1,2-Annulated pyrrolo[2,1,5-de]quinolizin-5-ones (cycl[3.3.2]azin-5-ones) 6a–6k, 8a–8b and 9 have been synthesized by one pot tandem reactions of 2-acetyl-N-phenacylpyridinium bromides (1a–1d) with electron-deficient cyclic alkenes (N-alkyl(aryl)maleimides, benzoquinones and naphthoquinone) in the presence of sodium carbonate as a base and tetrakispyridinecobalt(II) dichromate (TPCD) as an oxidant. These products are formed by 1.3-dipolar cycloaddition of the 1-oxoquinolizinium ylides generated in situ from 1a–1d with the alkene followed by dehydrogenation of the primary cycloadduct under the action of TPCD. Similar reactions of the ylides generated in situ from 1a–1f with maleic anhydride gave the 1,2-unsubstituted pyrrolo[2,1,5-de]quinolizin-5-ones 7a–7f via oxidative bisdecarboxylation and dehydrogenation of the primary cycloadducts under the action of TPCD.
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