Pyridazines with heteroatom substituents in position 3 and 5. 3. 2‐aryl‐5‐hydroxypyridazin‐3(2<i>H</i>)‐ones as potential herbicides: Synthesis and some reactions

Abstract

Abstract The coupling of dimethyl acetonedicarboxylate 1 with a variety of aryldiazonium salts 2a‐i produces the hydrazones 3a‐i which can be cyclized in boiling dichlorobenzene to yield the pyridazone esters 4a‐i , or in sodium hydroxide solution to give the pyridazone acids 5a‐f,h,i , which can be decarboxylated at elevated temperatures. The hydroxy group in 4a,d can be acylated, sulfonated or alkylated yielding compounds 8a‐n . Condensation of 4a,d with magic malonates 9a‐d produces the pyronopyridazinones 10a‐f . The reaction of 4a with hydrazine yields the hydrazide 12 via the salt 11 , and with ammonia the amide 14 .