Organophotocatalytic Alkene Reduction Using Water as a Hydrogen Donor.

The chemical activation and functionalization of water are considered an ideal method for converting earth-abundant sources into valuable chemicals. Here, we show that a non-activated free water molecule can be applied directly as a hydrogen donor to achieve the carbanion-mediated alkene reduction with 9-HTXTF serving as an organophotocatalyst. Notably, direct syntheses of high-value-added drugs and bioactive molecules are readily achieved by utilizing plentiful energy and an earth-abundant resource, showcasing the usefulness of the protocol in chemical synthesis.

Discovery of a Thioxanthone-TfOH Complex as a Photoredox Catalyst for Hydrogenation of Alkenes Using p-Xylene as both Electron and Hydrogen Sources.

Hydrogenation of alkenes is one of the most fundamental transformations in organic synthesis, and widely used in the petrochemical, pharmaceutical, and food industries. Although numerous hydrogenation methods have been developed, novel types of catalysis with new mechanisms and new hydrogen sources are still desirable. Thioxanthone (TX) is widely used in energy-transfer photoreactions, but rarely in photoredox processes. Herein we show that a catalytic amount of TfOH as a co-catalyst can tune the properties of TX to make it a photoredox catalyst with highly enhanced oxidative capability in the hydrogenation of carbonylated alkenes with the cheap petroleum industrial product p-xylene serving as the hydrogen source. Deuterium can also be introduced by this method by using D2 O as the D source. To the best of our knowledge, this is the first example of using p-xylene as a hydrogen source.

Visible light-induced one-pot synthesis of CF3/CF2-substituted cyclobutene derivatives.

An efficient one-pot approach for the controllable synthesis of trifluoromethyl/gem-difluoromethylene substituted cyclobutene derivatives has been developed. The mechanism may involve visible light-induced [2+2]-cycloaddition of quinolinones with 1-bromo-1-trifluoromethylethene, followed by base-promoted dehydrobromination, [1,3]-H shift and further dehydrofluorination. A variety of CF3/CF2-substituted cyclobutenes that are currently difficult to obtain are afforded in good yields in this protocol, which may find its way into future fluorinated cyclobutene preparation.

Photochemical Synthesis of 1,4-Dicarbonyl Bifluorene Compounds via Oxidative Radical Coupling Using TEMPO as the Oxygen Atom Donor.

A visible-light-induced metal-free synthesis of 1,4-dicarbonyl compounds from alkyne-containing aryl iodides via photochemical C-I bond cleavage, intramolecular cyclization, oxidation, and intermolecular radical coupling sequence is reported. TEMPO was employed as the oxygen atom donor in this transformation. This protocol provided a new strategy for the synthesis of 1,4-dicarbonyl bifluorene compounds.

Synthesis of microporous hydrogen-bonded supramolecular organic frameworks through guanosine self-assembly.

Extending the structural hierarchy and complexity through small-molecular self-assembly is a powerful way to obtain large discrete, functional molecular architecture. A hydrogen-bonded supramolecular organic framework (HSOF) with nanometer-size pores is constructed in a solid state with simple guanosine-monomer self-assembly. To extend the hierarchy of the G-quartet self-assembly to a higher order thanthatofthetraditionalG-quadruplex,H-bondacceptorsontheC-8 position of guanosine are introduced to establish inter-quadruplex linkage via H bonding to N(2)-HB from the neighboring G-quartet. After screening different C-8 substitution groups and various synthesis conditions, HSOF-G1a' is obtained by solvent evaporation under diluted condition. Single-crystal X-ray structure reveals that cubic repeating units formed by G8 are the supermolecule secondary building block (SBU) with large pores (d=34A). To our knowledge, this is the first G-quartet self-assembly with an organized structure beyond cylindrical G-quadruplexes.

Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer.

We report herein the synthesis of a polymeric photosensitizer and its application in aerobic photooxidative hydroxylation of boronic acids. The polymeric photosensitizer was synthesized by the condensation of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly (2-hydroxyethyl methacrylate) (PHEMA). The photo-oxidative hydroxylation of boronic acids using anthraquinone-containing-poly (2-hydroxyethyl methacrylate) (AQ-PHEMA) was then explored and shown to exhibit high efficiency and broad scope. Moreover, AQ-PHEMA could be easily recovered and reused for more than 20 times without significant loss of the catalytic activity.

