The chemistry of Quinones. I. Directive effects in the Substitution of Naphthoquinones

Abstract

The reaction of dimethylamine with 5-methoxy-1,4-naphthoquinone gives approximately equal amounts of the two possible substitution products and with 6-methyl-1,4-naphthoquinone followed by acid hydrolysis 2-hydroxy-6-methyl-l,4-naphtho-quinone is the principal product. Similar treatment of 5-methyl-1,4-naphthoquinone gives mostly 3-hydroxy-5-methyl-l,4-naphtlioquinone. The isomer, 2-hydroxy-5- methyl-1,4-naphthoquinone, has been prepared by another method. The product of Thiele-Winter addition of acetic anhydride to juglone is shown to be a mixture of the two possible isomers, but authentic 1,3,4,5-tetra-acetoxynaphthalene has been prepared from 3,5-dihydroxy-1,4-naphthoquinone. The reaction of acetic anhydride with plumbagin gives three compounds, the composition of the mixture depending on the time of contact. Juglone and plumbagin have been selectively brominated in the 6-position and certain other halogen derivatives of these quinones have been prepared. The preparation of 3-chloro-5-hydroxy-2-methyl-1,4-naphthoquinone provides a new route by which droserone may be obtained from plumbagin.