Acid-Catalyzed Rearrangements of [4.3.2]- and [3.3.3]Propellanes, Tricyclo[4.3.2.0^1,5]undecanes, and Tricyclo[6.3.0.0^1,5]undecanes

Acid-catalyzed rearrangements of [4.3.2]propellanols 2x and 2n, [3.3.3]propellanol (3b), tricyclo[4.3.2.0^1,5]-undecanes 4b-d and 5, and tricyclo[6.3.0.0^1,5]undecanes 6a,b were studied. Tricycloundecanes 4d and 6b rearranged under CF₃S0₃H catalysis to 1- and 2-methyladamantanes together with 12 tricyclic hydrocarbons. The [4.3.2]-and [3.3.3]propellan-2-ols 2x, 2n, and 3b, the tricyclo[4.3.2.0^1,5]undecan-6(5)-ols 4b,c, and tricyclo[6.3.0.0^1,5]-undecan-5-ol (6a) were converted into mixtures of tricyclic hydrocarbons by reductive rearrangement with hydride transfer (97% H₂SO₄-pentane) and into tricyclic carboxylic acids by the Koch-Haaf reagent (97% H2SO4-HCO2H). The alcohol 3b also rearranged in 50% H₂SO₄-THF at reflux to the alcohols 4c and 6a plus tricyclo-[6.3.0.0^1,5]undec-6-ene (34). The structures of products were assigned by comparison of ¹³C NMR spectra, chemical correlation with known compounds, and single-crystal X-ray analysis. Rearrangement pathways at the early stage of the reaction are discussed.