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An anomeric effect drives the regiospecific ring-opening of 1,3-oxazolidines under acetylating conditions

An anomeric effect drives the regiospecific ring-opening of 1,3-oxazolidines under acetylating conditions
An anomeric effect drives the regiospecific ring-opening of 1,3-oxazolidines under acetylating conditions
A series of oxazolidines derived from tris(hydroxymethyl)aminomethane (TRIS; 1), have been prepared efficiently. Geometries optimized at the B3LYP/6-31G* level of theory, along with the crystal data of compounds 9 and 12 and NOESY correlations, point to a strong endo anomeric effect that anchors a preferential conformation and subsequently dictates the completely regioselective ring-opening of the oxazolidine moiety under acetylating conditions to afford imines instead of N-acetyloxazolidines. This process was monitored by 1H NMR spectroscopy, corroborated by synthesis, and rationalized by the intermediacy of an iminium ion. Oxazolidine–imine equilibria are also described for TRIS and other aminopolyols. The equilibria are shifted to the heterocyclic partner as the number of reactive hydroxy groups increases. The structures of an unprotected imine (31) and a per-O-acetylated derivative (43) have also been established by crystallographic analyses.

heterocycles, acylation, regioselectivity, anomeric effect
1434-193X
5263-5273
Martínez, R. Fernando
25456861-d6d7-4964-ac9c-54f5a1e5c2ba
Ávalos, Martín
2d0b39c7-15a3-4f90-bdfb-8e4b6e69c64a
Babiano, Reyes
b7ffd91c-bacd-4372-ab99-fc30ac2450ae
Cintas, Pedro
29979233-8382-47a8-bde7-1faf4869308c
Jiménez, José L.
074cc8fd-9ea1-41fc-b8b6-551d26e5fcd3
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Palacios, Juan C.
2c06e379-89b3-46b1-95c8-7f5057732f9f
Pérez, Esther M.S.
ef821a32-3f5b-4a33-a123-f6adf462a26e
Martínez, R. Fernando
25456861-d6d7-4964-ac9c-54f5a1e5c2ba
Ávalos, Martín
2d0b39c7-15a3-4f90-bdfb-8e4b6e69c64a
Babiano, Reyes
b7ffd91c-bacd-4372-ab99-fc30ac2450ae
Cintas, Pedro
29979233-8382-47a8-bde7-1faf4869308c
Jiménez, José L.
074cc8fd-9ea1-41fc-b8b6-551d26e5fcd3
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Palacios, Juan C.
2c06e379-89b3-46b1-95c8-7f5057732f9f
Pérez, Esther M.S.
ef821a32-3f5b-4a33-a123-f6adf462a26e

Martínez, R. Fernando, Ávalos, Martín, Babiano, Reyes, Cintas, Pedro, Jiménez, José L., Light, Mark E., Palacios, Juan C. and Pérez, Esther M.S. (2010) An anomeric effect drives the regiospecific ring-opening of 1,3-oxazolidines under acetylating conditions. European Journal of Organic Chemistry, 2010 (27), 5263-5273. (doi:10.1002/ejoc.201000636).

Record type: Article

Abstract

A series of oxazolidines derived from tris(hydroxymethyl)aminomethane (TRIS; 1), have been prepared efficiently. Geometries optimized at the B3LYP/6-31G* level of theory, along with the crystal data of compounds 9 and 12 and NOESY correlations, point to a strong endo anomeric effect that anchors a preferential conformation and subsequently dictates the completely regioselective ring-opening of the oxazolidine moiety under acetylating conditions to afford imines instead of N-acetyloxazolidines. This process was monitored by 1H NMR spectroscopy, corroborated by synthesis, and rationalized by the intermediacy of an iminium ion. Oxazolidine–imine equilibria are also described for TRIS and other aminopolyols. The equilibria are shifted to the heterocyclic partner as the number of reactive hydroxy groups increases. The structures of an unprotected imine (31) and a per-O-acetylated derivative (43) have also been established by crystallographic analyses.

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More information

Published date: September 2010
Keywords: heterocycles, acylation, regioselectivity, anomeric effect

Identifiers

Local EPrints ID: 179389
URI: http://eprints.soton.ac.uk/id/eprint/179389
ISSN: 1434-193X
PURE UUID: 9e30bb73-e885-4483-8624-61a6aed975ed
ORCID for Mark E. Light: ORCID iD orcid.org/0000-0002-0585-0843

Catalogue record

Date deposited: 04 Apr 2011 13:38
Last modified: 07 Oct 2020 07:26

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Contributors

Author: R. Fernando Martínez
Author: Martín Ávalos
Author: Reyes Babiano
Author: Pedro Cintas
Author: José L. Jiménez
Author: Mark E. Light ORCID iD
Author: Juan C. Palacios
Author: Esther M.S. Pérez

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