Preparation by reaction of propionic acid with resorcinol,
in the presence of zinc chloride (Nencki reaction), at reflux (160–165°) ? for 15 min, at 150° for 20 min
in the presence of boron trifluoride for 2 h at 70° (79%), at 80° (67%) ? or at 105–108° for 15 min (71%)
in the presence of polyphosphoric acid for 10–20 min in a boiling water bath ? (65%)
in the presence of 70% perchloric acid at reflux for 30 min (70%)
in the presence of Amberlite IR-120 (cation exchange resin sulfonic acid type) ? at 160° for 2–3 h (76%)
Preparation by reaction of propionitrile with resorcinol (Hoesch reaction) (75%) (65%) (46%)(35%)
Preparation by reaction of propionic anhydride with resorcinol
in the presence of Amberlite IR-120 (cation exchange resin sulfonic acid ? type) at 160° for 2–3 h (82%)
in the presence of concentrated sulfuric acid (small drops) at 130° for some ? min (60%)
Also obtained by Fries rearrangement of resorcinol dipropionate
with aluminium chloride at 180–185° for 90 min (25%)
with boron trifluoride, in the presence of resorcinol, at 75° for 1 h (83%)
Also obtained by reaction of ethylmagnesium bromide with 2,4-dihydroxy-N, N-diethylbenzamide in refluxing benzene (12%).
