- BiCl3-Facilitated removal of methoxymethyl-ether/ester derivatives and DFT study of -O-C-O- bond cleavage
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A simple method for the cleavage of methoxymethyl (MOM)-ether and ester derivatives using bismuth trichloride (BiCl3) is described. The alkyl, alkenyl, alkynyl, benzyl and anthracene MOM ether derivatives, as well as MOM esters of both aliphatic and aromatic carboxylic acids, were deprotected in good yields. To better understand the molecular roles of BiCl3and water for MOM cleavage, two possible binding pathways were investigated using the density functional theory (DFT) method. The theoretical results indicate the differential initial binding site preferences of phenolic and alcoholic MOM substrates to the Bi atom and suggest that water plays a key role in facilitating the cleavage of the MOM group.
- Pacherille, Angela,Tuga, Beza,Hallooman, Dhanashree,Dos Reis, Isaac,Vermette, Mélodie,Issack, Bilkiss B.,Rhyman, Lydia,Ramasami, Ponnadurai,Sunasee, Rajesh
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supporting information
p. 7109 - 7116
(2021/05/03)
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- Synthesis and Photoswitching Properties of Bioinspired Dissymmetric I-Pyrone, an Analogue of Cyclocurcumin
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Cyclocurcumin (CC), a turmeric curcuminoid with potential therapeutic properties, is also a natural photoswitch that may undergo E/Z photoisomerization under UV light. To be further exploited in relevant biological applications, photoactivation under near-infrared (NIR) irradiation is required. Such requirement can be met through opportune chemical modifications, by favoring two-photon absorption (TPA) probability. Herein, a general and efficient synthesis of a biomimetic 2,6-disubstituted-δ-pyrone analogue of CC is described, motivated by the fact that molecular modeling previews an order of magnitude increase of its NIR TPA compared to CC. Three retrosynthetic pathways have been identified (i) via an aryl-oxazole intermediate or via aryl-diynone through (ii) a bottom-up or (iii) a top-down approach. While avoiding the passage through unstable synthons or low-yield intermediate reactions, only the latest approach could conveniently afford the 2,6-disubstituted-I-pyrone analogue of CC, in ten steps and with an overall yield of 18%. The photophysical properties of our biomimetic analogue have also been characterized showing an improved photoisomerization yield over the parent natural compound. The potentially improved nonlinear optical properties, as well as enhanced stability, may be correlated to the enforcement of the planarity of the pyrone moiety leading to a quadrupolar D-π-A-π-D system.
- Pecourneau, Jérémy,Losantos, Raúl,Monari, Antonio,Parant, Stéphane,Pasc, Andreea,Mourer, Maxime
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p. 8112 - 8126
(2021/06/30)
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- Catalytic asymmetric synthesis of 2,5-dihydrofurans using synergistic bifunctional Ag catalysis
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We report a bifunctional Ag catalyst promoted intramolecular capture of oxonium ylides with alkynes for the enantioselective synthesis of 2,5-dihydrofurans. This represents unprecedented synergistic catalysis of a bifunctional Ag catalyst. Mechanistic studies revealed that [(R)-3,5-DM-BINAP](AgSbF6)2 (9) is likely to be the active catalytic species and that the reaction involves second order kinetics with respect to 9, suggesting that two molecules of 9 are involved in the intramolecular trapping of a Ag-associated oxonium ylide with a Ag-activated alkyne. Based on our mechanistic hypothesis, we further optimized the reaction, rendering a facile approach to 2,5-dihydrofurans in good to excellent yields in a highly chemo- and enantioselective fashion.