Synthesis of an anthraquinone-containing polymeric photosensitizer and its application in aerobic photooxidation of thioethers.

Work on the synthesis of a polymeric photosensitizer and its application in the photooxidation of thioethers is reported herein. Firstly, the polymeric photosensitizer was designed and synthesized by the reaction of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly(2-hydroxyethyl methacrylate) (PHEMA). Then, the visible light-induced photooxidation of thioethers under aerobic conditions was investigated. The results revealed that the reaction yielded sulfoxides highly chemoselectively in excellent yields with good substrate tolerance. Importantly, AQ-PHEMA could be easily recovered and reused more than 20 times without significant loss of the catalytic activity.

New development in the enantioselective synthesis of spiro compounds.

The enantioselective synthesis of spirocycles has long been pursued by organic chemists. Despite their unique 3D properties and presence in several natural products, the difficulty in their enantioselective synthesis makes them underrepresented in pharmaceutical libraries. Since the first pioneering reports of the enantioselective construction of spirosilanes by Tamao et al., significant effort has been devoted towards the development of new promising asymmetric methodologies. Remarkably, with the advent of organocatalysis, particularly over six years, the reported methodologies for the synthesis of spirocycles have increased exponentially. The aim of this review is to summarize the latest trends and developments in the enantioselective synthesis of spirocompounds during these last six years.

Visible light sensitizer-catalyzed highly selective photo oxidation from thioethers into sulfoxides under aerobic condition.

We report herein a visible light sensitizer-catalyzed aerobic oxidation of thioethers, affording sulfoxides in good to excellent yields. The loading of the catalyst was as low as 0.1 mol%. The selectivity was excellent. Mechanism studies showed both singlet oxygen and superoxide radical anion were likely involved in this transformation.

Transformation of Organostannanes Based on Photocleavage of C-Sn Bond via Single Electron Transfer Process.

In this work, we developed a new method for the transformation of organostannanes via radical process. In this reaction, highly reactive carbon radical species can be efficiently generated through HBr-catalyzed photocleavage of C-Sn bond via single electron transfer process. Under aerobic conditions, the in situ formed primary/secondary alkyl radicals can be further highly selectively oxidized into carboxylic acids/ketones, respectively.

PHEA-g-PMMA Well-Defined Graft Copolymer: ATRP Synthesis, Self-Assembly, and Synchronous Encapsulation of Both Hydrophobic and Hydrophilic Guest Molecules.

A series of well-defined amphiphilic graft copolymer bearing a hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophobic poly(methyl methacrylate) (PMMA) side chains was synthesized by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) through the grafting-from strategy. A well-defined PHEA-based backbone with Cl-containing ATRP initiating group in every repeated unit (M w/M n = 1.08), poly(2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate) (PHECPMA), was first prepared by RAFT homopolymerization of 2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate (HECPMA), a Cl-containing trifunctional acrylate. ATRP of methyl methacrylate was subsequently initiated by PHECPMA homopolymer to afford the target well-defined poly(2-hydroxyethyl acrylate)-graft-poly(methyl methacrylate) (PHEA-g-PMMA) graft copolymers (M w/M n ≤ 1.36) with 34 PMMA side chains and 34 pendant hydroxyls in PHEA backbone using CuCl/dHbpy as catalytic system. The critical micelle concentration (cmc) of the obtained graft copolymer was determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as probe while micellar morphologies in aqueous media were visualized by transmission electron microscopy. Interestingly, PHEA-g-PMMA graft copolymer could self-assemble into large compound micelles rather than common spherical micelles, which can encapsulate hydrophilic rhodamine 6 G and hydrophobic pyrene separately or simultaneously.

Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate.

A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances.

Cu(II)-Catalyzed 6π-Photocyclization of Dienynes.

The first 6π-photocyclization of dienynes was developed, which provides a new and effective protocol for the synthesis of the phenyl ring in excellent yields with nice functional group tolerance. In this transformation, the Cu(OTf)2 catalyst plays a key role in the conversion of alkyne moiety into an alkene-type moiety, which means that the dienyne reactant is converted into a triene-type substrate. Thus, this reaction proceeds via a Cu(II)-catalyzed 6π-photocyclization of triene-type derivatives.

Merging photoredox catalysis with Lewis acid catalysis: activation of carbon-carbon triple bonds.

