Isothianaphthene monomer, 1,3-bis(tert-butyldimethylsilyl)isothianaphthene (abbreviated as ITN-2TBSi) was synthesized in three steps, according to the previously reported method by Okuda et al. Benzaldehyde monomers with chiral side chains were synthesized by the Mitsunobu reaction, as shown in Scheme 1. The monomer ((−)-mono and (+)-mono2) having chiral alkyl group can be obtained in one step.