- Shi, Taoda,Teng, Shenghan,Gopi Krishna Reddy, Alavala,Guo, Xin,Zhang, Yueteng,Moore, Kohlson T.,Buckley, Thomas,Mason, Damian J.,Wang, Wei,Chapman, Eli,Hu, Wenhao
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supporting information
p. 8737 - 8744
(2019/10/16)
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- Nickel(II)-Catalyzed Asymmetric Propargyl [2,3] Wittig Rearrangement of Oxindole Derivatives: A Chiral Amplification Effect
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A highly enantioselective [2,3] Wittig rearrangement of oxindole derivatives was realized by using a chiral N,N′-dioxide/NiII complex as the catalyst under mild reaction conditions. A strong chiral amplification effect was observed, and allowed access to chiral 3-hydroxy 3-substituted oxindoles bearing allenyl groups in high yields and enantioselectivities (up to 92 % ee) by using a ligand with only 15 % ee. A reasonable explanation was given based on the experimental investigations and X-ray crystal structures of enantiomerically pure and racemic catalysts. Moreover, the first catalytic kinetic resolution of racemic oxindole derivatives by a [2,3] Wittig rearrangement was realized with high efficiency and stereoselectivity.
- Xu, Xi,Zhang, Jianlin,Dong, Shunxi,Lin, Lili,Lin, Xiaobin,Liu, Xiaohua,Feng, Xiaoming
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supporting information
p. 8734 - 8738
(2018/07/14)
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- Electrochemical Deprotection of para-Methoxybenzyl Ethers in a Flow Electrolysis Cell
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Electrochemical deprotection of p-methoxybenzyl (PMB) ethers was performed in an undivided electrochemical flow reactor in MeOH solution, leading to the unmasked alcohol and p-methoxybenzaldehyde dimethyl acetal as a byproduct. The electrochemical method removes the need for chemical oxidants, and added electrolyte (BF4NEt4) can be recovered and reused. The method was applied to 17 substrates with high conversions in a single pass, yields up to 92%, and up to 7.5 g h-1 productivity. The PMB protecting group was also selectively removed in the presence of some other common alcohol protecting groups.
- Green, Robert A.,Jolley, Katherine E.,Al-Hadedi, Azzam A. M.,Pletcher, Derek,Harrowven, David C.,De Frutos, Oscar,Mateos, Carlos,Klauber, David J.,Rincón, Juan A.,Brown, Richard C. D.
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supporting information
p. 2050 - 2053
(2017/04/27)
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- A 1 - bromo - 2 - ethyl-acetylene production method (by machine translation)
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The invention relates to a 1 - bromo - 2 - ethyl-acetylene production method, including in the THF bromoethane with magnesium metal in the reaction to prepare the Grignard reagent, then to the Grignard reagent in the form after adding poly-formaldehyde reaction, format after the reaction separation and recovery 2 - ethyl-acetylene - 1 - ol; and will 2 - ethyl-acetylene - 1 - ol with phosphorus tribromide bromination reaction, bromination reaction after the end of the separation and recovery of 1 - bromo - 2 - ethyl-acetylene. In this invention the format adopted for the more common reaction currently in use, and does not need special production equipment, the reaction condition is comparatively mild, in industrialized production process is more stable, with a low risk. The phosphorus tribromide to 2 - ethyl-acetylene - 1 - ol performing the bromination, the utilization rate of high, produce by-products phosphoric acid and in pyridine and easy processing. (by machine translation)
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Paragraph 0014
(2017/06/13)
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- Stereoselective synthesis of the KJ ring system of yessotoxin by Pd(II)-catalyzed cyclization
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Yessotoxin was isolated from the digestive glands of the scallop, Patinopecten yessoensis, and would be of use as a promising therapeutic tool. We attained the stereoselective construction of KJ ring system of yessotoxin by the intramolecular cyclization of the trisubstituted allylic alcohol using Pd(II) catalyst.
