(1S,2S,6S,9S)-6-Methyl-5-oxobicyclo­[4.4.0]decane-2,9-diyl diacetate

The chiral title compound, C15H22O5, is an inter­mediate in the total synthesis of biologically active 9,11-secosterols. In the crystal, the cyclo­hexane rings are trans-fused and both adopt chair conformations. In the crystal, mol­ecules are loosely held together in a layer parallel to (100) by weak inter­molcular C—H⋯O hydrogen bonds accepted by carbonyl O atoms of the acetyl groups

1,6-Conjugate Additions of Carbon Nucleophiles to 2-[(1E,3E)-4-Arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones

KGaA, Weinheim The 1,6-conjugate addition of nitromethane to 2-[(1E,3E)-4-arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones was accomplished and led mainly to the corresponding β-(nitromethyl)chromones. (E)-5′-(Nitromethyl)-3′-styryl-[1,1′-biphenyl] -2-ol and 3′-aryl-2′-nitro-5′-(nitromethyl)spiro[chromane-2,1′-cyclohexan]-4-one derivatives were also isolated as minor products from tandem processes, which result from the addition of a second molecule of nitromethane. The nucleophile scope was investigated with malononitrile, acetylacetone, ethyl cyanoacetate, and diethyl malonate, which gave the expected 1,6-addition products; in the last case, it was also possible to isolate a minor product formed through a 1,8-/1,6-addition sequence. Computational calculations provided a rationale for the experimental reactivity of carbon nucleophiles with 2-[(1E,3E)-4-arylbuta-1,3-dien-1-yl] -4H-chromen-4-ones. The further functionalization of some adducts allowed the preparation of new nitrogen-containing heterocyclic compounds, such as new styrylpyrrolidines and new pyrazole and bis(pyrazole) derivatives.Thanks are due to the University of Aveiro and Fundação para a Ciência e a Tecnologia (FCT)/Ministerio de Educación y Ciencia (MEC) for the financial support of the QOPNA research unit (FCT UID/QUI/00062/2013) through national funds and, where applicable, cofinanced by Fundo Europeu de Desenvolvimento Regional (FEDER) within the PT2020 Partnership Agreement, and to the Portuguese NMR Network as well as the Instituto Politécnico de Bragança. H. M. T. A. is grateful to Fundação para a Ciência e a Tecnologia (FCT) for his PhD grant (SFRH/BD/86277/ 2012).info:eu-repo/semantics/publishedVersio

Asymmetric diastereodivergent Michael addition of 2-chloromalonate esters to conjugated imines enabled by catalyst metal change

Despite recent progress in asymmetric diastereodivergent reactions leading to products bearing two stereogenic centers, little research has been devoted to processes were a stereogenic center and a double bond are formed. Here, we report the asymmetric diastereodivergent Michael addition of 2-chloromalonate esters to N-tosyl β,γ-unsaturated α-ketimino esters to give chiral α,β-dehydro-α-aminoesters bearing either a Z or E enamine moiety, using pyBOX-metal complexes. Diastereodivergency is achieved by simply changing the metal ion from a trivalent La(III) to a divalent Ca(II) ion, providing the Z or E enamines. Computational studies reveal the crucial role of London interactions between the aromatic residues on the imine and the pyBOX ligand, which are conditioned by the different coordination modes of La(III) and Ca(II), in the change of selectivity depending on the used metal

Automaatne sisukokkuvõtete tegemine eestikeelsetele tekstidele

https://www.ester.ee/record=b5407141*es

ChemInform Abstract: Bimorpholines as Alternative Organocatalysts in Asymmetric Aldol Reactions

Asymmetric organocatalytic aldol condensation is discussed on the basis of intramolecular and inter-molecular reactions. In addition to the widely used proline and its derivatives an application of the new type of the organocatalyst – bimorpholines in the above-mentioned reactions is described. The new catalyst has a unique C2-symmetric skeleton with four acceptor sites that makes it stereoselective and efficient. Small changes in the structure of the catalyst lead to a remarkable loss of selectivity