Visible-Light-Induced and Iodoform-Promoted Functionalization of Ether with Secondary Sulfonyl Amides.

An iodoform-promoted functionalization of ether with secondary sulfonyl amides under visible-light irradiation was developed toward synthesis of hemiaminal skeleton with good to excellent isolated yields. The characterization of the isolated ether and iodoform complex revealed regioselective hydrogen atom transfer to initiate carbon radical formation and enabled the amination reaction with the sulfonamide.

Visible-Light-Mediated Radical Hydroalkylative Cyclization of 1,6-Enynes.

A radical hydroalkylative cyclization approach accessing various alkenyl heterocyclic compounds was developed using dimethyl malonate and 1,6-enynes in the presence of visible-light photoredox catalysis. The use of Ir(dtbbpy)(ppy)2PF6 as a photosensitizer enables carbon atom radical formation and initiates the cascade cyclization reaction under mild conditions.

Polarity reversal and strain modulation of Janus MoSSe/GaN polar semiconductor heterostructures.

Beyond three-dimensional (3D) architectures, polar semiconductor heterostructures are developing in the direction of two-dimensional (2D) scale with mix-dimensional integration for novel properties and multifunctional applications. Herein, we stacked 2D Janus MoSSe and 3D wurtzite GaN polar semiconductors to construct MoSSe/GaN polar heterostructures by polarity configurations. The structural stability was enhanced as binding energy changed from -0.08 eV/-0.17 eV in the N polarity to -0.24 eV/-0.42 eV in the Ga polarity. In particular, the polarity reversal of GaN in contact with Janus MoSSe not only determined the charge transfer direction but also significantly increased the electrostatic potential difference from 0.71 eV/0.78 eV in the N polarity to 3.13 eV/2.24 eV in the Ga polarity. In addition, strain modulation was further utilized to enhance interfacial polarization and tune the electronic energy band profiles of Janus MoSSe/GaN polar heterostructures. By applying in-plane biaxial strains, the AA and AA' polarity configurations induced band alignment transition from type I (tensile) to type II (compressive). As a result, both the polarity reversal and strain modulation provide effective ways for the multifunctional manipulation and facile design of Janus MoSSe/III-nitrides polar heterostructures, which broaden the Janus 2D/3D polar semiconducting devices in advanced electronics, optoelectronics, and energy harvesting applications.

Photoinduced Copper-Catalyzed 1,2-Difunctionalization of 1,3-Dienes with Aryl Diselenides.

Described herein is a photoinduced copper-catalyzed 1,2-difunctionalization of 1,3-dienes. The selenium atom radical was generated by the visible light irradiation of diselenides, triggering radical addition with 1,3-dienes to form allyl radical intermediate. Subsequent rapid Z/E isomerization allowed for thermodynamically favorable intermediate formation and enabled copper catalyzed stereoselective functionalization with various nucleophiles.

Palladium-Catalyzed Borylative Cyclization and Cyclopropanation of Terminal Alkyne-Derived Enynes.

Described herein is a palladium-catalyzed borylative cyclization and cyclopropanation of terminal alkyne-derived enynes, affording borylated bicycles, fused cycles, and bridged cycles in good isolated yields. The synthetic utility of this protocol was fully demonstrated by large scale reaction and synthetic derivatization of the borate group.

Visible-Light Photoredox Catalyzed Regioselective 1,4-Hydroalkylation of 1,3-Enyne.

Described herein is a visible-light photoredox-catalyzed regioselective 1,4-hydroalkylation of 1,3-enynes. Various of di- and tri-substituent allenes were really accessible under the present reaction conditions. The visible-light photoredox activation of the carbon nucleophile to generate its radical species, allowing the addition with un-activated enynes. The synthetic utility for the present protocol was demonstrated by a large-scale reaction, as well as the derivatization of the allene product.

Copper-Catalyzed Oxidative Dearomatized Oxyalkylation of Indoles with Alcohols: Synthesis of 3-Alkoxy-2-Oxindoles.

