2',5'-Dihydroxypropiophenone

PreparationPreparation by Fries rearrangement of quinol dipropionate (hydroquinone dipropionate),with aluminium chloride without solvent at 130–140° for 4 h (75%), at 142° for 30 min (80%), at 160–165° for 3 h (good yields) or at 190–200° for 90 min (60%) by using various quantities of aluminium chloride at 180° for 2 h (to see below) with aluminium chloride (2 equiv) in nitromethane at 20° for a week (7%) or in nitrobenzene (24%) with boron trifluoride complex (BF 3-OBu2) at reflux for 1 h (42%) by using titanium tetrachloride (2 equiv) at 130° for 2 h gave only 6% yield Also obtained by treatment ofhydroquinone dipropionate with aluminium chloride in the presence of hyd- roquinone (61%) 2-hydroxy-5-(propionyloxy)propiophenone with aluminium chloride (5 equiv) at 180° for 30 min in the presence of hydroquinone (57%) Also obtained by acylation of hydroquinone with propionic acidin the presence of boron trifluoride in ethylene dichloride at 50–55° (59%) , in tetrachloroethane at 90–95° for 5 h (70%) or at 50° for 4 h (70%) or without solvent (67%) at 80° for 2 h (54%) or at 125° for 2 h (71%) in the presence of zinc chloride at 190° few min (Nencki reaction) in the presence of 70% perchloric acid at reflux for 1 h (12%) Also obtained by Friedel–Crafts acylation of hydroquinone with propionyl chlo-ride in nitrobenzene in the presence of aluminium chloride (40%) Also obtained from 2-hydroxy-5-(propionyloxy)propiophenone; the ester group elimination on hydrolysis with 85% sulfuric acid at r.t. or by treatment with by aluminium chloride Also obtained by reaction of benzoquinone (2.5 equiv) with 2-oxobutanoic acid in aqueous acetonitrile or an acetonitrile/methylene chloride mixture (91%).