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A concise transition-metal-free strategy for the synthesis of pyrrolo[1,2-a]pyrazines with enone substituents has been developed. It includes the following key steps: (a) cross-coupling of pyrroles with acyl(bromo)acetylenes in solid alumina at room temperature to give 2-(acylethynyl)pyrroles; (b) addition of propargylamine to the above acetylenes to form the corresponding N-propargylenaminones; and (c) chemo- and stereoselective base-catalyzed (Cs2CO3/DMSO) intramolecular cyclization of the synthesized propargylic derivatives to form (acylmeth­ylidene)pyrrolo[1,2-a]pyrazines of Z-configuration.

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A concise, atom-economic strategy for the synthesis of pyrrolizines with amino and keto substituents has been developed. It includes the following key steps: (i) the base-catalyzed (KPO/DMSO) addition of a benzylamine to 2-acylethynylpyrroles and (ii) noncatalyzed addition of enaminones obtained to the triple bond of acylacetylenes followed by intramolecular cyclization of the intermediate pentadiendiones thus formed to the target 1-(benzylamino)-2-acyl-3-methylenoacylpyrrolizines.