3',4'-디하이드록시프로피오페논

Obtained by Fries rearrangement of pyrocatechol dipropio-nate with aluminium chloride in chlorobenzene at 80° for 2 h (84%) or in nitrobenzene at 100° for 15 min;Obtained by Fries rearrangement of pyrocatechol dipropionate with aluminium chloride in the presence of pyrocatechol, in nitrobenzene at 80° for 1 h (37%) or in nitromethane at r.t. for 72 h (76%) Also obtained by Fries rearrangement of o-methoxyphenyl propionate (1 mol) by aluminium chloride (2 mol) without solvent at 140° for 2 h (51–55%) or in nitrobenzene at 80° for 30–60 min. A demethylation occurs during the reaction. Also obtained by acylation of pyrocatechol with propionic acidin the presence of boron trifluoride, at 150° for 2 h in a sealed tube (36%)in the presence of polyphosphoric acid for 15 min in a boiling water bath (12%) Preparation by demethylation of 4-hydroxy-3-methoxypropiophenone with refluxing pyridinium chloride for 10 min (80%) Also obtained when propiovanillone was heated with an alkali sulfide under conditions used in the kraft cooking process.