Synthesis of end‐functionalized polymer by means of living anionic polymerization, 5. Syntheses of polystyrenes and polyisoprenes with hydroxy and mercapto end groups by reactions of the living polymers with haloalkanes containing silyl ether and silyl thioether functions

Anionic living polystyrene and polyisoprene were allowed to react with six tert ‐butyl‐dimethylsilyl ethers of ω‐halo‐1‐alkanols 1–6 , the trimethylsilyl ether of bromohydrin ( 7 ), the tert ‐butyldimethylsilyl ether of 4‐bromophenol ( 8 ), and tert ‐butyldimethylsilyl 3‐chloropropyl sulfide ( 9 ), followed by acid‐catalyzed cleavage of SiO and SiS bonds to afford polystyrene and polyisoprene, respectively, with hydroxy or mercapto end groups. The alcoholic hydroxy groups were introduced quantitatively to the polymer chain end regardless of the kind of halogen atom, length of methylene spacer separating the protected hydroxy group from the halogen, and structure of protecting groups. The tert ‐butyldimethylsilyl ether of 4‐bromophenol ( 8 ) was not suitable for this reaction, since most (≈90%) of the original living polyisoprene was dimerized due to metal‐halogen exchange followed by the coupling reaction of the polymeric allyl bromide derivatives thus formed with remaining living polyisoprene. Polystyrene and polyisoprene with tert ‐butyldimethylsilyl sulfide end group were obtained quantitatively by the reaction of their anionic living polymers with 9 . Generation of mercapto groups through deprotection was confirmed by I 2 oxidation and reaction with acrylonitrile.