Selective Chlorination of Hydroxynaphthazarins with Dichlorine Monoxide. Remarkable Stability of some Geminal Diols Derived from 2,3-Dihydro-2-oxonaphthazarin

The ration of 2-hydroxynaphthazarins with dichlorine monoxide in CC1 4 affords the stable gem-diols - 3,3-dichloro-2,3-dihydro-2,2-dihydroxy-paphthazarins in quantitative yields. In the case of 2-hydroxy-3-methyl-iiaphthazarins the formation of the mixture of corresponding monochlorinated at 3 position 2,3-dihydro-3-methyl-2-oxonaphthazarins and 2,3-dihydro-3-methyl-2,2-dihydroxynaphthazarins takes place. For these compounds, under certain conditions, the keto - gem-diol equilibrium is observed.