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1.
Org Biomol Chem ; 20(13): 2615-2620, 2022 03 30.
Artigo em Inglês | MEDLINE | ID: mdl-35297934

RESUMO

The P-O bond of epimerized alkoxyl phosphine-borane was cleaved by naphthalene-lithium, to form two diastereomers of P-anions in a ratio of 86 : 14, which was then converted to secondary phosphine-borane via acidification, and to tertiary phosphines with alkyl halides with enhanced 96 : 4 dr. The isolated tertiary phosphine containing hydroxyl (in >99 : 1 dr) was converted to multi-stereogenic tertiary phosphines via O-alkylation with alkylene dihalides.


Assuntos
Boranos , Fosfinas , Ânions , Boranos/química , Lítio/química , Fosfinas/química
2.
ChemSusChem ; 14(24): 5340-5358, 2021 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-34750973

RESUMO

C-N bonds are pervasive throughout organic-based materials, natural products, pharmaceutical compounds, and agricultural chemicals. Considering the widespread importance of C-N bonds, the development of greener and more convenient ways to form C-N bonds, especially in late-stage synthesis, has become one of the hottest research goals in synthetic chemistry. Copper-catalyzed radical reactions involving N-centered radicals have emerged as a sustainable and promising approach to build C-N bonds. As a chemically popular and diverse radical species, N-centered radicals have been used for all kinds of reactions for C-N bond formation by taking advantage of their inherently incredible reactive flexibility. Copper is also the most abundant and economic catalyst with the most relevant activity for facilitating the synthesis of valuable compounds. Therefore, the aim of the present Review was to illustrate recent and significant advances in C-N bond formation methods and to understand the unique advantages of copper catalysis in the generation of N-centered radicals since 2016. To provide an ease of understanding for the readers, this Review was organized based on the types of nitrogen sources (amines, amides, sulfonamides, oximes, hydrazones, azides, and tert-butyl nitrite).


Assuntos
Aminas , Cobre , Amidas , Catálise , Nitrogênio
3.
Org Biomol Chem ; 19(41): 8874-8885, 2021 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-34610071

RESUMO

Benzimidazo[2,1-a]isoquinolin-6(5H)-one constitutes a structurally unique class of tetracyclic N-heterocycles that are found throughout a myriad of biologically active natural products, pharmaceutical compounds, and functional materials. Various synthetic routes for the preparation of benzimidazo[2,1-a]isoquinolin-6(5H)-ones have been reported. In particular, the use of N-methacryloyl-2-phenylbenzoimidazoles to construct benzimidazo[2,1-a]isoquinolin-6(5H)-ones through various radical strategies have attracted widespread attention due to the versatility and simple preparation of raw materials, as well as the step-economy and mild reaction conditions. Using representative examples, we highlight significant progress in the synthesis of benzimidazo[2,1-a]isoquinolin-6(5H)-ones, including the selection of the catalytic system, substrate scope, mechanistic understanding, and applications. The contents of this review focus on the development of C-, S-, P-, and Si-centered radical addition-intramolecular cyclization strategies.

4.
Org Biomol Chem ; 19(34): 7333-7347, 2021 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-34612358

RESUMO

The direct use structurally simple ketones as α-ketone radical sources for α-C(sp3)-H functionalization is a sustainable and powerful approach for constructing complex and multifunctional chemical scaffolds with diverse applications. The reactions of α-ketone radicals with alkenes, alkynes, enynes, imides, and imidazo[1,2-a]pyridines have broadened the structural diversity and complexity of ketones. Through chosen illustrative examples, we outline the recent progress in the development of methods that enable the radical α-C(sp3)-H functionalization of ketones, with an emphasis on radical initiation systems and possible mechanisms of the transformations. The application of these strategies is illustrated by the synthesis of several biologically active molecules and drug molecules. Further subdivision is based on substrate type and reaction type.

5.
Org Biomol Chem ; 19(43): 9501-9505, 2021 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-34709283

RESUMO

An efficient, selective, and step economical radical cyclization of 1,6-dienes with alkyl nitriles initiated by α-C(sp3)-H functionalization under the Sc(OTf)3 and Ag2CO3 system is described here. The selective divergent cyclization relies on the substitution effect at the α-position of the acrylamide moiety and nitriles, which is terminated by hydrogen abstraction, direct cyclization with the aryl ring, or further cyclization with the CN bond and hydrolysis, respectively.