- Yokoyama, Hajime,Nishida, Kazuki,Togawa, Takashi,Yamagami, Masaki,Miyazawa, Masahiro,Hirai, Yoshiro
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p. 4379 - 4381
(2016/09/13)
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- A kind of 2-butyne-1-ol synthesis method
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The invention discloses a synthetic method for 2-butyne-1-ol. Innovation points of the invention are as follows: a waste liquid containing 1,3-dichloro-2-butylene and produced in rubber production is used as a starting raw material and undergoes hydrolysis so as to obtain 3-chloro-2-butenyl-1-ol, then elimination is carried out so as to obtain 2-butyne-1-ol, and finally high-purity 2-butyne-1-ol is prepared. According to the synthetic method for 2-butyne-1-ol, the raw material is the waste liquid produced in rubber production and is cheap and widely available, so utilization of the waste, greenness and environmental protection are realized. The synthetic method is simple and is safe and easy to operate; and consumed labor force and resources by the method are substantially reduced. Product yield reaches more than 88%, and product purity reaches 96 to 98%.
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Paragraph 0030-0035
(2017/02/24)
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- Benzannulation of triynes to generate functionalized arenes by spontaneous incorporation of nucleophiles
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The thermal reaction of ester-tethered 1,3,8-triynes provides novel benzannulation products with concomitant incorporation of a nucleophile. Evidence suggests that this reaction proceeds via an allene-enyne intermediate generated by an Alder-ene reaction in the first step. Depending on the substituent of the alkyne moiety on the allene-enyne intermediate, the subsequent transformation can take one of two different paths, each leading to discrete aromatization products. The benzannulation of a silane-substituted 1,3,8-triynes provides arene products with a nucleophile incorporated onto the newly formed benzene core, whereas an aryl substituent leads to nucleophile trapping at the benzylic carbon atom connected to the aryl substituent. The formation of these two different products results from the involvement of two regioisomeric allene-enyne intermediates.
- Karmakar, Rajdip,Yun, Sang Young,Chen, Jiajia,Xia, Yuanzhi,Lee, Daesung
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supporting information
p. 6582 - 6586
(2015/06/02)
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- Highly enantioselective nickel-catalyzed intramolecular reductive cyclization of alkynones
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The first asymmetric nickel-catalyzed intramolecular reductive cyclization of alkynones is reported. A P-chiral monophosphine and triethylsilane were used as the ligand and the reducing reagent, respectively, to form a series of tertiary allylic alcohols bearing furan/pyran rings in excellent yields and enantioselectivities. This reaction has a broad substrate scope and enabled the efficient synthesis of dehydroxycubebin and chiral dibenzocyclooctadiene skeletons.
- Fu, Wenzhen,Nie, Ming,Wang, Aizhen,Cao, Ziping,Tang, Wenjun
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supporting information
p. 2520 - 2524
(2015/03/04)
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- Substrate scope and stereocontrol in the Rh(II)-catalysed oxyamination of allylic carbamates
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Application of a modified Du Bois protocol for rhodium-stabilised nitrenoid generation to a variety of allylic carbamates results in 4-acetoxymethyl-1,3-oxazolidin-2-one derivatives with moderate to high levels of stereocontrol.
- Unsworth, William P.,Lamont, Scott G.,Robertson, Jeremy
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p. 7388 - 7394
(2017/09/12)
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- Gosteli-claisen rearrangement: Substrate synthesis, simple diastereoselectivity, and kinetic studies
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The results of kinetic studies on the uncatalyzed [3,3]-sigmatropic rearrangement of 2-alkoxycarbonyl- substituted allyl vinyl ethers are reported. Apparently first reported by Gosteli in 1972, this variation of a Claisen rearrangement enjoyed a shadowy existence for three decades until its potential for the development of a catalytic asymmetric Claisen rearrangement was discovered. Inspired by this development, we have studied substituent and solvent rate effects, and we provide evidence that a chairlike transition state is highly favorable for the uncatalyzed Gosteli-Claisen rearrangement.
