- Cleavage of Carboxylic Esters by Aluminum and Iodine
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A one-pot procedure for deprotecting carboxylic esters under nonhydrolytic conditions is described. Typical alkyl carboxylates are readily deblocked to the carboxylic acids by the action of aluminum powder and iodine in anhydrous acetonitrile. Cleavage of lactones affords the corresponding ω-iodoalkylcarboxylic acids. Aryl acetylates undergo deacetylation with the participation of the neighboring group. This method enables the selective cleavage of alkyl carboxylic esters in the presence of aryl esters.
- Sang, Dayong,Yue, Huaxin,Fu, Yang,Tian, Juan
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p. 4254 - 4261
(2021/03/09)
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- Synthesis method of methyl coumalate
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The invention discloses a synthesis method of methyl coumalate. The synthesis method comprises the following steps: adding water-containing sulfuric acid into a kettle, stirring, heating to a temperature of less than 100 DEG C, and adding a pre-prepared saturated malic acid solution in a dropwise manner; carrying out a constant-temperature reaction after the adding, and monitoring the reaction process by using gas chromatography until the malic acid reaction is finished; stopping the stirring, layering, cooling to below 50 DEG C, and separating out a lower layer sulfuric acid aqueous solution;continuously stirring, heating to reflux, and adding a large amount of methanol in a dropwise manner; carrying out a reflux reaction for a certain time, and carrying out gas phase monitoring until coumalic acid disappears; evaporating out most of the solvent to form a slurry in the system, cooling to room temperature, and adding an aqueous solution of an alkaline compound in a dropwise manner toform a large amount of precipitates; and filtering, washing with water, and drying to obtain the methyl coumalate.
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Paragraph 0028-0029; 0031-0032; 0034-0035; 0037-0038; 0040
(2020/04/06)
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- A 6 - chloro nicotinic acid preparation method and separation and purification method
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The invention discloses a preparation method and a separation and purification method for 6-chloronicotinic acid, belonging to the field of fine chemical engineering. The preparation method comprises the following steps: by taking low-cost DL-malic acid as a raw material, carrying out a cyclization reaction and an ammonification reaction, thereby obtaining 6-hydroxynicotinic acid; by taking 6-hydroxynicotinic acid as a raw material, carrying out a chlorination reaction, thereby obtaining 6-chloronicotinic acid. The reaction conditions are simple, operation is easy, the environmental pollution is slight, and the yield is high. The purification method disclosed by the invention comprises the following step: refining crude 6-chloronicotinic acid by virtue of methanol and activated carbon to finally obtain 6-chloronicotinic acid with the purity of more than 99.5 percent. The requirement of a medical intermediate on the purity is met. The method disclosed by the invention has the advantages of reasonable design, low cost and high economic benefits and has wide application prospects.
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Paragraph 0035; 0039-0092
(2017/08/24)
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- Four hydrogen pyrane two fluorine Asia armor propoxycyclohexyl linking group containing a liquid crystal compound, preparation method and application thereof
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The invention discloses a liquid crystal compound containing a tetrahydropyrane difluoro methoxy-linking group and a preparation method and application thereof. The liquid crystal compound is represented by a formula I. In a molecular structure of the compound represented by the formula I, the liquid crystal compound containing the tetrahydropyrane difluoro methoxy-linking group (img file='DDA0000475765100000011. TIF' wi='384' he='112'/) has high dielectric anisotropy. What's more important is that the liquid crystal compound further has high response speed and clearing points and low rotational viscosity. Compared with blended liquid crystal compounds, the liquid crystal compound has very important significance. As the formula I, (img file='DDA0000475765100000012. TIF' wi='984' he='256'/).
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Paragraph 0039; 0041-0044
(2017/03/08)
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- Stereoselective construction of a key hydroindole precursor of epidithiodiketopiperazine (ETP) natural products
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An asymmetric synthetic strategy for constructing the divergent-synthesis monomer of epidithiodiketopiperazine (ETP) natural products has been successfully developed. The functionalized 2,3,3a,4,7,7a-hexahydroindole scaffold was constructed by a diastereoselective inverse electron-demand Diels-Alder (IEDDA) reaction. This journal is the Partner Organisations 2014.
