Microwave-assisted organic acid–base-co-catalyzed tandem Meinwald rearrangement and annulation of styrylepoxides

2020 ◽  
Vol 56 (14) ◽  
pp. 2131-2134 ◽  
Author(s):  
Yi Shi ◽  
Siqi Li ◽  
Yang Lu ◽  
Zizhen Zhao ◽  
Pingfan Li ◽  
...  
Keyword(s):  
Organic Acid ◽  
High Efficiency ◽  
Tandem Reaction ◽  
Acid Base ◽  
Microwave Assisted ◽  
Acid And Base ◽  
Very High

A microwave-assisted acid and base co-catalyzed strategy shows very high efficiency in the tandem reaction for the conversion of styrylepoxides into [1,1′-biaryl]-3-carbaldehydes.

Metal-free and regiospecific synthesis of 3-arylindoles

2020 ◽  
Vol 18 (14) ◽  
pp. 2661-2671
Author(s):  
Chuangchuang Xu ◽  
Wenlai Xie ◽  
Jiaxi Xu
Keyword(s):  
Ring Opening ◽  
High Efficiency ◽  
Metal Free ◽  
Microwave Assisted ◽  
Fischer Indolization ◽  
Acid And Base ◽  
Nucleophilic Ring Opening

A microwave-assisted acid and base co-catalyzed strategy shows high efficiency in the synthesis of 3-arylindoles through tandem nucleophilic ring-opening and Fischer indolization of aryloxiranecarbonitriles and arylhydrazine hydrochlorides.

scholarly journals Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yingfeng Yang ◽  
Hanze Ying ◽  
Zhixia Li ◽  
Jiang Wang ◽  
Yingying Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Molecular Structures ◽  
High Yield ◽  
Kinetic Control ◽  
High Concentration ◽  
Weak Association ◽  
Quantitative Synthesis ◽  
Thermodynamic Stabilization ◽  
Discrete Structures ◽  
Very High

AbstractMacrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentrations are rare. Here we report the use of dynamic hindered urea bond (HUB) for the construction of urea macrocycles with very high efficiency. Mixing of equal molar diisocyanate and hindered diamine leads to formation of macrocycles with discrete structures in nearly quantitative yields under high concentration of reactants. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C = O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. The bulky N-tert-butyl can be readily removed by acid to eliminate the dynamicity of HUB and stabilize the macrocycle structures.

scholarly journals Lewis acid / Base-free Strategy for the Synthesis of 2-Arylthio and Selenyl Benzothiazole / Thiazole and Imidazole

2021 ◽  
Vol 27 (1) ◽  
pp. 17-23
Author(s):  
Guniganti Balakishan ◽  
Gullapalli Kumaraswamy ◽  
Vykunthapu Narayanarao ◽  
Pagilla Shankaraiah
Keyword(s):  
Lewis Acid ◽  
Bond Formation ◽  
Acid Base ◽  
Mechanistic Pathway ◽  
Wide Range ◽  
Acid And Base ◽  
Lewis Acid And Base ◽  
Sulfur Bond

Abstract A Cu(II)-catalyzed Csp2-Se and Csp2-Sulfur bond formation was achieved with moderate to good yields without the aid of Lewis acid and base. The reaction is compatible with a wide range of heterocycles such as benzothiazole, thiazole, and imidazole. Also, this typical protocol is found to be active in thio-selenation via S-H activation. Additionally, we proposed a plausible mechanistic pathway involving Cu(III) putative intermediate.

An uncoordinatedly tertiary nitrogen based tricarboxylate Calcium network with Lewis acid-base dual catalytic sites for cyanosilylation of aldehydes

2020 ◽  
Author(s):  
Xian-Ming Zhang ◽  
Ying-Xia Wang ◽  
Hui-Min Wang ◽  
Pan Meng ◽  
Dong-Xia Song ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Efficient Method ◽  
High Efficiency ◽  
Acid Base ◽  
Catalytic Sites ◽  
Tertiary Nitrogen

The design and utilization of dual sites for synergistic catalysts has been recognised as an efficient method towards high-efficiency catalysis in the cyanosilylation of aldehydes, which gives the key intermediates...

One-pot synthesis of furfural derivatives from pentoses using solid acid and base catalysts

2014 ◽  
Vol 4 (4) ◽  
pp. 971-978 ◽  
Author(s):  
Mahiro Shirotori ◽  
Shun Nishimura ◽  
Kohki Ebitani
Keyword(s):  
Solid Acid ◽  
Acid Base ◽  
One Pot ◽  
Amberlyst 15 ◽  
Base Catalysts ◽  
One Pot Synthesis ◽  
Combined Use ◽  
Acid And Base

One-pot synthesis of (2-furanylmethylene)malononitrile, a Knoevenagel product of furfural with malononitrile, from xylose efficiently proceeded by combined use of acid Amberlyst-15 and acid-base Cr/hydrotalcites in 44% yield.

