Organomercury compounds. XXV. The mercuration of 1,2,4-trichlorobenzene

Abstract

Mercuration of boiling 1,2,4-trichlorobenzene with mercuric trifluoroacetate yields complex species, which were shown to contain mainly µ-(2,5,6-trichloro-1,3-phenylene)dimercury bridging units and 2,3,6-trichlorophenylmercury terminal groups by halogenodemercuration reactions, and bis(2,3,6-tri-chlorophenyl)mercury, which was independently synthesized from 2,3,6-trichlorophenyllithium and mercuric chloride. The organolithium compound was formed regiospecifically on reaction of 1,2,4-tri-chlorobenzene with butyllithium. Mercuration of 1,2,4-trichlorobenzene with mercuric trifluoroacetate (mole ratio 1 : 1) in trifluoroacetic acid results in regiospecific monomercuration giving 2,4,5-trichlorophenylmercuric trifluoroacetate. This compound undergoes rearrangement in boiling 1,2,4-trichlorobenzene to give a 2,3,6-trichlorophenylmercurial, and is considered to be an intermediate in the mercuration synthesis of bis(2,3,6-trichloropheny1)mercury. Thus, in 1,2,4-trichlorobenzene, the kinetically and thermodynamically favoured mercuration positions differ by contrast with the reported behaviour of 1,2,3-trichlorobenzene. Formation of the complex mercuration products is considered to involve µ-(2,5,6-trichloro-1,3-phenylene)bis(trifluoroacetato)dimercury and bis(2,3,6-trichlorophenyl)mercury as intermediates. The new mercurials, bis(2,3,5-trichloro-phenyl)-, bis(3,4,5-trichlorophenyl)- and bis(2,4-dichlorophenyl)-mercury, have been prepared from the appropriate polychloroanilines by the diazonium route.