ChemInform Abstract: Models of Folate Cofactors. Part 22. Lewis Acid Catalyzed Cyclization of Carbon-Fragment Transfer Products of Folate Cofactor Models. Synthesis of Enantiomerically Pure Tetracyclic (ABCE) Ring System of Aspidosperma Alkaloids.

ChemInform ◽  
2010 ◽  
Vol 22 (34) ◽  
pp. no-no
Author(s):  
R. H. HUIZENGA ◽  
U. K. PANDIT
Keyword(s):  
Lewis Acid ◽  
Ring System ◽  
Enantiomerically Pure ◽  
Carbon Fragment ◽  
Acid Catalyzed

scholarly journals Activated cyclooctenones are effective dienophiles

1997 ◽  
Vol 75 (6) ◽  
pp. 899-912 ◽  
Author(s):  
Hsing-Jang Liu ◽  
Dan-Xiong Wang ◽  
Jeung Bea Kim ◽  
Eric N.C. Browne ◽  
Yu Wang
Keyword(s):  
Lewis Acid ◽  
Alder Reaction ◽  
Ring System ◽  
Diels Alder ◽  
Substitution Pattern ◽  
Diels Alder Reaction ◽  
Factors Influencing ◽  
Fused Ring ◽  
Acid Catalyzed ◽  
Fused Ring System

The first Diels–Alder addition of a diene to a cyclooctenone dienophile has been observed. Three activated cyclooctenone dienophiles 1, 2, and 3 are studied with a variety of simple and functionalized dienes. Diels–Alder adducts are produced in excellent yields under very mild Lewis acid catalyzed conditions. The usual orientation rules are followed and, as predicted, the products are formed for the most part exclusively by ester-endo addition. The stereoselectivity is influenced by the substitution pattern of the diene in some cases. The factors influencing the stereochemical selectivity of the addition are discussed in some detail. Keywords: 2-carbalkoxy-2-cyclooctenones, Diels–Alder reaction, six–eight fused ring system.

The total synthesis of (±)-petasitolone

1984 ◽  
Vol 62 (12) ◽  
pp. 2676-2681 ◽  
Author(s):  
Hsing-Jang Liu ◽  
Teng Ko Ngooi
Keyword(s):  
Total Synthesis ◽  
Lewis Acid ◽  
Good Yield ◽  
Ring System ◽  
Diels Alder ◽  
Efficient Synthesis ◽  
Target Molecule ◽  
Rapid Construction ◽  
Excellent Control ◽  
Acid Catalyzed

The total synthesis of petasitolone (1), a sesquiterpenoid of the eremophilane family, has been accomplished. The key step of this efficient synthesis is the Lewis acid catalyzed Diels–Alder addition of 2-carbomethoxy-2-cyclohexenone (3) to diene 9. The cycloaddition, which gives adduct 16 in good yield, facilitates the rapid construction of the parent ring system of the target molecule and allows an excellent control of the required stereochemistry.

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 Comparison of Corn Stover Pretreatments with Lewis Acid Catalyzed Choline Chloride, Glycerol and Choline Chloride-Glycerol Deep Eutectic Solvent

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1170
Author(s):  
Yuan Zhu ◽  
Benkun Qi ◽  
Xinquan Liang ◽  
Jianquan Luo ◽  
Yinhua Wan
Keyword(s):  
Corn Stover ◽  
Lewis Acid ◽  
Choline Chloride ◽  
Deep Eutectic Solvent ◽  
Enzymatic Saccharification ◽  
Glycerol Solution ◽  
Cellulose Conversion ◽  
Biomass Processing ◽  
Acid Catalyzed ◽  
Highly Correlated

Herein, corn stover (CS) was pretreated by less corrosive lewis acid FeCl3 acidified solutions of neat and aqueous deep eutectic solvent (DES), aqueous ChCl and glycerol at 120 °C for 4 h with single FeCl3 pretreatment as control. It was unexpected that acidified solutions of both ChCl and glycerol were found to be more efficient at removing lignin and xylan, leading to higher enzymatic digestibility of pretreated CS than acidified DES. Comparatively, acidified ChCl solution exhibited better pretreatment performance than acidified glycerol solution. In addition, 20 wt% water in DES dramatically reduced the capability of DES for delignification and xylan removal and subsequent enzymatic cellulose saccharification of pretreated CS. Correlation analysis showed that enzymatic saccharification of pretreated CS was highly correlated to delignification and cellulose crystallinity, but lowly correlated to xylan removal. Recyclability experiments of different acidified pretreatment solutions showed progressive decrease in the pretreatment performance with increasing recycling runs. After four cycles, the smallest decrease in enzymatic cellulose conversion (22.07%) was observed from acidified neat DES pretreatment, while the largest decrease (43.80%) was from acidified ChCl pretreatment. Those findings would provide useful information for biomass processing with ChCl, glycerol and ChCl-glycerol DES.

scholarly journals Metal-Free Catalysts for the Polymerization of Alkynyl-Based Monomers

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 1 ◽  
Author(s):  
Jie Zhang ◽  
Zhiming Zhang ◽  
Fulin Yang ◽  
Haoke Zhang ◽  
Jingzhi Sun ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Research Focus ◽  
Catalytic Systems ◽  
Metal Free ◽  
Catalyst Free ◽  
Material Sciences ◽  
Acid Catalyzed

Novel polymerizations based on alkyne monomers are becoming a powerful tool to construct polymers with unique structures and advanced functions in the areas of polymer and material sciences, and scientists have been attracted to develop a variety of novel polymerizations in recent decades. Therein, catalytic systems play an indispensable role in the influence of polymerization efficiencies and the performances of the resultant polymers. Concerning the shortcomings of metallic catalysts, much of the recent research focus has been on metal-free polymerization systems. In this paper, metal-free catalysts are classified and the corresponding polymerizations are reviewed, including organobase-catalyzed polymerizations, Lewis-acid-catalyzed polymerizations, as well as catalyst-free polymerizations. Moreover, the challenges and perspectives in this area are also briefly discussed.

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