The Synthesis of Anthracenes from Anthraquinones

Abstract

The preparation of a series of halogen-substituted anthracenes and anthroic acids was of interest in connection with work in another area.¹ The classical zinc-ammonia procedure² for the reduction of anthraquinones to anthracenes was satisfactory for a number of these compounds, but an unacceptable yield of very difficult-to-purify product mixture from 6,7-dichloroanthraquinone-1-carboxylic acid induced a search for a more efficient conversion. A further concern was the possibility of halogen expulsion under these conditions as noted much earlier by Fischer and Sapper³ for 4-chloronthraquionone-1-carboxylic acid and by Kircher⁴ for 1,2,3,4-tetrachloroanthraquionone.