NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes
The addition of aldehyde enamines to nitroalkenes affords cyclobutanes in all solvents, with all of the pyrrolidine and proline derivatives tested by us and with all of the substrates we have examined. Depending on the temperature, concentration of water, solvent polarity, and other factors, the ope...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/146582 |
| Acceso en línea: | https://hdl.handle.net/2445/146582 |
| Access Level: | acceso abierto |
| Palabra clave: | Enamines Reaccions d'addició Reacció aldòlica Catàlisi heterogènia Addition reactions Aldol reaction Heterogeneus catalysis |
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NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanesCastro Álvarez, AlejandroCarneros García, HéctorCalafat, JaumeCosta i Arnau, Anna M.Marco Correas, CristianVilarrasa i Llorens, JaumeEnaminesReaccions d'addicióReacció aldòlicaCatàlisi heterogèniaEnaminesAddition reactionsAldol reactionHeterogeneus catalysisThe addition of aldehyde enamines to nitroalkenes affords cyclobutanes in all solvents, with all of the pyrrolidine and proline derivatives tested by us and with all of the substrates we have examined. Depending on the temperature, concentration of water, solvent polarity, and other factors, the opening and hydrolysis of such a four-membered ring may take place rapidly or last for several days, producing the final Michael-like adducts (4-nitrobutanals). Thirteen new cyclobutanes have now been characterized by NMR spectroscopy. As could be expected, s-trans-enamine conformers give rise to all-trans-(4S)-4-nitrocyclobutylpyrrolidines, while s-cis-enamine conformers afford all-trans-(4R)-4-nitrocyclobutylpyrrolidines. These four-membered rings can isomerize to adduct enamines, which should be hydrolyzed via their iminium ions. MP2 and M06-2X calculations predict that one iminium ion is more stable than the other iminium species, so that protonation of the adduct enamines can be quite stereoselective; in the presence of water, the so-called syn adducts (e.g., OCH-*CHR-*CHPh-CH2NO2, with R and Ph syn) eventually become the major products. Why one syn adduct is obtained with aldehydes, whereas cyclic ketones (the predicted ring-fused cyclobutanes of which isomerize to their enamines more easily) produce the other syn adduct, is also explained by means of molecular orbital calculations. Nitro-Michael reactions of aldehyde enamines that "stop" at the nitrocyclobutane stage and final enamine stage do not work catalytically, as known, but those of cyclic ketone enamines that do not work stop at the final enamine stage (if their hydrolysis to the corresponding nitroethylketones is less favorable than expected). These and other facts are accounted for, and the proposals of the groups led by Seebach and Hayashi, Blackmond, and Pihko and Papai are reconciled.American Chemical Society2019info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionapplication/pdfhttps://hdl.handle.net/2445/146582Articles publicats en revistes (Química Inorgànica i Orgànica)reponame:Dipòsit Digital de la UBinstname:Universidad de BarcelonaInglésReproducció del document publicat a: https://doi.org/10.1021/acsomega.9b02074ACS Omega, 2019, vol. 4, p. 18167-18194https://doi.org/10.1021/acsomega.9b02074(c) American Chemical Society, 2019info:eu-repo/semantics/openAccessoai:diposit.ub.edu:2445/1465822026-05-27T06:46:51Z |
| dc.title.none.fl_str_mv |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| title |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| spellingShingle |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes Castro Álvarez, Alejandro Enamines Reaccions d'addició Reacció aldòlica Catàlisi heterogènia Enamines Addition reactions Aldol reaction Heterogeneus catalysis |
| title_short |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| title_full |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| title_fullStr |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| title_full_unstemmed |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| title_sort |
