Chlorination of 5-nitro-6-methyluracil and its N(1),N(3)-dimethyl analogue with molecular chlorine

The chlorination of 6-methyl-5-nitrouracil with chlorine in methanol results in a two-component mixture of 5-chloro-6-methyl-6-methoxy-5-nitro-5,6-dihydrouracils, while the chlorination of 5-nitro-1,3,6-trimethyluracil under similar conditions gives a mixture of 5-chloro-6-hydroxy-5-nitro-1,3,6-trimethyl-5,6-dihydrouracils. The structures of the chlorination products were suggested based on quantum-chemical calculations