The Nitration of Tetrachlorocatechol and 3,4,6-Trichloro-5-methylcatechol. The Formation of 1-Hydroxycyclopent-3-enecarboxylic Acids

Abstract

Reaction of tetrachlorocatechol (la) with nitric acid (d 1.48) gives the ring-contracted hydroxy dinitro acid (4), which was isolated as its ether solvate. Similar nitration of 3,4,6-trichloro-5-methylcatechol (lb) gives a mixture of stereoisomeric hydroxy dinitro acids (5), from which the methoxy methyl ester (8) can be isolated after methylation of the mixture with diazomethane. X-Ray crystal structure determinations are reported for the etherate of hydroxy dinitro acid (4) and the methoxy methyl ester (8).