Fluoride salts-alcohols-alumina as reagents for nucleophilic substitution of chlorine atoms for alkoxy groups in 2,3-dichlorosubstituted juglones, naphthazarines, and quinizarines
作者:Victor Ph. Anufriev、Vyacheslav L. Novikov
DOI:10.1016/0040-4039(95)00295-n
日期:1995.4
Direct displacement of chlorine atoms by alkoxy groups in 2,3-dichlorosubstituted juglones (5-hydroxy-1,4-naphthoquinones), naphthazarines (5,8-dihydroxy-1,4-naphthoquinones), and quinizarines (1,4-dihydroxy-9,10-anthraquinones) is generally ineffective, however high yields are obtained when methanol or cellosolves activated by fluoride anion are used as nucleophiles and the reaction goes in the presence
A series of 6,7-disubstituted 2-hydroxy-3-nitronaphthazarins were prepared by treatment of 2,3-dichloronaphthazarins with sodium nitrite. Acid-catalyzed hydrolysis of a mixture of two isomeric 6(7)-ethoxy-7(6)-ethyl-substituted 2-hydroxy-3-nitronaphthazarins followed by chromatographic separation led to the individually precursors of echinamines A and B. Further reduction of nitroquinones using various reducing agents gave echinamines and related 3-amino-2-hydroxynaphthazarins in good yields.
Cycloacylation of chloro-substituted hydroquinone dimethyl ethers with dichloromaleic anhydride
作者:V. L. Novikov、N. N. Balaneva、O. P. Shestak、V. Ph. Anufriev、V. P. Glazunov
DOI:10.1007/s11172-016-1402-3
日期:2016.4
Under the drastic conditions of Zahn—Ochwat cycloacylation of 2-chloroand 2,3-dichlorohydroquinones with dichloromaleic anhydride (a melt of anhydrous AlCl3 and NaCl, 185—195 °C), the substrates undergo various degrees of disproportionation, which reduces the yields of the target triand tetrachloronaphthazarins. Quantum chemical calculations showed that the cycloacylation in question proceeds as a