- Concise synthesis and applications of enantiopure spirobiphenoxasilin-diol and its related chiral ligands
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The development of chiral architectures for chiral ligand and catalyst discovery is essential for asymmetric catalysis. Herein, we report the concise synthesis of a Si-centered spirocyclic skeleton, spirobiphenoxasilin-diol (SPOSiOL), and its derived chiral ligands. Using the chemical resolution method, the optical SPOSiOL could be obtained in high yield on a gram scale. Preliminary studies indicated that this ligand scaffold has great potential in transition metal-catalyzed asymmetric reactions. This finding further highlights that the Si-centered spirocyclic scaffolds are of great value in asymmetric catalysis. This journal is
- Liu, Tao,Wang, Biqin,Wang, Peng,Wu, Yichen,Xu, Wen-Qiang,Yang, Lei
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supporting information
p. 13365 - 13368
(2021/12/17)
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- Synthetic method of acetaldehyde alcohol optical active ester
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The invention discloses a synthetic method of acetaldehyde alcohol optical active ester. The method comprises the following steps: under the condition of a catalyst solvent, carrying out a reaction on triphosgene andn L-menthol to obtain a reaction product containing L-menthyl chloroformate; adding 1, 4-cis-butenediol into the reaction product obtained in the step 1, adding a proper amount of a catalyst and a proper amount of a solvent, carrying out a reaction to obtain a reaction product containing menthyl dicarbonate, and carrying out post-treatment on the reaction product to obtain purified menthyl dicarbonate; and dissolving the obtained menthyl dicarbonate in a solvent, and introducing ozone to oxidize the menthyl dicarbonate into the acetaldehyde alcohol optical active ester. According to the invention, the conditions of the reaction steps are mild, the operation is simple and convenient, the initial raw materials are cheap and easy to obtain, the reaction steps are short, the generated three-waste pollutants are less, the yield is high, the method is suitable for industrial large-scale production, the reaction steps are simplified to a certain extent, and the subsequent reaction is facilitated.
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Page/Page column 0038-0039; 0043-0044; 0048-0049
(2021/09/04)
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- Preparation method of alicyclic and aromatic-aliphatic chloroformate
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The invention belongs to the technical field of fine chemistry, and in particular relates to a preparation method of alicyclic and aromatic-aliphatic chloroformate. The preparation method is characterized in that alicyclic alcohol chloroformate or aromatic-aliphatic alcohol chloroformate is obtained by taking alicyclic alcohol or aromatic-aliphatic alcohol and bis(trichlormethyl)carbonate as raw materials, taking organic base as a catalyst and reacting in an organic solvent under certain reaction temperature and certain reaction time, wherein molar ratio among the alicyclic alcohol or the aromatic-aliphatic alcohol, the bis(trichlormethyl)carbonate and the organic base is 1 to (0.4 to 1) to (1.2 to 3); experiment time and experiment temperature are different in two stages, in the first stage, the reaction temperature is -10 to 0 DEG C, and the reaction time is 2 to 5 hours; in the second stage, the reaction temperature is 0 to 25 DEG C, and the reaction time is 7 to 13 hours; a mass ratio between the organic solvent and the alicyclic alcohol or the aromatic-aliphatic alcohol is (10 to 25) to 1; residue in a reaction system is effectively treated, and reaction waste is also recycled and utilized. The preparation method disclosed by the invention has the characteristics of stable reaction, high reaction yield and product purity, environment protection of a reaction process, low production cost, less emission of three wastes, simpleness in preparation technology and easiness in industrialization.
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Paragraph 0025; 0032-0033
(2017/05/16)
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- Diastereofacial selectivity in ketene [2+2] cycloaddition to endocyclic enecarbamates bearing a chiral auxiliary. Synthesis of the (-)-Geissman-Waiss lactone
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The diastereofacial selectivity of enecarbamates bearing a chiral auxiliary was evaluated for the [2+2]cycloaddition with dichloroketenes. Diastereofacial selectivity ranged from zero (bornyl and menthyl) to 60% (Greene's auxiliary and 8-phenylmenthyl). Chromatography separation of the diastereomeric azacyclobutanones derived from the 8-phenylmenthyl enecarbamate permitted an enantiodivergent synthesis of the (-)-Geissman-Waiss lactone, a key intermediate in the synthesis of necine bases.
- Miranda, Paulo Cesar M. L.,Correia, Carlos Roque D.
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p. 7735 - 7738
(2007/10/03)
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- Synthesis of chiral diazanedicarboxylate and diazenedicarboxylate esters: electrophilic amination reactions of achiral ester and amide enolates
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A series of chiral dialkyl (bornyl, isobornyl, menthyl) diazenedicarboxylates 4a-c were prepared by conversion of the corresponding alcohols into chloroformates, condensation with hydrazine, and oxidation of the corresponding dialkyl diazanedicarboxylates 3a-c with N-bromosuccinimide and pyridine (50-90percent yield).Their reaction with achiral enolates of esters and N,N-dimethyl amides at -70 deg C gave α-hydrazino acid derivatives with little or no stereoselectivity.Analogous amination of chiral oxazolidinone (Evans enolate) anions were highly selective, but were controlled exclusively by enolate geometry.
- Harris, Joanna M.,Bolessa, Evon A.,Mendonca, Aubrey J.,Feng, Sheng-Chu,Vederas, John C.
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p. 1945 - 1950
(2007/10/02)
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- BOTRYDIAL SYNTHETIC STUDIES. ASYMMETRIC SYNTHESIS OF QUATERNARY CARBON CENTRES.
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The synthesis of the optically active 4 has been accomplished by asymmetric formation of cyclic β-keto esters fully substituted at the α Carbon followed by chemoselective reduction of the ester group.Of the asymmetric reactions examined the Koga procedure proved to be the most selective.
- Kunisch, Franz,Hobert, Kurt,Welzel, Peter
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p. 5433 - 5436
(2007/10/02)
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