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Catalysts ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 59
Author(s):  
Renyuan Zhong ◽  
Wulin Xiong ◽  
Haoyuan Zhang ◽  
Tongtong Zeng ◽  
Shanshan Gong ◽  
...  

An efficient method for ambient-temperature synthesis of a variety of 2-substituted and 1,2-disubstituted benzimidazoles from aldehyde and phenylenediamine substrates has been developed by utilizing Co(III)/Co(II)-mediated redox catalysis. The combination of only 1 mol% of Co(acac)2 and stoichiometric amount of hydrogen peroxide provides a fast, green, and mild access to a diversity of benzimidazoles under solvent-free conditions.


Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1513
Author(s):  
Pavol Lopatka ◽  
Michal Gavenda ◽  
Martin Markovič ◽  
Peter Koóš ◽  
Tibor Gracza

This work describes the total synthesis of jaspine B involving the highly diastereoselective Pd(II)-catalysed carbonylative cyclisation in the preparation of crucial intermediates. New conditions for this transformation were developed and involved the pBQ/LiCl as a reoxidation system and Fe(CO)5 as an in situ source of stoichiometric amount of carbon monoxide (1.5 molar equivalent). In addition, we have demonstrated the use of a flow reactor adopting proposed conditions in the large-scale preparation of key lactones.


2021 ◽  
Vol 882 (1) ◽  
pp. 012007
Author(s):  
I Rodliyah ◽  
R Wijayanti ◽  
A Septiarani ◽  
A Sudrajat ◽  
D Firmansyah

Abstract More than half of the world’s tin production is from secondary ore deposits. However, along with its depletion, PT Timah Tbk has explored and mined the primary deposits in Belitung, one that is expected to become tin’s new source. Tin was found liberated as cassiterite in the secondary deposits, while in the primary, it was associated with other minerals requiring more complex processing. Therefore, a suitable technology is needed to extract the tin from the primary ore deposits. This research aims to observe the extraction of tin from primary deposits (oxide and skarn ores) using HCl wet chlorination, observed at different temperature (60 – 90°C), HCl concentrations (10 – 50 % excess of stoichiometric amount), leaching time (60 – 300 minutes), and with or without the addition of oxidant (hydrogen peroxide, H2O2). The research found that the highest percentage of tin extraction from oxide and skarn ores was 92.32% and 97.28%, respectively. Both results were achieved at the same optimum condition: temperature of 60°C, 50% excess of HCl, 240 minutes of leaching time, and at two-fold excess of the stoichiometric amount of H2O2. It was concluded that oxidative wet chlorination could be used to recover tin from its primary ore deposits.


2021 ◽  
Author(s):  
Akira Shiozuka ◽  
Kohei Sekine ◽  
Yoichiro Kuninobu

Herein, direct unactivated C-N borylation of aromatic amines by a photocatalyst was achieved under mild and metal-free conditions. The C-N borylation of aromatic amines with bis(pinacolato)diboron (B<sub>2</sub>pin<sub>2</sub>) proceeded in the presence of a pyrene catalyst under light irradiation (λ = 365 nm) <a>to afford desired borylated products</a> and aminoborane as a byproduct. The yield of borylated product improved under a CO<sub>2</sub> atmosphere. Reactions conducted in the presence of a stoichiometric amount of aminoborane under N<sub>2</sub> or CO<sub>2</sub> indicated that CO<sub>2</sub> reduced the inhibitory effect of aminoborane. Optimal reaction conditions were applied to a variety of aromatic amines. Mechanistic studies suggested that the C-N bond cleavage and C-B bond formation proceeded via a concerted pathway.


2021 ◽  
Author(s):  
Akira Shiozuka ◽  
Kohei Sekine ◽  
Yoichiro Kuninobu

Herein, direct unactivated C-N borylation of aromatic amines by a photocatalyst was achieved under mild and metal-free conditions. The C-N borylation of aromatic amines with bis(pinacolato)diboron (B<sub>2</sub>pin<sub>2</sub>) proceeded in the presence of a pyrene catalyst under light irradiation (λ = 365 nm) <a>to afford desired borylated products</a> and aminoborane as a byproduct. The yield of borylated product improved under a CO<sub>2</sub> atmosphere. Reactions conducted in the presence of a stoichiometric amount of aminoborane under N<sub>2</sub> or CO<sub>2</sub> indicated that CO<sub>2</sub> reduced the inhibitory effect of aminoborane. Optimal reaction conditions were applied to a variety of aromatic amines. Mechanistic studies suggested that the C-N bond cleavage and C-B bond formation proceeded via a concerted pathway.


Synthesis ◽  
2021 ◽  
Author(s):  
Yoshiya Fukumoto ◽  
Motohiro Shiratani ◽  
Hikaru Noguchi ◽  
Naoto Chatani

AbstractRegioselective coupling reaction of N-substituted imidazoles with isocyanates in the presence of a stoichiometric amount of hydrosilanes catalyzed by Ir4(CO)12 to give imidazole-2-carboxamides is reported. Imidazoles bearing an (O-silyl)carboximidate group at the 2-position appear to be initially formed in the reaction; these are then hydrolyzed to the final products in situ. The addition of the hydrosilane was essential for the catalytic reaction to proceed. Substituents on the imidazole ring had no effect on the reaction, except for certain bulky substituents such as t Bu and Ph groups at the 4-position. Triazoles such as 4-methyl-4H-1,2,4-triazole and 1-methyl-1H-1,2,4-triazole were also applicable to this C–H amidation, and the latter reaction proceeded regioselectively at the carbon atom between the sp3 and sp2 nitrogen atoms of the ring, and not between the two sp2 nitrogen atoms.


2021 ◽  
Author(s):  
Isabelle Gillaizeau ◽  
Cyril NICOLAS ◽  
Sylvain Bertho ◽  
Radhouan Maazaoui ◽  
Damla Torun ◽  
...  

An attractive atom-economic way was developed for the β-C(sp2)‒H (fluoro)alkylation of a range of acyclic and cyclic non-aromatic enamides using either FeCl2 as a catalyst or a stoichiometric amount of...


2021 ◽  
Author(s):  
Zi-Chen Wang ◽  
Rui-Tao Li ◽  
Qiang Ma ◽  
Jia-Yi Chen ◽  
Shao-Fei Ni ◽  
...  

Herein, the electrochemically driven, Rh(III)-catalyzed regioselective annulations of arenes with alkynes have been established. The strategy combined by rhodium catalyst with electricity not only avoids the need for stoichiometric amount...


2021 ◽  
Author(s):  
Debajit Maiti ◽  
Ranajit Das ◽  
Subhabrata Sen

Here in we have reported a blue LED mediated reaction of aryl diazoacetate with stoichiometric 1, 4-dioxane/ tetrahydropyran (THP) and various heterocycles like indoles, pyrroles, phthalimide, thiazolidinedione and hydantoin in...


Synthesis ◽  
2020 ◽  
Author(s):  
Hiroto Takahashi ◽  
Yusaku Honjo ◽  
Yu Shibata ◽  
Yuki Nagashima ◽  
Ken Tanaka

It has been established that the dienylation of unfunctionalized arenes with 1,6-diynes, possessing aryl groups at the diyne termini, proceeds to give the corresponding dienylated arenes in the presence of a catalytic amount of an electron-deficient cyclopentadienyl rhodium(III) complex, [CpERhCl2]2 (1), and a stoichiometric amount of silver carbonate. Experimental and theoretical mechanistic studies revealed that an in-situ generated CpERh(I) complex might catalyze the present dienylation reaction.


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