Browse
Submit Data
Databases
API
Help
Login

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Divergent stereocontrol of acid catalyzed intramolecular aldol reactions of 2,3,7-triketoesters: synthesis of highly functionalized cyclopentanones.

ABSTRACT: The intramolecular acid catalyzed aldol cyclization of 2,3,7-triketoesters formed from ?-keto-?-diazo-?-ketoesters provides highly functionalized cyclopentanones with good diastereoselectivity in high overall yields via kinetically controlled and stereodivergent catalytic processes. Lewis acid catalysis gives high selectivity for the 1,2-anti tetrasubstituted cyclopentanones, whereas Brønsted acid catalysis produces the corresponding 1,2-syn diastereomer.

SUBMITTER: Truong P

PROVIDER: S-EPMC3480983 | BioStudies | 2012-01-01

REPOSITORIES: biostudies

ACCESS DATA

Json Xml

Similar Datasets

Asymmetric synthesis of functionalized cyclopentanones via a multicatalytic secondary amine/N-heterocyclic carbene catalyzed cascade sequence.

Project description:A one-pot, asymmetric multicatalytic formal [3+2] reaction between 1,3-dicarbonyls and alpha,beta-unsaturated aldehydes is described. The multicatalytic process involves a secondary amine catalyzed Michael addition followed by a N-heterocyclic carbene catalyzed intramolecular crossed benzoin reaction to afford densely functionalized cyclopentanones with high enantioselectivities. The reaction proceeds with a variety of alkyl and aryl enals as well as a range of 1,3-dicarbonyls (diketones and beta-ketoesters). The functionalized products are obtained from cheap, readily available starting materials in a rapid and efficient manner in a one-pot, one-step operation.

2009-01-01 | S-EPMC2785226 | BioStudies

Oxidatively Initiated NHC-Catalyzed Enantioselective Synthesis of 3,4-Disubstituted Cyclopentanones from Enals.

Project description:An unprecedented N-heterocyclic carbene (NHC)-catalyzed annulation of enals to form 3,4-disubstituted cyclopentanones has been discovered. Aryl enals undergo dimerization in the presence of a single-electron oxidant to form C2 symmetric cyclopentanones. A cross-reaction has also been developed, allowing for the synthesis of differentially substituted cyclopentanones. Mechanistically, the reaction is thought to proceed through radical intermediates, further establishing the synthetic utility of this class of reactivity.

2015-01-01 | S-EPMC4986695 | BioStudies

Palladium-Catalyzed Enantioselective Decarboxylative Allylic Alkylation of Cyclopentanones.

Project description:The first general method for the enantioselective construction of all-carbon quaternary centers on cyclopentanones by enantioselective palladium-catalyzed decarboxylative allylic alkylation is described. Employing the electronically modified (S)-(p-CF3)3-t-BuPHOX ligand, ?-quaternary cyclopentanones were isolated in yields up to >99% with ee's up to 94%. Additionally, in order to facilitate large-scale application of this method, a low catalyst loading protocol was employed, using as little as 0.15 mol % Pd, furnishing the product without any loss in ee.

2015-01-01 | S-EPMC4640231 | BioStudies

Diastereodivergent organocatalysis for the asymmetric synthesis of chiral annulated furans.

Project description:Disclosed herein is a stereoselective method for the synthesis of 2,3-furan fused carbocycles bearing adjacent quaternary and tertiary carbon stereocenters. The chemistry is based on an asymmetric addition of ?-ketoesters to 2-(1-alkynyl)-2-alkene-1-ones catalysed by natural cinchona alkaloids followed by a silver-catalysed intramolecular cycloisomerisation. By exploiting the distinct catalysis modes of quinine, which can act either as a general base or, upon opportune modifications, as a phase transfer catalyst, a complete switch of the enforced sense of diastereoinduction is achieved. The stereodivergent systems enable access to the full matrix of all possible stereoisomeric products.

1000-01-01 | S-EPMC5707493 | BioStudies

Distal-Bond-Selective C-C Activation of Ring-Fused Cyclopentanones: An Efficient Access to Spiroindanones.

