Rhodium-Catalyzed Enantioselective Hydroselenation of Heterobicyclic Alkenes

Chiral sulfide and achiral sulfonic acid cocatalyzed enantioselective electrophilic tandem selenylation semipinacol rearrangement of allenols

A highly enantioselective electrophilic selenylation/semipinacol rearrangement of allenols has been developed, which is enabled by the cooperative catalysis of a chiral sulfide and an achiral sulfonic acid. The designed and synthesized chiral sulfide catalyst and selenylating reagent play a crucial role in enhancing both enantioselectivity and reactivity. This approach exhibits excellent regio-, chemo-, and enantioselectivity, providing access to diverse enantioenriched cyclopentanones featuring an arylselenovinyl-substituted quaternary carbon stereocenter. Furthermore, these products can be transformed into synthetically valuable alkyne, vinyl bromide, and aniline derivatives. Mechanistic studies reveal that the combination of a chiral sulfide and an achiral sulfonic acid not only facilitates the formation of catalytically active species, but also governs the enantioselectivity of the reaction. Meanwhile, density functional theory calculations disclose that four hydrogen bond interactions and a π‧‧‧π interaction are responsible for the observed enantioselectivity.

A stereochemical model and origins of selectivity for the rhodium-catalyzed hydroselenation of styrene

A deeper understanding of the mechanisms underlying transition metal-catalyzed transformation is crucial for developing innovative strategies to synthesize chiral organoselenium compounds. In this study, we developed and investigated a three-layer chirality relay model for the rhodium-catalyzed asymmetric hydroselenation of alkenes through density functional theory (DFT) calculations. In the back layer of this model, the four bulky substituents on the phosphorus atom of the bidentate chiral MeO-BIPHEP ligand were positioned on axial and equatorial bonds, thereby influencing the configuration of the middle layer. The middle layer involved the coordination of selenium to Rh(I) hydride. Carbon chirality in alkanes facilitated reductive elimination in the front layer. The independent gradient model based on the Hirshfeld partition (IGMH) analysis supports this model, and the origins of enantioselectivity were explained through the three-layer chirality relay mechanism. Additionally, computational results revealed that selenol exhibited higher reactivity compared with phenol and thiol. This difference was attributable to its lower bond dissociation energy.

Copper(I)-Catalyzed Asymmetric α-Selenenylation of 2-Acylimidazoles

A general method for the catalytic asymmetric α-selenenylation of simple carbonyl compounds is lacking. Herein, a copper(I)-catalyzed enantioselective α-selenenylation of 2-acylimidazoles with electrophilic selenosulfonates is uncovered. The reaction enjoys the advantages of mild conditions, easy reaction protocol, and broad substrate scopes on both 2-acylimidazoles and selenosulfonates. Mechanistic studies reveal a pincer Cu(I)-(S,S)-Ph-BOPA complex as the active catalyst. Some traditional electrophilic selenenylation reagents, such as PhSeCl, PhSeSePh, and 2-(phenylselanyl)isoindoline-1,3-dione lead to inferior results in terms of both yield and enantioselectivity, highlighting the superiority of selenosulfonates. Finally, several transformations based on both the 2-acylimidazole group and the selenoether group are successfully carried out, demonstrating the synthetic utilities of the present methodology.

Asymmetric Carbene Insertion into Se-S Bonds by Synergistic Rh(II)/Guanidine Catalysis Involving Chalcogen-Bond Assistance

The efficient construction of chalcogen-atom-based chiral compounds remains a challenge, despite the importance of organoselenium and organosulfur compounds in life and materials science. Chalcogen atoms can form net attractive interactions called chalcogen bonds, but it is an undeveloped tool to assist asymmetric catalysis. Herein, we report an enantioselective insertion platform to install a stereogenic center bearing selenyl and thiocyano functional groups. Our method operates by synergistic catalysis by a chiral guanidine and an achiral dirhodium complex in a three-component or four-component reaction, through Se-S bond insertion into carbene species, competing successfully with the spontaneous racemic process and showing high regioselectivity. As elucidated by spectroscopic experiments and computational studies, a unique mechanism involving chalcogen as well as hydrogen bonding was established to account for the enantiocontrol. The high stereoselectivity holds for a broad array of selenylthiocyanatopropanoates, which showed excellent anti-inflammatory toward IL-1β and low cytotoxicity.

