Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

(Poly)cationic λ³-Iodane Mediated Oxidative Ring Expansion of Secondary Alcohols.

ABSTRACT: Herein, we report a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ³-iodanes (N-HVI). Excellent levels of selectivity are achieved for C-O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting HFIP-acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.

SUBMITTER: Walters JC

PROVIDER: S-EPMC6107298 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

(Poly)cationic λ3-Iodane Mediated Oxidative Ring Expansion of Secondary Alcohols.

Walters Jennifer C JC Tierno Anthony F AF Dubin Aimee H AH Wengryniuk Sarah E SE

European journal of organic chemistry 20180131 12

Herein, we report a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVI). Excellent levels of selectivity are achieved for C-O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting HFIP-acetals are readily derivatized with a range of nucleophiles, providing a versatile functional ...[more]

PMID: 30147437

Similar Datasets

Chemoselective Oxidation of Equatorial Alcohols with N-Ligated λ3-Iodanes.

Project description:The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ3-iodanes (N-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent (Py-HVI) is readily synthesized from commercial PhI(OAc)2 and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.

| S-EPMC7060929 | biostudies-literature

Synthesis of Benzannulated Medium-ring Lactams via a Tandem Oxidative Dearomatization-Ring Expansion Reaction.

Project description:Medium-ring natural products exhibit diverse biological activities but such scaffolds are underrepresented in probe and drug discovery efforts due to the limitations of classical macrocyclization reactions. We report herein a tandem oxidative dearomatization-ring-expanding rearomatization (ODRE) reaction that generates benzannulated medium-ring lactams directly from simple bicyclic substrates. The reaction accommodates diverse aryl substrates (haloarenes, aryl ethers, aryl amides, heterocycles) and strategic incorporation of a bridgehead alcohol generates a versatile ketone moiety in the products amenable to downstream modifications. Cheminformatic analysis indicates that these medium rings access regions of chemical space that overlap with related natural products and are distinct from synthetic drugs, setting the stage for their use in discovery screening against novel biological targets.

| S-EPMC6242278 | biostudies-literature

A diversity-oriented synthesis approach to macrocycles via oxidative ring expansion.

Project description:Macrocycles are key structural elements in numerous bioactive small molecules and are attractive targets in the diversity-oriented synthesis of natural product-based libraries. However, efficient and systematic access to diverse collections of macrocycles has proven difficult using classical macrocyclization reactions. To address this problem, we have developed a concise, modular approach to the diversity-oriented synthesis of macrolactones and macrolactams involving oxidative cleavage of a bridging double bond in polycyclic enol ethers and enamines. These substrates are assembled in only four or five synthetic steps and undergo ring expansion to afford highly functionalized macrocycles bearing handles for further diversification. In contrast to macrocyclization reactions of corresponding seco acids, the ring expansion reactions are efficient and insensitive to ring size and stereochemistry, overcoming key limitations of conventional approaches to systematic macrocycle synthesis. Cheminformatic analysis indicates that these macrocycles access regions of chemical space that overlap with natural products, distinct from currently targeted synthetic drugs.

| S-EPMC3359144 | biostudies-literature

Photoredox-mediated remote C(sp3)-H heteroarylation of free alcohols.

Project description:We report an efficient and economical method for remote δ C(sp3)-H heteroarylation of free aliphatic alcohols using a hypervalent iodine PFBI-OH oxidant under photoredox catalysis. The reaction sequence involves in situ alcoholysis of PFBI-OH with alcohol, generation of an alkoxy radical intermediate by SET reduction, 1,5-HAT, and Minisci-type C-C bond formation. This method uses a slight excess of alcohols, can facilitate reaction at δ methyl and methylene positions, and has been successfully applied to modification of complex drug molecules.

| S-EPMC6345347 | biostudies-literature

Isothiourea-Catalysed Acylative Kinetic Resolution of Aryl-Alkenyl (sp2 vs. sp2 ) Substituted Secondary Alcohols.

Project description:The non-enzymatic acylative kinetic resolution of challenging aryl-alkenyl (sp2 vs. sp2 ) substituted secondary alcohols is described, with effective enantiodiscrimination achieved using the isothiourea organocatalyst HyperBTM (1 mol %) and isobutyric anhydride. The kinetic resolution of a wide range of aryl-alkenyl substituted alcohols has been evaluated, with either electron-rich or naphthyl aryl substituents in combination with an unsubstituted vinyl substituent providing the highest selectivity (S=2-1980). The use of this protocol for the gram-scale (2.5 g) kinetic resolution of a model aryl-vinyl (sp2 vs. sp2 ) substituted secondary alcohol is demonstrated, giving access to >1 g of each of the product enantiomers both in 99:1 e.r.

| S-EPMC6680239 | biostudies-literature

Manganese complex-catalyzed oxidation and oxidative kinetic resolution of secondary alcohols by hydrogen peroxide.

