Acid-Catalyzed Rearrangement of [m.3.2]Propellanols

The acid-catalyzed rearrangement of exo[5.3.2]propellanol (8x) gave (lS*,6R*,7S*)-tricyclo[5.3.2.0^1,6]dodecane derivatives 22 and 23, while endo alcohol 8n gave (lS*,6S*,7S*)-tricyclo[5.3.2.0^1,6]dodecane derivatives 24 and 25, both by 1,2-alkyl shifts of the central propellane bonds. Similarly, exo-[4.3.2]propellanol (9x) rearranged in acid to (1S*,5R*,6S*)-tricyclo[4.3.2.0¹'⁵]undecane derivatives 32 and 33 via 1,2-alkyl shift of the central propellane bond. On the other hand, endo alcohol 9n yielded (lS*,5R*,6S*)-tricyclo[4.3.2.0^1,5]undecan-5-ol (38) as the initial reaction product via 1,2-alkyl shift of the external cyclobutane bond. However, 38 underwent a second alkyl shift to give as major products the cis, cis-tricyclo[6.3.0.0^1,5]undecane derivatives 39 and 40. The structures of these products were established by chemical transformations.