Pfizer Corporation

Robert P Allingham

Paul D Weeks

A process for preparing a compound of the formula: ##STR1## wherein R is hydrogen, lower alkyl of 1 to 6 carbon atoms, lower alkenyl of 2 to 6 carbon atoms, phenyl or benzyl; and R' is lower alkyl of 1 to 6 carbon atoms which comprises contacting a compound of the formula ##STR2## wherein R and R' are defined as above at -10.degree. to 50.degree. C. with an essentially anhydrous acid selected from the group consisting of formic acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, citric acid, oxalic acid, chloroacetic acid, sulfuric acid, hydrochloric acid, phosphoric acid and hydrofluoric acid.

Preparation of gamma-pyrone intermediates

Maltol (3-hydroxy-2-methyl-gamma-pyrone) is prepared from furfural through intermediates (a) 1-(2-furyl)-1-ethanol; (b) 2-(1-hydroxyethyl)-2,5-dialkoxy-2,5-dihydrofuran; (c) alkyl or aralkyl-2-methyl-2H-pyran-3(6H)-one; and (d) 2-alkyl or aralkyl-4-methyl-3,7-dioxabicyclo[4.1.0]heptan-5-one. Pyromeconic acid (3-hydroxy-gamma-pyrone), ethyl maltol (3-hydroxy-2-ethyl-gamma-pyrone) and other valuable 2-substituted-3-hydroxy-gamma-pyrones are prepared in an analogous manner from furfural.

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Groton, CT, United States of America

Robert P Allingham