RESUMEN
Herein, we describe an effective method for the synthesis of 2-alkoxyamides and 1,2-diamines through visible-light-mediated difunctionalization of alkenes. N-Aminopyridinium salts were employed as appropriate precursors to generate key amidyl radical intermediates via a photoinduced single-electron transfer (SET) process. The amidyl radicals would react with alkenes, followed by oxidation and nucleophilic addition. Excellent functional group tolerance and good yields demonstrate the synthetic potential of this transformation.
RESUMEN
Thiols and thioesters play crucial roles in pharmaceuticals, biology, and material science as essential organosulfur compounds. Leveraging readily available and cost-effective inert alkanes through direct thioetherification holds promise for yielding high-value-added products. Herein, we present a photoinduced strategy for sulfur-containing modification of inert alkanes utilizing decatungstate as hydrogen atom transfer reagent, offering a straightforward and practical approach for synthesizing thioethers and thioesters.
RESUMEN
A visible-light-promoted research protocol for constructing dihydropyrido[1,2-a]indolone skeletons is herein described proceeding through a cascade cyclization mediated by trifluoromethyl radicals. This method allows the efficient synthesis of various indole derivatives without the need of photocatalysts or transition-metal catalysts. Mechanism experiments indicate that the process involves a radical chain process initiated by the homolysis of Umemoto's reagent. This straightforward method enables a rapid access to heterocycles containing a trifluoromethyl group.
RESUMEN
Catalytic C(sp3)-H functionalization has provided enormous opportunities to construct organic molecules, facilitating the derivatization of complex pharmaceutical compounds. Within this framework, direct hydrogen atom transfer (HAT) photocatalysis becomes an appealing approach to this goal. However, the viable substrates utilized in these protocols are limited, and the site selectivity shows preference to activated and thermodynamically favored C(sp3)-H bonds. Herein, we describe the development of undirected iron-catalyzed C(sp3)-H borylation, thiolation, and sulfinylation reactions enabled by the photoinduced ligand-to-metal charge transfer (LMCT) process. These reactions exhibit remarkably broad substrate scope (>150 examples in total), and most importantly, all of these three reactions show unconventional regioselectivity, with the occurrence of C(sp3)-H borylation, thiolation, and sulfinylation preferentially at the distal methyl position. The procedures are operationally simple and readily scalable and provide access to high-value products from simple hydrocarbons in one step. Mechanistic studies and control experiments indicate that the afforded site selectivity is not only relevant to the HAT species but also largely affected by the use of boron- and sulfone-based radical acceptors.
RESUMEN
ß-(Hetero)arylethylamines are privileged structural motifs found in many high-value organic molecules, including pharmaceuticals and natural products. To construct these important molecular skeletons, previous methods are mainly achieved by amino(hetero)arylation reaction with the aid of transition metals and preactivated substrates. Herein, we report a metal-free and photoinduced intermolecular amino(hetero)arylation reaction for the single-step installation of both (hetero)aryl and iminyl groups across alkenes in an efficient and regioselective manner. This method shows broad scope (up to 124 examples) and excellent tolerance of various olefinsâfrom the simplest ethylene to complex multisubstituted alkenes can all participate in the reaction. Furthermore, aminosulfonylation of alkenes can be also conducted in the presence of sodium bisulfite as the SO2 source.
RESUMEN
The first total syntheses of polycyclic diterpenes phomopsene (1), methyl phomopsenonate (2), and iso-phomopsene (3) have been accomplished through the unusual cascade reorganization of C-C single bonds. This approach features: (i) a synergistic Nazarov cyclization/double ring expansions in one-step, developed by authors, to rapid and stereospecific construction of the 5/5/5/5 tetraquinane scaffold bearing contiguous quaternary centers and (ii) a one-pot strategic ring expansion through Beckmann fragmentation/recombination to efficiently assemble the requisite 5/5/6/5 tetracyclic skeleton of the target molecules 1-3. This work enables us to determine that the correct structure of iso-phomopsene is, in fact, the C7 epimer of the originally assigned structure. Finally, the absolute configurations of three target molecules were confirmed through enantioselective synthesis.
RESUMEN
An electrochemical nickel catalyzed hydroarylation reaction of various alkynes is herein described. In this reaction, alkynes were coupled with aryl iodides by electrochemical Ni catalysis to obtain highly selective trans-olefins. The outstanding features of this protocol include mild reaction conditions, operational simplicity, and excellent functional group tolerance.
RESUMEN
Herein, a visible light-induced synthesis of polysubstituted oxazoles from diazo compounds is reported. This developed synthetic method differs from traditional routes that rely on transition metals and external chemical oxidants. Our method uses readily available and inexpensive diazonium compounds as well as nitrile substrates with a catalytic amount of (i-Pr)3SiCl species, delivering the corresponding valuable multi-substituted oxazole products (up to 95% yield). This protocol exhibits a broad substrate scope and is easily carried out under mild reaction conditions. Notably, gram-scale synthesis in a continuous flow fashion has been performed.
RESUMEN
(Deuterium-labeled) CF2 H- and CFH2 -moieties are of high interest in drug discovery. The high demand for the incorporation of these fluoroalkyl moieties into molecular structures has witnessed significant synthetic progress, particularly in the (deutero)hydrodefluorination of CF3 -containing compounds. However, the controllable replacement of fluorine atoms while maintaining high chemoselectivity remains challenging. Herein, we describe the development of a selective (deutero)hydrodefluorination reaction via electrolysis. The reaction exhibits a remarkable chemoselectivity control, which is enabled by the addition of different organoboron sources. The procedure is operationally simple and scalable, and provides access in one step to high-value building blocks for application in medicinal chemistry. Furthermore, density functional theory (DFT) calculations have been carried out to investigate the reaction mechanism and to rationalize the chemoselectivity observed.
