Synthesis of Pyridazines and Pyradizones

Question 1

formation of pyridazines

Answer 1

double condensation of hydrazine and double a,-b, unsaturated ketone then oxidation
[4+2] cycloadditions with tetrazines then reverse [4+2] to remove N2

Question 2

furans in pyridazine synthesis

Answer 2

forms a 1,4-dicarbonyl in situ

Question 3

formation of pyridazinones

Answer 3

condensation of gamma-keto ester and hydrazine then oxidation