- Enantioselective Cyclopropanation of 4-Nitroisoxazole Derivatives
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The present study reports an asymmetric organocatalytic cascade reaction of 4-nitroisoxazole derivative with α,β-unsaturated aldehydes catalysed by chiral secondary amine. Using this approach, 1,2,3-trisubstituted cyclopropane products were obtained in isolated yields up to 98% with moderate diastereoselectivities, and enantiopurity up to 99% ee. Moreover, this synthetic protocol can be used for further applications, as shown by a set of additional transformations of the corresponding cyclopropanes and by the formal synthesis of GABA ligands. (Figure presented.).
- Do?ekal, Vojtěch,Petr?elová, Simona,Císa?ová, Ivana,Vesely, Jan
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supporting information
p. 2597 - 2603
(2020/04/30)
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- 184. Stereoselective Hydrolysis of Substituted Cyclopropanedicarboxylates with Pig Liver Esterase
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The hydrolysis of the meso-cyclopropane-1,2-dicarboxylates 1a-3a, 4, 5a, 6a, and 9, containing various substituents at C(3), and of the rac-3-phenylcyclopropane-1,2-dicarboxylates 7a, 8a, and 10 with pig liver esterase (PLE) is described.The stereoselectivity and absolute configurations of the products were determined.An interpretation of results was attempted on the basis of a recent active-site model for PLE.
- Walser, Paula,Renold, Peter,N'Goka, Victor,Hosseinzadeh, Fatemeh,Tamm, Christoph
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p. 1941 - 1952
(2007/10/02)
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- Cyclopropanediamines, 3. - Pure Diastereomers of 1,2-Cyclopropanedicarboxylic Acids and Derivatives
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Efficient preparations of pure diastereomers of dimethyl 1,2-cyclopropanedicarboxylates 2, dicarboxylic acids 3, dicarbonyl dichlorides 4, and dihydrazides 5 are reported.Mixtures of diastereomers of dimethyl dicarboxylates 2a, b, d, e are obtained from α,β-unsaturated methyl carboxylates 7 and methyl α-chlorocarboxylates 8 as well as from 7c, d and the sulfur ylide 10 (2c, d).The diastereomers are separated by fractionating distillations (2a, b, c, e) or crystallization (2d) on a 100-g to 1-kg scale (d.e. >99percent).Only low yields of 2c are obtained in the reaction of methyl crotonate (7c) with methyl α-chloroacetate (8a), since 7c predominantly dimerizes to afford 12.The diesters 2 are converted into the pure diastereomeric diacids 3, dicarbonyl dichlorides 4, and dihydrazides 5. 3,3-Dimethyl-cis-1,2-cyclopropanedicarboxylic acid (cis-3f) is obtained by trans-->cis isomerization of trans-3f with the help of acetic anhydride and sodium acetate as catalyst.The configurations of 2-6 and 12 are confirmed by 1H NMR spectroscopy.Derivatives of cis-1,2-dimethyl-1,2-cyclopropanedicarboxylic acid tend to form bicyclic products.Thus, the reaction of cis-3e with phosphorus pentachloride yields mainly the cyclic anhydride 6e and only small amounts of the dicarbonyl dichloride cis-4e.Furthermore, the dihydrazide cis-5e slowly cyclizes in the solid state to give the N-aminoimide 13 and hydrazine, a reaction which is fast in solution.Pure 13 is obtained by thermolysis of cis-5e at 60-65 deg C under high vacuum.
- Saal, Wolfgang von der,Reinhardt, Robert,Seidenspinner, Hubert-Matthias,Stawitz, Josef,Quast, Helmut
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p. 703 - 712
(2007/10/02)
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