Benzyl chloride anionic living polymer

Hirao et al. have further developed the above functionahzation reactions using DPE derivatives in an excellent procedure referred to as the chain-multi-functionalization of living anionic polymers [176]. For this purpose, a new DPE derivative, l,l-bis(3-terFbutyldimethylsilyloxymethylphenyl)ethylene (12). has been synthesized. This DPE is designed in such a way that the tert-butyldimethylsilyl ether acts as a protected functionality in a reaction with living anionic polymers, and is quantitatively transformed into a benzyl bromide (BnBr) or even chloride and iodide functions [176, 183]. As illustrated in Scheme 5.18,12 was first reacted with PSLi to introduce two silyl ether functionalities at the chain-end, followed by treatment with Me3SiCl/LiBr to transform into two BnBr fimctions as a result, a well-defined chain-end-(BnBr)2-functionalized PS was obtained. The same functionalized DPE-derived anion was then separately synthesized, and reacted with the above chain-end-(BnBr)2-functionalized PS. The four silyl ether functionalities thus introduced were transformed into four BnBr functions by the same treatment with MesSiCl/LiBr, and this resulted in a chain-end-(BnBr)4-functionalized PS. As the coupling and transformation reactions proceeded both cleanly and quantitatively, the same reaction sequence could be repeated four more times to successfiiUy introduce 8,16, 32, and 64 BnBr functions at the chain-ends (Scheme 5.19 Table 5.3) [184]. Furthermore, the same reaction sequence could be carried out with a-(BnBr)2-functionalized PMMA to afford a series of weU-defined chain-end-BnBr-multi-functionalized PMMAs with up to 16 BnBr functions [185]. 

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