A group of compounds defined by the general formula (I) can be used to anionically initiate polymerization of unsaturated monomers. In the formula, M is an alkali metal atom, R1 is an aryl group having at least one OR2 substituent group where each R2 is a group that is nonreactive toward M, and R is a hydrocarbyl group. The subject initiators can be used in semi-batch and continuous polymerization processes, even those which are performed at elevated temperatures.