The first 1,1'-spirocyclobutenones 5 are obtained from ynamines and carbon suboxide via a double cycloaddition. The X-ray analysis data are discussed in detail.
Polanc, S. ; Labille, MC. ; Janousek, Z. ; Merenyi, R. ; Vermander, M. ; et. al. Synthesis and X-ray-analysis of Spiro Compounds From Twofold [2+2] Cycloaddition of Ynamines To Carbon Suboxide. In: New Journal of Chemistry, Vol. 15, no. 1, p. 79-83 (1991)