- Rehbein, Julia,Leick, Sabine,Hiersemann, Martin
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supporting information; experimental part
p. 1531 - 1540
(2009/09/05)
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- Synthesis of novel 2H,5H-dihydrofuran-3-yl ketones via ISNC reactions
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Unique 1-[2H,5H-dihydrofur-3-yl]ketones have been synthesized from propargylic nitroethers via intramolecular cycloadditions involving silyl nitronates. Various substituent groups were placed on the 2 and 5 positions of the dihydrofuran rings. We examined the scope of the long-range coupling in proton NMR of the oxo-dihydrofuran products. The identities of the diastereomers resulting from the Michael addition/cycloaddition reactions were tentatively assigned for the first time. CAChe MNDO PM5 and CONFLEX programs were engaged to assist with the identification of these stereoisomers. The reaction times and conditions for these oxo-dihydrofurans were found to be different than that of the published dihydrofuranals, which led us to propose a different mechanism.
- Grandbois, Matthew L.,Betsch, Kelsie J.,Buchanan, William D.,Duffy-Matzner, Jetty L.
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supporting information; scheme or table
p. 6446 - 6449
(2011/02/23)
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- Method for preparing a benzylic-type ether
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The invention concerns a method for preparing a benzylic-type ether from an aromatic compound. The inventive method for preparing a benzylic-type ether from an aromatic compound is characterised in that it consists in: in a first step, acylating an aromatic compound by reacting said aromatic compound with an acylating agent, in the presence of an efficient amount of zeolite or a Friedel-Crafts catalyst leading to a ketonic compound; in a second step, reducing the carbonyl group into carbinol leading to a benzylic alcohol; in a third step, etherifying the hydroxyl group, by reacting the benzylic alcohol with another alcohol, in the presence of an efficient amount of zeolite.
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- P(MeNCH2CH2)3N: An efficient catalyst for the desilylation of tert- butyldimethylsilyl ethers
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tert-Butyldimethylsilyl (TBDMS) ethers of primary, secondary, and tertiary alcohols and phenolic TBDMS ethers are desilylated to their corresponding alcohols and phenols, respectively, in DMSO, at 80 °C, in 68- 94% yield in the presence of 0.2-0.4 equiv of P(MeNCH2CH2)3N. Using P(i- PrNCH2CH2)3N as the catalyst, 85-97% yields of desilylated alcohols were obtained from TBDMS ethers of 1-octanol, 2-phenoxyethanol, and racemic α- phenyl ethanol. These are the first examples of desilylations of silyl ethers catalyzed by nonionic bases. Both catalysts were much less effective for the desilylation of tert-butyldiphenylsilyl (TBDPS) ethers (22-45% yield) under the same conditions as used for TBDMS ethers. Possible pathways involving nucleophilic attack of the anion of the solvent molecule (generated by the catalyst) at the Si-O bond of silyl ether or a prior activation of the silyl ether by the catalyst via a P-Si interaction followed by nucleophilic attack of the solvent anion are proposed on the basis of 1H and 31P NMR experimental data.
- Yu, Zhengkun,Verkade, John G.
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p. 2065 - 2068
(2007/10/03)
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- An experimental (flash vacuum pyrolysis) and theoretical study of the tautomerism of pyrazolinones at high temperatures
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Flash vacuum pyrolysis experiments were carried out between 500 and 800°C on 3(5)-phenyl- and 3(5)-methylpyrazolinones and on 3(5)-methoxy-5(3)-phenylpyrazole. The origin of the isolated products (mainly indanone, hydroxyalkynes and α,β-unsaturated aldehydes) can be explained as arising from the hydroxy tautomers of pyrazolinones. Temperature effects on the tautomeric equilibrium of 1-phenyl-3-methylpyrazolinone in solution show that the percentage of the CH tautomer increases with the temperature. MP2 ab initio calculations on the model compound, pyrazolinone itself, have been used to rationalize these findings. The problem of the aromaticity of the four tautomers of pyrazolinone has been examined through Schleyer's NICS (nuclear independent chemical shifts) calculations.