Project description:A site-selective rhodium-catalyzed C-C activation of ring-fused cyclopentanones was achieved to afford efficient access to a range of spiroindanones. The use of bulky 2-amino-6-picoline as a cocatalyst is key to the excellent selectivity of this C-C bond cleavage in cyclopentanones.

2017-01-01 | S-EPMC5503198 | BioStudies

Enamine/Carbene Cascade Catalysis in the Diastereo- and Enantioselective Synthesis of Functionalized Cyclopentanones.

Project description:Herein we report an enantioselective synthesis of complex cyclopentanones using aliphatic aldehydes and activated enones. With the combination of a chiral secondary amine and a chiral triazolium catalyst, high diastereoselectivity and excellent enantioselectivity can be achieved. We present evidence of a clear cooperative effect when these two catalysts are present simultaneously in the system.

2011-01-01 | S-EPMC3173771 | BioStudies

Catalytic enantioselective O-nitrosocarbonyl aldol reaction of ?-dicarbonyl compounds.

Project description:The first example of a Cu-catalyzed asymmetric O-nitrosocarbonyl aldol reaction is described. This novel protocol allows convenient access to highly enantioenriched ?-hydroxy-?-ketoesters including the antibacterial natural product kjellmanianone (up to 99% ee). MnO(2) was introduced as a mild efficient oxidant for the in situ generation of nitrosocarbonyl species from hydroxamic acid derivatives.

2012-01-01 | S-EPMC3515642 | BioStudies

Rhodium-catalyzed intramolecular C-H insertion of alpha-aryl-alpha-diazo ketones.

Project description:Direct diazo transfer proceeds smoothly with alpha-aryl ketones. The derived alpha-aryl-alpha-diazo ketones cyclize efficiently with Rh catalysis to give the corresponding alpha-aryl cyclopentanones.

2007-01-01 | S-EPMC3248813 | BioStudies

A cooperative N-heterocyclic carbene/chiral phosphate catalysis system for allenolate annulations.

Project description:The highly enantioselective NHC-catalyzed [3+2] annulation reaction with ?,?-alkynals and ?-ketoesters has been developed. A new mode of cooperative catalysis involving the combination of a chiral Brønsted acid and a C1-symmetric biaryl saturated-imidazolium precatalyst was required to generate the desired ?-crotonolactones in high yields and levels of enantioselectivity.

2014-01-01 | S-EPMC4142640 | BioStudies

Catalytic activation of carbon-carbon bonds in cyclopentanones.

Project description:In the chemical industry, molecules of interest are based primarily on carbon skeletons. When synthesizing such molecules, the activation of carbon-carbon single bonds (C-C bonds) in simple substrates is strategically important: it offers a way of disconnecting such inert bonds, forming more active linkages (for example, between carbon and a transition metal) and eventually producing more versatile scaffolds. The challenge in achieving such activation is the kinetic inertness of C-C bonds and the relative weakness of newly formed carbon-metal bonds. The most common tactic starts with a three- or four-membered carbon-ring system, in which strain release provides a crucial thermodynamic driving force. However, broadly useful methods that are based on catalytic activation of unstrained C-C bonds have proven elusive, because the cleavage process is much less energetically favourable. Here we report a general approach to the catalytic activation of C-C bonds in simple cyclopentanones and some cyclohexanones. The key to our success is the combination of a rhodium pre-catalyst, an N-heterocyclic carbene ligand and an amino-pyridine co-catalyst. When an aryl group is present in the C3 position of cyclopentanone, the less strained C-C bond can be activated; this is followed by activation of a carbon-hydrogen bond in the aryl group, leading to efficient synthesis of functionalized ?-tetralones-a common structural motif and versatile building block in organic synthesis. Furthermore, this method can substantially enhance the efficiency of the enantioselective synthesis of some natural products of terpenoids. Density functional theory calculations reveal a mechanism involving an intriguing rhodium-bridged bicyclic intermediate.

2016-01-01 | S-EPMC5502808 | BioStudies

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data