Pyridazines with heteroatom substituents in positions 3 and 5. 6. S_<i>N</i> reactions in position 5 of 2‐aryl‐5‐hydroxypyridazin‐3(2<i>H</i>)‐ones

Abstract

Abstract The nucleophilic introduction of chloro‐ ( 2 ), azido‐ ( 4 ), (substituted) amino ( 3, 6 ), mercapto ( 10 ) and hydrazino‐groups ( 13 ) into 2‐aryl‐5‐hydroxypyridazin‐3(2 H )‐ones [3] is described. The 5‐aminopyridazin‐3(2 H )‐one ( 6 ) also reacts with activated malonates 8 [4] to give pyrido[2,3‐ d ]pyridazines 9 . Hydrazino compounds 13 can be treated with aldehydes to yield compounds 14 . Iodine can be introduced into position 4 of 5 ‐amino ‐(15 ) and 5‐hydroxypyridazin‐3(2 H )‐ones ( 17 ) by electrophilic substitution to afford compounds 18 .