Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

A more comprehensive and highly practical solution to enantioselective aldehyde crotylation.

ABSTRACT: The enantioselective crotylation of aldehydes with 1,2-diaminochlorocrotylsilane reagents is effectively catalyzed by Sc(OTf)(3). The one significant limitation on the utility of these reagents--substrate scope--has thus been addressed. The net result is the most comprehensive and highly practical method for enantioselective aldehyde crotylation yet advanced.

SUBMITTER: Kim H

PROVIDER: S-EPMC3090146 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

A more comprehensive and highly practical solution to enantioselective aldehyde crotylation.

Kim Hyunwoo H Ho Stephen S Leighton James L JL

Journal of the American Chemical Society 20110412 17

The enantioselective crotylation of aldehydes with 1,2-diaminochlorocrotylsilane reagents is effectively catalyzed by Sc(OTf)(3). The one significant limitation on the utility of these reagents--substrate scope--has thus been addressed. The net result is the most comprehensive and highly practical method for enantioselective aldehyde crotylation yet advanced. ...[more]

PMID: 21486033

Similar Datasets

A new and more powerfully activating diamine for practical and scalable enantioselective aldehyde crotylsilylation reactions.

Project description: Not available

| S-EPMC4142653 | biostudies-literature

Enantioselective C-H crotylation of primary alcohols via hydrohydroxyalkylation of butadiene.

Project description:The direct, by-product-free conversion of basic feedstocks to products of medicinal and agricultural relevance is a broad goal of chemical research. Butadiene is a product of petroleum cracking and is produced on an enormous scale (about 12 × 10(6) metric tons annually). Here, with the use of a ruthenium catalyst modified by a chiral phosphate counterion, we report the direct redox-triggered carbon-carbon coupling of alcohols and butadiene to form products of carbonyl crotylation with high levels of anti-diastereoselectivity and enantioselectivity in the absence of stoichiometric by-products.

| S-EPMC3439217 | biostudies-other

A practical solution for preserving single cells for RNA sequencing

Project description:We present a method for histological tissue fixation using dithio-bis(succinimidyl propionate) (DSP), or Lomant's Reagent, to stabilise cell samples for single-cell transcriptomic applications.

2017-05-11 | GSE98734 | GEO

Solution structures of lithium amino alkoxides used in highly enantioselective 1,2-additions.

Project description:Lithium ephedrates and norcarane-derived lithium amino alkoxides used to effect highly enantioselective 1,2-additions on large scales have been characterized in toluene and tetrahydrofuran. The method of continuous variations in conjunction with (6)Li NMR spectroscopy reveals that the lithium amino alkoxides are tetrameric. In each case, low-temperature (6)Li NMR spectra show stereoisomerically pure homoaggregates displaying resonances consistent with an S4-symmetric cubic core rather than the alternative D2d core. These assignments are supported by density functional theory computations and conform to X-ray crystal structures. Slow aggregate exchanges are discussed in the context of amino alkoxides as chiral auxiliaries.

| S-EPMC3985715 | biostudies-literature

anti-Diastereo- and enantioselective carbonyl crotylation from the alcohol or aldehyde oxidation level employing a cyclometallated iridium catalyst: alpha-methyl allyl acetate as a surrogate to preformed crotylmetal reagents.

Project description:Under the conditions of transfer hydrogenation employing an ortho-cyclometallated iridium catalyst generated in situ from [Ir(cod)Cl](2), 4-cyano-3-nitrobenzoic acid and the chiral phosphine ligand (S)-SEGPHOS, alpha-methyl allyl acetate couples to alcohols 1a-1j with complete levels of branched regioselectivity to furnish products of carbonyl crotylation 3a-3j, which are formed with good levels of anti-diastereoselectivity and exceptional levels of enantioselectivity. An identical set of optically enriched carbonyl crotylation products 3a-3j is accessible from the corresponding aldehydes 2a-2j under the same conditions, but employing isopropanol as the terminal reductant. Experiments aimed at probing the origins of stereoselection establish a matched mode of ionization for the (R)-acetate and the iridium catalyst modified by (S)-SEGPHOS, as well as reversible ionization of the allylic acetate with rapid pi-facial interconversion of the resulting pi-crotyl intermediate in advance of C-C bond formation. Additionally, rapid alcohol-aldehyde redox equilibration in advance of carbonyl addition is demonstrated. Thus, anti-diastereo- and enantioselective carbonyl crotylation from the alcohol or aldehyde oxidation level is achieved in the absence of any stoichiometric metallic reagents or stoichiometric metallic byproducts.

| S-EPMC3165013 | biostudies-literature

Enantioselective aldehyde alpha-nitroalkylation via oxidative organocatalysis.

