[Effect of Partial Substitution of Chemical Fertilizers with Organic Fertilizers on N2O and NO Emissions from a Peach Orchard].

Organic fertilizer substitution has been promoted as a weight loss, efficient, and diversified fertilizer substitution technology in agricultural production. However, there is a lack of comprehensive assessment of the impact of organic fertilizers on N2O and NO emissions from orchards. In this study, N2O and NO emissions from peach orchards were observed annually using static dark box-gas chromatography to compare the effects of chemical fertilizer application alone and partial replacement of chemical fertilizer treatment on NO emissions from peach orchards. The results showed that the partial replacement of chemical fertilizers with organic fertilizers reduced the total N2O and NO emissions from peach orchards by 15.0 % and 9.4 %, respectively. The N2O and NO emission factors were reduced by 21.3 % and 21.1 %. The mineral N content of the soil in the organic fertilizer treatment was lower than that in the chemical fertilizer treatment alone. The organic fertilizer treatment increased the contribution of AOA to nitrification and decreased the contribution of AOB, thus reducing N2O and NO from nitrification. In addition, the results of the dual isotope mixing model[δ18O(N2O/H2O) vs. δ15NSP] indicated that the bacterial denitrification/nitrifying bacterial denitrification (bD/nD) process served as the primary pathway for N2O emissions in peach orchards. Partial substitution with organic fertilizers enhanced soil denitrification, resulting in larger reductions in the amounts of N2O and NO. Therefore, partial substitution of organic fertilizer is a viable measure to mitigate nitrogen oxide emissions from orchards and to achieve green and low-carbon development in agriculture.

Introduction of the difluoromethyl group at the meta- or para-position of pyridines through regioselectivity switch.

Difluoromethyl pyridines have gained significant attention in medicinal and agricultural chemistry. The direct C-H-difluoromethylation of pyridines represents a highly efficient economic way to access these azines. However, the direct meta-difluoromethylation of pyridines has remained elusive and methods for site-switchable regioselective meta- and para-difluoromethylation are unknown. Here, we demonstrate the meta-C-H-difluoromethylation of pyridines through a radical process by using oxazino pyridine intermediates, which are easily accessed from pyridines. The selectivity can be readily switched to para by in situ transformation of the oxazino pyridines to pyridinium salts upon acid treatment. The preparation of various meta- and para-difluoromethylated pyridines through this approach is presented. The mild conditions used also allow for the late-stage meta- or para-difluoromethylation of pyridine containing drugs. Sequential double functionalization of pyridines is presented, which further underlines the value of this work.

Meta-Selective Copper-Catalyzed C-H Arylation of Pyridines and Isoquinolines through Dearomatized Intermediates.

C(sp2)-H functionalization offers an efficient strategy for the synthesis of various elaborated N-containing heteroarenes. Along these lines, oxazino pyridines that can be readily prepared from pyridines, have been introduced as powerful substrates in radical- and ionic-mediated meta-C-H functionalization. However, the regioselective meta-C-H arylation of pyridines remains a great challenge. Herein, a copper-catalyzed meta-selective C-H arylation of pyridines and isoquinolines through bench-stable dearomatized intermediates is reported. Electrophilic aryl-Cu(III) species, generated from readily accessible aryl I(III) reagents, enable the efficient meta-arylation of a broad range of pyridines and isoquinolines. The method also allows the meta-selective alkenylation of these heteroarenes using the corresponding alkenyl I(III)-reagents. Late-stage arylation of drug-derived pyridines and larger-scale experiments demonstrate the potential of this synthetic methodology.

A C-H activation-based enantioselective synthesis of lower carbo[n]helicenes.

