Hyperconjugation involving strained carbon-carbon bonds. Application of the variable oxygen probe to ester and ether derivatives of cubylmethanol

摘要

Application of the variable oxygen probe to derivatives of (4-methoxycarbonyl)cubylmethanol 11 demonstrated a strong response of C-OR bond distance to the electron demand of the OR substituent, consistent with an enhanced σ-donor ability of the strained C-C bonds of cubane. The extent of cubane donor ability was found to be superior to an unstrained donor 13, comparing data extracted from the Cambridge Structural Database (T. W. Cole, Ph.D. Dissertation, University of Chicago, 1966), but weaker than the previously studied cyclopropane donors. Structural evidence is also found for σ_cc-π~*_co interactions in these structures.