Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Stereochemical lability of azatitanacyclopropanes: dynamic kinetic resolution in reductive cross-coupling reactions with allylic alcohols.

ABSTRACT: Azatitanacyclopropanes (titanaziridines) are shown to be stereochemically labile under reaction conditions for reductive cross-coupling. This fundamental property has been employed to realize highly selective asymmetric coupling reactions with allylic alcohols that proceed by dynamic kinetic resolution.

SUBMITTER: Yang D

PROVIDER: S-EPMC4012230 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Stereochemical lability of azatitanacyclopropanes: dynamic kinetic resolution in reductive cross-coupling reactions with allylic alcohols.

Yang Dexi D Micalizio Glenn C GC

Chemical communications (Cambridge, England) 20131001 78

Azatitanacyclopropanes (titanaziridines) are shown to be stereochemically labile under reaction conditions for reductive cross-coupling. This fundamental property has been employed to realize highly selective asymmetric coupling reactions with allylic alcohols that proceed by dynamic kinetic resolution. ...[more]

PMID: 23963189

Similar Datasets

Iridium-catalyzed enantioselective alkynylation and kinetic resolution of alkyl allylic alcohols.

Project description:Herein, we report an efficient kinetic resolution of alkyl allylic alcohols enabled by an iridium-catalyzed enantioselective alkynylation of alkyl allylic alcohols with potassium alkynyltrifluoroborates. A wide range of chiral 1,4-enynes bearing various functional groups and unreacted enantioenriched allylic alcohols were obtained with excellent enantioselectivities and high kinetic resolution performance (s-factor up to 922). Additionally, this method is particularly effective for preparing some useful optically pure alkyl allylic alcohols, such as the key components towards the synthesis of prostaglandins and naturally occurring matsutakeols, which are difficult to access via other asymmetric reactions. Mechanistic studies revealed that the efficient kinetic resolution might be due to the significant distinction of the η2-coordination between the (R)- and (S)-allylic alcohols with the iridium/(phosphoramidite, olefin) complex.

| S-EPMC9710208 | biostudies-literature

Preparation of stereodefined homoallylic amines from the reductive cross-coupling of allylic alcohols with imines.

Project description:Regio-, diastereo-, and enantioselective coupling reactions between imines and allylic alcohols have been developed. These coupling reactions deliver complex homoallylic amine products through a convergent C-C bond forming process that does not proceed through intermediate allylic organometallic reagents. In general, convergent coupling, by exposure of an allylic alkoxide to a preformed Ti-imine complex, occurs with allylic transposition in a predictable and stereocontrolled manner. While simple diastereoselection in these reactions is high, delivering anti-products with ?20:1 selectivity, the organometallic transformation described is compatible with a diverse range of functionality and substrates (including aliphatic and aromatic imines, allylic silanes, trisubstituted alkenes, vinyl- and aryl halides, trifluoromethyl groups, thioethers, and aromatic heterocycles). Alkene geometry of the products is a complex function of the allylic alcohol structure and is consistent with a mechanistic proposal based on syn-carbometalation followed by syn-elimination by way of a boat-like transition state geometry. Single asymmetric coupling reactions provide a means to translate the stereochemical information of the allylic alcohol to the homoallylic amine or to control diastereoselection in the coupling reactions of achiral allylic alcohols with chiral imines. Double asymmetric coupling reactions are also described that afford a unique means to control stereoselection in these complex convergent coupling processes. Finally, empirical models are proposed that are consistent with the observed stereochemical course of these coupling reactions en route to chiral homoallylic amines possessing di- or trisubstituted alkenes and anti- or syn- relative stereochemistry at the allylic and homoallylic positions.

| S-EPMC2993781 | biostudies-literature

Asymmetric hydrogenation of exocyclic γ,δ-unsaturated β-ketoesters to functionalized chiral allylic alcohols <i>via</i> dynamic kinetic resolution.

Project description:An iridium catalyzed asymmetric hydrogenation of racemic exocyclic γ,δ-unsaturated β-ketoesters via dynamic kinetic resolution to functionalized chiral allylic alcohols was developed. With the chiral spiro iridium catalysts Ir-SpiroPAP, a series of racemic exocyclic γ,δ-unsaturated β-ketoesters bearing a five-, six-, or seven-membered ring were hydrogenated to the corresponding functionalized chiral allylic alcohols in high yields with good to excellent enantioselectivities (87 to >99% ee) and cis-selectivities (93 : 7 to >99 : 1). The origin of the excellent stereoselectivity was also rationalized by density functional theory calculations. Furthermore, this protocol could be performed on gram scale and at a lower catalyst loading (0.002 mol%) without the loss of reactivity and enantioselectivity, and has been successfully applied in the enantioselective synthesis of chiral carbocyclic δ-amino esters and the β-galactosidase inhibitor isogalactofagomine.

| S-EPMC8188505 | biostudies-literature

Stereoselective cross-coupling between allylic alcohols and aldimines.

Project description:A cross-coupling reaction between an allylic alcohol and an imine is described for stereoselective allylation of aromatic and aliphatic imines. This method provides operationally simple, enantioselective access to functionalized homoallylic amines. Particularly noteworthy is direct use of a functionalized allylic alcohol as an allylating reagent without prederivatization, which obviates the use of preformed organometallic reagents or activated imine derivatives.

| S-EPMC2720054 | biostudies-literature

Generation of quaternary centers by reductive cross-coupling: shifting of regioselectivity in a subset of allylic alcohol-based coupling reactions.