Green-light-induced selective hydroselenation of olefins with diselenides

A selective green-light-induced hydroselenation of alkenes with diselenides using Hantzsch ester as the hydrogen donor has been developed. In the case of electron-neutral diaryl diselenides and diacyl ones, alkenes undergo anti-Markovnikov-selective hydroselenation. When switching to electron-deficient diaryl diselenides and dialkyl ones, Markovnikov-selective hydroselenation occurs.

Hydroselenation of olefins: elucidating the β-selenium effect

We report a light-promoted hydroselenation of alkenes with high anti-Markovnikov selectivity. Blue light activates an aryl diselenide to generate a seleno radical with subsequent addition into an alkene to form a β-seleno carbon radical. Hydrogen atom transfer (HAT) from the selenol to the carbon radical generates the linear selenide with high selectivity in preference to the branched isomer. These studies reveal a unique β-selenium effect, where a selenide β to a carbon radical imparts high anti-selectivity for radical addition through delocalization of the HAT transition state.

Asymmetric Synthesis and Applications of Chiral Organoselenium Compounds: A Review

The synthesis and application of organoselenium compounds have developed rapidly, and chiral organoselenium compounds have become an important intermediate in the field of medicine, materials, organic synthesis. The strategy of developing a green economy is still a challenge in the synthesis of chiral organoselenium compounds with enantioselective properties. This review covers in detail the synthesis of chiral organoselenium compounds from 1979 to 2024 and their application in the fields of asymmetric synthesis and catalysis.

Recent Progress in Synthetic and Biological Application of Diorganyl Diselenides

Diorganyl diselenides have emerged as privileged structures because they are easy to prepare, have distinct reactivity, and have broad biological activity. They have also been used in the synthesis of natural products as an electrophile in the organoselenylation of aromatic systems and peptides, reductions of alkenes, and nucleophilic substitution. This review summarizes the advancements in methods for the transformations promoted by diorganyl diselenides in the main functions of organic chemistry. Parallel, it will also describe the main findings on pharmacology and toxicology of diorganyl diselenides, emphasizing anti-inflammatory, hypoglycemic, chemotherapeutic, and antimicrobial activities. Therefore, an examination detailing the reactivity and biological characteristics of diorganyl diselenides provides valuable insights for academic researchers and industrial professionals.

Electrophotocatalysis Versus Indirect Electrolysis: Electrochemical Selenocyclization of 3-Aza-1,5-dienes Facilitated by Energy Transfer, Direct Photolysis or N-Hydroxyphthalimide

Three hybrid electrochemical protocols, which involve the energy transfer, direct photolysis and N-hydroxyphthalimide catalyst, respectively, are presented for the selenylation/cyclization of the fragile substrates of 3-aza-1,5-dienes with diorganyl diselenides to afford 3-selenomethyl-4-pyrrolin-2-ones. The two electrophotocatalytic reactions and the indirect electrolysis one are both regioselective and external-oxidant- and transition-metal-free, and are associated with a broad substrate scope and high Se-economy, and all three methods are amenable to gram-scale syntheses, late-stage functionalizations, sunlight-induced experiments and all-solar-driven syntheses.

Transition metal-free C(sp3)-H selenation of β-ketosulfones

The installation of selenium groups has become an essential step across a number of industries such as agrochemicals, drug discovery, and materials. However, direct C(sp3)-H selenation, which is most atom economical, remains a formidable challenge, and only a few examples have been reported to date. In this article, we introduce the transition metal-free C(sp3)-H selenation with the easily available β-ketosulfones and diselenides as the material source. This benign protocol permits access to a broad spectrum of α-aryl(alkyl) seleno-β-ketosulfones in high yields with outstanding functional group compatibility. Distinct advantages of this protocol over all previous methods encompass the utilization of base and air as an oxidant, room temperature, and enhanced green chemistry matrices.

Regiodivergent Carbonylation of Alkenes: Selective Palladium-Catalyzed Synthesis of Linear and Branched Selenoesters

An unprecedented regiodivergent palladium-catalyzed carbonylation of aromatic alkenes has been developed. Utilizing commercially available Pd(CH3 CN)2 Cl2 in the presence of 1,1'-ferrocenediyl-bis(tert-butyl(pyridin-2-yl)phosphine) ligand L8 diverse selenoesters are obtained in a straightforward manner. Key to success for the control of the regioselectivity of the carbonylation step is the concentration of the acidic co-catalyst. This general protocol features wide functional group compatibility and good regioselectivity. Mechanistic studies suggest that the presence of stoichiometric amounts of acid changes the properties and coordination mode of the ligand leading to reversed regioselectivity.