Here, we demonstrate that merging photoredox catalysis with Lewis acid catalysis provides a fundamentally new activation mode of C-C triple bonds, to achieve the bond-forming reaction of alkynes with weak nucleophiles. Using a synergistic merger of Eosin Y and Cu(OTf)2, a highly efficient cyclization reaction of arene-ynes was developed.

Construction of Nontoxic Polymeric UV-Absorber with Great Resistance to UV-Photoaging.

In this article, we developed a series of new nontoxic polymeric UV-absorbers through covalently attaching a benzophenone derivative onto the main chain of poly(vinyl chloride) (PVC) via mild and quantitative click chemistry. Azide groups were firstly introduced into the backbone of PVC via a nucleophilic reaction without affecting polymeric skeleton. Copper-catalyzed Husigen-Click cycloaddition reaction was performed between the pendant azide groups of PVC and alkynyl of (2-hydroxy-4-(prop-2-ynyloxy)phenyl)(phenyl)methanone at ambient temperature for affording the desired PVC-based UV-absorbers (PVC-UV) with different amounts of benzophenone moieties, which displayed great resistance to photoaging without degradation while exposed to UV irradiation. These polymeric UV-absorbers also showed good solubilities in common organic solvents and no cytotoxicity vs. HaCat cell. Small amounts of PVC-UV were homogeneously mixed with PVC as additive for stabilizing PVC against UV-photoaging without degradation and releasing small molecule even after 200 h while keeping thermal stability. This route of polymeric additive clearly paved an efficient way for solving the puzzle of separation of small molecule additive.

Visible light induced cyclopropanation of dibromomalonates with alkenes via double-SET by photoredox catalysis.

We report herein a visible light induced generation of a carbanion via double-SET and its application in cyclopropanation of alkenes. This new synthetic approach to form cyclopropane derivatives was conducted under mild conditions, using sunlight in open air, showing the features such as environmental benignness and an easy to handle procedure.

Amine-catalyzed direct photoarylation of unactivated arenes.

Constructing biaryls through direct aromatic C-H functionalization of unactivated arenes has become a popular topic in organic chemistry. Many efficient methods have been developed. In this Communication, a direct arylation of unactivated arenes with a broad range of aryl iodides is reported. This reaction proceeds through a new type of amine-catalyzed single electron transfer initiated radical coupling procedure to form biaryls in high yields under UV irradiation at room temperature. Only 20 mol% of TMEDA is used as the catalyst. No other additives are required for this transformation, thus avoiding the use of toxic transition metal catalysts, strong bases, or large amounts of other organic additives. This greener protocol provides a new strategy to achieve direct aromatic C-H functionalization and offers a new example of cost-effective and environmentally benign access to biaryls.

(7R,8S,9S,12S)-1-Benz-yloxy-13,14-didehydro-12-hy-droxy-2,13-dimeth-oxy-N-methyl-morphinane.

In the title compound, C(26)H(31)NO(4), a sinomenine derivative, the angle between the two aromatic rings is 53.34 (4)°. The N-containing ring is in a chair conformation, while the other two non-planar rings are in a half-boat conformation. In the crystal, mol-ecules are linked by O-H⋯N inter-actions into a C(8) chain along [100].

(7R,8S,9S,12S)-1-(4-Chloro-benz-yloxy)-13,14-didehydro-12-hy-droxy-2,13-dimeth-oxy-N-methyl-morphinane.

The title compound, C(26)H(30)ClNO(4), a sinomenine derivative, has five six-membered rings, two of which are aromatic, with a dihedral angle of 34.13 (20)° between these. The N-containing ring and the fourth ring exhibit chair conformations, while the fifth ring approximates an envelope conformation. A single inter-molecular O-H⋯N hydrogen-bonding inter-action gives a one-dimensional chain structure which extends along the a axis. The absolute configuration for the mol-ecule has been determined.

(9S,13R,14S)-7,8-Didehydro-4-(4-fluoro-benz-yloxy)-3,7-dimeth-oxy-17-methyl-morphinan-6-one sesquihydrate.

In the title sinomenine derivative, C(26)H(28)FNO(4)·1.5H(2)O, the dihedral angle between the two aromatic rings is 55.32 (6)°. The N-containing ring has an approximate chair conformation, while other two rings have approximate envelope and half-chair conformations. One water mol-ecule is located on a twofold symmetry axis. In the crystal, the water mol-ecules form O-H⋯O and O-H⋯N hydrogen bonds, bridging symmetry-related main mol-ecules.