Project description:Regioselective titanium alkoxide-mediated reductive cross-coupling reactions of allylic alcohols with vinylsilanes and imines have previously been demonstrated to proceed with allylic transposition by formal metallo-[3,3]-rearrangement [thought to proceed by a sequence of: 1) directed carbometalation, and 2) syn-elimination]. While many examples have been described that support this reaction path, a collection of substrates have recently been identified that react by way of an alternative pathway, delivering a concise convergent route to coupled products bearing a quaternary center.

| S-EPMC3110011 | biostudies-literature

Reductive enzymatic dynamic kinetic resolution affording 115 g/L (S)-2-phenylpropanol.

Project description:BackgroundPublished biocatalytic routes for accessing enantiopure 2-phenylpropanol using oxidoreductases afforded maximal product titers of only 80 mM. Enzyme deactivation was identified as the major limitation and was attributed to adduct formation of the aldehyde substrate with amino acid residues of the reductase.ResultsA single point mutant of Candida tenuis xylose reductase (CtXR D51A) with very high catalytic efficiency (43·103 s-1 M-1) for (S)-2-phenylpropanal was found. The enzyme showed high enantioselectivity for the (S)-enantiomer but was deactivated by 0.5 mM substrate within 2 h. A whole-cell biocatalyst expressing the engineered reductase and a yeast formate dehydrogenase for NADH-recycling provided substantial stabilization of the reductase. The relatively slow in situ racemization of 2-phenylpropanal and the still limited biocatalyst stability required a subtle adjustment of the substrate-to-catalyst ratio. A value of 3.4 gsubstrate/gcell-dry-weight was selected as a suitable compromise between product ee and the conversion ratio. A catalyst loading of 40 gcell-dry-weight was used to convert 1 M racemic 2-phenylpropanal into 843 mM (115 g/L) (S)-phenylpropanol with 93.1% ee.ConclusionThe current industrial production of profenols mainly relies on hydrolases. The bioreduction route established here represents an alternative method for the production of profenols that is competitive with hydrolase-catalyzed kinetic resolutions.

| S-EPMC8507385 | biostudies-literature

Broad-spectrum kinetic resolution of alcohols enabled by Cu-H-catalysed dehydrogenative coupling with hydrosilanes.

Project description:The enantioselective silylation of racemic alcohols, where one enantiomer reacts faster than the other, is an alternative approach to established enzymatic and non-enzymatic acylation techniques. The existing art is either limited to structurally biased alcohols or requires elaborate catalysts. Simple substrates, such as benzylic and allylic alcohols, with no coordinating functionality in the proximity of the hydroxy group have been challenging in these kinetic resolutions. We report here the identification of a broadly applicable chiral catalyst for the enantioselective dehydrogenative coupling of alcohols and hydrosilanes with both the chiral ligand and the hydrosilane being commercially available. The efficiency of kinetic resolutions is characterized by the selectivity factor, that is, the ratio of the reaction rates of the fast-reacting over the slow-reacting enantiomer. The selectivity factors achieved with the new method are good for acyclic benzylic alcohols (?170) and high for synthetically usefully cyclic benzylic (?40.1) and allylic alcohols (?159).

| S-EPMC5461486 | biostudies-literature

Nonenzymatic dynamic kinetic resolution of secondary alcohols via enantioselective acylation: synthetic and mechanistic studies.

Project description:Because of the ubiquity of the secondary carbinol subunit, the development of new methods for its enantioselective synthesis remains an important ongoing challenge. In this report, we describe the first nonenzymatic method for the dynamic kinetic resolution (DKR) of secondary alcohols (specifically, aryl alkyl carbinols) through enantioselective acylation, and we substantially expand the scope of this approach, vis-à-vis enzymatic reactions. Simply combining an effective process for the kinetic resolution of alcohols with an active catalyst for the racemization of alcohols did not lead to DKR, due to the incompatibility of the ruthenium-based racemization catalyst with the acylating agent (Ac(2)O) used in the kinetic resolution. A mechanistic investigation revealed that the ruthenium catalyst is deactivated through the formation of a stable ruthenium-acetate complex; this deleterious pathway was circumvented through the appropriate choice of acylating agent (an acyl carbonate). Mechanistic studies of this new process point to reversible N-acylation of the nucleophilic catalyst, acyl transfer from the catalyst to the alcohol as the rate-determining step, and carbonate anion serving as the Brønsted base in that acyl-transfer step.

| S-EPMC3447740 | biostudies-literature

Palladium-Catalyzed Enantioselective Intermolecular Coupling of Phenols and Allylic Alcohols.

Project description:An enantioselective intermolecular coupling of oxygen nucleophiles and allylic alcohols to give β-aryloxycarbonyl compounds is disclosed using a chiral pyridine oxazoline-ligated palladium catalyst under mild conditions. As opposed to the formation of traditional Wacker-type products, enantioselective migratory insertion is followed by β-hydride elimination toward the adjacent alcohol. Deuterium labeling experiments suggest a syn-migratory insertion of the alkene into the Pd-O bond. A broad scope of phenols, various allylic alcohols, and an alkyl hydroperoxide are viable coupling partners in this process.

| S-EPMC5180452 | biostudies-literature

The regio- and stereochemical course of reductive cross-coupling reactions between 1,3-disubstituted allenes and vinylsilanes: Synthesis of (Z)-dienes.

Project description:In investigations aimed at exploring the potential of disubstituted allenes in stereoselective synthesis, we report studies that explore the reductive cross-coupling reaction of vinylsilanes with a range of substituted allenes. Regiochemical control is attained by employing allenic alkoxides, where the proximal heteroatom dictates the site-selectivity in a process that proceeds by net formal metallo-[3,3] rearrangement (directed carbometalation/elimination). Stereoselectivity in these reactions is complex, with both the nature of allene substitution and relative stereochemistry of the substrate impacting the stereoselective generation of each alkene of a substituted 1,3-diene. 2009 Elsevier Ltd. All rights reserved.

| S-EPMC3769195 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

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