P/N-Heteroleptic Cu(I)-Photosensitizer-Catalyzed [3 + 2] Regiospecific Annulation of Aminocyclopropanes and Functionalized Alkynes.

We report here a regiospecific [3 + 2] annulation between aminocyclopropanes and various functionalized alkynes enabled by a P/N-heteroleptic Cu(I) photosensitizer under photoredox catalysis conditions. Thus, a divergent construction of 3-aminocyclopentene derivatives including methylsulfonyl-, arylsulfonyl-, chloro-, ester-, and trifluoromethyl-functionalized aminocyclopentenes could be achieved with advantages of high regioselectivity, broad substrate compatibility, and mild and environmentally benign reaction conditions.

Donor-acceptor fluorophores as efficient energy transfer photocatalysts for [2 + 2] photodimerization.

Mild [2 + 2] photodimerization of enone substrates was induced by donor-acceptor fluorophores. Enone substrates were activated efficiently for anti-head to head dimerizations with a high yield (up to 83%) and high selectivity. The adjustable excited state potential also allows donor-acceptor fluorophores to be used for isomerization of the above substrates, confirming the potential of donor-acceptor fluorophores as energy transfer photocatalysts.

Selective and Catalytic Hydrocarboxylation of Enamides and Imines with CO2 to Generate α,α-Disubstituted α-Amino Acids.

The first catalytic hydrocarboxylation of enamides and imines with CO2 to generate valuable α,α-disubstituted α-amino acids is reported. Notably, excellent chemo- and regio-selectivity are achieved, significantly different from previous reports on ß-carboxylation of enamides, homocoupling or reduction of imines. Moreover, this transition-metal-free procedure exhibits low loading of an inexpensive catalyst, easily available substrates, mild reaction conditions, high efficiency, facile scalability and easy product derivatization, providing great potential for application in organic synthesis, pharmaceutical chemistry, and biochemistry.

Structure-Activated Copper Photosensitisers for Photocatalytic Water Reduction.

A series of phenanthroline-based ligands have been synthesised and their influence as bidentate nitrogen ligands in heteroleptic [Cu(P^P)(N^N)]+ photosensitisers in light-driven water reduction has been studied. In this noble-metal-free Cu-Fe-based photocatalytic water reduction system, the structural effects of the nitrogen ligands have been explored, including the steric and electronic effects of substituents at the 2,9- and 4,7-positions of phenanthroline. Ligands were prepared that led to increased hydrogen generation, with turnover numbers (TONCu ) of up to 1388 being observed. All the new complexes were electrochemically and photophysically characterised. We demonstrate for the first time that the presence of fluorine in nitrogen ligands increases the efficacy of copper complexes in photocatalytic hydrogen production.

Ligand-Controlled Cobalt-Catalyzed Transfer Hydrogenation of Alkynes: Stereodivergent Synthesis of Z- and E-Alkenes.

Herein, we report a novel cobalt-catalyzed stereodivergent transfer hydrogenation of alkynes to Z- and E-alkenes. Effective selectivity control is achieved based on a rational catalyst design. Moreover, this mild system allows for the transfer hydrogenation of alkynes bearing a wide range of functional groups in good yields using catalyst loadings as low as 0.2 mol %. The general applicability of this procedure is highlighted by the synthesis of more than 50 alkenes with good chemo- and stereoselectivity. A preliminary mechanistic study revealed that E-alkene product was generated via sequential alkyne hydrogenation to give Z-alkene intermediate, followed by a Z to E alkene isomerization process.

Copper-Based Photosensitisers in Water Reduction: A More Efficient In Situ Formed System and Improved Mechanistic Understanding.

The reduction of water has been achieved through a non-noble-metal-based homogeneous catalyst system that is formed in situ. Optimisation of the ligand quantities increased catalyst turnover numbers compared to preformed complexes. Mechanistic studies confirm a heteroleptic Cu complex as the active photosensitiser (PS) and an in situ formed Fe-phosphido dimer complex as the water reduction catalyst. The in situ method has been used to screen a range of ligands for the active PS, which has led to the identification a number of structural features important to longevity and performance.

Insecticide Toxicity to Adelphocoris lineolatus (Hemiptera: Miridae) and its Nymphal Parasitoid Peristenus spretus (Hymenoptera: Braconidae).

