Cationic Ring‐Opening Polymerization of 1,3‐Dehydroadamantanes

Ring‐opening polymerizations of [3.3.1]propellane derivatives, 1,3‐dehydroadamantane ( 1 ) and 5‐butyl‐1,3‐dehydroadamantane ( 2 ), were carried out with CF 3 SO 3 H in CH 2 Cl 2 at 0 °C for 6–42 h. The central σ‐bonds in 1 and 2 were exclusively opened to afford novel poly([3.3.1]propellane)s, poly(1,3‐adamantane)s, in 52–95% yields. The resulting poly( 2 ) possessing flexible butyl substituent was soluble in chloroform, THF, and 1,2‐dichlorobenzene, and the degree of polymerization was estimated to be greater than 30, while the poly( 1 ) was hardly soluble in the common organic solvents. All aliphatic poly( 1 ) and poly( 2 ) showed high thermal stability, their 10% weight loss temperatures were 421 and 486 °C, respectively.