METHOD OF PRODUCING 2,3,5,6,8-PENTAGHYDROXY-1,4-NAPHTHOQUINONE (SPINOCHROME D) AND INTERMEDIATE COMPOUNDS USED IN THIS METHOD Russian patent published in 2017 - IPC C07C46/00 C07C50/32 

FIELD: chemistry.

SUBSTANCE: invention relates to the method of producing 2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (spinochrome D) of formula I

,

where R₁=OH and R₂=H, which is used in medicine and cosmetology, as well as to new intermediate compounds of formula V, where R=n-propyl-O-, n-butyl-O-, n-amyl-O-. The method comprises reacting a compound of formula II

,

where R₁=OH and R₂=H, with primary unbranched alcohols C₃-C₅ when catalyzed by sulfuric or methanesulphonic acid, with removal of water thus formed by azeotropic distillation of alcohol C₃-C₅, to produce compounds of formula II, where R₁=N-propyl-O- and R₂=H, R₁=N-butyl-O- and R₂=H, R₁=N-amyl-O- and R₂=H, followed by reacting the resulting 6-alkoxy-substituted compounds of formula II with a 4-, 6-fold mole excess of sodium nitrite in acetone-ethanol at reflux to produce compounds of formula III

as a mixture of isomers, where R₁=H, and R₂=N-propyl-O-, n-butyl-O-, n-amyl-O- and R₂=H, and R₁=N-propyl-O-, n-butyl-O-, n-amyl-O-. The resulting compounds of formula III are reduced by sodium dithionite or sodium sulphide to produce a compound of formula IV

,

where R₁ and R₂ are defined above, followed by conversion of the compound of formula IV by acid catalyzed hydrolysis in a dimethylsulfoxide-formic acid-sulfuric acid-water mixture at the reflux temperature to the compound of formula V

,

where R=n-propyl-O-, n -Butyl-O-, n-amyl-O-, which, by acid catalyzed hydrolysis in the mixture of formic acid-methanesulfonic acid-water at the reflux temperature, is converted to the desired compound by spinochrome D.

EFFECT: producing the desired product with high yield.

2 cl, 22 ex