- PREPARATION D'ESTERS γ-ETHYLENIQUES PAR ALLYLATION DU REACTIF DE REFORMATSKY EN PRESENCE DE SELS DE CUIVRE
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The Reformatsky organozinc compounds react easily with allylic halides in the presence of copper salts.The reaction is stereoselective and can be made regioselective with a proper choice of reaction conditions.
- Gaudemar, M.
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- Allyltris(trimethylsilyl)silane as Radical Allylating Agent for Organic Halides
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Reaction of allyltris(trimethylsilyl)silane with organic halides under the free radical conditions resulted in allylation of the halides in moderate to good yields.The presence of three trimethylsilyl groups on the silicon could enhance the homolytic dissociation of a Si-C bond in the β-silylalkyl radical.
- Kosugi, Masanori,Kurata, Hiroshi,Kawata, Ken-ichi,Migita, Toshihiko
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- Efficient one-pot ring-opening/aldol reactions using (cyclopropyl) methylstannanes
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(Cyclopropyl)methylstannanes, substituted with an electron-withdrawing group, have been found to be effective homoallylating reagents of aldehydes and ketones. The reaction proceeds by Lewis-acid catalyzed ring opening, followed by an aldol condensation of the resulting enolate, providing homoallylation products in excellent yields. The diastereoselectivity of the process was found to be highly dependent upon the temperature and the solvent, the reaction giving mainly anti adducts at -78°C and syn compounds at 0°C.
- Leroy, Bernard
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- A New Route to the Prostaglandin Skeleton via Radical Alkylation. Synthesis of 6-Oxoprostaglandin E1
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A new, mild, and efficient method for the construction of the prostanoid skeleton involving cuprate addition to α-(phenylseleno)cyclopentenones followed by radical-based coupling to the resulting products with allylstannane derivatives is described.The method is applied to the synthesis of 6-oxoprostaglandin E1, a biologically active and naturally occurring compound.
- Toru, Takeshi,Yamada, Yoshio,Ueno, Toshio,Maekawa, Eturo,Ueno, Yoshio
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- Solvent- and structure-dependent regioselectivity in the boron-mediated aldol reaction of 2-(1,3-dioxolan-2-yl)ethyl ethyl ketones
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The regioselectivity of the Chx2BCl/Et3N-mediated (Chx = cyclohexyl) aldol reactions of ketones of general structure 2 has been studied and was shown to depend on both ketone structure and solvent. Useful levels of regioselectivity in favour of any of the two possible regioisomers were obtained in either pentane or diethyl ether. The relative configuration of the aldol products was assigned by 1H NMR studies of six-membered-ring derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Lanners, Steve,Norouzi-Arasi, Hassan,Khiri, Naima,Hanquet, Gilles
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- Diastereoselective and Stereodivergent Synthesis of 2-Cinnamylpyrrolines Enabled by Photoredox-Catalyzed Iminoalkenylation of Alkenes
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A photoredox-catalyzed iminoalkenylation of γ-alkenyl O-acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)- and (Z)-cinnamylpyrrolines are accessible depending on the reaction solvent. In dichloromethane, (E)-cinnamylpyrrolines are produced through a photoredox-mediated single-electron-transfer process. In tetrahydrofuran, (Z)-cinnamylpyrrolines are generated by photocatalytic contra-thermodynamic E-to-Z isomerization of (E)-cinnamylpyrrolines though an energy-transfer pathway. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated.
- Shen, Xu,Huang, Congcong,Yuan, Xiang-Ai,Yu, Shouyun
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supporting information
p. 9672 - 9679
(2021/03/16)
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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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- Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
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A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
- Lai, Yin-Long,Huang, Jing-Mei
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supporting information
p. 2022 - 2025
(2017/04/28)
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- Merger of Johnson-Claisen rearrangement and alkoxycarbonylation for atom efficient diester synthesis
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The orthoester Johnson-Claisen rearrangement of allyl alcohol with triethyl orthoacetate for the synthesis of ethyl 4-pentenoate has been optimized, in order to allow for a selective and efficient subsequent alkoxycarbonylation using formates in an atom efficient manner. Diethyl adipate was successfully yielded in up to 89% applying very low orthoester excess, formic acid and mild reaction conditions in an innovative, one-pot procedure.
- Seidensticker, Thomas,M?ller, David,Vorholt, Andreas J.
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supporting information
p. 371 - 374
(2016/01/12)
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- An improved solvent-free system for the microwave-assisted decarboxylation of malonate derivatives based on the use of imidazole
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A comparative study of the thermal and microwave-assisted decarboxylation of a series of mono- and disubstituted monohydrolyzed malonate derivatives has been carried out. It has been found out that in both circumstances the use of imidazole has a profound effect on the success of the reaction. In general terms the assistance of microwave irradiation accelerates the decarboxylation process significantly and, at the same time, permits the use of minored temperatures with respect to the thermal via. It has been also found that both the thermal and the microwave-assisted transformation can be developed under solvent-free conditions.