NMR and computational studies on the reactions of enamines with nitroalkenes that may pass through cyclobutanes |
| dc.creator.none.fl_str_mv |
Castro Álvarez, Alejandro Carneros García, Héctor Calafat, Jaume Costa i Arnau, Anna M. Marco Correas, Cristian Vilarrasa i Llorens, Jaume |
| author |
Castro Álvarez, Alejandro |
| author_facet |
Castro Álvarez, Alejandro Carneros García, Héctor Calafat, Jaume Costa i Arnau, Anna M. Marco Correas, Cristian Vilarrasa i Llorens, Jaume |
| author_role |
author |
| author2 |
Carneros García, Héctor Calafat, Jaume Costa i Arnau, Anna M. Marco Correas, Cristian Vilarrasa i Llorens, Jaume |
| author2_role |
author author author author author |
| dc.subject.none.fl_str_mv |
Enamines Reaccions d'addició Reacció aldòlica Catàlisi heterogènia Enamines Addition reactions Aldol reaction Heterogeneus catalysis |
| topic |
Enamines Reaccions d'addició Reacció aldòlica Catàlisi heterogènia Enamines Addition reactions Aldol reaction Heterogeneus catalysis |
| description |
The addition of aldehyde enamines to nitroalkenes affords cyclobutanes in all solvents, with all of the pyrrolidine and proline derivatives tested by us and with all of the substrates we have examined. Depending on the temperature, concentration of water, solvent polarity, and other factors, the opening and hydrolysis of such a four-membered ring may take place rapidly or last for several days, producing the final Michael-like adducts (4-nitrobutanals). Thirteen new cyclobutanes have now been characterized by NMR spectroscopy. As could be expected, s-trans-enamine conformers give rise to all-trans-(4S)-4-nitrocyclobutylpyrrolidines, while s-cis-enamine conformers afford all-trans-(4R)-4-nitrocyclobutylpyrrolidines. These four-membered rings can isomerize to adduct enamines, which should be hydrolyzed via their iminium ions. MP2 and M06-2X calculations predict that one iminium ion is more stable than the other iminium species, so that protonation of the adduct enamines can be quite stereoselective; in the presence of water, the so-called syn adducts (e.g., OCH-*CHR-*CHPh-CH2NO2, with R and Ph syn) eventually become the major products. Why one syn adduct is obtained with aldehydes, whereas cyclic ketones (the predicted ring-fused cyclobutanes of which isomerize to their enamines more easily) produce the other syn adduct, is also explained by means of molecular orbital calculations. Nitro-Michael reactions of aldehyde enamines that "stop" at the nitrocyclobutane stage and final enamine stage do not work catalytically, as known, but those of cyclic ketone enamines that do not work stop at the final enamine stage (if their hydrolysis to the corresponding nitroethylketones is less favorable than expected). These and other facts are accounted for, and the proposals of the groups led by Seebach and Hayashi, Blackmond, and Pihko and Papai are reconciled. |
| publishDate |
2019 |
| dc.date.none.fl_str_mv |
2019 |
| dc.type.none.fl_str_mv |
info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion |
| format |
article |
| status_str |
publishedVersion |
| dc.identifier.none.fl_str_mv |
https://hdl.handle.net/2445/146582 |
| url |
https://hdl.handle.net/2445/146582 |
| dc.language.none.fl_str_mv |
Inglés |
| language_invalid_str_mv |
Inglés |
| dc.relation.none.fl_str_mv |
Reproducció del document publicat a: https://doi.org/10.1021/acsomega.9b02074 ACS Omega, 2019, vol. 4, p. 18167-18194 https://doi.org/10.1021/acsomega.9b02074 |
| dc.rights.none.fl_str_mv |
(c) American Chemical Society, 2019 info:eu-repo/semantics/openAccess |
| rights_invalid_str_mv |
(c) American Chemical Society, 2019 |
| eu_rights_str_mv |
openAccess |
| dc.format.none.fl_str_mv |
application/pdf |
| dc.publisher.none.fl_str_mv |
American Chemical Society |
| publisher.none.fl_str_mv |
American Chemical Society |
| dc.source.none.fl_str_mv |
Articles publicats en revistes (Química Inorgànica i Orgànica) reponame:Dipòsit Digital de la UB instname:Universidad de Barcelona |
| instname_str |
Universidad de Barcelona |
| reponame_str |
Dipòsit Digital de la UB |
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Dipòsit Digital de la UB |
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