Vilsmeier synthesis vinylogous

Vilsmeier-type reagent 749 reacted with imines 750 to afford enaminoimine hydrochlorides 751, which were transformed to pyrazoles 752 upon addition of hydrazine (Scheme 94) <2000JHC1309>. A variety of vinylogous iminium salts 753 were useful precursors for the regiocontrolled synthesis of heterocyclic appended pyrazoles 754 (Equation 161) <2002T5467>. 

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