Carbon-13 chemical shifts of bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives

¹³C chemical shifts of more than fifty bicyclo3.2.1]octane and bicyclo2.2.1]heptane derivatives (hydrocarbons, alcohols, ketones and esters) have been determined. The usefulness of ethyl derivatives for the assignment of close ¹³C chemical shifts in bicyclic methyl derivatives is shown both for the bicyclo3.2.1]octane and bicyclo2.2.1]heptane series. Comparison of substituent effects on α-, β-, γ- and δ-carbons in both series of compounds shows remarkable differences in steric interactions. In contrast to the rigid bicyclo2.2.1]heptane system, both chair and boat conformations can be predominant in the bicyclo3.2.1]octane series with the conformationally flexible 6-membered ring.