Obtained by reaction of phenylacetic acid with pyrogallol,
? in the presence of zinc chloride at 150° for 30 min (Nencki reaction) or at 120° for 2.5 h (60%) ;
? in the presence of Amberlite IR-120 cation exchange resin (sulfonic acid type) at 160° for 2–3 h (34%). N.B.: Zeokarb 225 was found to be as effective;
? in the presence of 70% perchloric acid at 150° for 30 min (25%) ;
? in the presence of boron trifluoride in chloroform, first in ice cooling, then at r.t. overnight (96%).
