Functionalized polymer, rubber composition with such a polymer and pneumatic tire

A functionalized elastomer comprising the reaction product of a living anionic elastomeric polymer and a polymerization terminator of formula I is disclosed. R 1 , R 2 and R 3 are independently selected from a C1 to C8 alkyl or a C1 to C8 alkoxy, with the proviso that at least two of R 1 , R 2 and R 3 are C1 to C8 alkoxy. R 4 is selected from a C1 to C8 alkyl, Si is silicon, S is sulfur; and Z is R 5 or of formula II where R 5 is an alkyl, an aryl, an alkylaryl or an arylalkyl. Also, a respective rubber composition and a tire comprising such a rubber composition is disclosed.