Structural factors for the formation of propellane-type products in the solvolysis of bicyclic bridgehead compounds

Methanolyses of 2-oxobicyclo3.3.1]non-1-yl triflate, 3, 3-dimethyl-2-oxobicyclo3.3.1]non-1-yl triflate, and 2-oxobicyclo4. 3.1]dec-1-yl mesylate gave the corresponding propellanone in 12%, 20%, or 3.2% yield, respectively, beside substitution or rearranged products under typical conditions. No propellane-type product was obtained in the solvolyses of 1-bromobicyclo3.3.1]nonane, 2-methylidenebicyclo3.3.1]non-1-yl heptafluorobutyrate, and 3, 3-dimethyl-2-thioxobicyclo3.3.1]non-1-yl tosylate. The factors that permit the formation of the propellane-type product from the intermediate bridgehead cations are examined with the aid of theoretical calculations at PM3 and B3LYP/6-31G.