6.
Chem Asian J ; 16(20): 3068-3081, 2021 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-34423568

RESUMO

2-Pyrrolidones have aroused enormous interest as a useful structural moiety in drug discovery; however, not only does their syntheses suffer from low selectivity and yield, but also it requires high catalyst loadings. The radical cyclization of 1,n-enynes and 1,n-dienes has demonstrated to be an attractive method for the synthesis of 2-pyrrolidones due to its mild reaction conditions, fewer steps, higher atom economy, excellent functional group compatibility, and high regioselectivity. Furthermore, radical receptors with unsaturated bonds (i. e. 1,n-enynes and 1,n-dienes) play a crucial role in realizing radical cyclization because of the ability to selectively introduce one or more radical sources. In this review, we discuss representative examples of methods involving the radical cyclization of 1,n-enynes and 1,n-dienes published in the last five years and discuss each prominent reaction design and mechanism, providing favorable tools for the synthesis of valuable 2-pyrrolidone for a variety of applications.

7.
Inorg Chem ; 60(17): 13041-13050, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34375075

RESUMO

The zeolitic imidazolate framework (ZIF)-67 microcrystal was employed as a precursor to synthesize the hollow ZIF-8/ZIF-67 composite via the epitaxial growth of ZIF-8 on ZIF-67, in situ self-sacrifice, and excavation of ZIF-67. The hollow ZIF-8/ZIF-67 composite was successfully transformed to the ZnO-Co3O4/N-C cage by thermal treatment, which was further used as the catalyst for the oxidative degradation of bisphenol A (BPA) in the presence of potassium persulfate (PS). In comparison with the Co3O4/N-C and Co3O4 obtained from pure ZIF-67 and cobalt nitrate, the ZnO-Co3O4/N-C cage demonstrated a more than four fold-higher activity and robust reusability. Based on structural analysis, the enhanced catalytic performance could be ascribed to the small, highly dispersed cobalt oxide particles, the hollow structure that facilitated the transportation of the molecules, and the synergistic effect between cobalt oxide and nitrogen-doped carbon in the composite. Besides, the effect of dosage of PS, BPA, and the co-existing components such as chloride ion, methanol, and t-butyl alcohol was carefully investigated to propose the possible mechanism. This study would give new insights into the design of functional composite materials from metal organic frameworks and the development of their application in environmental pollution disposal.

8.
ChemSusChem ; 14(21): 4658-4670, 2021 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-34402206

RESUMO

Five-membered N-heterocycles play an important role in organic synthesis and material chemistry, as they are widespread through pharmaceutical molecules and natural products. Chemists have developed many synthetic strategies for constructing five-membered N-heterocycles from N-centered radicals, but the availability of mild and green methods for these transformations is still limited. The cyclization of visible-light-generated N-centered radicals with alkenes has emerged as a powerful tool to enable these chemical transformations in recent years. Through chosen representative examples, the significant developments in this promising field were outlined, including the selection of catalysts, substrate scope, mechanistic understanding (especially density functional theory calculations), and applications. The contents of this Minireview are categorized by intramolecular cyclization and intermolecular N-centered radical addition/cyclization reactions.

9.
Chem Commun (Camb) ; 57(67): 8288-8291, 2021 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-34318821

RESUMO

A novel sulfonyl radical triggered selective iodosulfonylation and bicyclization of 1,6-dienes has been described for the first time. High selectivity and efficiency, mild reaction conditions, excellent functional group compatibility, and broad substrate scope are the attractive features of this synthetic protocol, which provides a unique platform for precise radical cyclization.

10.
ACS Appl Mater Interfaces ; 13(30): 35889-35896, 2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34282897

RESUMO

Two dimensional (2D) tin disulfide (SnS2) has attracted growing interest as a promising high performance photodetector with superior performance such as fast response time, high responsivity, and good stability. However, SnS2-based photodetectors still face great challenges, and the photodetection performance needs to be improved for practical applications. Herein, indium-doped SnS2 (In-SnS2) few layers were exfoliated from CVT-grown single crystals, which were synthesized by chemical vapor transport. Photodetectors based on In-SnS2 few layers were fabricated and detected. Compared with photodetectors based on pristine SnS2, photodetectors based on In-SnS2 few layers exhibited better photodetection performances, including higher responsivities, higher external quantum efficiencies, and greater normalized detectivities. The responsivity (R), external quantum efficiency (EQE), and normalized detectivity (D*) were increased by up to 2 orders of magnitude after In doping. Considering responsivity and response time, the photodetector based on 1.4 at. % In-SnS2 few layers exhibited an optimal photodetection performance with a high R of 153.8 A/W, a high EQE of 4.72 × 104 %, a great D* of 5.81 × 1012 Jones, and a short response time of 13 ms. Our work provides an efficient path to enhance photodetection performances of photodetectors based on SnS2 for future high-performance optoelectronic applications.

