A series of benzoxazine dimer based difunctional 30-membered macrocyclic and linear oligomer esters are selectively obtained in simple and mild condition. The unique intramolecular hydrogen bond of the dimer is a key factor to proceed the "self-selective reaction" in esterification between terephthaloyl chloride and benzoxazine dimers. This is a so-called "simple, effective, and selective synthesis route" since we can obtain a well-defined structure product in a high yield without using expensive catalysts for multistep reactions in specific conditions.