Theoretical studies on carbometalation of cyclopropene. Transition structures of addition of methyl anion, methyllithium, methylcopper, and Me2Cu- and origin of the high reactivity of the strained double bond

1993 ◽  
Vol 115 (1) ◽  
pp. 99-106 ◽  
Author(s):  
Eiichi Nakamura ◽  
Masaharu Nakamura ◽  
Yoshimitsu Miyachi ◽  
Nobuaki Koga ◽  
Keiji Morokuma
Keyword(s):  
Double Bond ◽  
High Reactivity ◽  
Theoretical Studies ◽  
Transition Structures

scholarly journals σ-Bond Hydroboration of Cyclopropanes

2020 ◽  
Author(s):  
Hiroki Kondo ◽  
Shin Miyamura ◽  
Chisa Kobayashi ◽  
Arifin ◽  
Stephan Irle ◽  
...  
Keyword(s):  
Double Bond ◽  
Natural Product ◽  
Organic Synthesis ◽  
Bond Cleavage ◽  
Cross Coupling ◽  
High Reactivity ◽  
Natural Product Synthesis ◽  
Theoretical Studies ◽  
Single Bond

Hydroboration of alkenes is a classical reaction in organic synthesis, in which alkenes react with boranes to give alkylboranes, with subsequent oxidation resulting in alcohols. The double bond (π-bond) of alkenes can be readily reacted with boranes owing to its high reactivity. However, the single bond (σ-bond) of alkanes has never been reacted. To pursue the development of σ-bond cleavage, we selected cyclopropanes as model substrates since they present a relatively weak σ-bond. Herein, we describe an iridium-catalyzed hydroboration of cyclopropanes, resulting in β-methyl alkylboronates. These unusually branched boronates can be derivatized by oxidation or cross-coupling chemistry, accessing “designer” products that are desired by practitioners of natural product synthesis and medicinal chemistry. Furthermore, mechanistic investigations and theoretical studies revealed the enabling role of the catalyst.

scholarly journals Teaching an old carbocation new tricks: Intermolecular C–H insertion reactions of vinyl cations

Science ◽  
2018 ◽  
Vol 361 (6400) ◽  
pp. 381-387 ◽  
Author(s):  
Stasik Popov ◽  
Brian Shao ◽  
Alex L. Bagdasarian ◽  
Tyler R. Benton ◽  
Luyi Zou ◽  
...  
Keyword(s):  
Theoretical Studies ◽  
Computational Studies ◽  
Mechanistic Studies ◽  
Insertion Reactions ◽  
Bond Forming ◽  
The Past ◽  
Carbon Carbon Bond ◽  
Transition Structures ◽  
The Subject ◽  
Experimental And Theoretical Studies

Vinyl carbocations have been the subject of extensive experimental and theoretical studies over the past five decades. Despite this long history in chemistry, the utility of vinyl cations in chemical synthesis has been limited, with most reactivity studies focusing on solvolysis reactions or intramolecular processes. Here we report synthetic and mechanistic studies of vinyl cations generated through silylium–weakly coordinating anion catalysis. We find that these reactive intermediates undergo mild intermolecular carbon-carbon bond–forming reactions, including carbon-hydrogen (C–H) insertion into unactivated sp3 C–H bonds and reductive Friedel-Crafts reactions with arenes. Moreover, we conducted computational studies of these alkane C–H functionalization reactions and discovered that they proceed through nonclassical, ambimodal transition structures. This reaction manifold provides a framework for the catalytic functionalization of hydrocarbons using simple ketone derivatives.

Regioselective and Catalyst-Free Epoxidation of (E)-3-[3-(2-Hydroxyaryl)-3-oxoprop-1-en-1-yl]chromones

Synlett ◽  
2018 ◽  
Vol 29 (20) ◽  
pp. 2633-2637 ◽  
Author(s):  
Mohamed Hammadi ◽  
Oualid Talhi ◽  
Artur Silva ◽  
Rachid Ameraoui ◽  
Ridha Hassaine ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Double Bond ◽  
Single Crystal ◽  
Density Functional ◽  
2D Nmr ◽  
Theoretical Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Uncatalyzed Reaction ◽  
High Yields

The uncatalyzed reaction of hydrogen peroxide with (E)-3-[3-(2-hydroxyaryl)-3-oxoprop-1-en-1-yl]chromones resulted in a regio­selective epoxidation of the chromone intracyclic C(2)=C(3) double bond to afford unique isomeric (E)-7a-[3-(2-hydroxyphenyl)-3-oxoprop-1-en-1-yl]-1aH-oxireno[2,3-b]chromen-7(7aH)-ones in high yields. 2D NMR and single-crystal X-ray diffraction were used to elucidate the structures of the chromanone epoxides. Density functional theoretical studies demonstrated a high electrophilicity of the starting chromones.

Theoretical Studies on Heterocumulated Double Bond Systems

1999 ◽  
Vol 21 (4) ◽  
pp. 373-400 ◽  
Author(s):  
Rudolf Janoschek
Keyword(s):  
Double Bond ◽  
Theoretical Studies

scholarly journals Synthesis and Reactivity of Electron-Deficient 3-Vinylchromones

SynOpen ◽  
2021 ◽  
Vol 05 (03) ◽  
pp. 255-277
Author(s):  
Vyacheslav Y. Sosnovskikh
Keyword(s):  
Double Bond ◽  
Chemical Properties ◽  
Building Blocks ◽  
High Reactivity ◽  
Cycloaddition Reactions ◽  
Chemical Transformations ◽  
Pyrone Ring ◽  
The Past ◽  
Palladium Catalyzed ◽  
First Time

AbstractThe reported methods and data for the synthesis and reactivity of electron-deficient 3-vinylchromones containing electron-withdrawing­ groups at the exo-cyclic double bond are summarized and systematized for the first time. The main methods for obtaining these compounds are Knoevenagel condensation, Wittig reaction, and palladium-catalyzed cross-couplings. The most important chemical properties are transformations under the action of mono- and dinucleophiles, ambiphilic cyclizations, and cycloaddition reactions. The cross-conjugated and polyelectrophilic dienone system in 3-vinylchromones provides their high reactivity and makes these compounds valuable building blocks for the preparation of more complex heterocyclic systems. Chemical transformations of 3-vinylchromones usually begin with an attack of the C-2 atom and are accompanied by the opening of the pyrone ring followed by recyclization, in which the carbonyl group of chromone, an exo-double bond or a substituent on it can take part. The mechanisms of the reactions are discussed, the conditions for their implementation are described, and the yields of the resulting products are given. This review focuses on an analysis and generalization of the knowledge that has accumulated on the chemistry of electron-deficient 3-vinylchromones, mostly over the past 15 years.1 Introduction2 Synthesis of 3-Vinylchromones3 Reactions with Mononucleophiles4 Reactions with Dinucleophiles5 Ambiphilic Cyclization6 Cycloaddition Reactions7 Other Reactions8 Conclusion

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