Browse
Submit Data
Databases
API
Help

Dataset Information

15 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Formation of Fused Aromatic Architectures via an Oxidative Dearomatization - Radical Cyclization Rearomatization Approach.

ABSTRACT: A new mild C-C bond forming cyclization approach of catechol derivatives is reported. This approach relies on an initial dearomatization step using lead (IV) acetate followed by a carefully controlled radical cyclization step, which under the reaction conditions also facilitates rearomatization. Triethylborane is the key to the success of this reaction as it enables the reaction to proceed at low temperatures and is also believed to aid rearomatization. The amount and ratio of triethylborane and reducing agent (tributyltinhydride) that is employed as well as the concentration the reaction is run at are all essential to the success of this new approach.

SUBMITTER: Vitaku E

PROVIDER: S-EPMC4517290 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Formation of Fused Aromatic Architectures via an Oxidative Dearomatization - Radical Cyclization Rearomatization Approach.

Vitaku Edon E Njardarson Jon T JT

Tetrahedron letters 20150601 23

A new mild C-C bond forming cyclization approach of catechol derivatives is reported. This approach relies on an initial dearomatization step using lead (IV) acetate followed by a carefully controlled radical cyclization step, which under the reaction conditions also facilitates rearomatization. Triethylborane is the key to the success of this reaction as it enables the reaction to proceed at low temperatures and is also believed to aid rearomatization. The amount and ratio of triethylborane and ...[more]

PMID: 26236054

Similar Datasets

An efficient oxidative dearomatization-radical cyclization approach to symmetrically substituted bicyclic guttiferone natural products.

Project description:Detailed in this communication is an efficient synthetic approach towards the guttiferone family of natural products. Oxidatively unraveling a para-quinone monoketal followed by consecutive 5-exo radical cyclizations provides the bicyclic core. An additional strength of this approach is a late stage asymmetric desymmetrization of an advanced symmetric intermediate.

| S-EPMC3107033 | biostudies-literature

Expeditious synthesis of the fused hexacycle of puberuline C <i>via</i> a radical-based cyclization/translocation/cyclization process.

Project description:The fused 6/7/5/6/6/6-hexacyclic ring system of puberuline C was assembled in 18 steps from 2-(ethoxycarbonyl)cyclohexanone. After the azabicyclo[3.3.1]nonane derivative was sequentially coupled with propargyl magnesium bromide, 2-iodo cyclopentenone and allyl bromide, the pentacycle was constructed in a single step via a radical-based cyclization/translocation/cyclization process. The C11-bridgehead radical generated via C-Br homolysis participated in a 7-endo cyclization, and the 1,5-hydrogen translocation of the resultant radical was followed by transannular 6-exo cyclization to simultaneously realize the construction of the two rings and the introduction of the five contiguous stereocenters. The last 6-exo cyclization was induced by the Mukaiyama aldol reaction, and the C16-ketone was stereoselectively reduced by the action of SmI2/t-BuOH, leading for the first time to the synthesis of the entire hexacycle of puberuline C.

| S-EPMC6014077 | biostudies-literature

Copper-catalyzed oxidative benzylic C-H cyclization via iminyl radical from intermolecular anion-radical redox relay.

Project description:Base-promoted C-H cleavage without transition metals opens a practical alternative for the one based on noble metals or radical initiators. The resulting carbanion can pass through radical addition to unsaturated bonds like C-N or C-C triple bonds, in which stoichiometric oxidants are needed. When in situ C-H cleavage meets catalytic carbanion-radical relay, it turns to be challenging but has not been accomplished yet. Here we report the combination of base-promoted benzylic C-H cleavage and copper-catalyzed carbanion-radical redox relay. Catalytic amount of naturally abundant and inexpensive copper salt, such as copper(II) sulfate, is used for anion-radical redox relay without any external oxidant. By avoiding using N-O/N-N homolysis or radical initiators to generate iminyl radicals, this strategy realizes modular synthesis of N-H indoles and analogs from abundant feedstocks, such as toluene and nitrile derivatives, and also enables rapid synthesis of large scale pharmaceuticals.

| S-EPMC6385223 | biostudies-literature

Electrophilic aromatic prenylation via cascade cyclization.

Project description:To gain access to prenylated hexahydroxanthenes, tandem cascade cyclization-electrophilic aromatic substitution reactions have been studied on substrates bearing allylic and propargylic substituents. Both BF3·OEt2 and TMSOTf can be used to initiate this reaction sequence, resulting in different ratios of the C-2 and C-6 substitution products. Even though allylic transposition is observed in some cases, the results of a crossover experiment are consistent with an intramolecular reaction sequence. Taken together, these studies now allow preparation of either the C-2 or C-6 prenylated hexahydroxanthene products.

| S-EPMC3940164 | biostudies-literature

Asymmetric Dearomatization/Cyclization Enables Access to Polycyclic Chemotypes.

Project description:Enantioenriched, polycyclic compounds were obtained from a simple acylphloroglucinol scaffold. Highly enantioselective dearomatization was accomplished using a Trost ligand-palladium(0) complex. A computational DFT model was developed to rationalize observed enantioselectivities and revealed a key reactant-ligand hydrogen bonding interaction. Dearomatized products were used in visible light-mediated photocycloadditions and oxidative free radical cyclizations to obtain novel polycyclic chemotypes including tricyclo[4.3.1.01,4]decan-10-ones, bicyclo[3.2.1]octan-8-ones and highly-substituted cycloheptanones.

| S-EPMC5222469 | biostudies-literature

An Oxidative Dearomatization Approach To Prepare the Pentacyclic Core of Ryanodol.

