New Dihydropyrans: Lewis Acid Catalyzed Cycloadditions of ?,?-Unsaturated Acyl Cyanides to Simple, Unactivated Olefins and Dienes: A Readily Accessible Route to Derivatives of Rose Oxide

1982 ◽  
Vol 21 (11) ◽  
pp. 859-860 ◽  
Author(s):  
Zeinhom M. Ismail ◽  
H. M. R. Hoffmann
Keyword(s):  
Lewis Acid ◽  
Unsaturated Acyl ◽  
Acid Catalyzed ◽  
Derivatives Of

N-Allyloxycarbonyl derivatives of D-glucosamine as promotors of 1,2-trans-glucosylation in Koenigs–Knorr reactions and in Lewis acid catalyzed condensations

1987 ◽  
Vol 65 (6) ◽  
pp. 1343-1348 ◽  
Author(s):  
Paul Boullanger ◽  
Joseph Banoub ◽  
Gérard Descotes
Keyword(s):  
Lewis Acid ◽  
Protective Group ◽  
Acid Catalyzed ◽  
Derivatives Of

The use of suitably blocked D-glucosamine derivatives possessing the N-allyloxycarbonyl protective group of the amino function represents potential new routes to 1,2-trans-glucosylations. Both 3,4,6-tri-O-acetyl-2-N-allyloxycarbonyl-2-amino-2-deoxy-α-D-glucopyranosyl bromide (2) and 1,3,4,6-tetra-O-acetyl-2-N-allyloxycarbonyl-2-amino-2-deoxy-β-D-glucopyranose (3) could be used in Koenigs–Knorr reactions or Lewis acid catalyzed condensations, respectively. Glucosides of simple alcohols and disaccharides were synthesized in good to excellent yields. The N-allyloxycarbonyl protective group was, moreover, easy to remove with Pd(0) complexes, thus affording, after acetylation, the corresponding N-acetyl-β-D-glucosamine glucosides under very smooth conditions.

Sixfold Peripheral Halogenation of Tribenzotriquinacenes: An Alternative Access to Useful TBTQ Building Blocks

Synthesis ◽  
2017 ◽  
Vol 50 (01) ◽  
pp. 175-183 ◽  
Author(s):  
Dietmar Kuck ◽  
Jens Linke ◽  
Natalia Bader ◽  
Jörg Tellenbröker
Keyword(s):  
Microwave Irradiation ◽  
Lewis Acid ◽  
Elevated Temperatures ◽  
Cross Coupling ◽  
Building Blocks ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Electrophilic Bromination ◽  
Acid Catalyzed ◽  
Derivatives Of

Sixfold electrophilic bromination and iodination of the molecular periphery of the bridgehead-tetramethylated tribenzotriquinac­ene (TBTQ) with N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS), respectively, under various conditions was studied to develop an alternative preparative approach to the classical Lewis acid catalyzed bromination. Running these reactions in trifluoroacetic acid either in pure form or with chloroform as a co-solvent at elevated temperatures, or under sonication or microwave irradiation was found to give increasingly fast and efficient conversion of TBTQ to the target hexahalogenated TBTQ derivatives in excellent yields. NIS was found to be markedly more reactive than NBS, whereas N-chlorosuccimide reacted hardly. The new method was applied to the sixfold functionalization of the 4b,8b,12b-tripropyl-12d-methyl-TBTQ analogue to give the corresponding hexabromo and hexaiodo derivatives. Some sixfold C–C cross-coupling reactions of hexahalo derivatives of TBTQ were carried out in excellent yields to enlarge the three spatially orthogonal indane wings of the TBTQ core.

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>

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

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.

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