Project description:The first enantioselective organocatalytic alpha-nitroalkylation of aldehydes has been accomplished. The aforementioned process involves the oxidative coupling of an enamine intermediate, generated transiently via condensation of an amine catalyst with an aldehyde, with a silyl nitronate to produce a beta-nitroaldehyde. Two methods, one that furnishes the syn beta-nitroaldehyde and a second that provides access to the anti isomer, have been developed. Data are presented to support a hypothesis that explains this phenomenon in terms of a silyl group-controlled change in mechanism. Finally, a three-step procedure for the synthesis of both syn- and anti-alpha,beta-disubstituted beta-amino acids is presented.

| S-EPMC3259685 | biostudies-literature

Practical structure solution with ARCIMBOLDO.

Project description:Since its release in September 2009, the structure-solution program ARCIMBOLDO, based on the combination of locating small model fragments such as polyalanine ?-helices with density modification with the program SHELXE in a multisolution frame, has evolved to incorporate other sources of stereochemical or experimental information. Fragments that are more sophisticated than the ubiquitous main-chain ?-helix can be proposed by modelling side chains onto the main chain or extracted from low-homology models, as locally their structure may be similar enough to the unknown one even if the conventional molecular-replacement approach has been unsuccessful. In such cases, the program may test a set of alternative models in parallel against a specified figure of merit and proceed with the selected one(s). Experimental information can be incorporated in three ways: searching within ARCIMBOLDO for an anomalous fragment against anomalous differences or MAD data or finding model fragments when an anomalous substructure has been determined with another program such as SHELXD or is subsequently located in the anomalous Fourier map calculated from the partial fragment phases. Both sources of information may be combined in the expansion process. In all these cases the key is to control the workflow to maximize the chances of success whilst avoiding the creation of an intractable number of parallel processes. A GUI has been implemented to aid the setup of suitable strategies within the various typical scenarios. In the present work, the practical application of ARCIMBOLDO within each of these scenarios is described through the distributed test cases.

| S-EPMC3322593 | biostudies-literature

Enantioselective carbonyl allylation, crotylation, and tert-prenylation of furan methanols and furfurals via iridium-catalyzed transfer hydrogenation.

Project description:5-Substituted-2-furan methanols 1a-c are subject to enantioselective carbonyl allylation, crotylation and tert-prenylation upon exposure to allyl acetate, alpha-methyl allyl acetate, or 1,1-dimethylallene in the presence of an ortho-cyclometalated iridium catalyst modified by (R)-Cl,MeO-BIPHEP, (R)-C3-TUNEPHOS, and (R)-C3-SEGPHOS, respectively. In the presence of 2-propanol, but under otherwise identical conditions, the corresponding substituted furfurals 2a-c are converted to identical products of allylation, crotylation, and tert-prenylation. Optically enriched products of carbonyl allylation, crotylation, and reverse prenylation 3b, 4b, and 5b were subjected to Achmatowicz rearrangement to furnish the corresponding gamma-hydroxy-beta-pyrones 6a-c, respectively, with negligible erosion of enantiomeric excess.

| S-EPMC2830394 | biostudies-literature

Diastereo- and enantioselective ruthenium-catalyzed hydrohydroxyalkylation of 2-silyl-butadienes: carbonyl syn-crotylation from the alcohol oxidation level.

Project description:Exposure of alcohols 2a-2j to 2-silyl-butadienes in the presence of ruthenium complexes modified by (R)-SEGPHOS or (R)-DM-SEGPHOS results in redox-triggered generation of allylruthenium-aldehyde pairs, which combine to form products of carbonyl crotylation 4a-4j in the absence of stoichiometric byproducts and with high levels of syn-diastereo- and enantioselectivity. In the presence of isopropanol under otherwise identical conditions, aldehydes 3a-3j are converted to an equivalent set of adducts 4a-4j. Whereas reactions conducted using conventional heating require 48 h, microwave irradiation enables full conversion in only 4 h. Finally, as illustrated in the conversion of adduct 4a to compounds 6a and 6b, diastereoselective hydroboration-Suzuki cross-coupling with aryl and vinyl halides followed by Fleming-Tamao oxidation enables generation of anti,syn-stereotriads found in numerous polyketide natural products.

| S-EPMC3131435 | biostudies-literature

A practical and efficient route for the highly enantioselective synthesis of mexiletine analogues and novel beta-thiophenoxy and pyridyl ethers.

Project description:A practical and efficient procedure for the enantioselective synthesis of mexiletine analogues with use of 10% of spiroborate ester 6 as chirality transfer agent is presented. A variety of mexiletine analogues were prepared in good yield with excellent enantioselectivities (91-97% ee) from readily available starting materials. The developed methodology was also successfully applied for the synthesis of novel beta-amino ethers containing thiophenyl and pyridyl fragments.

| S-EPMC2668572 | 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