HIGHLY STEREOSPECIFIC PROTONATION OF STEREOREGULAR LIVING PMMA ANIONS WITH SEVERAL ALCOHOLS

Living and highly isotactic poly(methyl methacrylate) (PMMA) anion (MnBAR = 2.5 x 10(3)) prepared with t-C4H9MgBr as an initiator was protonated with phenol in toluene at -78-degrees-C. The reaction was stereospecific toward meso addition, and the meso/racemo ratio at the chain-end of the resultant polymer was 89/11. Addition of 1,4-dioxane to the living isotactic PMMA anion in toluene at -78-degrees-C remarkably reduced the viscosity of the system, and protonation of the PMMA anion with phenol in the presence of 1,4-dioxane enhanced the meso-specificity to 94%. On the other hand, the protonation reaction of the living syndiotactic PMMA anion (MnBAR = 2.5 x 10(3)), which was generated by t-C4H9Li/(n-C4H9)3Al in toluene at -93-degrees-C, with t-butanol was found to be 97% racemo-specific. These highly stereospecific protonation reactions of the stereoregular PMMA anions were in contrast to the protonation of the anions with methanol or benzyl alcohol which was almost non-stereospecific.