- Tellitu, Imanol,Beitia, Itziar,Díaz, Marta,Alonso, Argi?e,Moreno, Isabel,Domínguez, Esther
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p. 8251 - 8255
(2015/10/05)
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- Hydrogenation of γ-valerolactone in ethanol over Pd nanoparticles supported on sulfonic acid functionalized MIL-101
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A ligand-based solid solution approach is employed to incorporate sulphonic acid functional groups into the porous coordination polymer Cr-MIL-101. Loaded with Pd nanoparticles these Pd/MIL-101-SO3H materials act as bifunctional catalysts for the one-pot conversion of γ-valerolactone into ethyl valerate (up to 83% yield). The catalysts were extensively characterized before and after reaction. The influence of the sulfonic acid group density and the reaction conditions on the catalytic activity was systematically investigated and the reaction network for γ-valerolactone upgrading was discussed.
- Zhang, Damin,Ye, Feiyang,Guan, Yejun,Wang, Yimeng,Hensen, Emiel J. M.
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p. 39558 - 39564
(2014/12/09)
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- Synthesis, antiviral activity, and conformational studies of a P3 aza-peptide analog of a potent macrocyclic tripeptide HCV protease inhibitor
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BILN 2061 is a macrocyclic tripeptide inhibitor of hepatitis C virus NS3-4A protease that has shown efficacy in the clinic for treating patients infected with HCV. We have synthesized a P3 aza-peptide analog of a potent macrocyclic tripeptide inhibitor closely related to BILN 2061. This aza-derivative was found to be >2 orders of magnitude less active than the parent macrocycle in both isolated enzyme (HCV NS3-4A) and HCV subgenomic replicon assays. NMR studies of P3 aza-peptides revealed these compounds adopt a β-turn conformation stabilized by an intramolecular H-bonding interaction. Molecular models of these structures indicate a d-like configuration of the P3 aza-residue. Thus, the configurationally undefined nature at P3 in the aza-peptide allows the compound to adopt an H-bond stabilized conformation that is substantially different from that necessary for tight binding to the active site of HCV NS3 protease.
- Randolph, John T.,Zhang, Xiaolin,Huang, Peggy P.,Klein, Larry L.,Kurtz, Kevin A.,Konstantinidis, Alex K.,He, Wenping,Kati, Warren M.,Kempf, Dale J.
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p. 2745 - 2750
(2008/12/21)
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- A PROCESS FOR THE PREPARATION OF AN ALKYL ALKENOATE
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A process for the preparation of an alkyl alkenoate, wherein a lactone of the general molecular formula (I) wherein n is 1, 2 or 3, R1 is a C1-C4 alkyl group, and R2, R3 and R4 are, independently, a H atom or a C1-C4 alkyl group, is reacted with a C1-C4 alkyl alcohol in a liquid phase in the presence of a strong acid catalyst at transesterification conditions to form the alkyl alkenoate, wherein alkyl alkenoate and alcohol are continuously removed from the liquid phase by distillation.
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Page/Page column 11-14
(2008/06/13)
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- VALPROIC ACID ANALOGUES AND PHARMACEUTICAL COMPOSITIONS THEREOF
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Analogues of valproic acid useful in treating neuroaffective disorders including convulsions, bipolar disorder, and migraine headache are disclosed. The analogues are halide substituted analogues, cyclic analogues, and conjugated diene analogues of valproic acid. Pharmaceutical compositions or prodrugs containing the analogues or pharmaceutically acceptable salts thereof are disclosed. Methods of making the compounds and treating mammals with neuroaffective disorders are also disclosed.
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- A mild and efficient protocol for the conversion of carboxylic acids to olefins by a catalytic decarbonylative elimination reaction
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A new method for the conversion of aliphatic carboxylic acids to olefins under unprecedented mild conditions is disclosed, wherein the carboxylic acids are converted in situ with pivalic anhydride to the mixed anhydrides, which regioselectively add to a PdCl2-DPE-Phos catalyst. At a temperature of only 110°C, smooth decarbonylation and β-hydride elimination occur, and the corresponding olefins along with CO, CO2 and pivalic acid are liberated.
- Goossen, Lukas J.,Rodriguez, Nuria
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p. 724 - 725
(2007/10/03)
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- POLYMERIZATION OF OLEFINS
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Olefins containing selected functional groups such as silyl, ether and alkenyl, and often containing a blocking group, may be copolymerized with unsubstituted olefins such as ethylene and propylene in the presence of certain coordination compounds of nickel or palladium. The resulting polymers are useful as molding resins, elastomers, in adhesives and for films.