11.
Sensors (Basel) ; 21(10)2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-34065325

RESUMO

Mission planning is the guidance for a UAV team to perform missions, which plays the most critical role in military and civil applications. For complex tasks, it requires heterogeneous cooperative multi-UAVs to satisfy several mission requirements. Meanwhile, airborne sensor allocation and path planning are the critical components of heterogeneous multi-UAVs system mission planning problems, which affect the mission profit to a large extent. This paper establishes the mathematical model for the integrated sensor allocation and path planning problem to maximize the total task profit and minimize travel costs, simultaneously. We present an integrated mission planning framework based on a two-level adaptive variable neighborhood search algorithm to address the coupled problem. The first-level is devoted to planning a reasonable airborne sensor allocation plan, and the second-level aims to optimize the path of the heterogeneous multi-UAVs system. To improve the mission planning framework's efficiency, an adaptive mechanism is presented to guide the search direction intelligently during the iterative process. Simulation results show that the effectiveness of the proposed framework. Compared to the conventional methods, the better performance of planning results is achieved.

12.
Chem Commun (Camb) ; 57(50): 6111-6120, 2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34113948

RESUMO

Radical-mediated functionalization of alkenes has been emerging as an elegant and straightforward protocol to increase molecule complexity. Moreover, the abstraction of a hydrogen atom from aldehydes to afford acyl radicals has evolved as a rising star due to its high atom-economy and the ready availability of aldehydes. Considering the great influence and synthetic potential of acyl radical enabled reactions between aldehydes and alkenes, we provide a summary of the state of the art in this field with a specific emphasis on the working models and corresponding mechanisms. The discussion is divided according to the kind of alkenes and reaction type.

13.
Adv Mater ; 33(9): e2006711, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33491810

RESUMO

Heterogeneous noble-metal-based catalysis plays an essential role in the production of fine chemicals. Rh-based catalysts are one of the most active candidates for indole synthesis. However, it is still highly desired to develop heterogeneous Rh-based catalysts with high activity and selectivity. In this work, a general, facile wet-chemical method is reported to synthesize ultrathin amorphous/crystalline heterophase Rh and Rh-based bimetallic alloy nanosheets (NSs), including RhCu, RhZn, and RhRu. Impressively, the amorphous/crystalline heterophase Rh NSs exhibit enhanced catalytic activity toward the direct synthesis of indole compared to the crystalline counterpart. Importantly, the obtained amorphous/crystalline heterophase RhCu alloy NSs can further enhance the selectivity to indole of >99.9% and the conversion is 100%. This work demonstrates the importance of phase engineering and metal alloying in the rational design and synthesis of tandem heterogeneous catalysts toward fine chemical synthesis.

14.
J Org Chem ; 85(23): 15726-15735, 2020 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-33174420

RESUMO

A facile oxidative heterocyclization of commercially available amines and tert-butyl nitrite with alkynes or alkenes leading to isoxazoles or isoxazolines is described. The unprecedented strategy of the oxidation of an amine directly to a nitrile oxide was used in this cyclization process. This reaction is highly efficient, regiospecific, operationally simple, mild, and tolerant of a variety of functional groups. Control experiments support a nitrile oxide intermediate mechanism for this novel class of oxidative cyclization reactions. Moreover, synthetic applications toward bioactive molecular skeletons and the late-stage modification of drugs were realized.

15.
Sensors (Basel) ; 20(18)2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-32899674

RESUMO

The complexity of unmanned aerial vehicle (UAV) missions is increasing with the rapid development of UAV technology. Multiple UAVs usually cooperate in the form of teams to improve the efficiency of mission execution. The UAVs are equipped with multiple sensors with complementary functions to adapt to the complex mission constraints. Reasonable task assignment, task scheduling, and UAV trajectory planning are the prerequisites for efficient cooperation of multi-functional heterogeneous UAVs. In this paper, a multi-swarm fruit fly optimization algorithm (MFOA) with dual strategy switching is proposed to solve the multi-functional heterogeneous UAV cooperative mission planning problem with the criterion of simultaneously minimizing the makespan and the total mission time. First, the multi-swarm mechanism is introduced to enhance the global search capability of the fruit fly optimization algorithm. Second, in the smell-based search phase, the local search strategies and large-scale search strategies are designed to drive multiple fruit fly swarms, and the dual strategy switching method is presented. Third, in the vision-based search stage, the greedy selection strategy is adopted. Finally, numerical simulation experiments are designed. The simulation results show that the MFOA algorithm is more effective and stable for solving the multi-functional heterogeneous UAV cooperative mission planning problem compared with other algorithms.

16.
Org Lett ; 22(20): 7947-7951, 2020 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-32996768

RESUMO

Phosphine ligands with up to six chiral sites were prepared, starting from 2-phenylphenol, via O- and P-alkylation, cyclization, and coupling. The chirality was transferred from (L)-menthyl to phosphorus, α-carbon, and axis, to achieve excellent diastereoselectivities. During an intramolecular SNAr reaction with alkoxyl as the leaving groups, the C-O bond was converted to a C-C bond. Both phosphine boranes and oxides could be used for the conversions, affording a series of cyclic phosphines.

