4074-22-0Relevant academic research and scientific papers
Synthesis of novel 1,4-bissulfonamide ligands for enantioselective addition of diethylzinc to aldehydes
Yang, Minghua,Sun, Jiangtao,Zhu, Chengjian
experimental part, p. 1697 - 1702 (2012/01/13)
Several novel chiral sulfonamide ligands based on (1R,2S,4R,5S)-1,4- diamino-2,5-dimethylcyclohexane skeleton have been synthesized and their application in the enantioselective addition of diethylzinc to aldehydes was investigated in the presence of Ti(O
Synthesis of optically active 2,5-dialkylcyclohexane-1,4-diols and their application in the asymmetric oxidation of sulfides
Sun, Jiangtao,Yang, Minghua,Dai, Zhenya,Zhu, Chengjian,Hu, Hongwen
scheme or table, p. 2513 - 2518 (2009/04/11)
A simple and efficient approach to obtain optically pure 1,4-diols was established. The asymmetric oxidation of sulfides to sulfoxides with cumyl hydroperoxide in moderate yields and moderate to high enantioselectivities (up to 84%) catalyzed by chiral Ti/ 1,4-diols complexes has been achieved. A 76% ee value was obtained in the asymmetric synthesis of esomeprazole. Georg Thieme Verlag Stuttgart.
C2-Symmetric nitroxides and their potential as enantioselective oxidants
Graetz, Benjamin,Rychnovsky, Scott,Leu, Wen-Hao,Farmer, Patrick,Lin, Rong
, p. 3584 - 3598 (2007/10/03)
The synthesis and evaluation of four C2-symmetric nitroxides are presented. The nitroxides were evaluated for their ability to mediate the oxidation of several alcohols and found to have good catalytic activity. One enantioenriched nitroxide was found to kinetically resolve selected secondary alcohols with very modest selectivities.
Ozonolysis of 1,4-cyclohexadienes in the presence of methanol and acid. Mechanism and intermediates in the conversion of 1,4-cyclohexadiene derivatives to β-keto esters
Gbara-Haj-Yahia, Isra,Zvilichovsky, Gury,Seri, Noa
, p. 4135 - 4139 (2007/10/03)
Conditions for the preparation of β-keto esters directly from 1,4-cyclohexadiene derivatives are described. This procedure is a further step in the application of the synthetic methodology, which consists of the combination of Birch reduction of available benzene derivatives followed by ozonolysis. In this work, the syntheses of derivatives of dimethyl γ-keto-α-aminoadipate and dimethyl β-keto glutamate from the corresponding 1,4-cyclohexadiene derivatives are described. The latter compounds are prepared from phenylalanine and phenylglycine, respectively. The study of the ozonolysis of simple alkyl derivatives of 1,4-cyclohexadiene in the presence of methanol, both in the presence and absence of acid, helped to establish the mechanism of this reaction. The proximity of the two double bonds, which are cleaved, leads to the intermediate formation of 1,2-dioxolane derivatives that could be identified by NMR spectroscopy. It is shown that regardless of the regioselectivity of the cleavage of the primary ozonide, which is formed, all 1,2-dioxolane derivatives can lead to β-keto esters. This is due to the equilibrium between these dioxolanes in the presence of methanol and acid.
Enzymatic desymmetrization of a centrosymmetric diacetate
Boehm, C.,Austin, W. F.,Trauner, D.
, p. 71 - 74 (2007/10/03)
An enantiomerically pure cyclohexanol was synthesized starting from para-xylene 1. The key steps are a stereoselective twofold hydroboration and a pig liver esterase (PLE)-catalyzed desymmetrization of the centrosymmetric cyclohexanediacetate 4.
Reaction of Azoalkanes with Isolable Cation Radical Salts
Engel, Paul S.,Robertson, Donald M.,Scholz, John N.,Shine, Henry J.
, p. 6178 - 6187 (2007/10/02)
Three tertiary azoalkanes related in the sense acyclic, cyclic, and bicyclic are shown to evolve nitrogen upon oxidation with stable cation radical salts.Thus azo-tert-octane (ATO), 3,3,6,6-tetramethyl-1,2-diazacyclohexene (TMDAC), and 1,4-dimethyl-2,3-diazabicyclooct-2-ene (Me2DBO) react rapidly with thianthrenium perchlorate (Th(.1+)ClO4(1-)), tris(p-bromophenyl)aminium hexachloroantimonate (TBPA(.1+)SbCl6(1-)), and TBPA(.1+)SbF6(1-).The ether and olefin products, which are formed in high yield in CH2Cl2/MeOH solvent, are not those expected from the usual free-radical decomposition of azoalkanes but instead implicate carbocations.Althrough the reaction stoichiometry clearly requires 2 equiv of cation radical salt to one of azoalkane, the mechanism is not yet clearly defined.A complication in these studies is found in the ability of certain cation radical salts to oxidize more azoalkane than expected based on the 2:1 stoichiometry.
Composition of Mixtures of Hydrocarbons after BIRCH-Reduction of Substituted Benzenes and Acid Catalyzed Addition of Alcohols to Alkylsubstituted Cyclohexenes and Carbohexa-1,4-dienes
Beger, J.,Thomas, B.,Vogel, T.,Kirmse, K.,Lang, R.
, p. 481 - 488 (2007/10/02)
10 different benzene hydrocarbons 1, indane, tetraline, anisol and phenol are reduced by sodium in liquid ammonia in the presence of methanol to the BIRCH products 2.The product mixture compositions are determined through capillary GLC.On storage at +6 deg C some rearomatization of the 1,4-cyclohexadienes 2 occurs.Data of the 1H- and 13C-.n.m.r. spectra and also mass spectra of the BIRCH 1,4-dienes 2 are given.For comparison 4-alkoxycyclohexenes 4 and 1-alkoxy-1-methylcyclohexanes 8 are prepared and spectroscopically characterized.Acid-catalyzed addition of alcohols to the 1,4-cyclohexadienes systems is a slow process and gives the 4-alkoxy-4-alkylcyclohex-1-enes (4) only in moderate yields up to 30percent.Most of the products are dimers 5 and also oligomers 6 of the parent hydrocarbons 2.
REVERSAL OF THE REGIOSELECTIVITY OF THE BIRCH REDUCTION OF XYLENES
Epling, Gary A.,Florio, Emily
, p. 1469 - 1472 (2007/10/02)
The "Photo-Birch" reduction of o-, m-, and p-xylene, using NaBH4, 1,3-dicyanobenzene, and photolysis, gives 1,4-dienes as products.The regioselectivity of these reactions is greatly different from the normal Birch reduction.
