Biomimetic Cyclization of Epoxide Precursors of Indole Mono-, Sesqui- and Diterpene Alkaloids by Lewis Acids

2011 ◽  
Vol 75 (11) ◽  
pp. 2213-2222 ◽  
Author(s):  
Tetsuya ISAKA ◽  
Morifumi HASEGAWA ◽  
Hiroaki TOSHIMA
Keyword(s):  
Lewis Acids ◽  
Diterpene Alkaloids ◽  
Biomimetic Cyclization

C18 diterpene alkaloids from Aconitum toxicum Rchb.

Planta Medica ◽  
2007 ◽  
Vol 73 (09) ◽  
Author(s):  
D Csupor ◽  
P Forgo ◽  
K Csedő ◽  
J Hohmann
Keyword(s):  
Diterpene Alkaloids

ChemInform Abstract: THE DITERPENE ALKALOIDS, THE STRUCTURE AND STEREOCHEMISTRY OF HETERATISINE

1974 ◽  
Vol 5 (7) ◽  
pp. no-no
Author(s):  
R. ANEJA ◽  
D. M. LOCKE ◽  
S. W. PELLETIER
Keyword(s):  
Diterpene Alkaloids

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

scholarly journals Understanding How Lewis Acids Dope Organic Semiconductors: A “Complex” Story

2021 ◽  
Author(s):  
Pablo Simon Marques ◽  
Giacomo Londi ◽  
Brett Yurash ◽  
Thuc-Quyen Nguyen ◽  
Stephen Barlow ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Lewis Acids ◽  
Computational Studies

We report on computational studies of the potential of three borane Lewis acids (LAs) (B(C6F5)3 (BCF), BF3, and BBr3) to form stable adducts and/or to generate positive polarons with three...

scholarly journals Bulky Polyfluorinated Terphenyldiphenylboranes. Water Tolerant Lewis Acids

2020 ◽  
Author(s):  
Corina Stoian ◽  
Marian Olaru ◽  
Theodor Cucuiet ◽  
Krisztina Kegyes ◽  
Alexandru Sava ◽  
...  
Keyword(s):  
Lewis Acids

Novel and Efficient Lewis Acids as Catalysts for Single-step Synthesis of Pyrano- and Furoquinolines

2004 ◽  
Vol 33 (11) ◽  
pp. 1526-1527 ◽  
Author(s):  
Biswanath Das ◽  
M. Ravinder Reddy ◽  
V. Saidi Reddy ◽  
R. Ramu
Keyword(s):  
Lewis Acids ◽  
Single Step

scholarly journals Analysis of the possibility and molecular mechanism of carbon dioxide consumption in the Diels-Alder processes

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Karolina Kula ◽  
Agnieszka Kącka-Zych ◽  
Agnieszka Łapczuk-Krygier ◽  
Radomir Jasiński
Keyword(s):  
Carbon Dioxide ◽  
Molecular Mechanism ◽  
Lewis Acids ◽  
Chemical Reactivity ◽  
Carbon Dioxide Concentration ◽  
Diels Alder ◽  
Wide Range ◽  
Bet Analysis ◽  
Earth’S Climate ◽  
Step Mechanism

Abstract The large and significant increase in carbon dioxide concentration in the Earth’s atmosphere is a serious problem for humanity. The amount of CO2 is increasing steadily which causes a harmful greenhouse effect that damages the Earth’s climate. Therefore, one of the current trends in modern chemistry and chemical technology are issues related to its utilization. This work includes the analysis of the possibility of chemical consumption of CO2 in Diels-Alder processes under non-catalytic and catalytic conditions after prior activation of the C=O bond. In addition to the obvious benefits associated with CO2 utilization, such processes open up the possibility of universal synthesis of a wide range of internal carboxylates. These studies have been performed in the framework of Molecular Electron Density Theory as a modern view of the chemical reactivity. It has been found, that explored DA reactions catalyzed by Lewis acids with the boron core, proceeds via unique stepwise mechanism with the zwitterionic intermediate. Bonding Evolution Theory (BET) analysis of the molecular mechanism associated with the DA reaction between cyclopentadiene and carbon dioxide indicates that it takes place thorough a two-stage one-step mechanism, which is initialized by formation of C–C single bond. In turn, the DA reaction between cyclopentadiene and carbon dioxide catalysed by BH3 extends in the environment of DCM, indicates that it takes place through a two-step mechanism. First path of catalysed DA reaction is characterized by 10 different phases, while the second by eight topologically different phases.

Sign in / Sign up

Export Citation Format

Share Document