Described herein is a copper-catalyzed efficient oxidative dearomatized functionalization of indoles by using alcohols as the nucleophiles. Various 3-alkoxy-2-oxindoles were accessible with good isolated yields. The synthetic potential applications are demonstrated by the large-scale reaction, as well as the derivatization of the desired 3-alkoxy substituted-2-oxindole products.

Visible-Light-Mediated Three-Component Radical Iodosulfonylative Cyclization of Enynes.

An efficient three-component radical iodosulfonylative cyclization of enynes is described. The visible-light irradiation of iodoform with sulfinates enables sulfonyl radical generation under catalyst- and oxidant-free conditions and triggers the radical addition, cyclization and iodination cascade reactions, giving various vinyl iodide containing sulfones in moderate to good yields.

Copper-Catalyzed Bromo-cyanomethylative Cyclization of Enynes.

A copper-catalyzed bromo-cyanomethylative cyclization of 1,6-enynes is demonstrated. The treatment of 2-bromoacetonitrile with CuI enables the alkyl radical generation and triggers the radical addition/cyclization/bromination sequence, giving various vinyl C-Br bonds containing functionalized heterocycles in good yields.

Three-Component Radical Iodonitrosylative Cyclization of 1,6-Enynes under Metal-Free Conditions.

A three-component, metal-free radical cascade iodonitrosylative cyclization reaction was described. The nitroso radical was generated from tert-butyl nitrite and triggered the radical addition/cyclization/iodination/oxidation sequences. A variety of 1,6-enynes were tested and proved to be compatible, delivering various highly functionalized hetero- and all-carbon cycles and nitro and vinyl C-I bonds containing pyrrolidines, tetrahydrofuran, and cyclopentane in moderate to excellent isolated yields.

Visible-light-induced ligand to metal charge transfer excitation enabled phosphorylation of aryl halides.

We herein described a visible light induced nickel(II)-catalyzed cross-coupling of secondary phosphine oxides with aryl halides. The Ni(I) species and chlorine atom radical Cl˙ were generated via the ligand to metal charge transfer (LMCT) process of the NiCl2(PPh3)2, which allows nickel(IV)-phosphorus species in situ formation, giving various tertiary phosphine oxides under photocatalyst-free conditions.

Stereo- and Regioselective cis-Hydrophosphorylation of 1,3-Enynes Enabled by the Visible-Light Irradiation of NiCl2(PPh3)2.

Described herein is a stereo- and regioselective cis-hydrophosphorylation reaction of the internal alkyne of 1,3-enynes that accesses various 1,3-dienes in good isolated yields. The visible-light irradiation of NiCl2(PPh3)2 allows the generation of highly reactive nickel(II)-phosphorus species that subsequently migrate into the internal alkyne of the 1,3-enynes and protonate the resulting vinyl nickel species, leading to various phosphinoyl 1,3-butadienes under mild reaction conditions.

Visible-Light Mediated Diarylselenylative Cyclization of 1,6-Enynes.

We herein described a selenylative cyclization reaction of enynes by the utilization of diselenides as radical sources. The visible-light irradiation of the reaction mixture enables the generation of the selenium atom radical to trigger the radical addition/cyclization/selenation sequences. Both terminal alkyne and internal alkyne derived 1,6-enynes were tested and suitable for the current synthetic protocol, delivering various kinds of selenium-containing cycles in good yields.

Copper-Catalyzed Bromodifluoroacetylative Cyclization of Enynes.

A copper-catalyzed bromodifluoroacetylative cyclization reaction is described. The treatment of bromodifluoroacete derivatives by CuI and B2Pin2 enables difluoroalkyl radical generation and triggers the radical addition/cyclization/bromination sequences. Bromodifluoroacetyl-derived ester, amide, and ketone were compatible and gave various vinyl C-Br bonds containing functionalized heterocycles in good yields.

