Visible Light/Copper Catalysis-Enabled Arylation and Alkenylation of Phosphorothioates via Site-Selective C-H Thianthrenation.

An efficient visible light/copper-enabled arylation and alkenylation of phosphorothioates with thianthrenium salts via a C(sp)-S cross-coupling reaction have been demonstrated. This strategy uses aryl/alkenyl thianthrenium salts as new electrophilic reagents, which can be easily prepared by the site-selective C-H thianthrenation of arenes/alkenes with high regioselectivity. Mechanistic studies revealed a crucial role of the in situ formed copper-sulfur complex, which undergoes a facile SET process with the thianthrenium salts under visible light conditions, thereby successfully achieving the desired cross-coupling reactivity.

Arylcyanation of Styrenes by Photoactive Electron Donor-Acceptor Complexes/Copper Catalysis.

A novel electron donor-acceptor (EDA) complex/copper catalysis model has been proposed for the construction of 2,3-diarylpropionitriles under visible light conditions. The developed protocol proceeds via intermolecular charge transfer between the photoactive EDA complex of dibutamine (DBA), aryl thianthrenium salts, and trimethylsilyl cyanide (TMSCN), followed by a copper catalytic cycle. UV-vis absorption measurements confirm the participation of EDA complexes as reactive intermediates.

Asymmetric 1,4-Reduction of Pyrano[2,3-]indoles with Hantzsch Ester by Chiral Phosphoric Acid.

A highly regioselective and enantioselective transfer hydrogenation of pyrano[2,3-]indoles with Hantzsch ester has been successfully realized using spiro-chiral phosphoric acid, affording a series of optically active 1,4-reductive adducts, 4,9-dihydropyrano[2,3-]indoles, in 34-99% yields with 61-99% .

Switchable Chemoselectivity in [3 + 3] Annulation of β,γ-Unsaturated α-Ketoesters and 1Pyrazol-5-amines by Cooperative Acid Catalysis with Ni and In.

The exchange of the metal ion from Ni(II) to In(I) leads to a switch in the chemoselectivity of the [3 + 3] annulation of β,γ-unsaturated α-ketoesters and 1pyrazol-5-amines in the presence of phosphoric acid , affording functionalized 1pyrazolo[3,4-]pyridines in up to 97% yields and highly enantioselective 4,5-dihydro-1-pyrazolo[3,4-]pyridines in up to 92% yield and 99% ee.

Synthesis of Sulfur-Containing Trisubstituted Imidazoles by One-Pot, Multicomponent Reaction via Electron Donor-Acceptor Complex Photoactivation.

Rapid and efficient construction of multifunctionalized skeletons through a one-pot multicompound domino reaction has been recognized as a simple and practical strategy. Herein, a visible-light-enabled three-component reaction of isothiocyanates, isocyanides, and thianthrenium salt-functionalized arenes is presented, which affords a facile approach to sulfur-containing trisubstituted imidazoles in good yields with a broad substrate scope and excellent functional group tolerance. The byproduct thianthrene is recovered in quantity, thereby ultimately reducing the production of chemical waste.

Switchable Enantioselectivity in Conjugate Alkyne Addition of β,γ-Unsaturated α-Keto Esters by Asymmetric Binary Acid Catalysis.

Switchable enantioselectivity was uncovered in the enantioselective catalytic conjugate addition of β,γ-unsaturated α-keto esters with terminal alkynes to the chiral Lewis acid complex of In(BF) and chiral phosphoric acid.

Arylthianthrenium Salts as the Aryl Sources: Visible Light/Copper Catalysis-Enabled Intermolecular Azidosulfonylation of Alkenes.

The difunctionalization of alkenes using aryl thianthrenium salts as the aryl sources has been reported sporadically. However, the four-component difunctionalization of alkenes on the basis of aryl thianthrenium salts has not been reported thus far and still remains a challenge. Herein, a visible light/copper catalysis-enabled four-component reaction of aryl thianthrenium salts, DABCO·(SO), alkenes, and TMSN is presented, which affords a facile approach to β-azidosulfones in good yields with broad substrate scope and excellent functional group tolerance.

Cu(OTf)-Phosphoric Acid-Catalyzed Tandem Oxa-Nazarov Cyclization and Dibromination of Conjugated 1,2-Diketones.

A facile tandem oxa-Nazarov cyclization and dibromination has been developed. The combination of Cu(OTf) and diphenyl phosphate (DPP-H) was found to synergistically promote the coupling of conjugated 1,2-diketones and bromosuccinimide to form 2,4-dibromo-3(2-furanones in good yields.

