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Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism

p-Methyl benzaldehyde (p-MBA) is a class of key chemical intermediates of pharmaceuticals. Conventional industrial processes for p-MBA production involve the consecutive photochlorination, amination, and acid hydrolysis of petroleum-derived p-xylene, while producing vast pollutants and waste water....

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Detalles Bibliográficos
Autores principales: Wang, Qing-Nan, Liu, Xianghui, Wang, Kai, Liu, Yan, Lu, Sheng-Mei, Li, Can
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Elsevier 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8426279/
https://www.ncbi.nlm.nih.gov/pubmed/34522868
http://dx.doi.org/10.1016/j.isci.2021.103028
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author Wang, Qing-Nan
Liu, Xianghui
Wang, Kai
Liu, Yan
Lu, Sheng-Mei
Li, Can
author_facet Wang, Qing-Nan
Liu, Xianghui
Wang, Kai
Liu, Yan
Lu, Sheng-Mei
Li, Can
author_sort Wang, Qing-Nan
collection PubMed
description p-Methyl benzaldehyde (p-MBA) is a class of key chemical intermediates of pharmaceuticals. Conventional industrial processes for p-MBA production involve the consecutive photochlorination, amination, and acid hydrolysis of petroleum-derived p-xylene, while producing vast pollutants and waste water. Herein, we report a direct, green route for selective synthesis of p-MBA from acetaldehyde using a diphenyl prolinol trimethylsilyl ether catalyst. The optimized p-MBA selectivity is up to 90% at an acetaldehyde conversion as high as 99.8%. Intermediate structure and (18)O-isotope data revealed that the conversion of acetaldehyde to p-methylcyclohexadienal intermediates proceeds in an enamine-iminium intermediate mechanism. Then, controlled experiments and D-isotope results indicated that the dehydrogenation of p-methylcyclohexadienal to p-MBA and H(2) is catalyzed by the same amines through an iminium intermediate. This is an example that metal-free amines catalyze the dehydrogenation (releasing H(2)), rather than using metals or stoichiometric oxidants.
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spelling pubmed-84262792021-09-13 Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism Wang, Qing-Nan Liu, Xianghui Wang, Kai Liu, Yan Lu, Sheng-Mei Li, Can iScience Article p-Methyl benzaldehyde (p-MBA) is a class of key chemical intermediates of pharmaceuticals. Conventional industrial processes for p-MBA production involve the consecutive photochlorination, amination, and acid hydrolysis of petroleum-derived p-xylene, while producing vast pollutants and waste water. Herein, we report a direct, green route for selective synthesis of p-MBA from acetaldehyde using a diphenyl prolinol trimethylsilyl ether catalyst. The optimized p-MBA selectivity is up to 90% at an acetaldehyde conversion as high as 99.8%. Intermediate structure and (18)O-isotope data revealed that the conversion of acetaldehyde to p-methylcyclohexadienal intermediates proceeds in an enamine-iminium intermediate mechanism. Then, controlled experiments and D-isotope results indicated that the dehydrogenation of p-methylcyclohexadienal to p-MBA and H(2) is catalyzed by the same amines through an iminium intermediate. This is an example that metal-free amines catalyze the dehydrogenation (releasing H(2)), rather than using metals or stoichiometric oxidants. Elsevier 2021-08-23 /pmc/articles/PMC8426279/ /pubmed/34522868 http://dx.doi.org/10.1016/j.isci.2021.103028 Text en © 2021 The Authors https://creativecommons.org/licenses/by-nc-nd/4.0/This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Article
Wang, Qing-Nan
Liu, Xianghui
Wang, Kai
Liu, Yan
Lu, Sheng-Mei
Li, Can
Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
title Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
title_full Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
title_fullStr Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
title_full_unstemmed Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
title_short Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
title_sort direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8426279/
https://www.ncbi.nlm.nih.gov/pubmed/34522868
http://dx.doi.org/10.1016/j.isci.2021.103028
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