Brønsted acid catalyzed Prins-Ritter reaction for selective synthesis of terpenoid-derived 4-amidotetrahydropyran compounds
A number of SO3H-functionalized solids (biochar, montmorillonites, carbon and halloysite nanotubes) has been studied as catalysts in the cascade Prins-Ritter reaction of (-)-isopulegol with benzaldehyde and acetonitrile for synthesis of octahydro-2H-chromene amides (as 4R- and 4S-isomers). A high se...
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Published in: | Applied catalysis. A, General Vol. 649; p. 118967 |
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Main Authors: | , , , , , , , , , , , |
Format: | Journal Article |
Language: | English |
Published: |
Amsterdam
Elsevier B.V
05-01-2023
Elsevier Science SA |
Subjects: | |
Online Access: | Get full text |
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Summary: | A number of SO3H-functionalized solids (biochar, montmorillonites, carbon and halloysite nanotubes) has been studied as catalysts in the cascade Prins-Ritter reaction of (-)-isopulegol with benzaldehyde and acetonitrile for synthesis of octahydro-2H-chromene amides (as 4R- and 4S-isomers). A high selectivity to these products at 30 °C in the presence of H2O was observed on catalysts modified with chlorosulfonic acid (CSA) reaching 84% (4R/4S of 5.7) in the case of biochar, while a relatively large amount of octahydro-2H-chromenols (up to 31%), products of Prins condensation, was formed on the materials functionalized by 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (CSP). Although Prins condensation proceeds efficiently on weak acid sites, the Prins-Ritter reaction requires sulfated materials with strong (0.33 – 5.8 mmol/g) Brønsted acidity. Catalysts functionalized by CSP were stable, while for the materials modified with chlorosulfonic acid, leaching of -SO3H groups was observed. Nonetheless, on resistant Bioсhar-CSP, selectivity to the amides at 30 °C (67%) was higher than that with the commercial Amberlyst-15 (47%), and triflic acid at − 25 °C (62%). Similar selectivity to the desired products on Biochar-CSA (-SO3H groups) and H2SO4 (81–84%) as well as on Biochar-CSP (-PhSO3H) and with p-toluenesulfonic acid (67–70%) was observed. DFT calculations and experimental results showed that at 30 °C formation of 4S-amide thermodynamically is more beneficial than of alcohols and dehydration products. However, addition of water results in a sharp increase in the reaction rate and 4R-amide selectivity due to a change to the kinetic control, leading eventually to both high yields and stereoselectivity. The proposed reaction pathways also were confirmed by kinetic modelling.
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•Heterogeneous and homogeneous catalysts for the Prins-Ritter reaction at ambient conditions.•The reaction requires sulfated materials with strong Brønsted acidity.•Selectivity to amides up to 84% (4 R/4 S of 5.7) on Biochar-CSA or sulfuric acid.•Formation of 4S-amide is thermodynamically more favorable.•Addition of water results in a kinetic control with high stereoselectivity. |
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ISSN: | 0926-860X 1873-3875 |
DOI: | 10.1016/j.apcata.2022.118967 |