Project description:An approach to synthesize the pentacyclic framework of the polyol diterpenoid ryanodol is reported. The ABC tricycle was constructed by a Co-mediated Pauson-Khand reaction, and both radical and anionic cyclization pathways were developed to form the E-ring. In addition, a reaction sequence involving SeO2-mediated enone oxidation and hydroxyl-directed oxy-Michael addition was developed to introduce the A-ring oxidation. The feasibility of forming the bridging D-ring by an oxidative dearomatization was established.

| S-EPMC6103443 | biostudies-literature

Formation of an Angular Aromatic Polyketide from a Linear Anthrene Precursor via Oxidative Rearrangement.

Project description:Bacterial aromatic polyketides are a group of natural products synthesized by polyketide synthases (PKSs) that show diverse structures and biological activities. They are structurally subclassified into linear, angular, and discoid aromatic polyketides, the formation of which is commonly determined by the shaping and folding of the poly-β-keto intermediates under the concerted actions of the minimal PKSs, cyclases and ketoreductases. Murayaquinone, found in several streptomycetes, possesses an unusual tricyclic angular aromatic polyketide core containing a 9,10-phenanthraquinone. In this study, genes essential for murayaquinone biosynthesis were identified, and a linear anthraoxirene intermediate was discovered. A unique biosynthetic model for the angular aromatic polyketide formation was discovered and confirmed through in vivo and in vitro studies. Three oxidoreductases, MrqO3, MrqO6, and MrqO7, were identified to catalyze the conversion of the linear aromatic polyketide intermediate into the final angularly arranged framework, which exemplifies a novel strategy for the biosynthesis of angular aromatic polyketides.

| S-EPMC5584589 | biostudies-literature

Unified short syntheses of oxygenated tricyclic aromatic diterpenes by radical cyclization with a photoredox catalyst.

Project description:The biomimetic two-phase strategy employing polyene cyclization and subsequent oxidation/substitution is an effective approach for divergent syntheses of [6-6-6]-tricyclic diterpenes. However, this strategy requires lengthy sequences for syntheses of oxygenated tricyclic aromatic abietane/podocarpane diterpenes owing to the many linear oxidation/substitution steps after cyclization. Here, we present a new synthetic route based on a convergent reverse two-phase strategy employing a reverse radical cyclization approach, which enabled the unified short syntheses of four aromatic abietane/podocarpane diterpenes and the divergent short syntheses of other related diterpenes. Oxygenated and substituted precursors for cyclization were convergently prepared through Friedel-Crafts acylation and rhodium-catalyzed site-selective iodination. Radical redox cyclization using an iridium photoredox catalyst involving neophyl rearrangement furnished the thermodynamically favored 6-membered ring preferentially. (±)-5,6-Dehydrosugiol, salvinolone, crossogumerin A, and Δ5-nimbidiol were synthesized in only 8 steps. An oxygenated cyclized intermediate was also useful for divergent derivatization to sugiol, ferruginol, saprorthoquinone, cryptomeriololide, and salvinolone.

| S-EPMC10442340 | biostudies-literature

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings.

Project description:A wide range of derivatives with new pyrido[2,1-a]pyrrolo[3,4-c]isoquinoline skeleton was synthesized by free-radical intramolecular cyclization of o-bromophenyl-substituted pyrrolylpyridinium salts using the (TMS)3SiH/AIBN system. The cyclization provides generally good yields of pyrido[2,1-a]pyrrolo[3,4-c]isoquinoline hydrobromides having no additional radical-sensitive substituents. The free bases can be obtained from the synthesized hydrobromides in quantitative yield by basification at room temperature. The selectivity control of intramolecular arylation was achieved by replacing the halogen: the use of 1-(2-(ortho-bromophenyl)-4-(ortho-iodophenyl)pyrrol-3-yl)pyridinium bromide makes it possible to obtain a monocyclization product, and the bicyclization product from the dibromo derivative. The procedure is also applicable to obtain 3-arylpyrido[2,1-a]pyrrolo[3,2-c]isoquinoline derivatives including 2-unsubstituted skeletons that are inaccessible via Pd-catalyzed cyclization.

| S-EPMC8239278 | biostudies-literature

Dearomatization of aromatic asmic isocyanides to complex cyclohexadienes.

Project description:A dearomatization-dislocation-coupling cascade rapidly transforms aromatic isocyanides into highly functionalized cyclohexadienes. The facile cascade installs an exceptional degree of molecular complexity: three carbon-carbon bonds, two quaternary stereocenters, and three orthogonal functionalities, a cyclohexadiene, a nitrile, and an isocyanide. The tolerance of arylisocyanides makes the method among the mildest dearomatizations ever reported, typically occurring within minutes at -78 °C. Experimental and computational analyses implicate an electron transfer-initiated mechanism involving an unprecedented isocyanide rearrangement followed by radical-radical anion coupling. The dearomatization is fast, proceeds via a complex cascade mechanism supported by experimental and computational insight, and provides complex, synthetically valuable cyclohexadienes.

| S-EPMC9616822 | 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