scholarly journals Stereoselective nucleophilic addition reactions to cyclic N-acyliminium ions using the indirect cation pool method: Elucidation of stereoselectivity by spectroscopic conformational analysis and DFT calculations

2018 ◽  
Vol 14 ◽  
pp. 1192-1202 ◽  
Author(s):  
Koichi Mitsudo ◽  
Junya Yamamoto ◽  
Tomoya Akagi ◽  
Atsuhiro Yamashita ◽  
Masahiro Haisa ◽  
...  
Keyword(s):  
Low Temperature ◽  
Dft Calculations ◽  
Conformational Analysis ◽  
Nucleophilic Addition ◽  
Addition Reactions ◽  
Acyliminium Ions

In this study, six-membered N-acyliminium ions were generated by the “indirect cation pool” method and reacted with several nucleophiles. These reactions afforded disubstituted piperidine derivatives with high diastereoselectivities and good to excellent yields. The conformations of the obtained N-acyliminium ions were studied by low temperature NMR analyses and DFT calculations and were found to be consistent with the Steven’s hypothesis.

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

The Concerted Nature of the Enzymatic Cyclization of Rings A-D of Squalene to Hopene

2008 ◽  
Vol 73 (6-7) ◽  
pp. 786-794 ◽  
Author(s):  
B. Andes Hess ◽  
Lidia Smentek
Keyword(s):  
Dft Calculations ◽  
Conformational Analysis ◽  
X Ray

A conformational analysis of squalene encapsulated in squalene-hopene cyclase has been performed based on Schulz's X-ray structure and our DFT calculations. Based on this analysis it is concluded that the formation of rings A-D in the cyclization of squalene are likely to be a concerted but highly asynchronous reaction.

scholarly journals Nucleophilic Addition Reactions of Nitriles to Nitrones under Mild Silylation Conditions

Synlett ◽  
2014 ◽  
Vol 25 (13) ◽  
pp. 1863-1868 ◽  
Author(s):  
Fumihiko Yoshimura ◽  
Keiji Tanino ◽  
Taiki Abe
Keyword(s):  
Nucleophilic Addition ◽  
Addition Reactions

Conformational analysis of trans-1,4-dihalocyclohexanes

1967 ◽  
Vol 45 (21) ◽  
pp. 2477-2479 ◽  
Author(s):  
Gordon Wood ◽  
E. P. Woo
Keyword(s):  
Low Temperature ◽  
Conformational Analysis ◽  
Conformational Equilibria ◽  
Equatorial Proton

The conformational equilibria of trans-1,4-dibromo- (I), trans-1,4-dichloro- (II), and trans-1,4-bromochloro-cyclohexane (III) were determined by integration of the separate axial and equatorial proton signals at low temperature. The [Formula: see text] values for compounds I, II, and III were found to be approximately 200 cal/mole.

Amide-Directed Reactions of Small Carbocycles

2021 ◽  
Vol 25 ◽  
Author(s):  
Pavel M. Yamanushkin ◽  
Marina Rubina ◽  
Michael Rubin
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Nucleophilic Addition ◽  
Addition Reactions ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

: The topic of this review is the amide-directed functionalization of strained carbocycles — specifically, unsaturated or saturated three- and four-membered rings. The following approaches are discussed: a) directed carbometallation and hydrometallation of cyclopropenes catalyzed by transition metals; b) directed metal-templated nucleophilic addition reactions; c) directed C-H functionalization, including transition metal-catalyzed C-H-activation reactions; and d) directed radical additions.

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