Design of pyrazolo-pyrrolo-pyrazines and pyrazolo-pyrrolo-diazepines via AuCl₃-catalyzed and NaH-supported cyclization of N-propargyl pyrazoles.

A concise synthetic methodology for new heterocyclic scaffolds, such as pyrazolo-pyrrolo-pyrazine and pyrazolo-pyrrolo-diazepine skeletons, was developed. The key features of this method include (i) synthesis of pyrrole-derived α,β-alkynyl ketones, (ii) introduction of various substituents into the alkyne functionality by Sonogashira cross-coupling, (iii) synthesis of pyrazole units by the reaction of α,β-alkynyl compounds with hydrazine monohydrate, (iv) gold-catalyzed cyclization of pyrazoles with alkyne units, and (v) cyclization with NaH. Furthermore, this methodology allows various substituents to be introduced into all positions of the target compounds.