RESUMEN
A transition metal-free photoredox cascade cyclization is herein reported. In this protocol, sustainable visible light was used as the energy source and organic light-emitting molecule eosin Y served as an efficient photocatalyst. A variety of easily available 2-aryl-N-acryloyl indoles can readily react with alkyl radicals, which are generated from organohalides and tertiary amines via either the halogen-atom-transfer (XAT) or the hydrogen-atom-transfer (HAT) process, furnishing the desired indolo[2,1-α]isoquinoline derivatives in good to moderate yields. This protocol features broad substrate scope and good functional group tolerance under mild conditions.
RESUMEN
Cyclic compounds constitute a great important class of substances in the science of medicine and biology, which renders the research on facile and efficient construction of such complex scaffolds from simple starting materials to be hot and appealing. Recently, the radical cascade reaction involving multiple bond formation/cleavage has emerged as an ideal and powerful route to give high-value cyclic products, along with diminished cost and waste. As a simple and benign methodology, photoredox catalysis offers a readily available access to the generation of radical species. Alkenes have been recognized as one of the most valuable building blocks for the reason they allow installation of different functional groups simultaneously through addition to the C=C bonds. This account summarizes the recent advances in photoinduced radical cascade cyclization to the synthesis of cyclic compounds with C=C bonds working as the initial radical acceptors, and emphasis is put on the related reaction mechanisms.
RESUMEN
A direct defluorinative multifluoroarylation of unactivated sp3 C-H bonds through hydrogen atom transfer using photoredox catalysis has been developed. The C(sp3)-C(sp2) couplings between C(sp2)-F bonds and corresponding C(sp3)-H bonds adjacent to heteroatoms proceeded smoothly to afford the desired products in moderate to good yields. Preliminary mechanistic investigations on this novel transformation revealed that the C-H cleavage process might be involved in the rate-determining step.
RESUMEN
Alkylated (hetero)arenes constitute one of the most fundamental skeletons in organic molecules, which prompts a growing number of research studies on the construction of (hetero)aryl C(sp2)-C(sp3) bonds especially using C-H bonds of feedstocks. With the flourishing resurgence of photoredox catalysis in organic synthesis, fruitful achievements have been witnessed in photochemical (hetero)aryl C(sp2)-C(sp3) bond formation through C-H bond coupling such as (hetero)arylation of C(sp3)-H bonds and alkylation of (hetero)aryl C(sp2)-H bonds. Photoinduced generation of alkyl radicals from various alkylating agents is the key point to the success of these reactions. This review will summarise advances in this area with emphasis on the reaction mechanisms.
RESUMEN
The employment of nitrogen sources with free N-H bonds for amination is considered to be most straightforward and desirable, especially when the C-N bonds are prepared from N-H bonds and non-functionalized carbon sources, such as C-H bonds and C-C double/triple bonds, since this obviates the needs for the pre-installation of reactive groups in the starting materials and leads to a high atom and step economy. Recently, radical chemistry has been resuscitated owing to its great value in organic synthesis, and notable advances have been made in the direct use of N-H bonds for radical-based C-N bond formation with photo-/electrotechniques. Apart from the well-studied N-radical species addition pathway, radical-mediated aminations also proceed through N-atom nucleophilic addition, C-/N-radical cross-coupling, and a hydrogen-atom transfer (HAT) process. This review highlights the recent advances in this area with emphasis on the related reaction mechanisms.
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Here we describe a straightforward and efficient approach for regiospecific introduction of an allyl group into cycloalkanol molecules employing a visible-light-mediated ring-opening strategy. A wide range of distally allylated or formylated ketones is furnished from 1-aryl cycloalkanol precursors of variable ring sizes, providing a concise and practical access for the modification of complex natural products. Preliminary mechanistic studies demonstrate that the key O-centered radicals mediate the sequential ring cleavage and allylation/formylation.
RESUMEN
A novel and efficient method for the synthesis of highly substituted benzobicyclo[2.2.2]octane skeletons has been explored. Under UV-light irradiation, o-divinylbenzenes underwent a pericyclic reaction to form the cyclic o-quinodimethane intermediates which were subsequently reacted with olefins through [4+2] addition to construct the benzobicyclo[2.2.2]octane skeletons in mild conditions. Gram scale reactions demonstrated the synthetic potential application of this protocol.
RESUMEN
The photolysis of substituted o-divinylbenzenes promotes a one-step and metal-free conversion to oxatricycles at room temperature. Irradiation o-divinylbenzenes results in an pericyclic reaction to form cyclic o-quinodiemthane intermediates, which subsequently undergo intramolecular oxa-[4+2] cycloaddition to form oxacyclic derivatives.
RESUMEN
In this article, a photoredox protocol for the synthesis of furans via oxidative coupling of olefin generated in situ from cyclopropyl ketones with ketonic oxygen atom is presented. Moreover, bromination of furans in the presence of overstoichiometric oxidant has been achieved with high regioselectivity.
RESUMEN
A metal-free and cost-effective protocol for UV light-mediated difunctionalization of alkenes with CF3SO2Na was developed. This strategy realized the direct formation of Csp(3)-CF3 and C-C bonds through a proposed tandem radical cyclization process, which produced a variety of phenanthrene and anthrone derivatives in moderate yields.