acid is especially preferred. The process involves the slow (e.g., dropwise) addition of isoprene to the carboxylic acid to form a prenyl ester. The ester-formation reaction proceeds at room temperature in most cases; use of an organic base catalyst, preferably a sodium or potassium salt of the reactant carboxylic acid, improves the yield. The resultant prenyl ester can be converted to prenyl alcohol by reaction with a base. Prenyl alcohol can be readily converted to citral, a chemical intermediate in the synthesis of vitamins A and E, and several widely-used carotenoids.
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- Biosynthesis of 2-Methylbutyl, 2-Methyl-2-butenyl, and 2-Methylbutanoate Esters in Red Delicious and Granny Smith Apples Using Deuterium-Labeled Substrates
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2-Methylbutanoate esters, especially ethyl 2-methylbutanoate, are key contributors to fruit aroma. The biosynthetic origins and interconversions of 2-methylbutyl and 2-methylbutanoate esters in Red Delicious and Granny Smith apples were determined by feeding deuterium-labeled substrates with GC-MS identification of the deuterated aroma volatiles produced. Deuterium-labeled isoleucine was fed to apple peel, and 2-methylbutanoic-d3 acid, 2-methylbutanol-d3, and ethyl 2-methylbutanoate-d3 were fed as vapor to whole apples. An array of labeled 2-methylbutyl and 2-methylbutanoate esters was produced from each substrate with significant differences in products and product distributions between the two apple cultivars. Novel 2-methyl-(2E)-butenyl esters were identified as biosynthetic products in the aroma of Red Delicious but not Granny Smith apples.
- Rowan, Daryl D.,Lane, Heather P.,Allen, John M.,Fielder, Simon,Hunt, Martin B.
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p. 3276 - 3285
(2007/10/03)
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- Alcoholyses and acetolyses of allylic and tertiary benzylic alcohols catalyzed by 2,3-dichloro-5,6-dicyanobenzoquinone
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Allylic and tertiary benzylic alcohols can be converted into their corresponding ethers and acetates selectively and efficiently in the presence of catalytic amounts of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ).
- Iranpoor,Mottaghinejad
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p. 2253 - 2260
(2007/10/02)
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- Cobalt(II)-Catalyzed Conversion of Allylic Alcohols/Acetates to Allylic Amides in the Presence of Nitriles
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Various secondary allylic alcohols or their acetates and tertiary allylic alcohols can be converted to the corresponding transposed allylic amides in the presence of a catalytic quantity of cobalt(II) chloride and acetic anhydride in acetonitrile.Tertiary alcohols undergo complete rearrangement whereas secondary ones afford a mixture of regioisomers.Moderate yields of amides are also obtained by reacting acrylonitrile with secondary alcohols in 1,2-dichloroethane.The presence of acetic anhydride or acetic acid is crucial to the formation of amides as the absence of the former affords no amides and the allylic alcohols are mainly recovered as regioisomeric mixtures.The regioselectivity during amide formation can be enhanced by using cobalt complexes 14-16 in acetic acid medium.Some preliminary studies indicate that these reactions are proceeding via an ?-allyl complex or tight ion pair rather than a sigmatropic rearrangement of acetamidate obtained in a Pinner reaction.
- Mukhopadhyay, Manoj,Reddy, M. Madhava,Maikap, G. C.,Iqbal, Javed
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p. 2670 - 2676
(2007/10/02)
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- COBALT(II) CHLORIDE CATALYSED CONVERSION OF ALLYLIC ALCOHOLS TO REARRANGED ALLYLIC AMIDES
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Secondary and tertiary allylic alcohols can be converted to the corresponding allylically rearranged amides and acetates in presence of a catalytic quantity of cobalt(II) chloride and acetic anhydride in acetonitrile.Tertiary alcohols undergo complete rearrangement whereas the secondary ones yield a mixture of regioisomers.
- Nayyar, Naresh K.,Reddy, M. Madhava,Iqbal, Javed
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p. 6965 - 6968
(2007/10/02)
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- C-Allylation of L-Ascorbic acid under Palladium(0) Catalysis
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L-Ascorbic acid (1) is efficiently allylated at C-2 with primary and secondary allylic substrates by using palladium(0) catalysis.Hydrogenation of the resulting allylated compounds 6 affords L-ascorbic acid derivatives with saturated chains at C-2.
- Moreno-Manas, Marcial,Pleixats, Roser,Villarroya, Merce
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p. 4925 - 4928
(2007/10/02)
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- New Functionalized Horner-Wadsworth-Emmons Reagents: Useful Building Blocks in the Synthesis of Polyunsaturated Aldehydes. A Short Synthesis of (+/-)-(E,E)-Coriolic Acid
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The new Horner-Wadsworth-Emmons reagents 4 and 5 transform carbonyl compounds into 2,4-pentadienals and 3-methyl-2,4-pentadienals, respectively.Reagent 4 gives good yields of the desired products with a variety of aldehydes and ketones; reagent 5 generally gives good yields with aldehydes, but gives lower yields with ketones.The reactions proceed under mild conditions and give the products as predominantly 2E,4E isomers, with moderate to good stereoselectivity.In general, pure samples of the 2E,4E-dienals can be obtained after chromatography.Reagents 4 have been used in the key step in a short synthesis of (+/-)-13-hydroxy-9(E),11(E)-octadecanoic acid ((E,E)-coriolic aicd, 45).
- Kann, Nina,Rein, Tobias,Akermark, Bjoern,Helquist, Paul
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p. 5312 - 5323
(2007/10/02)
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- Regiospecific Preparation of Primary Allyl Acetates (2-Alkenyl Acetates)
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The reaction of primary, secondary and tertiary allyl alcohols 1 with anhydrous magnesium iodide in benzene gives regiospecifically the primary allyl iodides 2.The corresponding primary allyl acetates 3 are obtained regiospecifically by reaction of 2 with anhydrous sodium acetate in dimethylformamide.
- Martinez, Antonio Garcia,Villalobos, Angeles Cruces,Ruiz, Manuel Oliver
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