Gca. Luijkx et al., HYDROTHERMAL FORMATION OF HYDROXYLATED BENZENES FROM FURAN-DERIVATIVES, Journal of analytical and applied pyrolysis, 28(2), 1994, pp. 245-254
Several furan derivatives were subjected to hydrothermolysis at 340-de
grees-C and 27.5 MPa for 1 to 33 min in a flow system to study their c
onversion to hydroxylated benzenes. Hydrothermolysis of 0.05 M aq. 5-m
ethyl-2-furaldehyde, 2-acetylfuran and 2-propionylfuran led to the for
mation of 1,4-benzenediol, 1,2-benzenediol and 3-methyl-1,2-benzenedio
l, respectively, with selectivities ranging from 10 to 65%. The additi
on of 5 mM HCl increased the rate of hydrolysis of the furan ring, but
in the case of 2-acetylfuran or 2-propionylfuran it also reduced the
selectivity towards the corresponding benzenediol. Hydrothermolysis of
0.01 M aq. 2-acetyl-5-(hydroxymethyl) furan and 5-(1-hydroxyethyl)-2-
furaldehyde did not produce the expected benzenetriols; instead, 2-met
hyl-1,4-benzenediol could be identified as a product. Hydrothermolysis
of 2-vinylfuran did not produce any phenol, an indication that the fo
rmation of benzene rings from furans is not accomplished by electrocyc
lic ring closure. 2,6-Dimethyl-gamma-pyrone, a compound that is known
to produce 5-methyl-1,3-benzenediol via an aldol condensation under al
kaline conditions, also gave this product when subjected to hydrotherm
al conditions. A reaction pathway for the hydrothermal formation of hy
droxylated benzenes from furan derivatives is presented which is based
on carbon ring formation via an intramolecular aldol condensation.