Chlorination of 2,3,6-trialkyl-5,8-dihydroxy-1,4-naphthoquinones with HCl-MnO2 in acetic acid. effective transformation of 2,3,6-trialkyl-2,3,7-trichloro-1,2,3,4-tetrahydronaphthalene-1,4-diones into 7-chloro-2,3,6-trialkyl-5,8-dihydroxy-1,4-naphthoquinones

Abstract

Chlorination of 2,3,6-trialkyl-5,8-dihydroxy-1,4-naphthoquinones with HCl-MnO2 in acetic acid gave a mixture of 7-chloro-2,3,6-trialkyl-5,8-dihydroxy-1,4-naphthoquinones and 2,3,7-trichloro-2,3,6-trialkyl-1,2,3,4-tetrahydronaphthalene-1,4-diones, the latter being formed via addition of the second chlorine molecule to monochloro derivatives. The reduction of 2,3,7-trichloro-2,3,6-trialkyl-1,2,3,4-tetrahydronaphthalene-1,4-diones with sodium dithionite in alkaline medium resulted in the formation of 7-chloro-2,3,6-trialkyl-5,8-dihydroxy-1,4-naphthoquinones in high yield.