Reactions of hydrazonoyl halides 43 : Synthesis of some new 2,3-dihydro-1,3,4-thiadiazoles, pyrazoles, pyrazolo[3,4-d]-pyridazines, thieno[2,3-b]pyridines, pyrimidino[4′,5′:4,5]thieno[2,3-b]-pyridines and pyrrolo[3,4-d]pyrazoles†