TEMPERATURE DEPENDENT MIGRATION OF THE NITRO GROUP OF POTASSIUM 4-AMINO-3,5-DENfITROBENZENESULFONATE VS DESULFONATION

摘要

Electrophilic sulfonations of aromatic compounds such as naphthalene,performed under kinetic control,give products different from those carried out under thermodynamically controlled conditions.The possibility of hydrolytic removal of the sulfonic acid group under relatively mild conditions makes it a suitable protecting group,a process which,for example,has been claimed for the preparation of 2,6-dinitroaniline(5),starting from chlorobenzene(Scheme l).However,using this procedure2 we obtained a mixture of 2,6- and 2,4-dinitroani-lines from potassium 4-amino-3,5-dinitrobenzenesulfonate(4)which contains up to 20% of the second isomer(estimated by integrated intensity from ~1H NMR)which is practically impossible to separate from the desired product;2,4-dinitroaniline has been obtained cleanly by ammonolysis of 2,4-dinitrochlorobenzene.