Acid-Catalyzed Synthesis of Mono- and Dialkyl Benzenes over Zeolites: Active Sites, Zeolite Topology, and Reaction Mechanisms

ChemInform ◽  
2003 ◽  
Vol 34 (14) ◽  
Author(s):  
Jiri Cejka ◽  
Blanka Wichterlova
Keyword(s):  
Reaction Mechanisms ◽  
Active Sites ◽  
Acid Catalyzed

scholarly journals BIS-DEACETYLATION OF TETRAACETYLGLYCOLURYL UNDER ACTION OF UREAS

2018 ◽  
Vol 61 (7) ◽  
pp. 50
Author(s):  
Ngoc Phuoc Hoang ◽  
Abdigali A. Bakibaev ◽  
Victor S. Malkov
Keyword(s):  
Reaction Mechanisms ◽  
Nucleophilic Addition ◽  
Specific Effect ◽  
Independent Effect ◽  
Similar Reaction ◽  
Urea Molecule ◽  
Acid Catalyzed ◽  
Integrated Intensities ◽  
Cis Isomer ◽  
Methyl Phenyl

It is established that tetraacetylglycoluril under the action of urea, some N-substituted ureas and benzylidenebisurea in the acid-catalyzed conditions undergoes only bis-deacetylation with the formation of syn- and anti-regio-substituted N,N-diacetylglycolurils, rather than N-acetylation as it was previously shown in a similar reaction for a number of aromatic and heterocyclic amines. In the course of individual experiments, the absence of independent effect of organic solvents during boiling for several hours (alcohols, dioxane, tetrahydrofuran, dimethylsulfoxide) on the deacetylation of tetraacetylglycoluril was revealed, since in these conditions the original substrate remained unchanged. Based on the NMR spectroscopy data, by comparison the integrated intensities of methine and acetyl protons of glycoluryl fragments, we found that the bis-deacetylation of tetraacetylglycoluril in the studied conditions occurs regioselectively with an overwhelming majority of anti-N,N-diacetylglycoluril (up to 92-94%) except for benzylidenebisurea, when the content of the trans-isomer reaches 75%. A marked increase in the cis-isomer (up to 25%) of N,N-diacetylglycoluril in the case of benzylidenebisurea seems to be dictated by the specific effect on the intermediates of reaction of phenylmethylureido carbocation from eliminating urea molecule in acid-catalyzed conditions. It is shown that N,N-diacetylglycoluril in similar conditions under the action of urea and its derivatives does not undergo further deacetylation to the progenitor of bicyclic bisureas – glycoluril, primarily related to the high hydrolytic and steric resistance of these compounds. On the basis of the above research results, the reaction mechanisms of bis-deacetylation of tetraacetylglycoluril in the acid-catalyzed conditions under the action of urea and its N-methyl (phenyl) derivatives through an intermediate process of nucleophilic addition of ureas is proposed.Forcitation:Hoang N.P., Bakibaev A.A., Malkov V.S. Bis-deacetylation of tetraacetylglycoluryl under action of ureas. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 49-53

scholarly journals Efficient conversion of glucosamine to levulinic acid in a sulfamic acid-catalyzed hydrothermal reaction

RSC Advances ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 3198-3205 ◽  
Author(s):  
Hyo Seon Kim ◽  
Sung-Koo Kim ◽  
Gwi-Taek Jeong
Keyword(s):  
Levulinic Acid ◽  
Active Sites ◽  
Hydrothermal Reaction ◽  
Sulfamic Acid ◽  
Efficient Conversion ◽  
Platform Chemicals ◽  
Acid Catalyzed

Glucosamine, which is a monomer of chitosan, and sulfamic acid, which has dual active sites, were employed as substrate and catalyst, respectively, to produce the bio-based platform chemicals LA and 5-HMF.

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