Browse
Submit Data
Databases
API
Help

Dataset Information

28 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Chiral N-salicylidene vanadyl carboxylate-catalyzed enantioselective aerobic oxidation of alpha-hydroxy esters and amides.

ABSTRACT: A series of chiral vanadyl carboxylates derived from N-salicylidene-L-alpha-amino acids and vanadyl sulfate has been developed. These configurationally well defined complexes were examined for the kinetic resolution of double- and mono-activated 2 degrees alcohols. The best chiral templates involve the combination of L-tert-leucine and 3,5-di-t-butyl-, 3,5-diphenyl-, or 3,4-dibromo-salicylaldehyde. The resulting vanadyl(V)-methoxide complexes after recrystallization from air-saturated methanol serve as highly enantioselective catalysts for asymmetric aerobic oxidation of alpha-hydroxyl-esters and amides with a diverse array of alpha-, O-, and N-substituents at ambient temperature in toluene. The asymmetric inductions of the oxidation process are in the range of 10 to >100 in terms of selectivity factors (k(rel)) in most instances. The previously undescribed aerobic oxidation protocol is also applicable to the kinetic resolution of C-13 taxol side chain with high selectivity factor (k(rel) = 35). X-ray crystallographic analysis of an adduct between a given vanadyl complex and N-benzyl-mandelamide allows for probing the stereochemical origin of the nearly exclusive asymmetric control in the oxidation process.

SUBMITTER: Weng SS

PROVIDER: S-EPMC1382168 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

A convenient enantioselective decarboxylative aldol reaction to access chiral α-hydroxy esters using β-keto acids.

Project description:We show a convenient decarboxylative aldol process using a scandium catalyst and a PYBOX ligand to generate a series of highly functionalized chiral α-hydroxy esters. The protocol tolerates a broad range of β-keto acids with inactivated aromatic and aliphatic α-keto esters. The possible mechanism is rationalized.

| S-EPMC4077541 | biostudies-literature

Novel Effect of Zinc Nitrate/Vanadyl Oxalate for Selective Catalytic Oxidation of α-Hydroxy Esters to α-Keto Esters with Molecular Oxygen: An In Situ ATR-IR Study.

Project description:Selective oxidation of α-hydroxy esters is one of the most important methods to prepare high value-added α-keto esters. An efficient catalytic system consisting of Zn(NO₃)₂/VOC₂O₄ is reported for catalytic oxidation of α-hydroxy esters with molecular oxygen. Up to 99% conversion of methyl DL-mandelate or methyl lactate could be facilely obtained with high selectivity for its corresponding α-keto ester under mild reaction conditions. Zn(NO₃)₂ exhibited higher catalytic activity in combination with VOC₂O₄ compared with Fe(NO₃)₃ and different nitric oxidative gases were detected by situ attenuated total reflection infrared (ATR-IR) spectroscopy. UV-vis and ATR-IR results indicated that coordination complex formed in Zn(NO₃)₂ in CH₃CN solution was quite different from Fe(NO₃)₃; it is proposed that the charge-transfer from Zn2+ to coordinated nitrate groups might account for the generation of different nitric oxidative gases. The XPS result indicate that nitric oxidative gas derived from the interaction of Zn(NO₃)₂ with VOC₂O₄ could be in favor of oxidizing VOC₂O₄ to generate active vanadium (V) species. It might account for different catalytic activity of Zn(NO₃)₂ or Fe(NO₃)₃ combined with VOC₂O₄. This work contributes to further development of efficient aerobic oxidation under mild reaction conditions.

| S-EPMC6480123 | biostudies-literature

Chiral Bronsted Acid-Catalyzed Asymmetric Synthesis of N-Aryl-cis-aziridine Carboxylate Esters.

Project description:We report a multi-component asymmetric Brønsted acid-catalyzed aza-Darzens reaction which is not limited to specific aromatic or heterocyclic aldehydes. Incorporating alkyl diazoacetates and, important for high ee's, ortho-tert-butoxyaniline our optimized reaction (i.e. solvent, temperature and catalyst study) affords excellent yields (61-98 %) and mostly >90 % optically active cis-aziridines. (+)-Chloramphenicol was generated in 4 steps from commercial starting materials. A tentative mechanism is outlined.

| S-EPMC5502890 | biostudies-literature

Enantioselective synthesis of γ-chiral amides via copper-catalyzed reductive relay hydroaminocarbonylation.

Project description:Chiral amides are common and effective structural motifs found in many pharmaceuticals and biologically active molecules. Despite their importance, existing synthetic methods are predominantly employed for the synthesis of α-amides and β-amides. The synthesis of remote chiral amides, characterized by distal stereocenters, typically requires intricate synthetic steps conducted under demanding conditions. Here, we present a general procedure for the copper-catalyzed enantioselective synthesis of γ-chiral amides, employing a reductive relay hydroaminocarbonylation strategy with trisubstituted allylic benzoates and hydroxylamine electrophiles. This approach demonstrates a wide substrate scope with excellent enantioselectivity and regioselectivity, thus providing access to challenging enantioenriched γ-chiral amides.

| S-EPMC11306323 | biostudies-literature

Iridium-Catalyzed Enantioselective Allylic Substitution of Enol Silanes from Vinylogous Esters and Amides.