Design and Analysis of a High Pitch to Chord Ratio Cascade Representative of Ducted Propfans

1991 ◽  
Author(s):  
A. Weber ◽  
W. Steinert ◽  
H. Starken
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
High Pitch ◽  
Integral Boundary ◽  
Pressure Loss Coefficient ◽  
Distribution Boundary ◽  
Very High

Efforts to reduce the specific fuel consumption of a modern aero engine focus in particular on increasing the by-pass ratio beyond the current level of around 5. One concept is the counterrotating shrouded propfan operating at low overall pressure ratio and having only very few fan blades of extremely high pitch/chord ratios. The relative inlet Mach numbers cover a range from 0.7 at the hub to 1.1 at the tip section of the first rotor. A propfan cascade was designed by taking into account two characteristic features of a propfan blade-blade section: • a very high pitch/chord ratio of s/c = 2.25 • an inlet Mach number of M1 = 0.90 which leads to transonic flow conditions inside the blade passage In the design process a profile generator and a quasi-3D Euler solver were used iteratively to optimize the profile Mach number distribution. Boundary layer behavior was checked with an integral boundary layer code. The cascade design was verified experimentally in the transonic cascade wind tunnel of DLR at Cologne. The extensive experimental results confirm the design goal of roughly 5 degree flow turning. A total pressure loss coefficient of less than 1.5% was measured at design conditions. This validates the very high efficiency level the propfan concept is calling for. A 2D Navier-Stokes flow analysis code yields good results in comparison to the experimental ones.

scholarly journals Instantaneous Electromagnetic Torque Components in Synchronous Motors Fed by Load-Commutated Inverters

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3223
Author(s):  
Gabriel Ekemb ◽  
Fouad Slaoui-Hasnaoui ◽  
Joseph Song-Manguelle ◽  
P. M. Lingom ◽  
Issouf Fofana
Keyword(s):  
High Efficiency ◽  
Air Gap ◽  
International Standards ◽  
Synchronous Motors ◽  
Gas Compression ◽  
Variable Frequency Drives ◽  
Torsional Analysis ◽  
Analytical Expressions ◽  
Very High ◽  
Excitation Circuit

This paper proposes time-domain analytical expressions of the instantaneous pulsating torque components in a synchronous machine air gap when supplied by a load-commutated-inverter (LCI) system. The LCI technology is one of the most used variable frequency drives when very high power and low speed are required in applications such as pipeline recompression and decompression, as well as liquefied natural gas compression. In such applications, synchronous motors are used because of their high efficiency resulting from a separated supply of the current to their rotor through the excitation circuit. These applications usually have long and flexible shafts, which are very sensitive to torsional vibration excitation when their natural frequencies interact with any external torque applied to the shaft. A torsional analysis is required by international standards to assess the survivability of the shaft through the overall speed range of the motor. Therefore, the magnitude and frequencies of the motor air-gap torque are needed for such evaluation. The proposed developments are supported by numerical simulations of LCI systems in a large range of operation range. From the simulation results, torque harmonic families are derived and expressed in a parametric form, which confirm the accuracy of the proposed relationships.

Solid-state regioselective nitration of activated hydroxyaromatics and hydroxycoumarins with cerium (IV) ammonium nitrate

2005 ◽  
Vol 2005 (11) ◽  
pp. 733-735 ◽  
Author(s):  
Nemai C. Ganguly ◽  
Sanjoy Dutta ◽  
Mrityunjoy Datta ◽  
Prithwiraj De
Keyword(s):  
Solid State ◽  
Ammonium Nitrate ◽  
High Efficiency ◽  
Solvent Free ◽  
High Melting ◽  
Microwave Assisted ◽  
Solvent Free Conditions ◽  
High Yields ◽  
Regioselective Nitration ◽  
Cerium Iv Ammonium Nitrate

Predominant ortho-selective mononitration of low-melting and liquid phenols and hydroxycoumarins in moderate to high yields has been accomplished upon grinding with solid cerium (IV) ammonium nitrate (CAN). Microwave-assisted expeditious CAN-mediated nitration of relatively high melting phenols and hydroxycoumarins with high efficiency and selectively under solvent-free conditions has been also developed to address the problems of sluggishness and low yield for these reluctant substrates.

Acid–base synergistic catalysis of biochar sulfonic acid bearing polyamide for microwave-assisted hydrolysis of cellulose in water

Cellulose ◽  
2018 ◽  
Vol 26 (2) ◽  
pp. 751-762 ◽  
Author(s):  
Zengtian Chen ◽  
Qingfeng Li ◽  
Yuxue Xiao ◽  
Chao Zhang ◽  
Zaihui Fu ◽  
...  
Keyword(s):  
Sulfonic Acid ◽  
Acid Base ◽  
Synergistic Catalysis ◽  
Microwave Assisted ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of
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