Synthesis and Characterization of Some Polycyclic Cyclobutanones

A new stereospecific synthesis of 2,3-cis fused polycyclic cyclobutanone derivatives from readily available starting materials is described. The technique provides a valuable compliment to the use of dichloroketene in that it can be run on a large scale, makes efficient use of reagents, and in a number of cases (e.g., 16 and 22) gives much higher yields of the ketone than the former technique. In addition, the complimentary endo isomers 18, 20, 24, and 26 are formed in cases where dichloroketene has been demonstrated or predicted to occur stereospecifically to produce the exo isomers. The ultraviolet spectra of the ketones have been examined for evidence of nonconjugated chromophore interaction. The exo unsaturated derivative 22 shows a strong intensification of the n → π * transition most reasonably described in terms of a geometric dependent interaction between the π orbitals of the double bond and those of the carbonyl group via the exo σ bond α to the carbonyl group. © 1976, American Chemical Society. All rights reserved.