In China, Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) is an important pest of alfalfa, cotton, and other crops, while Peristenus spretus (Chen & van Achterberg) (Hymenoptera: Braconidae) is the dominant nymphal parasitoid of this mirid bug. In the present study, the toxicity of 17 common insecticides to A. lineolatus was evaluated, and the susceptibility of P. spretus to the insecticides with high toxicity to A. lineolatus was tested under laboratory conditions. Of the 17 insecticides tested, 12 (beta cypermethrin, deltamethrin, carbosulfan, acetamiprid, emamectin benzoate, imidacloprid, phoxim, chlorpyrifos, acephate, profenophos, hexaflumuron, and abamectin) had a highly toxic effect on second-instar nymphs of A. lineolatus, with LC(50) values ranging from 0.58 to 14.85 mg a.i. (active ingredient) liter(-1). Adults of P. spretus were most sensitive to chlorpyrifos, with LC(50) values of 0.03 mg a.i. liter(-1), followed by phoxim, acetamiprid, profenophos, carbosulfan, acephate, deltamethrin, emamectin benzoate, imidacloprid, beta-cypermethrin, and abamectin, with LC(50) values ranging from 0.06 to 3.09, whereas hexaflumuron exhibited the least toxicity to the parasitoid, with LC(50) values >500 mg a.i. liter(-1). A risk quotient analysis indicated that beta-cypermethrin, emamectin benzoate, abamectin, and hexaflumuron when applied against A. lineolatus were the least toxic to P. spretus.

Palladium-Catalyzed Hydrocyanation of Ynoates: En Route to the Stereodivergent Synthesis of ß-Cyanated α,ß-Unsaturated Esters via Ligand Controlled Regio- and Stereoselectivity.

A Pd-catalyzed highly regio- and stereoselective hydrocyanation was developed, providing a novel approach to the stereodivergent synthesis of ß-cyano-substituted acrylates in good yields with a wide substrate scope. The judicious selection of ligands was crucial for elegant control over the stereodivergence. Furthermore, the success of the E-hydrocyanation hinges on the right matching of Pd and L1, which not only ensured the catalytic activity but also prevented the formation of α-cyanation products.

Nickel-Catalyzed Cyanation of Allylic Alcohols: High Degree of Chiral Inversion in Aqueous Reaction Media.

Nickel-catalyzed aqueous cyanation of allylic alcohols is herein described. This catalytic protocol provided environmentally friendly and operationally simple access to a variety of allylic nitriles in good yields. For chiral allylic alcohols, the reaction gave chiral allylic nitriles with a high degree of chiral inversion. The accelerated release of cyanide in H2O was crucial for the success of this reaction.

A noble-metal-free system for photocatalytic hydrogen production from water.

A series of heteroleptic copper(I) complexes with bidentate PP and NN chelate ligands was prepared and successfully applied as photosensitizers in the light-driven production of hydrogen, by using [Fe3(CO)12] as a water-reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble-metal-free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton-reduction systems. Within these experiments, considerably long excited-state lifetimes of up to 54 µs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway.

Photocatalytic water reduction with copper-based photosensitizers: a noble-metal-free system.

Of noble descent: a fully noble-metal-free system for the photocatalytic reduction of water at room temperature has been developed. This system consists of Cu(I) complexes as photosensitizers and [Fe(3)(CO)(12)] as the water-reduction catalyst. The novel Cu-based photosensitizers are relatively inexpensive, readily available from commercial sources, and stable to ambient conditions, thus making them an attractive alternative to the widely used noble-metal based systems.

Single Cu(I)-Photosensitizer Enabling Combination of Energy-Transfer and Photoredox Catalysis for the Synthesis of Benzo[b]fluorenols from 1,6-Enynes.

An efficient, mild, and atom-economical synthesis of benzo[b]fluorenols from 1,6-enynes has been developed under photocatalytic conditions. A single P/N heteroleptic Cu(I)-photosensitizer might exhibit both energy-transfer and photoredox catalytic activities in the formation of benzo[b]fluorenols.

The highly enantioselective Michael addition of ketones to nitrodienes catalyzed by the efficient organocatalyst system of pyrrolidinyl-thioimidazole and chiral thioureido acid.

The highly enantioselective Michael addition reaction of ketones to nitrodienes was promoted efficiently by the accessible and fine-tunable organocatalytic system of pyrrolidinyl-thioimidazole and chiral thioureido acid. The corresponding adducts were afforded in good yields with high diastereoselectivities (up to 99 : 1) and excellent enantioselectivities (up to 99% ee).

1-Nitro-4-(2-nitro-prop-1-en-yl)benzene.

The asymmetric unit of the title compound, C(9)H(8)N(2)O(4), contains two crystallographically independent mol-ecules, both of which adopt an E configuration about the C=C bond. In the crystal, the mol-ecules stack into columns along the c axis through π-π inter-actions, with centroid-centroid distances of 3.695 (3) and 3.804 (3) Å. The columns are further connected into a three-dimensional network by C-H⋯O hydrogen bonds.

Reversible interconversion between methanol-diamine and diamide for hydrogen storage based on manganese catalyzed (de)hydrogenation.

