N-Alkylation of Amines Catalyzed by a Ruthenium-Pincer Complex in the Presence of in situ Generated Sodium Alkoxide

2019 ◽  
Vol 2019 (40) ◽  
pp. 6855-6866 ◽  
Author(s):  
Kanu Das ◽  
Pran Gobinda Nandi ◽  
Khadimul Islam ◽  
Hemant Kumar Srivastava ◽  
Akshai Kumar
Keyword(s):  
Pincer Complex ◽  
Sodium Alkoxide

Asymmetric α-Amination Reaction of Alkenoate Cyclic Esters Catalyzed by Chiral Tin Alkoxides

Synlett ◽  
2019 ◽  
Vol 30 (06) ◽  
pp. 738-742
Author(s):  
Akira Yanagisawa ◽  
Yoshiki Yamashita ◽  
Chika Uchiyama ◽  
Ryuta Nakano ◽  
Moe Horiguchi ◽  
...  
Keyword(s):  
Optically Active ◽  
Cyclic Esters ◽  
Amination Reaction ◽  
High Yields ◽  
Sodium Alkoxide

A catalytic enantioselective α-amination reaction of alkenoate cyclic esters with dialkyl azodicarboxylates was achieved by using a 3,3′-di(1-naphthyl)-substituted (R)-BINOL–dibromostannane complex as a chiral precatalyst in the presence of a sodium alkoxide and an alcohol. Optically active α-hydrazino ketones were obtained in moderate to high yields and with up to 91% ee in the presence of the chiral tin alkoxide generated in situ.

scholarly journals Mechanistic Investigations of Nickamine- catalyzed Hydrosilylation of Alkenes: Nickel Nanoparticles Are the Active Species

2020 ◽  
Vol 74 (6) ◽  
pp. 444-449
Author(s):  
Marten L. Ploeger ◽  
Ivan Buslov ◽  
Xile Hu
Keyword(s):  
Nickel Nanoparticles ◽  
Active Species ◽  
Mechanistic Studies ◽  
Mercury Poisoning ◽  
Pincer Complex ◽  
Transmission Electron ◽  
Silicone Polymers ◽  
Nickel Species ◽  
Sigma Bond

Hydrosilylation is an important chemical process for the synthesis of organosilanes and for the production of silicone polymers. The wide variety of catalysts developed for this reaction generally follow a Chalk-Harrod, or a sigma-bond metathesis mechanism. Recently, our group developed a nickel pincer complex, Nickamine, for highly selective hydrosilylation of alkenes. Preliminary mechanistic studies had suggested a pathway that deviates from both Chalk-Harrod and sigma-bond metathesis cycles. Here we used in situ NMR to monitor the hydrosilylation reaction. The observed induction period indicated that the species previously believed to be the resting state is merely a precatalyst. Via a combination of Transmission Electron Microscopy, mercury poisoning test, and competition reactions we show that the true catalyst is not a molecular nickel species, but rather nickel nanoparticles.

scholarly journals Empowering alcohols as carbonyl surrogates for Grignard-type reactions

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Chen-Chen Li ◽  
Haining Wang ◽  
Malcolm M. Sim ◽  
Zihang Qiu ◽  
Zhang-Pei Chen ◽  
...  
Keyword(s):  
Functional Group ◽  
Early Stage ◽  
Grignard Reaction ◽  
Synthetic Chemistry ◽  
Reaction Conditions ◽  
Type Reaction ◽  
Pincer Complex ◽  
Late Stages

AbstractThe Grignard reaction is a fundamental tool for constructing C-C bonds. Although it is widely used in synthetic chemistry, it is normally applied in early stage functionalizations owing to poor functional group tolerance and less availability of carbonyls at late stages of molecular modifications. Herein, we report a Grignard-type reaction with alcohols as carbonyl surrogates by using a ruthenium(II) PNP-pincer complex as catalyst. This transformation proceeds via a carbonyl intermediate generated in situ from the dehydrogenation of alcohols, which is followed by a Grignard-type reaction with a hydrazone carbanion to form a C-C bond. The reaction conditions are mild and can tolerate a broad range of substrates. Moreover, no oxidant is involved during the entire transformation, with only H2 and N2 being generated as byproducts. This reaction opens up a new avenue for Grignard-type reactions by enabling the use of naturally abundant alcohols as starting materials without the need for pre-synthesizing carbonyls.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

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