The reaction of concentrated or fuming sulfuric acid with pyrroles containing a carbethoxy group was first recognized by Fischer and Walach4 in 1925, using Knorr's pyrrole, 2, 4- dimethyl-3, 5-dicarbethoxypyrrole. These investigators found that the carbethoxy group in the 3 or,# position was changed to a carboxyl group by dissolving the pyrrole in the acid and warming to 35" for approximately thirty minutes, then pouring the solution over ice. Fischer ...