- Feng, Minghao,Jiang, Xuefeng
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supporting information
p. 9690 - 9692
(2014/08/18)
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- Upgrading malic acid to bio-based benzoates via a Diels-Alder-initiated sequence with the methyl coumalate platform
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The conversion of naturally-occurring malic acid to the 2-pyrone methyl coumalate was optimized using a variety of acid catalysts. Coupling methyl coumalate with electron-rich dienophiles in an inverse electron-demand Diels-Alder (IEDDA)/decarboxylation/elimination domino sequence resulted in an investigation of the scope and limitations of the methodology. The thermal, metal-free, and one-pot procedure allows regioselective access to diverse aromatic compounds including tricyclic, biphenyl, and pyridinyl systems for elaboration. A comparison with analogous pyrones demonstrates the striking efficacy of methyl coumalate as a versatile platform for the generation of biorenewable functionalized benzoates. This journal is
- Lee, Jennifer J.,Pollock Iii, Gerald R.,Mitchell, Donald,Kasuga, Lindsay,Kraus, George A.
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p. 45657 - 45664
(2015/02/19)
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- Claisen condensation of N-methylpyrrolidinone and α-chloronicotinic esters
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Reaction between α-halo-nicotinic esters and a nucleophilic source such as the N-methylpyrrolidin-2-one (NMP) gave unexpected results. The presence of the halide on the pyridine gave a very interesting migration reaction. Extension to 6-methylnicotinic ester derivatives lead to an unexpected carbanion condensation.
- Kaminski, Thomas,Kirsch, Gilbert
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p. 229 - 234
(2008/09/19)
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- A PROCESS FOR THE PREPARATION OF 3-CYANO-1-NAPHTHOIC ACID AND SOME ANALOGUES THEREOF
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The present invention is related to a process for the preparation of 3-cyano-1-naphthoic acid and some analogues thereof of formula (1), the intermediate 1-halo-3-cyano naphthalene and some analogues thereof used in this process and a process for the preparation of said intermediate.
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- A new route for manufacture of 3-cyano-1-naphthalenecarboxylic acid
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3-Cyano-1-naphthalenecarboxylic acid is an intermediate required for manufacture of tachykinin receptor antagonists. The 1,3-disubstitution pattern on the naphthalene skeleton complicates the synthesis of this cyano acid. Previous literature-based chemistry is unattractive for large-scale manufacture due to stoichiometric use of mercury salts, low yield, and other operational difficulties. An attractive new route has been developed by establishing the 1,3-substitution on the carbon atoms destined for only one-half of the naphthalene 2-ring system, via 3-bromocoumalate, and then building up the rest of the naphthalene ring system by Diels-Alder addition of 3-bromocoumalate to in situ-generated benzyne. The resulting 4-bromo-2-naphthoate was converted to the required cyanoacid by transformation of ester to nitrile followed by carbonylation of the bromo substituent. The new route has been scaled up successfully and offers significant advantages over previous literature chemistry in terms of improved process environmental implications, improved yield, lower cost, and improved robustness and ease of operation at larger scales of operation.
- Ashworth,Bowden,Dembofsky,Levin,Moss,Robinson,Szczur,Virica
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- Allo-, Epiallo- and Pseudoyohimbanes as well as Heteroyohimbanes by Reaction of a Tetracyclic Aldehyde with Acetoacetate in Different Solvents
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The reaction of methyl acetoacetate with 4 in CH3OH/ CH3ONa leads to 11 and 12 with yohimbane skeleton but bicyclo ring E.In DMF/ tBuOK, the epialloheteroyohimbane 13 is produced in fairly good yield, whereas in THF/ NaH the allo-19-hydroxyyohimbinone 17 is formed, which undergoes thermal decomposition to the alloyohimb-18-enone 19.Finally, a full description of an early mentioned synthesis of rac-deplancheine (7) is given.
- Rosenmund, Peter,Casutt, Michael,Wittich, Michael
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p. 233 - 238
(2007/10/02)
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