scholarly journals Probing the Lewis Acid Catalyzed Acyclic Pathway of Carbohydrate Conversion in Methanol by In Situ NMR

ChemCatChem ◽  
2019 ◽  
Vol 11 (20) ◽  
pp. 5077-5084 ◽  
Author(s):  
Pernille Rose Jensen ◽  
Esben Taarning ◽  
Sebastian Meier
Keyword(s):  
Lewis Acid ◽  
Acid Catalyzed ◽  
In Situ Nmr ◽  
Carbohydrate Conversion

Catalytic Carbonyl-Olefin Metathesis of Aliphatic Ketones: Iron(III) HomoDimers as Lewis Acidic Superelectrophiles

2018 ◽  
Author(s):  
Haley Albright ◽  
Paul S. Riehl ◽  
Christopher C. McAtee ◽  
Jolene P. Reid ◽  
Jacob R. Ludwig ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Olefin Metathesis ◽  
Acid Activation ◽  
Lewis Acid Catalysts ◽  
Distinct Mode ◽  
Aliphatic Ketones ◽  
Carbon Carbon Bond ◽  
Metathesis Reactions ◽  
Acid Catalyzed

<div>Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bond</div><div>formation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.</div>

Lewis acid-catalyzed tandem cyclization of in situ generated o-quinone methides and arylsulfonyl hydrazides for a one-pot entry to 3-sulfonylbenzofurans

2019 ◽  
Vol 6 (24) ◽  
pp. 3929-3933 ◽  
Author(s):  
Fan-Xiao Meng ◽  
Ruo-Nan Wang ◽  
Hong-Li Huang ◽  
Shu-Wen Gong ◽  
Qian-Li Li ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Quinone Methides ◽  
One Pot ◽  
Acid Catalyzed ◽  
Tandem Cyclization ◽  
First Time

Lewis acid-mediated one-pot tandem cyclization of o-QMs with arylsulfonyl hydrazides was described for the first time and the corresponding 3-sulfonylbenzofuran products were obtained in moderate to good yields.

scholarly journals A three-component, Zn(OTf)2-mediated entry into trisubstituted 2-aminoimidazoles

2019 ◽  
Vol 15 ◽  
pp. 1061-1064 ◽  
Author(s):  
Alexei Lukin ◽  
Anna Bakholdina ◽  
Anna Kryukova ◽  
Alexander Sapegin ◽  
Mikhail Krasavin
Keyword(s):  
Lewis Acid ◽  
Primary Amine ◽  
Three Component Reaction ◽  
Acid Catalyzed ◽  
In Situ Generation

A three-component reaction involving in situ generation of propargylureas and subsequent Zn(OTf)2-mediated cyclocondensation with a primary amine yielded trisubstituted 2-aminoimidazoles. These findings are in contrast to the previously reported base-promoted unimolecular cyclization of propargylureas (leading to 2-imidazolones) and extend the range of Lewis acid-catalyzed azole syntheses based on N-carbonyl propargylamines.

Catalytic Carbonyl-Olefin Metathesis of Aliphatic Ketones: Iron(III) HomoDimers as Lewis Acidic Superelectrophiles

2018 ◽  
Author(s):  
Haley Albright ◽  
Paul S. Riehl ◽  
Christopher C. McAtee ◽  
Jolene P. Reid ◽  
Jacob R. Ludwig ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Olefin Metathesis ◽  
Acid Activation ◽  
Lewis Acid Catalysts ◽  
Distinct Mode ◽  
Aliphatic Ketones ◽  
Carbon Carbon Bond ◽  
Metathesis Reactions ◽  
Acid Catalyzed

<div>Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bond</div><div>formation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.</div>

scholarly journals On the Thermodynamic Control of Ring Opening of 4-Substituted 1,3,3-Tris-Carbethoxycyclobutene and the Role of the C-3 Substituent in Masking the Kinetic Torquoselectivity. An alternate reaction pathway

2021 ◽  
Author(s):  
Veejendra Yadav ◽  
Dasari L V K Prasad ◽  
Arpita Yadav ◽  
Maddali L N Rao
Keyword(s):  
Lewis Acid ◽  
Ring Opening ◽  
Reaction Pathway ◽  
Chloride Ion ◽  
Thermodynamic Control ◽  
Heterolytic Cleavage ◽  
Acid Catalyzed ◽  
Halogen Acid

<p>The predominant transformations of 4-methyl- and 4-phenyl-1,3,3-<i>tris</i>-carbethoxycyclobutenes to s-<i>trans</i>-<i>trans</i>-1,1,3-<i>tris</i>-carbethoxy-4-methyl- and 4-phenyl-1,3-butadienes, respectively, proceed through pathways entailing heterolytic cleavage of the s<sub>C3C4</sub> bond rather than the usual four-electron conrotatory ring opening following the rules of torquoselectivity. The adventitious or in situ generated halogen acid from CDCl<sub>3</sub> catalyzes the reaction of 4-methyl-1,3,3-<i>tris</i>-carbethoxycyclobutene by protonation of one of the two ester groups on C3 and, thereby, weakening the s<sub>C3C4</sub> bond to allow its heterolytic S<sub>N</sub>2 cleavage by the chloride ion. This is followed by <i>cisoid</i><b>→</b><i>transoid</i> isomerization and loss of the elements of the halogen acid to form the products. In the Lewis acid-catalyzed reaction of 4-phenyl-1,3,3-<i>tris</i>-carbethoxycyclobutene in CH<sub>2</sub>Cl<sub>2</sub>, coordination of the Lewis acid with one of two ester groups on C3 is followed by heterolytic cleavage of the s<sub>C3C4</sub> bond. The resultant species subsequently undergoes <i>cisoid</i><b>→</b><i>transoid</i> isomerization before losing the Lewis acid to form the products.<br></p>

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