- Yranzo, Gloria I.,Moyano, Elizabeth L.,Rozas, Isabel,Dardonville, Christophe,Elguero, Jose
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p. 211 - 216
(2007/10/03)
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- Synthesis of 5,6,7-trinor-4,8-inter-m-phenylene PGI2 and Beraprost
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We have disclosed a new class of stable PGI2 analogue, 5,6,7-trinor- 4,8-inter-m-phenylene PGI2 which has a phenyl ether moiety instead of enol- ether skeleton in PGI2. The m-phenylene PGI2 and its derivative (Betaprost) were synthesized via dihydrocyclopenta[b]benzofuran derivatives as key intermediates by ortho-selective metal-halogen exchange reaction with Grignard reagents and subsequent copper-catalyzed cyclization. The ω-side chains were introduced by stereoselective epoxide formation or Prins reaction.
- Wakita, Hisanori,Matsumoto, Kazuhisa,Yoshiwara, Hideo,Hosono, Yutaka,Hayashi, Ryoji,Nishiyama, Hisao,Nagase, Hiroshi
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p. 2449 - 2474
(2007/10/03)
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- Cyclization-Activated Prodrugs: N-(Substituted 2-hydroxyphenyl and 2-hydroxypropyl)carbamates Based on Ring-Opened Derivatives of Active Benzoxazolones and Oxazolidinones as Mutual Prodrugs of Acetaminophen
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N-(Substituted 2-hydroxyphenyl)- and N-(substituted 2-hydroxypropyl)carbamates based on masked active benzoxazolones (model A) and oxazolidinones (model B), respectively, were synthesized and evaluated as potential drug delivery systems.A series of alkyl and aryl N-(5-chloro-2-hydroxyphenyl)carbamates 1 related to model A was prepared.These are open drugs of the skeletal muscle relaxant chlorzoxazone.The corresponding 4-acetamidophenyl ester named chloracetamol is a mutual prodrug of chloroxazone and acetaminophen.Chlorzacetamol and two other mutual prodrugs of active bezoxazolones and acetaminophen were obtained in a two-step process via condensation of 4-acetamidophenyl 1,2,2,2-tetrachloroethyl carbonate with the appropiate anilines.Based on model B, two mutual prodrugs of acetaminophen and active oxazolidinones (metaxalone and mephenoxalone) were similarly obtained using the appropiate amines.All the carbamate prodrugs prepared were found to release the parent drugs in aqueous (pH 6-11) and plasma (pH 7.4) media.The detailed mechanistic study of prodrugs 1 carried out in aqueous medium at 37 deg C shows a change in the Broensted-type relationship log t1/2 vs pKa of the leaving groups ROH: log t1/2 = 0.46pKa - 3.55 for aryl and trihalogenoethyl esters and log t1/2 = 1.46pKa - 16.03 for alkyl esters.This change is consistent with a cyclization mechanism involving a change in the rate-limiting step from formation of a cyclic tetrahedral intermediate (step k1) to departure of the leaving group ROH (step k2) when the leaving group ability decreases.This mechanism occurs for all the prodrugs related to model A.Regeneration of the parent drugs from mutual prodrugs related to model B takes place by means of a rate-limiting elimination-addition reaction (E1cB mechanism).This affords acetaminophen and the corresponding 2-hydroxypropyl isocyanate intermediates which cyclize at any pH to the corresponding oxazolidinone drugs.As opposed to model A, the rates of hydrolysis of mutual prodrugs of model B clearly exhibit a catalytic role of the plasma.It is concluded from the plasma studies that the carbamate substrates can be enzymatically transformed into potent electrophiles, i.e., isocyanates.In the case of the present study, the prodrugs are 2-hydroxycarbamates for which the propinquity of the hydroxyl residue and the isocyanate group enforces a cyclization reaction.This mechanistic particularity precludes their potential toxicity in terms of potent electrophiles capable of modifying critical macromolecules.
