Browse
Submit Data
Databases
API
Help

Dataset Information

15 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Stereo- and regioselective photocycloaddition of extended alkenes using ?-cyclodextrin.

ABSTRACT: Photoexcitation of dibenzalacetones (1a-d) in homogeneous media and solid state yields a mixture of products with poor conversions. Irradiation of the reactants complexed to ?-cyclodextrin predominantly affords a single dimer (syn adduct 6) despite the possibility for several monomeric and dimeric products. High selectivity in the cavitand-mediated reaction along with the structural characterization of the inclusion complex provides insight into the supramolecular interactions that drive the self-assembly of the host-guest system.

SUBMITTER: Kashyap A

PROVIDER: S-EPMC6215711 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Stereo- and regioselective photocycloaddition of extended alkenes using γ-cyclodextrin.

Kashyap Akshay A Bokosike Treyvon K TK Bhuvanesh Nattamai N Pattabiraman Mahesh M

Organic & biomolecular chemistry 20181001 38

Photoexcitation of dibenzalacetones (1a-d) in homogeneous media and solid state yields a mixture of products with poor conversions. Irradiation of the reactants complexed to γ-cyclodextrin predominantly affords a single dimer (syn adduct 6) despite the possibility for several monomeric and dimeric products. High selectivity in the cavitand-mediated reaction along with the structural characterization of the inclusion complex provides insight into the supramolecular interactions that drive the sel ...[more]

PMID: 30229798

Similar Datasets

Regioselective Markovnikov hydrodifluoroalkylation of alkenes using difluoroenoxysilanes.

Project description:Alkene hydrodifluoroalkylation is a fruitful strategy for synthesizing difluoromethylated compounds that are interesting for developing new medicinal agents, agrochemicals, and advanced materials. Whereas the anti-Markovnikov hydrodifluoroalkylation to linear-type products is developed, employing radical-based processes, the Markovnikov synthesis of branched adducts remains unexplored. Herein, we describe acid-catalyzed processes involving carbocation intermediates as a promising strategy to secure the Markovnikov regioselectivity. Accordingly, the Markovnikov hydrodifluoroalkylation of mono-, di-, tri-, and tetrasubstituted alkenes using difluoroenoxysilanes, catalyzed by Mg(ClO4)2·6H2O, is achieved. This allows the diversity-oriented synthesis of α,α-difluoroketones with a quaternary or tertiary carbon at the β-position that are otherwise difficult to access. The method is applied to the modification of natural products and drug derivatives. The resulting α,α-difluorinated ketones could be converted to the corresponding α,α-difluorinated esters or alcohols, or organofluorine compounds featuring a CF2H or CF2CF2Ph moiety. Mechanistic studies support that Mg(ClO4)2·6H2O functions as a hidden Brønsted acid catalyst.

| S-EPMC7599245 | biostudies-literature

Stereo- and Regioselective Alkyne Hydrometallation with Gold(III) Hydrides.

Project description:The hydroauration of internal and terminal alkynes by gold(III) hydride complexes [(C^N^C)AuH] was found to be mediated by radicals and proceeds by an unexpected binuclear outer-sphere mechanism to cleanly form trans-insertion products. Radical precursors such as azobisisobutyronitrile lead to a drastic rate enhancement. DFT calculations support the proposed radical mechanism, with very low activation barriers, and rule out mononuclear mechanistic alternatives. These alkyne hydroaurations are highly regio- and stereospecific for the formation of Z-vinyl isomers, with Z/E ratios of >99:1 in most cases.

| S-EPMC5113781 | biostudies-literature

Enantio- and regioselective CuH-catalyzed hydroamination of alkenes.

Project description:A highly enantio- and regioselective copper-catalyzed hydroamination reaction of alkenes has been developed using diethoxymethylsilane and esters of hydroxylamines. The process tolerates a wide variety of substituted styrenes, including trans-, cis-, and ?,?-disubstituted styrenes, to yield ?-branched amines. In addition, aliphatic alkenes coupled to generate exclusively the anti-Markovnikov hydroamination products.

| S-EPMC3874865 | biostudies-literature

Highly stereo- and regioselective synthesis of (Z)-trisubstituted alkenes via 1-bromo-1-alkyne hydroboration-migratory insertion-Zn-promoted iodinolysis and Pd-catalyzed organozinc cross-coupling.

Project description:Hydroboration of 1-bromo-1-alkynes with dibromoborane followed by addition of 3 or 4 equiv of Me2Zn provides an efficient and selective route to (Z)-2-alkenyldimethylboranes (3) or (Z)-2-alkenylmethylzincs (4), respectively, which have been successfully applied to one-pot Suzuki (B-I) or Negishi (Zn-I) coupling in some less demanding cases. However, in more demanding cross-coupling reactions, only the use of either (Z)-2-alkenyliodides (5) or the alkenylzincs prepared from lithiation and then zincation of 5 proves to be highly satisfactory (Zn-II or Zn-III protocol). On the contrary, the corresponding organoboron coupling under B-II or B-III protocol appears to be less satisfactory. Preliminary studies indicate that certain substituents proximal to trisubstituted alkenes seriously affect the course of the desired alkenylboron cross-coupling.

| S-EPMC3891656 | biostudies-literature

Stereo- and regioselective glycosylations to the bis-C-arylglycoside of kidamycin.