Organoselenium Compounds: Chemistry and Applications in Organic Synthesis

Selenium, originally described as a toxin, turns out to be a crucial trace element for life that appears as selenocysteine and its dimer, selenocystine. From the point of view of drug developments, selenium-containing drugs are isosteres of sulfur and oxygen with the advantage that the presence of the selenium atom confers antioxidant properties and high lipophilicity, which would increase cell membrane permeation leading to better oral bioavailability. In this article, we have focused on the relevant features of the selenium atom, above all, the corresponding synthetic approaches to access a variety of organoselenium molecules along with the proposed reaction mechanisms. The preparation and biological properties of selenosugars, including selenoglycosides, selenonucleosides, selenopeptides, and other selenium-containing compounds will be treated. We have attempted to condense the most important aspects and interesting examples of the chemistry of selenium into a single article.

Enantioselective Selenol-ene Using Rh-Hydride Catalysis

This study showcases the first enantioselective hydroselenation of styrenes. Organoselenium building blocks are accessed with selectivity for the branched isomer. Through a Rh-hydride pathway, C-Se bonds can be forged with excellent regio- and enantiocontrol.

Enantioselective Palladium-Catalyzed Hydrophosphinylation of Allenes with Phosphine Oxides: Access to Chiral Allylic Phosphine Oxides

A Pd-catalyzed hydrophosphinylation of alkyl and aryl-oxyallenes with phosphine oxides has been developed for the efficient and rapid construction of a family of chiral allylic phosphine oxides with a diverse range of functional groups. This methodology was further applied in the facile construction of chiral 2H-chromene and later stage functionalization of cholesterol.

Copper-Catalyzed Cycloaddition of Heterobicyclic Alkenes with Diaryl Disulfides to Synthesize Dihydrobenzo[b]thiophene Derivatives

A novel copper-catalyzed cycloaddition of diaryl disulfides to heterobicyclic alkenes has been developed. The C-S and C-C bonds can be formed simultaneously on the C═C bond of the olefins via a single-step cycloaddition to afford a series of 2,3-dihydrobenzo[b]thiophene derivatives. This reaction exhibits excellent diastereoselectivity and relatively broad substrate scope. Various functional groups attached to the substrates are tolerated in this protocol to give the corresponding exo adducts in moderate yields.

Enantioselective synthesis of indole derivatives by Rh/Pd relay catalysis and their anti-inflammatory evaluation

An efficient Rh/Pd relay catalyzed intermolecular and cascade intramolecular hydroamination for the synthesis of exclusive trans 1-indolyl dihydronaphthalenols (up to 88% yield, 99% ee) is described under mild conditions. Moreover, the in silico and in vitro screening showed that the novel 1-indolyl dihydronaphthalenol products are potent lead compounds for treating inflammation disease.

Chemistry of Unsymmetrical C1-Substituted Oxabenzonorbornadienes

Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate, which can be readily activated by transition metal complexes with great face selectivity due to its dual-faced nature and intrinsic angle strain on the alkene. To date, the understanding of transition-metal catalyzed reactions of OBD itself has burgeoned; however, this has not been the case for unsymmetrical OBDs. Throughout the development of these reactions, the nature of C1-substituent has proven to have a profound effect on both the reactivity and selectivity of the outcome of the reaction. Upon substitution, different modes of reactivity arise, contributing to the possibility of multiple stereo-, regio-, and in extreme cases, constitutional isomers, which can provide unique means of constructing a variety of synthetically useful cyclic frameworks. To maximize selectivity, an understanding of bridgehead substituent effects is crucial. To that end, this review outlines hitherto reported examples of bridgehead substituent effects on the chemistry of unsymmetrical C1-substituted OBDs.

Catalytic asymmetric transformations of oxa- and azabicyclic alkenes

This review provides an overview of the fundamental concepts and recent developments in a wide range of enantioselective transformations involving oxa- and azabicyclic alkenes.

Catalysis and regioselectivity in hydrofunctionalization reactions of unsaturated carbon bonds. Part III

The review addresses the possibility of obtaining Markovnikov and anti-Markovnikov isomers in the reactions of unsaturated hydrocarbons with organophosphorus and organosulfur compounds having P–H and S–H bonds using metal salts or complexes as catalysts.

The bibliography includes 247 references.