The three-dimensional structure of carbohelicenes has fascinated generations of molecular chemists and has been exploited in a wide range of applications. Their strong circularly polarized luminescence has attracted considerable attention in recent years due to promising applications in new optical materials. Although the enantioselective synthesis of fused carbo- and heterohelicenes has been achieved, a direct catalytic enantioselective method allowing the synthesis of lower, non-fused carbo[n]helicenes (n = 4-6) is still lacking. We report here that Pd-catalysed enantioselective C-H arylation in the presence of a unique bifunctional phosphine-carboxylate ligand provides a simple and general access to these lower carbo[n]helicenes. Computational mechanistic studies indicate that both the C-H activation and reductive elimination steps contribute to the overall enantioselectivity. The observed enantio-induction seems to arise from a combination of non-covalent interactions and steric repulsion between the substrate and ligand during the two key reductive elimination steps. The photophysical and chiroptical properties of the synthesized scalemic [n]helicenes have been systematically studied.

Intermolecular Palladium(0)-Catalyzed Atropo-enantioselective C-H Arylation of Heteroarenes.

Atropisomeric (hetero)biaryls are motifs with increasing significance in ligands, natural products, and biologically active molecules. The straightforward construction of the stereogenic axis by efficient C-H functionalization methods is extremely rare and challenging. An intermolecular and highly enantioselective C-H arylation of relevant heteroarenes providing an efficient access to atropisomeric (hetero)biaryls is reported. The use of a Pd(0) complex equipped with H8-BINAPO as a chiral ligand enables the direct functionalization of a broad range of 1,2,3-triazoles and pyrazoles in excellent yields and selectivities of up to 97.5:2.5 er. The method also allows for an atroposelective double C-H arylation for the construction of two stereogenic axes with >99.5:0.5 er.

Bioinspired enantioselective synthesis of crinine-type alkaloids via iridium-catalyzed asymmetric hydrogenation of enones.

A bioinspired enantioselective synthesis of crinine-type alkaloids has been developed by iridium-catalyzed asymmetric hydrogenation of racemic cycloenones. The method features a biomimetic stereodivergent resolution of the substrates bearing a remote arylated quaternary stereocenter. Using this protocol, 24 crinine-type alkaloids and 8 analogues were synthesized in a concise and rapid way with high yield and high enantioselectivity.

Asymmetric Total Synthesis of Gracilamine and Determination of Its Absolute Configuration.

(+)-Gracilamine, a biologically attractive and structurally unique pentacyclic Amaryllidaceae alkaloid, was biomimetically synthesized in 11 linear steps in 9.9% overall yield from the known racemic oxocrinine. The synthesis features an asymmetric hydrogenation, a ring-opening/benzylic oxidation/cyclization sequence, and a biomimetic intramolecular cycloaddition. This total synthesis not only allows the assignment of its absolute configuration, but also provides experimental support for the hypothesis that naturally occurring (+)-gracilamine is biogenetically derived from the crinine-type alkaloid (+)-epivittatine.

[Effect of a novel analgesic disposable urinary catheter in prevention of restlessness caused by catheter-related bladder discomfort in general anesthesia patients in recovery period].

OBJECTIVE: To investigate the effect of a novel analgesic disposable urinary catheter invented by the authors in prevention of restlessness caused by catheter-related bladder discomfort (CRBD) in general anesthesia patients in anesthesia recovery period. METHODS: Two hundred patients, who underwent general anesthesia for general surgical operation, were divided randomly into 2 equal groups: observation group, undergoing insertion of F16 novel analgesic disposable Foley urinary catheter after inducement of general anesthesia, and control group undergoing insertion of conventional F16 Foley urinary catheter after induction of anesthesia. The rate of restlessness caused by CBRD and the rate of catheter pulling-off were compared. RESULTS: The CRBD rate of the observation group was 9%, significantly lower than that of the control group (61%, P < 0.01), the rate of CRBD-caused restlessness of the observation group was 0, significantly lower then that of the control group (23%, P < 0.001). The extent of CRBD of the observation group was significantly lighter than that of the control group. CONCLUSION: The catheter inserting after the induction of anesthesia is an element related to the restlessness in anesthesia recovery period and other serious postoperative complications. The novel analgesic disposable urinary catheter effectively prevents CRBD-caused restlessness in general anesthesia patients in the anesthesia recovery period.