Thianthrenium-Enabled Phosphorylation of Aryl C-H Bonds via Electron Donor-Acceptor Complex Photoactivation.

An efficient strategy for the preparation of aryl phosphonates via blue-light-promoted single electron transfer process of an EDA complex between phosphites and thianthrenium salts has been demonstrated. The corresponding substituted aryl phosphonates were obtained in good to excellent yields, and the byproduct thianthrene can be recovered and reused in quantity. This developed method realizes the construction of aryl phosphonates through the indirect C-H functionalization of arenes, which has potential application value in drug discovery and development.

Visible light/copper catalysis enabled alkylation of silyl enol ethers with arylsulfonium salts.

An efficient protocol has been developed herein for the site-selective alkylation of silyl enol ethers with arylsulfonium salts giving access to valuable aryl alkyl thioethers under visible light conditions. Enabled by copper (I) photocatalysis, the C-S bond of arylsulfonium salts can be selectively cleaved to deliver C-centered radicals under mild conditions. This developed method provides a straightforward approach to utilize arylsulfonium salts as sulfur sources for the synthesis of aryl alkyl thioethers.

Visible-Light Copper Catalysis for the Synthesis of α-Alkyl-Acetophenones by the Radical-Type Ring Opening of Sulfonium Salts and Oxidative Alkylation of Alkenes.

Direct difunctionalization of simple alkenes has been treated as a powerful synthetic strategy for the construction of highly functionalized skeletons. In this study, direct oxidative coupling of sulfonium salts with alkenes was achieved under mild conditions by a blue-light-driven photoredox process using a copper complex as a photosensitizer. This protocol allows regioselective synthesis of aryl/alkyl ketones from simple sulfonium salts and aromatic alkenes via selective C-S bond cleavage of sulfonium salts and oxidative alkylation of aromatic alkenes using dimethyl sulfoxide (DMSO) as a mild oxidant.

Asymmetric Binary Acid Catalysis: Switchable Enantioselectivity in Enantioselective Conjugate Hydride Reduction.

The exchange of the metal ion from Zr(IV) to Fe(III) leads to a switch in the enantioselectivity of binary acid-catalyzed conjugate hydride reductions. In the presence of Hantzsch ester, γ-indolyl β,γ-unsaturated α-keto esters could be reduced to the desired ()- or ()-products, respectively, with good to excellent enantioselectivity (up to 98% ee).

Divergent Coupling of -Alkynylnaphthols and Benzofurans: [4 + 2] Cycloaddition and Friedel-Crafts Reaction.

Catalytic direct [4 + 2] cycloaddition reactions and Friedel-Crafts reactions of -alkynylnaphthols with benzofurans have been developed, affording functionalized hydrobenzofuro[3,2-]chromans and hydroarylation products, respectively, in high yields with high chemoselectivity.

Radial Type Ring Opening of Sulfonium Salts with Dichalcogenides by Visible Light and Copper Catalysis.

Herein, a copper-catalyzed, blue-light-induced free radical type ring opening of sulfonium salts with dichalcogenides has been initially developed. The developed method features an inexpensive copper catalyst and a broad substrate scope, affording practical access to alkyl chalcogenides in high yields. This reaction presents a novel ring-opening model of sulfonium salts, which breaks the limitation that only the nucleophilic ring-opening reaction could form C-heteroatom bonds and C-C bonds.

Enantioselective Friedel-Crafts Reaction of 2-Alkynyphenols with Aromatic Ethers by Chiral Brønsted Acid Catalysis.

Herein, we report chiral strong Brønsted acid-catalyzed enantioselective Friedel-Crafts reaction of 2-alkynyphenols with aromatic ethers. The reaction affords the corresponding axially chiral styrenes in up to 91% yield and 97% ee.

HfCl-Catalyzed [4 + 2] Cycloaddition of β,γ-Unsaturated α-Keto Esters with Alkynes.

Herein we report Lewis acid HfCl-catalyzed [4 + 2] cycloaddition between β,γ-unsaturated α-keto esters and various symmetric or unsymmetric alkynes, giving the desired polysubstituted 4-pyrans in up to 98% yield and with excellent regioselectivity (>99:1) via a vinyl carbocation under mild conditions.

Construction of Axially Chiral Styrenes Linking an Indole Moiety by Chiral Phosphoric Acid.