Project description:The highly efficient catalytic oxidation and oxidative kinetic resolution (OKR) of secondary alcohols has been achieved using a synthetic manganese catalyst with low loading and hydrogen peroxide as an environmentally benign oxidant in the presence of a small amount of sulfuric acid as an additive. The product yields were high (up to 93%) for alcohol oxidation and the enantioselectivity was excellent (>90% ee) for the OKR of secondary alcohols. Mechanistic studies revealed that alcohol oxidation occurs via hydrogen atom (H-atom) abstraction from an α-CH bond of the alcohol substrate and a two-electron process by an electrophilic Mn-oxo species. Density functional theory calculations revealed the difference in reaction energy barriers for H-atom abstraction from the α-CH bonds of R- and S-enantiomers by a chiral high-valent manganese-oxo complex, supporting the experimental result from the OKR of secondary alcohols.

| S-EPMC5676093 | biostudies-literature

Iridium-Catalyzed, Site-Selective Silylation of Secondary C(sp3)-H Bonds in Secondary Alcohols and Ketones.

Project description:We report the iridium-catalyzed, stereoselective conversion of secondary alcohols or ketones to anti-1,3-diols by the silylation of secondary C-H bonds γ to oxygen and oxidation of the resulting oxasilolane. The silylation of secondary C-H bonds in secondary silyl ethers derived from alcohols or ketones is enabled by a catalyst formed from a simple bisamidine ligand. The silylation occurs with high selectivity at a secondary C-H bond γ to oxygen over distal primary or proximal secondary C-H bonds. Initial mechanistic investigations suggest that the source of the newly achieved reactivity is a long catalyst lifetime resulting from the high binding constant of the strongly electron-donating bisamidine ligand.

| S-EPMC11620728 | biostudies-literature

Highly stereoselective ring expansion reactions mediated by attractive cation-n interactions.

Project description: Not available

| S-EPMC3509482 | biostudies-literature

Modulation of poly(ADP-ribose) polymerase-1 (PARP-1)-mediated oxidative cell injury by ring finger protein 146 (RNF146) in cardiac myocytes.

Project description:Poly(ADP-ribose) polymerase-1 (PARP-1) activation is a hallmark of oxidative stress-induced cellular injury that can lead to energetic failure and necrotic cell death via depleting the cellular nicotinamide adenine dinucleotide (NAD(+)) and ATP pools. Pharmacological PARP-1 inhibition or genetic PARP-1 deficiency exert protective effects in multiple models of cardiomyocyte injury. However, the connection between nuclear PARP-1 activation and depletion of the cytoplasmic and mitochondrial energy pools is poorly understood. By using cultured rat cardiomyocytes, here we report that ring finger protein 146 (RNF146), a cytoplasmic E3-ubiquitin ligase, acts as a direct interactor of PARP-1. Overexpression of RNF146 exerts protection against oxidant-induced cell death, whereas PARP-1-mediated cellular injury is augmented after RNF146 silencing. RNF146 translocates to the nucleus upon PARP-1 activation, triggering the exit of PARP-1 from the nucleus, followed by rapid degradation of both proteins. PARP-1 and RNF146 degradation occurs in the early phase of myocardial ischemia-reperfusion injury; it precedes the induction of heat shock protein expression. Taken together, PARP-1 release from the nucleus and its rapid degradation represent newly identified steps of the necrotic cell death program induced by oxidative stress. These steps are controlled by the ubiquitin-proteasome pathway protein RNF146. The current results shed new light on the mechanism of necrotic cell death. RNF146 may represent a distinct target for experimental therapeutic intervention of oxidant-mediated cardiac injury.

| S-EPMC4153837 | biostudies-literature

Cationic-anionic synchronous ring-opening polymerization.

Project description:Chemical reactions with incompatible mechanisms (such as nucleophilic reactions and electrophilic reactions, cationic polymerization and anionic polymerization) are usually difficult to perform simultaneously in one-pot. In particular, synchronous cationic-anionic polymerization has been an important challenge in the field of polymer synthesis due to possible coupling termination of both chain ends. We recently found that such terminal couplings can be significantly inhibited by a bismuth salt with a strong nucleophilic anion (e.g., BiCl3) and disclosed the mechanism. Accordingly, we propose a cationic-anionic polymerization (CAP) method where cationic ring-opening polymerization (CROP) of 2-oxazolines (Ox) and anionic ring-opening polymerization (AROP) of cyclic esters (CE) can be initiated sequentially and propagated simultaneously in one-pot, using bismuth salts as the initial initiators, to afford a multifunctional copolymer polyoxazoline-block-polyester (POx-b-PCE). Furthermore, a block copolymer PAPOZ20-b-PCL5 synthesized by CAP can self-assemble into micellar aggregates, which exhibit excellent intrinsic antibacterial activities without loading any extra antibiotic components. Overall, such a CAP method opens new avenues for synthesizing multi-component copolymers and biomaterials.

| S-EPMC11846916 | biostudies-literature