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  • Author: Benjamin Prek x
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The thermal metal-free [2+2] cycloadditions of electron-poor acetylenes to some polysubstituted systems with conjugated double bonds (polysubstituted butadienes) are described.


In this communication, a simple synthesis of dimethyl 2-[(Z)-3-amino-1-oxo-1-(substituted)but-2-en-2-yl]fumarates is described. Methyl ketones were transformed by treatment with N,N-dimethylacetamide dimethyl acetal (DMADMA) into 3-dimethylamino-1-(substituted)but-2-en-1-ones, followed by treatment with ammonium acetate into (Z)-3-amino-1-(substituted)but-2-en-1-ones and addition to dimethyl acetylenedicarboxylate. These novel polysubstituted butadienes are potential intermediates for the metal-free preparation of polysubstituted five- and six-membered heterocycles.

Herein a simple one-pot metal-free synthesis of 2,4,5-trisubstituted pyridines and pyridine Noxides by [2+2] cycloaddition of enaminones, which are prepared in situ from alkyl, aryl and heteroaryl methyl ketones using N,N-dimethylformamide dimethyl acetal (DMFDMA), and propyne iminium salts as electron-poor acetylenes, is described.