3-Chloro-5-halo-pyridazine derivs. prepn. - by reacting a 1,3,3,3-tetra:halo-propenyl ketone or aldehyde and cyclising the semicarbazone formed

摘要

Prepn. of 3-chloro-5-halopyridazines of formula (I):- (where R1 is H, opt. branched 1-5C alkyl or phenyl opt. monosubstd. with Me, Cl, Br or NO2; and R2 is Cl or Br) comprises reacting a cpd. of formula (II):- R1-CO-CR2=CH-CCl3 (II) with semicarbazide or its salt. (I) are intermediates for pharmaceuticals and plant protecting agents. The reaction is simple and (I) is obtd. in high yields. Reaction is at 10-80 (pref. 20-60) degrees C and pH 1-5, pref. in DMF and/or DMSO contg. up to 50 wt. %.