Welcome to LookChem.com Sign In|Join Free

Article Doi

Polyketoenols and Chelates. New Types of Xanthyrones Lacking Enolised Side-chain Termini: their Reactions with Magnesium Methoxide

DOI: 10.1039/P19810000165

Source and publish data:

Journal of the Chemical Society. Perkin transactions I p. 165 - 171 (1981)

Update date:2022-08-04

Topics:

Authors:

Baker, S. RichardBaker, S. Richard

Crombie LeslieCrombie Leslie

Dove, Roderick V.Dove, Roderick V.

Read Full Text PDF DownLoad Join now for total 90,000,000 free articles

Article abstract of DOI:10.1039/P19810000165

Xanthyrones (4) and (8) as well as (9), (11) and (13) have been synthesised: blocking the side-chain terminus, which is normally enolised as in (5), by dicyano or cyano-ester end groups, leads to enolisation of the 3-acetylpyrone end as shown by n.m.r. data in CDCl3.The dicyanobismethoxycarbonyl representative (9) exists in the 1'-H form in CDCl3-CF3CO2H whilst in CDCl3 the tetraester (13) is a 3'-H form.Xanthyrone (11) is present mainly in the 3'-H form in CDCl3 but some enolate (12) is observed.All the xanthyrones are highly ionised in ethanol, (9) especially so.Treated with exess (>6 mol. equiv.) magnesium methoxide, xanthyrones (4) and (8) cyclise by an aldol pathway and (9) and (13) by an analogous Claisen pathway.This contrasts with dimethylxanthophanic enol (5) with undergoes a different type of Claisen cyclisation.The results accord with the view that cyclisation in the latter case involves a bischelate (20) and in the other cases monochelates, e.g. (22) and (25).Reactions of xanthyrones (4) and (8) with boiling water follow expected pathways.

View More

Products guided by the article

Product name:5-Hydroxy-2-oxo-2H-chromene-3,6,8-tricarboxylic acid trimethyl ester

Cas No:72554-71-3

72554-71-3

R&D Labs maybe for 72554-71-3

Relevant to this article

Hot Product