After that, when pure 4,5-dihydropyrazole 250 reacted with substituted salicylic aldehydes, regiospeci-fically and in a one-step reaction, pyrazolinyliminochromenes 251(a-d) were generated via a typical Knoevenagel condensation reaction, as a result of the existence of an active methylenic center in the precursor 250 (Scheme 83) 114 . Also, it has been reported that the pyrazolo[1,5-c]pyrimidin-7-thione derivative 261 was obtained when 165 was allowed to react with benzoyl isothiocyanate. This reaction is believed to proceed via an initial attack of the nitrogen nucleophile in 165 on the electrophilic center (C = S) in the benzoyl isothiocyanate to yield the intermediate 260 which then cyclized under the reaction conditions to give the final isolable product1 261 as described in Scheme 86.