The development of cost-effective, sustainable, and efficient catalysts for liquid organic hydrogen carrier systems is a significant goal. However, all the reported liquid organic hydrogen carrier systems relied on the use of precious metal catalysts. Herein, a liquid organic hydrogen carrier system based on non-noble metal catalysis was established. The Mn-catalyzed dehydrogenative coupling of methanol and N,N'-dimethylethylenediamine to form N,N'-(ethane-1,2-diyl)bis(N-methylformamide), and the reverse hydrogenation reaction constitute a hydrogen storage system with a theoretical hydrogen capacity of 5.3 wt%. A rechargeable hydrogen storage could be achieved by a subsequent hydrogenation of the resulting dehydrogenation mixture to regenerate the H2-rich compound. The maximum selectivity for the dehydrogenative amide formation was 97%.

Tertiary Amines Acting as Alkyl Radical Equivalents Enabled by a P/N Heteroleptic Cu(I) Photosensitizer.

An unprecedented exploration of tertiary amines as alkyl radical equivalents for cross-coupling with aromatic alkynes to access allylarenes has been achieved by a P/N heteroleptic Cu(I)-based photosensitizer under photoredox catalysis conditions. Mechanistic studies reveal that the reaction might undergo radical addition of in situ-generated α-amino radical intermediates to alkynes followed by 1,5-hydrogen transfer, C-N bond cleavage, and concomitant isomerization of the resulting allyl radical species.

Chiral amine/chiral acid as an excellent organocatalytic system for the enantioselective tandem oxa-Michael-aldol reaction.

The asymmetric tandem oxa-Michael-aldol reaction of salicylic aldehyde derivatives with alpha,beta-unsaturated aldehydes catalyzed by a chiral amine/chiral acid organocatalytic system was investigated. The organocatalytic system of (S)-diphenylpyrrolinol trimethylsilyl ether with chiral shift reagent (S)-Mosher acid presented a synergistic effect in the improvement of reaction performance and offered an efficient steric effect in the transformation. The tandem oxa-Michael-aldol reaction proceeded with high yields (up to 90%) and with excellent ee values (up to 99%) to give the corresponding chromene derivatives. The structure of the chiral ammonium salt formed in situ and the corresponding mechanism were also studied by (1)H NMR.

(R)-7-Bromo-2,3,4,4a-tetra-hydro-1H-xanthen-1-one.

The title compound, C(13)H(11)BrO(2), contains a tricyclic ring system with one chiral center which exhibits an R configuration. The crystal structure is devoid of any classical hydrogen bonding.

In situ enamine activation in aqueous salt solutions: highly efficient asymmetric organocatalytic Diels-Alder reaction of cyclohexenones with nitroolefins.

Deep-sea Diels-Alder: The asymmetric organocatalytic Diels-Alder reaction of cyclohexenones with aromatic nitroolefins can be carried out in seawater and brine. The reaction proceeds by an in situ enamine activation involving a one-step concerted addition pathway (see scheme).

Characterization of antennal chemosensilla and associated odorant binding as well as chemosensory proteins in the Eupeodes corollae (Diptera: Syrphidae).

Aphidophagous syrphids are important for pest control and pollination in various agroecosystems. However, the mechanism underlying olfaction, which is critical for insect' behavioral processes and fitness, has not been well understood in the family Syrphidae. Hence, we performed a systematic identification and characterisation of the antennal sensilla and two groups of soluble proteins, odorant-binding proteins (OBPs) and chemosensory proteins (CSPs), in the hoverfly Eupeodes corollae. (i) With scanning electron microscopy, four major types of sensilla (chaetic sensilla [two subtypes], trichoid sensilla, basiconic sensilla [two subtypes] and coeloconic sensilla), with numerous microtrichia, were first observed along the entire surface of aristate antennae of both sexes of E. corollae. Of these, only chaetic sensillum was found on the first two antennal segments, scape and pedicel, while the other types of sensilla were located on the flagellum. No marked difference was observed in the morphological structure or distributional pattern of any of the sensilla between the two sexes. (ii) By molecular cloning and bioinformatic analysis, 7 EcorCSPs and 28 EcorOBPs (20 classic OBPs, 5 minus-C OBPs, and 3 plus-C OBPs) were directly identified from the species, which all share the characteristic hallmarks of their family, including the presence of a signal peptide and conserved cysteine signature. (iii) RT-qPCR of these chemosensory genes showed predominately tissue-biased expression patterns; 32 of the 35 EcorOBPs/CSPs were uniquely or primarily expressed in the main olfactory organs, either the antennae or head. (iv) Among these, several genes (EcorCSP2 and EcorOBP1, 9, 12, 15-17, 20) appeared to be antenna-biased. In situ hybridization assays indicated that each antenna-biased chemosensory gene was expressed in a different number of cells, suggesting they might play a more vital role in odour recognition and perception and could be potential candidates to study their biological functions in vivo and in vitro. Together, our current findings provide a basis for future studies on how syrphids utilize chemical cues to regulate their behavior during interactions among the natural enemy, its prey, and host plant in agro-ecosystems.