An Anomeric Effect Drives the Regiospecific Ring-Opening of 1,3-Oxazolidines under Acetylating Conditions

Autor:	José L. Jiménez, Pedro Cintas, R. Fernando Martínez, Juan C. Palacios, Martin Avalos, Mark E. Light, Reyes Babiano, Esther M. S. Pérez
Rok vydání:	2010
Předmět:	Oxazolidine chemistry.chemical_compound chemistry Anomeric effect Stereochemistry Organic Chemistry Imine Iminium Regioselectivity Moiety Hydroxymethyl Physical and Theoretical Chemistry Two-dimensional nuclear magnetic resonance spectroscopy
Zdroj:	European Journal of Organic Chemistry. 2010:5263-5273
ISSN:	1434-193X
Popis:	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.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::5a2bf4783e6ed4c2ffca28cec6d88868 https://doi.org/10.1002/ejoc.201000636 Zobrazit plný text záznamu Plný text