Project description:In explorations toward the total synthesis of the antitumor anthrapyran natural product kidamycin, the regioselective introduction of aminosugars angolosamine and vancosamine as C-arylglycosides has been accomplished onto hydroxylated anthrapyran aglycones. Specifically, the 9,11-dihydroxylated anthrapyran A undergoes sequential glycosylations with angolosamine synthon B and vancosamine synthon C to regio- and stereoselectively afford bis-C-glycoside D corresponding to the C-glycoside pattern of kidamycin.

| S-EPMC4604443 | biostudies-literature

Intermolecular Photocatalytic Chemo-, Stereo- and Regioselective Thiol-Yne-Ene Coupling Reaction.

Project description:The first example of an intermolecular thiol-yne-ene coupling reaction is reported for the one-pot construction of C-S and C-C bonds. Thiol-yne-ene coupling opens a new dimension in building molecular complexity to access densely functionalized products. The employment of Eosin Y/DBU/MeOH photocatalytic system suppresses hydrogen atom transfer (HAT) and associative reductant upconversion (via C-S three-electron σ-bond formation). Investigation of the reaction mechanism by combining online ESI-UHRMS, EPR spectroscopy, isotope labeling, determination of quantum yield, cyclic voltammetry, Stern-Volmer measurements and computational modeling revealed a unique photoredox cycle with four radical-involving stages. As a result, previously unavailable products of the thiol-yne-ene reaction were obtained in good yields with high selectivity. They can serve as stable precursors for synthesizing synthetically demanding activated 1,3-dienes.

| S-EPMC9313788 | biostudies-literature

Stereo- and Regioselective Synthesis of 4-Vinylpyrrolidine from N-Tethered Alkyne-Alkenol.

Project description:Indium(III) chloride can be efficiently used for the synthesis of 4-vinylpyrrolidine from N-tethered alkyne-alkenol in good yields. The reaction is highly stereo- and regioselective.

| S-EPMC6641446 | biostudies-literature

Copper-catalyzed stereo- and regioselective hydrophosphorylation of terminal alkynes: scope and mechanistic study.

Project description:Herein, a protocol for copper-catalyzed highly stereo- and regioselective hydrophosphorylation of terminal alkynes to E-alkenylphosphorus compounds was well developed. It represents a general and practical hydrophosphorylation method, of which diarylphosphine oxide, dialkylphosphine oxide and dialkyl phosphite all had effective P(O)H parts to react with different types of terminal alkynes. Contrary to previous air-sensitive reports, all the reactions proceeded well under air. This methodology is quite attractive owing to the high stereo- and regioselectivity, good functional group tolerance, scalability and facile late-stage derivatization of some natural product derivatives and commercially available herbicides. What's more, investigations on the reaction mechanism with deuterium-labeling experiments and DFT studies firstly disclosed the deprotonation-protonation equilibrium of terminal alkynes and P(O)H part during the catalytic hydrophosphorylation process.

| S-EPMC9241361 | biostudies-literature

Optimization of Regioselective ?-Glucosylation of Hesperetin Catalyzed by Cyclodextrin Glucanotransferase.

Project description:The regioselective ?-glucosylation of hesperetin was achieved by a transglycosylation reaction catalyzed by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. using soluble starch as glucosyl donor. By combining mass spectrometry (ESI-TOF) and 2D-NMR analysis, the main monoglucosylated derivative was fully characterized (hesperetin 7-O-?-d-glucopyranoside). In order to increase the yield of monoglucoside, several reaction parameters were optimized: Nature and percentage of cosolvent, composition of the aqueous phase, glucosyl donor, temperature, and the concentrations of hesperetin and soluble starch. Under the optimal conditions, which included the presence of 30% of bis(2-methoxyethyl) ether as cosolvent, the maximum concentration of monoglucoside was approximately 2 mM, obtained after 24 h of reaction. To our knowledge, this is the first report of direct glucosylation of hesperetin employing free enzymes instead of whole cells.

| S-EPMC6278433 | biostudies-literature

Direct and Regioselective Di-?-fucosylation on the Secondary Rim of ?-Cyclodextrin.

Project description:A straightforward glycosylation method is described to regio- and stereoselectively introduce two ?-l-fucose moieties directly to the secondary rim of ?-cyclodextrin. Using NMR and MS fragmentation studies, the nonasaccharide structure was determined, which was also visualized using molecular dynamics simulations. The reported glycosylation method proved to be robust on gram-scale, and may be generally applied to directly glycosylate ?-cyclodextrins to make well-defined multivalent glycoclusters.

| S-EPMC6563713 | biostudies-literature

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