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- Radical addition to carbenoids. Chain reactions of α-diazo carbonyl compounds with triorganotin hydrides, tris(trimethylsilyl)silane and allyltributylstannane
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α-Diazo ketones RC(O)CH=N2 react with tributyltin hydride at 60°C in benzene to give the corresponding α-stannyl ketones RC(O)CH2SnBu3, which exist in equilibrium with the stannyl enol ether tautomers R(Bu3SnO)C=CH2. The reactions are initiated by di-tert-butyl hyponitrite and follow a free-radical chain mechanism. Triphenyltin hydride and tris(trimethylsilyl)silane [(TMS)3SiH] react similarly, the latter to yield the α-silyl ketone RC(O)CH2Si(TMS)3 which does not isomerise to the more stable silyl enol ether R[(TMS)3SiO]C=CH2 under the reaction conditions. This result indicates that TMS3Si. reacts at the α-carbon atom of the α-diazo ketone to give R(CO)CHSiTMS3, probably via an initial diazenyl radical adduct; triorganotin radicals are assumed to react in the same way. When the group R in the α-diazo ketone is but-3-enyl, the intermediate α-metalloalkyl radical undergoes 5-exo-cyclisation. Allyltributylstannane reacts with α-diazo ketones and with ethyl α-diazoacetate in refluxing benzene, in the presence of 2,2′-azo(2-methylpropionitrile) as initiator, to give butenyl ketones RC(O)CH2CH2CH=CH2 and ethyl pent-4-enoate, respectively, after a hydrolytic work-up.
- Dang, Hai-Shan,Roberts, Brian P.
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p. 769 - 775
(2007/10/03)
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- Application of Microwave Heating Technique for Rapid Synthesis of γ,δ-Unsaturated Esters
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The use of microwave heating technique for the acceleration of ortho ester Claisen rearrangement (a three step transformation) is described.Irradiation of a DMF solution of the allyl alcohol 5, triethyl orthoacetate and propionic acid (catalytic) in an Erlenmeyer flask for 10 minutes in a microwave oven generated the ester 8 in 83percent yield.Analogously, ortho ester Claisen rearrangement of a variety of allyl and propargyl alcohols (9, 12-22) were achieved.The formation of the diester 10 from 2-butyne-1,4-diol (9) via the ortho ester Claisen rearrangement of two allyl alcohol moieties (involving six steps) in 15 minutes, demonstrates the versatility of the microwave heating technique.
- Srikrishna, Adusumilli,Nagaraju, Sankuratri,Kondaiah, Paturu
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p. 1809 - 1816
(2007/10/02)
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- Picosecond Radical Kinetics. Alkoxycarbonyl Accelerated Cyclopropylcarbinyl Radical Ring Openings
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Rate constants and Arrhenius functions for ring openings of the (trans-2-ethoxycarbonylcyclopropyl)methyl radical and the (trans-2-tert-butoxycarbonylcyclopropyl)methyl radical were determined by the PTOC-thiol method with PhSeH trapping.At 25 deg C, these radicals rearrange with rate constants of 7 and 12*1010 s-1, respectively.
- Choi, Seung-Yong,Newcomb, Martin
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p. 657 - 664
(2007/10/02)
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- Ethoxycarbonyl Acceleration of Cyclopropylcarbinyl Radical Ring Opening
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Rate constants for ring opening of the methyl radical were determined by competition kinetics employing benzeneselenol trapping.
- Newcomb, Martin,Choi, Seung-Yong
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p. 6363 - 6364
(2007/10/02)
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- Acceleration of Ortho Ester Claisen Rearrangement by a Commercial Microwave Oven
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Microwave irradiation, using a commercial microwave oven accelerates (in 10-15 min) the three-step ortho ester Claisen rearrangement of allyl and propynyl alcohols in dry DMF in open Erlenmeyer flasks.
- Srikrishna, Adusumilli,Nagaraju, Sankuratri
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p. 311 - 312
(2007/10/02)
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- STEREOKONVERGENT SYNTHESIS OF A POTENT MOSQUITO LARVICIDE : (2E,4E,8E,10Z)-N-(2-METHYL PROPYL)-2,4,8,10-DODECATETRAENEAMIDE
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First total synthesis of (2E,4E,8E,10Z)-N-(2-methyl propyl)-2,4,8,10-dodecatetraene amide (1), by the condensation of (4E,6Z)-octadienyl phenyl sulfone (2) and ethyl-4-oxobutanoate (3) followed by double elimination reaction, which involves easily accessible reagents and simple transformations is described.
