American Chemical Society
jo3014947_si_003.cif (22.22 kB)

One-Pot Five-Component Synthesis of Spirocyclopenta[b]chromene Derivatives and Their Acid-Catalyzed Rearrangement

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posted on 2012-10-19, 00:00 authored by Michael A. Terzidis, Tryfon Zarganes-Tzitzikas, Constantinos Tsimenidis, Julia Stephanidou-Stephanatou, Constantinos A. Tsoleridis, George E. Kostakis
The reaction of the zwitterionic intermediate, generated in situ from either tert-butylisocyanide or cyclohexylisocyanide and acetylenedicarboxylates, with 3-cyanochromones is described, whereupon spirochromenofuran derivatives 5 or 6 were obtained in good yields. The subsequent acid-catalyzed rearrangement of the isolated 2-imino-spirochromenofurans 5 to 2-amino-spirochromenofurans 7 has also been studied. Rational mechanistic schemes for the formation of compounds 5, 6, and 7 are proposed. The structure elucidation of the products was accomplished by 1D and 2D NMR experiments and confirmed by X-ray crystallographic analysis. Full assignment of all 1H and 13C NMR chemical shifts has been unambiguously achieved with the aid of DFT/GIAO calculations.