Project description:The enol silanes of vinylogous esters and amides are classic dienes for Diels-Alder reactions. Here, we report their reactivity as nucleophiles in Ir-catalyzed, enantioselective allylic substitution reactions. A variety of allylic carbonates react with these nucleophiles to give allylated products in good yields with high enantioselectivities and excellent branched-to-linear ratios. These reactions occur with KF or alkoxide as the additive, but mechanistic studies suggest that these additives do not activate the enol silanes. Instead, they serve as bases to promote the cyclometalation to generate the active Ir catalyst. The carbonate anion, which was generated from the oxidative addition of the allylic carbonate, likely activates the enol silanes to trigger their activity as nucleophiles for reactions with the allyliridium electrophile. The synthetic utility of this method was illustrated by the synthesis of the anti-muscarinic drug, fesoterodine.

| S-EPMC5342901 | biostudies-literature

Organocatalytic Enantioselective Mannich Reaction: Direct Access to Chiral β-Amino Esters.

Project description:An asymmetric Mannich reaction has been developed to generate chiral β-amino esters in good yields with excellent enantiomeric excesses (ee, up to 99%) using a chiral bifunctional thiourea catalyst derived from (R,R)-cyclohexyldiamine. This is the first report on the addition of 3-indolinone-2-carboxylates to N-Boc-benzaldimines generated in situ from α-amidosulfones, which proceeds under mild conditions.

| S-EPMC6648529 | biostudies-literature

Metal-free catalytic enantioselective C-B bond formation: (pinacolato)boron conjugate additions to ?,?-unsaturated ketones, esters, Weinreb amides, and aldehydes promoted by chiral N-heterocyclic carbenes.

Project description:The first broadly applicable metal-free enantioselective method for boron conjugate addition (BCA) to ?,?-unsaturated carbonyls is presented. The C-B bond forming reactions are promoted in the presence of 2.5-7.5 mol % of a readily accessible C(1)-symmetric chiral imidazolinium salt, which is converted, in situ, to the catalytically active diastereo- and enantiomerically pure N-heterocyclic carbene (NHC) by the common organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu). In addition to the commercially available bis(pinacolato)diboron [B(2)(pin)(2)], and in contrast to reactions with the less sterically demanding achiral NHCs, the presence of MeOH is required for high efficiency. Acyclic and cyclic ?,?-unsaturated ketones, as well as acyclic esters, Weinreb amides, and aldehydes, can serve as suitable substrates; the desired ?-boryl carbonyls are isolated in up to 94% yield and >98:2 enantiomer ratio (er). Transformations are often carried out at ambient temperature. In certain cases, such as when the relatively less reactive unsaturated amides are used, elevated temperatures are required (50-66 °C); nonetheless, reactions remain highly enantioselective. The utility of the NHC-catalyzed method is demonstrated through comparison with the alternative Cu-catalyzed protocols; in cases involving a polyfunctional substrate, unique profiles in chemoselectivity are exhibited by the metal-free approach (e.g., conjugate addition vs reaction with an alkyne, allene, or aldehyde).

| S-EPMC3354020 | biostudies-literature

Palladium-catalyzed chemo- and enantioselective oxidation of allylic esters and carbonates.

Project description:The palladium-catalyzed oxidation of allylic esters and carbonates using a novel potassium nitronate has been developed. This method is highly chemoselective, leaving other esters, alcohols, thioethers, and amines undisturbed. The oxidation can be operated in two modes: an achiral mode, using either PPh3 or rac-2 as ligand, or a chiral and highly enantioselective mode, using 2 as ligand. The oxidative enantioselective desymmetrization of meso bis-esters provides a significantly shorter method to arrive at commonly used synthetic intermediates compared to other strategies. Highly efficient kinetic resolution is also possible using this methodology.

| S-EPMC2531164 | biostudies-literature

Highly enantioselective direct alkylation of arylacetic acids with chiral lithium amides as traceless auxiliaries.

Project description:A direct, highly enantioselective alkylation of arylacetic acids via enediolates using a readily available chiral lithium amide as a stereodirecting reagent has been developed. This approach circumvents the traditional attachment and removal of chiral auxiliaries used currently for this type of transformation. The protocol is operationally simple, and the chiral reagent is readily recoverable.

| S-EPMC3373785 | biostudies-literature

Direct enantioselective conjugate addition of carboxylic acids with chiral lithium amides as traceless auxiliaries.

Project description:Michael addition is a premier synthetic method for carbon-carbon and carbon-heteroatom bond formation. Using chiral dilithium amides as traceless auxiliaries, we report the direct enantioselective Michael addition of carboxylic acids. A free carboxyl group in the product provides versatility for further functionalization, and the chiral reagent can be readily recovered by extraction with aqueous acid. The method has been applied in the enantioselective total synthesis of the purported structure of pulveraven B.

| S-EPMC4308744 | 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