Herein we report a chiral phosphoric acid-catalyzed intermolecular C2 Friedel-Crafts alkylation reaction between -alkynylnaphthols and various 3-substituted indoles, affording axially chiral alkenes with up to 93% yields ( > 20:1) and up to 98% ee under mild reaction condition. Other substituted indole derivatives could be also tolerated in this system, giving the corresponding axially chiral alkenes with high yields and in excellent enantioselectivity.

Binary-Acid Catalysis with Sc(OTf)/TfOH in the Alkenylation of Arenes with Alkynes.

Herein we report binary acid Sc(OTf)/TfOH-catalyzed alkenylation of arenes with alkynes. In this system, the high-energy vinyl carbocations with activated and weakly coordinating trifluoromethanesulfonate anions by Lewis acid Sc(III) can undergo facile Friedel-Crafts reactions with arenes to give the desired adducts in up to 90% yield and with high -selectivity.

Sulfonylation of Aryl Halides by Visible Light/Copper Catalysis.

An efficient visible-light-assisted, copper-catalyzed sulfonylation of aryl halides with sulfinates is reported. In our protocol, a single ligand Cu photocatalyst formed in situ was used in the photocatalytic transformation. Diverse organosulfones were obtained in moderate to good yields.

Degradation of polycarbonate to produce bisphenol A catalyzed by imidazolium-based DESs under metal-and solvent-free conditions.

Bisphenol A (BPA) is an important chemical raw material, but the traditional preparation process of BPA is costly and complicated, so it is necessary to find an efficient and environmentally friendly method for the production of BPA. Deep eutectic solvents (DESs) have attracted widespread attention due to their low cost, low toxicity, low melting point, non-volatilization, easy preparation, recyclablility and biodegradability. In this work, a series of imidazolium-based DESs were synthesized and used for the degradation of polycarbonate (PC), and BPA was obtained from the methanolysis of PC catalyzed by DESs under metal- and solvent-free conditions.

Photocatalyst-Free Visible-Light-Promoted C(sp)-S Coupling: A Strategy for the Preparation of -Aryl Dithiocarbamates.

We have successfully developed a green and efficient multicomponent reaction protocol to synthesize -aryl dithiocarbamates under visible light. Most appealingly, the reaction can proceed smoothly without adding any transition-metal catalysts, ligands, or photocatalysts while minimizing chemical wastes and metal residues in the end products. The advantages of this method meet the requirements of sustainable and green synthetic chemistry, and it provides a straightforward way to create valuable -aryl dithiocarbamates.

Metal-Free Catalytic Synthesis of Thiocarbamates Using Sodium Sulfinates as the Sulfur Source.

A novel molecular iodine-catalyzed protocol for the construction of thiocarbamates from readily available sodium sulfinates, isocyanides, and water has been described. The present methodology offers a facile and practical route to a variety of thiocarbamates in moderate to good yields with favorable functional group tolerance by use odorless sodium sulfinates as the sulfur source. The mechanistic studies suggest the present transformation involves a radical process.

Intermolecular Regio- and Stereoselective Hetero-[5+2] Cycloaddition of Oxidopyrylium Ylides and Cyclic Imines.

We have developed the first intermolecular hetero-[5+2] cycloaddition reaction between oxidopyrylium ylides and cyclic imines with excellent control of regio- and stereoselectivity. Surprisingly, divergent stereochemistry was observed depending on the substitution pattern of the oxidopyrylium ylide. This new reaction provides quick access to highly substituted nitrogen-containing seven-membered rings-azepanes.

Metal-Free C(sp)-H/N-H Cross-Dehydrogenative Coupling of Quinoxalinones with Aliphatic Amines under Visible-Light Photoredox Catalysis.

A novel and efficient visible-light-induced C(sp)-H/N-H cross-dehydrogenative coupling (CDC)-amination with both primary and secondary aliphatic amines at room temperature in air is developed. This photocatalytic reaction allows the direct formation of 3-aminoquinoxalin-2(1 H)-ones via CDC-amination in the absence of any external oxidant added from outside. Preliminary mechanistic studies reveal that the present reaction proceeds through a radical process.

Transition-metal-free KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins using Bunte salts.

An efficient and eco-friendly protocol for the KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins with Bunte salts was established. The reaction worked smoothly under metal-free conditions and afforded a wide range of sulfenylated 4-anilinocoumarins with potential bioactivity in moderate to excellent yields. This method would expand the still limited scope of synthesis methods for C-S bond formation using Bunte salts.