- Sharma, G. V. M.,Shekharam, T.,Upender, V.
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p. 5665 - 5672
(2007/10/02)
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- Fructose 1,6-Diphosphate Aldolase Catalyzed Stereoselective Synthesis of C-Alkyl and N-Containing Sugars: Thermodynamically Controlled C-C Bond Formations.
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Fructose 1,6-diphosphate aldolase catalyzed aldol condensations have been used in syntheses of several new N-containing and C-alkyl sugars on 4-20 mmol scales.The enzyme is highly specific for dihydroxyacetone phosphate as donor but accepts a number of achiral and chiral aldehydes (both D and L isomers) as acceptors.Due to the reversible nature of the aldol reaction, a thermodynamically controlled approach was employed for the syntheses in which racemic aldehydes were used as substrates and thermodynamically more stable products were preferentially produced.
- Durrwachter, John R.,Wong, Chi-Huey
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p. 4175 - 4181
(2007/10/02)
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- A BASE-MEDIATED ALTERNATIVE TO THE ORTHOESTER CLAISEN REARRANGEMENT
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The bromo-acetals (2), which may be prepared from allylic alcohols by reaction with 1,2-dibromo-1-ethoxyethane, may be converted in HMPA-Et3N to allyl 1-ethoxyvinyl ethers (1, R5=Et) which undergo Claisen rearrangement.
- Lidbetter, Paul S.,Marples, Brian A.
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p. 1529 - 1534
(2007/10/02)
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- Synthesis of 2,3-Secopyrethroids
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Some 2,3-secopyrethroids, viz. 3-phenoxybenzyl 2-alkyl-5-methylhex-4-enoates and 2-alkylpent-4-enoates (VI a-l) have been synthesized starting from diethyl malonate, employing simple reactions like alkylation, decarboethoxylation and transesterification.These esters exhibit insecticidal activity against musca domestica and adult Aedes aegyptii.
- Randad, R. S.,Kulkarni, G. H.
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p. 1085 - 1087
(2007/10/02)
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- CATIONIC CYCLIZATIONS INITIATED BY ELECTROCYCLIC CLEAVAGE OF CYCLOPROPANES. SYNTHESIS OF LACTONES, TETRAHYDROPYRANS, AND TETRAHYDROFURANS
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The electrocyclic opening of cyclopropane derivatives containing internal nucleophilic groups provides a new route to vinyl lactones, tetrahydropyrans, and tetrahydrofurans.
- Danheiser, Rick L.,Morin, John M.,Yu, Melvin,Basak, Ajoy
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p. 4205 - 4208
(2007/10/02)
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- Synthesis of Carnitine Homologues. Reactions of Tertiary Amines with Epoxy Esters
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A series of new carnitine homologues, 4-hydroxy-5-(trialkylammonio)pentanoates (2) and 5-hydroxy-6-(trialkylammonio)hexanoates (3), has been synthesized.The key step in this synthesis was the reaction of an epoxy ester with a tertiary amine to effect epoxide opening and hydrolysis in one step.The generality of this reaction is discussed, and the synthetic approach to 2 and 3 is compared to previously published routes to carnitine and its analogues.Attempts to apply the new reaction scheme to carnitine itself are described.
- Degenhardt, Charles R.
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p. 2763 - 2766
(2007/10/02)
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- A NOVEL SYNTHESIS OF TERMINAL OLEFINS BY ANODIC OXIDATION OF CARBOXYLIC ACIDS HAVING A TRIMETHYLSILYL GROUP ON THE β-POSITION
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Anodic oxidation of carboxylic acids having a trimethylsilyl group on the β-position gave exclusively terminal olefins in reasonable yields.
- Shono, Tatsuya,Ohmizu, Hiroshi,Kise, Naoki
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p. 1517 - 1520
(2007/10/02)
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- Crown ether catalysis of decarboxylation and decarbalkoxylation of β-keto acids and malonates: a synthetic application
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The effect of 18-crown-6 ether on the decarboxylation rates of the sodium and potassium salts of 3-camphor carboxylic acid 1 and of 1-carbomethoxy-1-carboxycyclohexane 2 was studied.For 2 the K-18C6 salt reacted ca. 104 times faster than the parent acid.This remarkable difference in reactivity was used in developing a one-pot, two-step procedure for decarbalkoxylation of malonic esters.This procedure was then applied to a range of malonates, β-keto esters, and an α-cyano ester.The effect of 15C5, other cations, and good nucleophiles was also studied.
- Hunter, Duncan H.,Patel, Vijay,Perry, Richard A.
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p. 2271 - 2277
(2007/10/02)
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