Visible-Light Mediated Hydrosilylative and Hydrophosphorylative Cyclizations of Enynes and Dienes.

Described herein is a visible-light mediated intermolecular radical cyclization approach to access heterocycles. Heteroatom radicals, such as silicon and phosphorus atom radicals, were generated via direct hydrogen atom abstraction by the photoexcited catalyst species with hydro-silanes and phosphine oxides. The radical addition/cyclization/HAT (hydrogen atom transfer) reaction sequences of 1,6-enynes and 1,6-dienes were highly efficient delivering the desired heterocycles in good yields.

Regioselective radical arylation: silver-mediated synthesis of 3-phosphorylated coumarins, quinolin-2(1H)-one and benzophosphole oxides.

A silver-mediated domino radical addition/cyclization reaction of diarylphosphine oxides with propynoic acid derivatives is described in this article. The reaction of diarylphosphine oxides with alkynoates or propynoic amide was regioselective, producing 3-phosphorylated coumarins and benzophosphole oxides in moderate to good isolated yield, respectively. The hydrogen bond between P[double bond, length as m-dash]O and N-H was proposed to assist the vinyl radical regioselective arylation process. The reaction conditions were also compatible with the conversion of dialkylphosphine oxides to 3-phosphorylated-coumarins and quinolin-2(1H)-one in good yields.

Visible-Light-Driven Chlorotrifluoromethylative and Chlorotrichloromethylative Cyclizations of Enynes.

Described herein is a visible-light-driven chlorotrifluoromethylative and chlorotrichloromethylative cyclization reaction to synthesize chlorotrifluoromethylated and chlorotrichloromethylated cyclic compounds. Visible-light photochemistry was utilized to generate trifluoromethyl and trichloromethyl radicals and trigger radical addition/cyclization/chlorination sequences. The use of terminal alkene-derived enynes enables the regioselective and stereoselective synthesis of chlorotrifluoromethylated and chlorotrichloromethylated pyrrolidines, piperidines, and cyclopentanes.

Sulfonylative and Azidosulfonylative Cyclizations by Visible-Light-Photosensitization of Sulfonyl Azides in THF.

The generation of sulfonyl radicals from sulfonyl azides using visible light and a photoactive iridium complex in THF is described. This process was used to promote sulfonylative and azidosulfonylative cyclizations of enynes to give several classes of highly functionalized heterocycles. The use of THF as the solvent is critical for successful reactions. The proposed mechanism of radical initiation involves the photosensitized formation of a triplet sulfonyl nitrene, which abstracts a hydrogen atom from THF to give a tetrahydrofuran-2-yl radical, which then reacts with the sulfonyl azide to generate the sulfonyl radical.

Visible-light photoredox-catalyzed synthesis of nitrones: unexpected rate acceleration by water in the synthesis of isoxazolidines.

A new oxidative [3 + 2] cycloaddition of N-substituted hydroxylamines with alkenes was established under visible light photoredox catalysis. This novel protocol provides a rapid, mild, and efficient access to valuable five-membered ring isoxazolidine heterocycles in a concise fashion.

Oxygen switch in visible-light photoredox catalysis: radical additions and cyclizations and unexpected C-C-bond cleavage reactions.

Visible light photoredox catalyzed inter- and intramolecular C-H functionalization reactions of tertiary amines have been developed. Oxygen was found to act as chemical switch to trigger two different reaction pathways and to obtain two different types of products from the same starting material. In the absence of oxygen, the intermolecular addition of N,N-dimethyl-anilines to electron-deficient alkenes provided γ-amino nitriles in good to high yields. In the presence of oxygen, a radical addition/cyclization reaction occurred which resulted in the formation of tetrahydroquinoline derivatives in good yields under mild reaction conditions. The intramolecular version of the radical addition led to the unexpected formation of indole-3-carboxaldehyde derivatives. Mechanistic investigations of this reaction cascade uncovered a new photoredox catalyzed C-C bond cleavage reaction.