- Vigroux, Alain,Bergon, Michel,Zedde, Chantal
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p. 3983 - 3994
(2007/10/03)
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- SYNTHESIS OF THE SEX PHEROMONE OF THE GRAIN MOTH Ephestia Elutella
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A most convenient synthesis of tetradeca-9Z,12E-dien-1-ol and its acetate - components of the sex pheromone of the grain moth - has been carried out on the basis of a scheme for obtaining a cis-1,trans-4-dienic system.
- Kasymzhanova, M.,Abdukakharov, V. S.,Kamaev, F. G.,Abduvakhabov, A. A.
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p. 708 - 713
(2007/10/02)
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- Cyclisation des alcools δ-alleniques par le nitrate d'argent ou les sels mercuriques. Synthese d'α-alcenyl-2 tetrahydropyrannes
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Eight diversely substituted δ-allenic alcohols have been synthesized by using three different methods for the formation of the allenic linkage.When treated with silver nitrate or mercuric salts, these alcohols are transformed in fairly good yields into α-alkenyl-2 tetrahydropyrans.In addition to its regioselectivity in the formation of the heterocycle this reaction shows in certain cases a high stereoselectivity.Alcohols monosubstituted on the thermal allenic carbon lead to more than 90percent of the E product whereas the 2,4 or 2,6 disubstituted tetrahydropyrans are obtained in predominantly the Z configuration.
- Audin, Patrick,Doutheau, Alain,Gore, Jacques
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p. 297 - 306
(2007/10/02)
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- 5,6,7-Trinor-4,8-inter-m-phenylene prostaglandin I2 derivatives useful in anti-ulcer, hypotensive and platelet aggregation inhibiting compositions
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A compound of the formula STR1 wherein R1 is a pharmaceutically acceptable cation, hydrogen or n-alkyl of 1 to 12 carbon atoms; R2 is hydrogen, acyl of 2 to 10 carbon atoms or aroyl of 7 to 13 carbon atoms; R3 is hydrogen, acyl of 2 to 10 carbon atoms or aroyl of 7 to 13 carbon atoms; R4 is hydrogen, methyl or ethyl; R5 is n-alkyl of 1 to 5 carbon atoms; n is an integer of 0 to 4; A is --CH2 --CH2 -- or trans --CH=CH--; and X is --CH2 --CH2 -- or trans --CH=CH--. The compounds are useful in anti-ulcer, hypotensive and platelet aggregation inhibiting compositions.
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- TOTAL STEREOSPECIFICITY IN FREE RADICAL INTRAMOLECULAR ADDITION: CYCLISATION OF CIS AND TRANS 1-METHYL 4-HEXENYL N-CHLOROAMINES BY MEANS OF METALLIC SALTS
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Extremely high stereospecificity (up to 100percent diastereoisomeric purity) can be obtained for the metallic salts induced radical cyclisation of the cis and trans 1-methyl 4-hexenyl N-chloroamines.A possible mechanism for the highly effective trans-addition using metal-complexed aminyl radical is proposed.
- Bougeois, Jean-Luc,Stella, Lucien,Surzur, Jean-Marie
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- METAL COMPLEXES IN ORGANIC SYNTHESIS-V ALKYLATIONS OF PENTANE-2,4-DIONE WITH ALLYLIC ALCOHOLS UNDER PALLADIUM CATALYSIS
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Pentane-2,4-dione with allylic alcohols or benzyl alcohol with palladium catalysts gives high yields of C-monoalkylated diketones, arising mainly from reaction at the terminal end of the allylic system for alkyl monosubstituted allyl alcohols.The effect of the catalyst on the alcohols has been evaluated; rearrangements and disproportionations have been observed.
- Moreno-Manas, M.,Trius, A.
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p. 3009 - 3016
(2007/10/02)
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