17.
Sci Total Environ ; 729: 138910, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32388128

RESUMO

Groundwater is experiencing a higher risk of aquifer depletion due to longer drought duration and increasing water demand induced by climate change. The climate impacts on groundwater can be propagated to changes in groundwater discharge to rivers, which will deeply alter the connection between groundwater and surface water and reshape the fundamental functions of the river system especially in maintaining environmental flows. In synchronization with the drying and warming climate, groundwater discharges estimated using digital filtering approaches are found to have experienced significant reduction since the 1990s for all our studied headwater catchments in the Murrumbidgee portion of the Murray-Darling Basin. The linkage between precipitation and groundwater discharge is demonstrated to be seasonally dependent. For most of the studied catchments, the dominant precipitation metrics affecting groundwater discharge are the winter precipitation followed by autumn and spring precipitation. Multivariate nonlinear regression modelling suggests that the relationship between groundwater discharge and the dominant climate variables can be represented statistically by a power law. The individual contribution of each dominant climate variable quantified based on the concept of elasticity shows that the decrease in precipitation outweighs the increase in potential evapotranspiration in contributing to the reduction in groundwater discharge. The autumn precipitation accounts for a larger proportion of the changes in groundwater discharge in all studied catchments because of its relatively higher elasticity and change rate. The reduction in groundwater discharge since the mid-late 1990s in the headwater catchments can largely (estimated here at >75%) be attributed to climate factors.

18.
Org Lett ; 22(11): 4553-4556, 2020 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-32437166

RESUMO

A transition-metal-free indole synthesis using radical coupling of 2-halotoluenes and imines via the later-stage C-N bond construction was reported for the first time. It includes an aminyl radical generation by C-H cleaving addition of 2-halotoluenes to imines via the carbanion radical relay and an intramolecular coupling of aryl halides with aminyl radicals. One standard condition can be used for all halides including F, Cl, Br, and I. No extra oxidant or transition metal is required.

19.
Org Biomol Chem ; 18(16): 3017-3021, 2020 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-32236276

RESUMO

P,C-Stereogenic propargyl alcohols RC-3/SC-3' were prepared by the addition of (L)-menthyl-derived SPOs to propynals, which were converted to P,axial-stereogenic allenyl bisphosphine oxides. The chirality transfer was controlled by α-carbon via syn [2,3]-sigmatropic rearrangement. For SC-3' linking weak WDG on the alkynyl moiety, the chirality on the axis depended on stereogenic phosphorus.

20.
Biol Trace Elem Res ; 194(2): 493-501, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31363990

RESUMO

Diabetic osteoporosis (DOP) is a complication of diabetes, with the characteristics of bone mineral density (BMD) reduction and bone structure destruction. Zinc was reported has a benefit effect on postmenopausal osteoporosise, it was also has hypoglycemic effect, whether zinc was beneficial on diabetes-induced osteoporosis has not been reported. So in the present study, we established a diabetic rat model by streptozotocin injection (60 mg/kg), and administered zinc sulfate by oral gavage to investigate the protective effects of zinc on DOP and the underline possible mechanism. Thirty six Sprague Dawley rats were divided into T1DM group (diabetic rats), control group (vehicle treatment), and T1DM-Zinc group (diabetic rats administered zinc sulfate 0.25 mg/kg by oral gavage). The bone histomorphological parameters, serum bone metabolism markers (including ALP, OPG, RUNX 2, and RANKL), BMD, and bone marrow adipocyte numbers were detected after eight weeks of zinc sulfate treatment. The results showed zinc sulfate administration (0.25 mg/kg/d) decreased blood glucose, increased the BMD, decreased serum ALP, and RANKL, increased serum OPG and RUNX 2 levels, as well as OPG/RANKL ratio of T1DM rats. Meanwhile, the bone histomorphological parameters, bone marrow adipocytes numbers were returned to be normal. The RUNX 2, and OPG mRNA expression levels in bone tissues of T1DM-Zinc group rats were increased after zinc sulfate treatment compared with the diabetic rats (P < 0.05). Those indicating that zinc sulfate can prevent DOP, the protective mechanism were mainly related to its hypoglycemic effect, bone marrow lipogenesis inhibition effect, OPG/RANKL ratio and RUNX 2 up-regulation effect.


Assuntos
Densidade Óssea , Diabetes Mellitus Experimental , Animais , Osso e Ossos , Diabetes Mellitus Experimental/tratamento farmacológico , Suplementos Nutricionais , Osteoprotegerina , Ligante RANK , Ratos , Ratos Sprague-Dawley , Zinco/farmacologia
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