A versatile method for the synthesis of gamma-pyrones

作者：Beye Garrison E; Karagiannis Athanasios; Kazemeini Alieh; Ward Dale E^*

来源：Canadian Journal of Chemistry, 2012, 90(11): 954-964.

DOI：10.1139/v2012-067

• gamma-pyrone synthesis
• 2-iodoxybenzoic acid (IBX)
• 1,3-dione
• dithiolane
• siphonariid polypropionates

A versatile three-step procedure to annulate a gamma-pyrone onto a methylene ketone was developed involving (i) aldol reaction with a dithiolane-protected beta-ketoaldehyde, (ii) oxidation of the aldol adduct to a beta-diketone, and (iii) treatment of the resulting dithiolane-protected 1,3,5-trione with 2-iodoxybenzoic acid (IBX) and trifluoromethanesulfonic acid (triflic acid; TfOH) in acetonitrile at ambient temperature to give the corresponding gamma-pyrone. Cyclization proceeded with IBX alone, but significantly improved yields were obtained with added acid, particularly triflic acid. A dithiolane was more effective than a dithiane or acyclic dithioacetal protecting group. The method was amenable to the preparation of a variety of substituted gamma-pyrones simply by altering the initial aldol reactants. Overall yields of 50%-60% were obtained in six examples. The method was applied to prepare a key fragment for the total synthesis of baconipyrones A and C and siphonarin B.

• 出版日期2012-11